JP7538985B2 - A method for forming a conductive layer on a surface of a substrate or a component by using a paste in which a collection of metal nanoparticles is dispersed in an organic compound, or a method for joining substrates or components, or joining substrates or components together - Google Patents

Description

In the present invention, crystals of a metal compound that precipitates a metal upon thermal decomposition are crushed to nano size, the crushed crystal clusters are dispersed in an organic compound having a boiling point higher than the thermal decomposition temperature of the metal compound, and then the crushed crystals are thermally decomposed to disperse the metal nanoparticle clusters in the organic compound.Furthermore, an organic solvent that dissolves in the organic compound is mixed in a mixing ratio that results in a preset viscosity of the paste, to produce a paste having a preset viscosity.
When this paste is applied to the surface of a substrate or a part and the organic compound is vaporized, a conductive layer consisting of a collection of metallic nanoparticles is formed on the surface of the substrate or part with a thickness according to the viscosity of the paste. In other words, when the coating film made of the paste is heated to the boiling point of the organic compound, the metallic nanoparticles are heated to a temperature higher than the temperature at which the metallic nanoparticles were precipitated, activating the nanoparticles, and the activated metallic nanoparticles are precipitated in overlapping groups, and the precipitated metallic nanoparticles are metallically bonded at the contact points, forming a conductive layer consisting of a collection of metallic nanoparticles on the surface of the substrate or part with a thickness according to the viscosity of the paste.
Furthermore, when the paste is applied or dropped onto a substrate or component and the organic compound is vaporized, a bonding layer consisting of a collection of metallic nanoparticles is formed on the substrate or component with a thickness or amount depending on the viscosity. The bonding strength of the bonding layer depends on the thickness or amount of the collection of metallic nanoparticles. Therefore, by increasing the thickness or amount, it can be used as a brazing material in conventional soldering or brazing. Furthermore, it can be used as a bonding agent for bonding substrates or components, or substrates or components together, via the collection of metallic nanoparticles.
The paste of the present invention has a viscosity that is preset according to the application, and the thickness or amount of the bonding layer that provides the bonding force can be changed by the viscosity of the paste, so that the bonding force of the bonding layer can be changed and the applications of the paste can be expanded. In the present invention, the substrate is defined as the material used when manufacturing the parts. For example, when manufacturing copper parts by processing a copper plate, the copper plate, which is the material used when processing the copper parts, becomes the substrate.

Prior to the present invention, the inventor filed an invention relating to the production of a suspension in which individual metal nanoparticles are surrounded and dispersed in an organic compound as Japanese Patent Application No. 2020-178481 (filed on October 23, 2020). In the prior application, a suspension in which individual fine crystals of a metal compound are surrounded by a liquid organic compound to disperse the fine crystals is prepared, and the fine crystals are further pyrolyzed to precipitate a collection of metal nanoparticles. Thereafter, the suspension is decompressed to a pressure lower than the vapor pressure of the organic compound, and the organic compound is vaporized from the suspension. In other words, in the prior application, in order to prevent the metal nanoparticles from being activated and the nanoparticles from agglomerating, the suspension is decompressed to a pressure lower than the vapor pressure of the organic compound, the organic compound is vaporized from the suspension, and a collection of metal nanoparticles is precipitated. For this reason, the organic compound of the prior application has a boiling point that is higher by a temperature within 30° C. than the thermal decomposition temperature of the metal compound.
In contrast, since the paste in the present invention is used to form a conductive layer or a bonding layer, the paste applied or dropped onto the substrate or component of various materials must wet the substrate or component, regardless of the material of the substrate or component. For this reason, the organic compound dispersing the metal nanoparticles in the present invention has a surface tension of 30 millinewtons per meter or less at 20° C. In addition, when bonding the substrate or component with the paste, it is necessary to change the thickness or amount of the bonding layer and change the bonding force according to the weight of the substrate or component. For this reason, the mixing ratio of the organic solvent dissolved in the organic compound is changed so that the viscosity of the paste at 20° C. is a preset viscosity of 20 millipascal seconds or less, and the paste has a preset viscosity.
Furthermore, when a conductive layer or a bonding layer is formed by using the paste of the present invention, the metal nanoparticles dispersed in the paste are activated, a collection of activated metal nanoparticles is precipitated in an overlapping manner, and the overlapping metal nanoparticles are metallically bonded at the contact portion to form a conductive layer or a bonding layer consisting of a collection of metallic nanoparticles that are metallically bonded. For this reason, an organic compound having a boiling point higher than the thermal decomposition temperature of the metal compound is used as a medium for dispersing the metal nanoparticles, and the organic compound is vaporized from the paste, thereby raising the temperature to a temperature higher than the temperature at which the metal nanoparticles were precipitated, activating the metal nanoparticles, causing the activated collection of metal nanoparticles to precipitate in an overlapping manner, and metallically bonding the precipitated metal nanoparticles.

Conventional conductive pastes in which metal nanoparticles are dispersed in an organic compound use metal nanoparticles covered with an organic compound. Therefore, when the organic compound covering the nanoparticles evaporates, voids are generated. In other words, since metal nanoparticles easily aggregate with each other, it is not possible to directly disperse a collection of metal nanoparticles in an organic compound. For this reason, a conductive paste is manufactured in which a collection of metal nanoparticles covered with an organic compound is used and the collection of metal nanoparticles is dispersed in an organic compound.
For example, Patent Document 1 describes a method of producing a conductive paste in which metal nanoparticles protected by an organic compound containing an amino group and having an average particle size of 30-400 nm, and metal particles protected by a higher fatty acid and having an average particle size of 1-5 μm are dispersed in an organic solvent and a resin component, and the conductive paste is fired to form a wiring board having a thickness of 30 μm or more.
According to the description of the examples, silver nanoparticles with a median diameter of 310 nm are protected with alkylamine. Next, silver particles with median diameters of 0.8 μm, 1 μm, 2.3 μm, 2.9 μm, 5 μm, and 7 μm are protected with higher fatty acid. Furthermore, silver nanoparticles and silver particles are dispersed in an organic solvent and a resin component to produce a conductive paste. The conductive paste is printed on a substrate and heat-treated at 150° C. for 30 minutes to form a silver film with a thickness of 30 μm or more.
In other words, if a conductive paste is formed only from a collection of metal nanoparticles coated with alkylamine, voids will occur as described above. Therefore, by coating silver particles with significantly different median diameters with higher fatty acids and using silver particles and silver nanoparticles together, even if voids occur, the silver nanoparticles will bond the silver particles together, and a conductive layer will be formed by a conductive path in which silver particles are continuously bonded.
However, since there is no description of the boiling point of the organic compound that protects the silver nanoparticles and the boiling point of the higher fatty acid that protects the silver particles and the resin component, it is unclear whether the precipitated silver nanoparticles will be bonded to each other or whether the silver nanoparticles will be bonded to the silver particles by heat treatment at 150°C for 30 minutes. It is also unclear whether the resin component will be completely vaporized at 150°C. In addition, the significance of forming a wiring board by a collection of silver particles through the above-mentioned complicated process on a thick wiring board with a film thickness of 30 μm or more is unclear.
Furthermore, Patent Document 2 describes a conductive paste used for filling vias or trenches, which is characterized by containing metal nanoparticles composited with an organic compound having a polyethylene oxide structure and having 8 to 200 carbon atoms, and an organic solvent having a boiling point of 150° C. or higher.
In Patent Document 2, metal nanoparticles having alkyl chains at the dispersion sites in the protective agent for the metal nanoparticles are used, so that when the conductive paste is baked, the organic compound covering the metal nanoparticles vaporizes, and voids are generated due to the large volume shrinkage rate caused by the vaporization of the organic compound. To solve this problem, metal nanoparticles are composited with an organic compound containing a polyethylene oxide structure having 8 to 200 carbon atoms, and further dispersed in an organic solvent having a boiling point of 150° C. or higher. Therefore, if metal nanoparticles can be directly precipitated in an organic compound without using existing metal nanoparticles, as in Patent Document 1, the technology described in Patent Document 2 will become unnecessary.

JP 2018-049735 A JP 2017-110295 A

As described above, when a conductive layer is formed by heating a conductive paste in which a group of metal nanoparticles is dispersed using metal nanoparticles in which each individual metal nanoparticle is covered with an organic compound, the organic compound covering the metal nanoparticles vaporizes, and the vaporization of the organic compound causes voids to form between adjacent metal nanoparticles, and the generation of the voids prevents direct bonding between the metal nanoparticles, and a conductive path formed by continuous bonding of the group of metal nanoparticles is not formed. Therefore, a conductive paste in which a group of metal nanoparticles covered with an organic compound is dispersed in an organic compound cannot be used as a raw material for forming a conductive layer.
In contrast, metal nanoparticles are directly precipitated in an organic compound with a boiling point higher than the temperature at which metal nanoparticles are precipitated, and a paste in which a collection of metal nanoparticles is dispersed is produced. That is, a metal compound that is a nano-sized raw material for precipitating metal nanoparticles is dispersed in an organic compound, and the raw material is chemically converted to metal nanoparticles in the organic compound, and the metal nanoparticles are precipitated. The organic compound is vaporized from the coating film on which the paste is applied. At this time, the raw material of the metal nanoparticles is chemically converted, and the paste is heated to a temperature higher than the temperature at which the metal nanoparticles are precipitated, so that the metal nanoparticles dispersed in the paste become active. Therefore, when the organic compound is vaporized, the collection of activated metal nanoparticles overlaps and precipitates. Furthermore, the activated metal nanoparticles are metallically bonded at the contact parts where they overlap, and the metallically bonded collection of metal nanoparticles forms a continuous conductive path. As a result, a conductive layer made of a collection of metal nanoparticles is formed. Furthermore, if the thickness or amount of the metal nanoparticles bonded together could be freely adjusted, the paste could be used not only for forming conductive layers but also as a brazing material or adhesive. To realize such a paste, the following seven conditions are necessary:
First, the size of the raw material of the metal nanoparticles is small, at the nano level. Second, the raw material of the metal nanoparticles is dispersed in an organic compound with a boiling point higher than the temperature at which the metal nanoparticles are precipitated. Third, the metal nanoparticles are precipitated in the organic compound, and the metal nanoparticles are dispersed in the organic compound. Fourth, the precipitated metal nanoparticles do not react with the organic compound. On the other hand, the lower the viscosity of the paste, the thinner the thickness of the coating film on which the paste is applied, and when the organic compound is evaporated from the coating film, the thickness of the conductive layer consisting of a collection of metal nanoparticles becomes thinner. However, the thickness of the conductive layer needs to be a thickness according to the application, and it is necessary to be able to change the thickness of the coating film. In addition, when the paste is used as a brazing material or a bonding agent, it is necessary to change the bonding force according to the weight of the substrate or part to be bonded, and it is necessary to be able to freely change the thickness of the dropped paste. Therefore, fifthly, the viscosity of the paste can be freely changed. On the other hand, when the organic compound is evaporated from the paste, the collection of metal nanoparticles overlap and precipitate. However, if the metal nanoparticles are not in an active state, the deposited metal nanoparticles will not be metallically bonded at the contact points. Sixthly, when the organic compound is vaporized from the paste, the metal nanoparticles are activated. Furthermore, if the wettability of the paste is excellent, when the paste is applied or dripped onto a substrate or a component, a coating film or droplets can be formed on the substrate or component, regardless of the material of the substrate or component. Seventhly, the surface tension of the organic compound constituting the paste is small. If a paste that satisfies these seven conditions can be manufactured, it can be used not only as a paste for forming a conductive layer, but also as a brazing material in soldering or brazing. Furthermore, by applying the paste to a joint, it can be used as a bonding agent that bonds substrates or components, or substrates or components together, via a collection of metallically bonded metal nanoparticles.
The object of the present invention is to realize a paste that satisfies the seven conditions.

The method for producing a paste in which a collection of metal nanoparticles is dispersed in an organic compound according to the present invention includes the steps of:
A metal compound having both a first property of being dispersed in methanol but not dissolved in methanol and a second property of precipitating a metal by thermal decomposition is dispersed in methanol to prepare a methanol dispersion of the metal compound; and further, methanol is evaporated from the methanol dispersion of the metal compound to precipitate a crystal cluster of the metal compound.
Then, the collection of crystals of the metal compound is filled into a container, a plate material that covers the entire surface of the collection of crystals of the metal compound in the container is placed on the surface of the collection of crystals of the metal compound, and a compressive load is applied to the entire surface of the plate material to crush the collection of crystals of the metal compound in the container. After the process of applying the compressive load to the plate material is stopped, impact acceleration is applied to the container in three directions, namely, front-back, left-right, and up-down, to move the crushed crystals of the metal compound to the gaps in the container formed by the crushing of the crystals of the metal compound, and rearrange the crushed collection of crystals of the metal compound in the container. Then, the compressive load is applied again to the entire surface of the plate material, and after the process of applying the compressive load to the plate material is stopped, impact acceleration is applied again to the container in the three directions. Such a pair of processes consisting of the process of applying the compressive load and the process of applying the impact acceleration are repeated, and when a repulsive force against the compressive load is generated in the plate material when the compressive load is applied to the plate material, it is determined that the crushing of the crystals of the metal compound is completed, and the pair of processes is stopped, and the plate material is removed from the container.
Then, a liquid organic compound having five properties, namely, a first property of a melting point lower than 15°C, a second property of the metal compound not dissolving or dispersing therein, a third property of a boiling point higher than the thermal decomposition temperature of the metal compound, a fourth property of not reacting chemically with metal nanoparticles precipitated by thermal decomposition of the metal compound, and a fifth property of a surface tension of 30 millinewtons per meter or less at 20°C, is weighed out in a weight greater than the weight of the aggregate of crystals of the metal compound, and the weighed liquid organic compound is filled into the container and stirred to create a suspension in the container in which the aggregate of crushed crystals of the metal compound is dispersed in the liquid organic compound.
Thereafter, the container is placed in an atmosphere in which the crushed metal compound crystals are thermally decomposed, and the temperature is raised to a temperature at which the crushed metal compound crystals are thermally decomposed. Through this process, metal nanoparticles are precipitated surrounded by the liquid organic compound, and a paste consisting of a collection of the metal nanoparticles dispersed in the liquid organic compound is produced in the container.
Then, an organic solvent having a first property of dissolving or being mixed in the liquid organic compound and a second property of having a boiling point lower than the boiling point of the liquid organic compound is mixed into the paste at varying mixing ratios so that the viscosity of the paste at 20°C becomes a preset viscosity of 20 millipascal seconds or less, thereby producing a paste having the preset viscosity in the container.

In other words, according to this manufacturing method, by carrying out the following six extremely simple steps in succession, a paste in which metal nanoparticles of about 10 nm in size are dispersed in an organic compound is produced in a container. This paste satisfies the seven conditions described in paragraph 5.
The first process is a process of simply dispersing the metal compound in methanol, which is the most commonly used solvent. The second process is a process of simply evaporating the methanol from the methanol dispersion. The third process is a process of repeating a pair of processes consisting of a process of applying a compressive load to a collection of crystals of the metal compound filled in a container and a process of further applying an impact acceleration in three directions to the container, thereby advancing the crushing of the crystals of the metal compound. The fourth process is a process of simply filling an organic compound having five properties into a container filled with a collection of crystals whose crushing has progressed. The fifth process is a process of simply pyrolyzing the crystals whose crushing has progressed. The sixth process is a process of simply mixing an organic solvent into the paste.
By carrying out these six extremely simple steps in succession, a paste containing a collection of metal nanoparticles dispersed in an organic compound with a preset viscosity is produced in a container.
Next, the phenomena caused by each process and the effects of each process will be described.
In the first process, when a metal compound that precipitates a metal by thermal decomposition is dispersed in methanol, which is the most commonly used solvent, the metal compound becomes a molecular state and disperses in the methanol. In contrast, when a metal compound dissolves in methanol, the metal that constitutes the metal compound becomes a metal ion and dissolves in the methanol, and the dissolved metal compound cannot return to the metal compound before dissolution. For this reason, when methanol is evaporated from a methanol solution of a metal compound, crystals of the metal compound before dissolution do not precipitate. Therefore, a metal compound that does not dissolve in methanol and disperses in methanol is used as a raw material for metal nanoparticles. In other words, when methanol is evaporated from a methanol dispersion of a metal compound, the metal compound before dispersion precipitates as crystals of the metal compound smaller than 100 nm. In addition, when a metal compound that precipitates a metal by thermal decomposition reaches a thermal decomposition temperature, the metal compound decomposes into an inorganic or organic substance and a metal, and when the evaporation of the inorganic or organic substance is completed, the metal precipitates. For this reason, the metal precipitated by thermal decomposition of a metal compound does not contain any impurities.
In the second process, when methanol is evaporated from the methanol dispersion of the metal compound, crystals of the metal compound smaller than 100 nm are precipitated as a collection of the crystals. That is, in the methanol dispersion of the metal compound, the metal compound is in a molecular state and uniformly dispersed in the methanol, so when the methanol is evaporated, the metal compound before dispersion is precipitated as granular crystals smaller than 100 nm. These granular crystals are a collection of crystals in which crystals formed by single molecules of the metal compound are accumulated, since the metal compound dispersed in the methanol in a molecular state is precipitated as crystals. Therefore, when stress is applied to the granular crystals, the crystals are easily crushed and become fine crystals. On the other hand, the finer the crystals, the more difficult it is to apply stress to the crystals, and there is a limit to how fine the crystals can be. The evaporated methanol is recovered by a recovery machine and reused as methanol.
In the third process, a plate material is placed over the collection of crystals of the metal compound filled in the container, the collection of crystals of the metal compound is restrained in the container by the plate material, and a compressive load is applied to the collection of crystals of the metal compound through the plate material. At this time, the larger the crystal size, the easier it is to crush. Therefore, the relatively larger crystals are crushed first, and the crushing of the crystals progresses while the compressive load is applied. On the other hand, in the collection of crystals in the container, voids are formed by the crushing of the crystals, and while the compressive load is applied, the crystals move to fill the voids and the crushing of the crystals progresses. Furthermore, after the application of the compressive load is stopped, the container is repeatedly subjected to impact acceleration in three directions, front and back, left and right, and up and down. At this time, the crystals do not scatter because they are restrained in the container by the plate material, and the crystals are forced to move to fill the voids, and the collection of crystals is rearranged in the container. Furthermore, after the application of the impact acceleration is stopped, a compressive load is applied again to the collection of crystals through the plate material. At this time, the crushing of the crystals progresses for the collection of finer crystals. After this, the container is repeatedly subjected to impact acceleration in three directions to rearrange the cluster of fine crystals. A pair of processes consisting of the process of applying a compressive load and the process of applying an impact acceleration in three directions is repeated. On the other hand, the finer the crystals are, the more difficult it becomes to apply compressive stress to the crystals even when a compressive load is applied, and there is a limit to the refinement of the crystals by the compressive load. When the refinement of the crystals reaches its limit, the crystals do not break even when a compressive load is applied to the plate material, and a repulsive force against the compressive stress is generated in the plate material. At this point, it is determined that the grinding of the crystals of the metal compound is completed, and the pair of processes is stopped. As a result, the size of the crystals becomes approximately 20 nm, which is nearly 1/5 of the size at the time when the crystals are precipitated. Note that when the crystals of the metal compound are precipitated, there is variation in the size of the crystals, and there is also variation in the size of the voids created by the grinding. Therefore, there is also variation in the size of the cluster of crystals that have been ground. In addition, the compressive load applied to the plate material is a compressive load equivalent to 10-100 kg weight depending on the size of the container. The impact acceleration applied to the container is 0.3 to 1.0 G depending on the size of the container.
In the fourth process, a liquid organic compound having five properties, namely, a first property of a melting point lower than 15°C, a second property of the metal compound not dissolving or dispersing, a third property of a boiling point higher than the thermal decomposition temperature of the metal compound, a fourth property of not chemically reacting with the metal nanoparticles precipitated at the thermal decomposition temperature of the metal compound, and a fifth property of a surface tension of 30 millinewtons per meter or less at 20°C, is weighed out to a weight greater than the weight of the metal compound crystal clusters, and the liquid organic compound is filled into a container and stirred, whereby a suspension in which the crushed crystal clusters are dispersed in the liquid organic compound is produced in the container. The weight of the organic compound is added to a weight greater than the weight of the metal compound crystal clusters to facilitate dispersion of the crushed crystals in the suspension.
That is, since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the organic compound is vaporized from the applied or dripped paste, the temperature of the metal nanoparticles rises to a temperature higher than the temperature at which the metal nanoparticles precipitated, and the metal nanoparticles become activated, and a group of activated metal nanoparticles is deposited overlapping on the coating film or droplets, and the overlapping activated metal nanoparticles are metallically bonded at the contact points. Therefore, when the organic compound is vaporized after the paste is applied, the metallically bonded group of metal nanoparticles forms a continuous conductive path in the coating film. Alternatively, when the organic compound is vaporized after the paste is applied or dripped, a bonding layer consisting of a group of metallically bonded metal nanoparticles is formed on the coating film or dripped droplets.
Furthermore, organic compounds have an extremely small surface tension of 30 millinewtons per meter or less. The surface tension of water is 73 millinewtons per meter at 20°C, which is more than twice the surface tension of organic compounds. In contrast, metals have a large surface tension, with iron at 1,360 millinewtons per meter and silicon at 1,240 millinewtons per meter . On the other hand, synthetic resins have the smallest surface tension of all solids, at 24-47 millinewtons per meter . That is, PTFE resin (a type of fluororesin, which is polytetrafluoroethylene resin) has the smallest surface tension of all synthetic resins, at 24 millinewtons per meter . Incidentally, the surface tension of another type of fluororesin, PVDF resin (polyvinyl fluoride resin), is 33 millinewtons per meter . In addition, the surface tension of polyethylene resin is 37 millinewtons per meter , that of polystyrene resin is 40 millinewtons per meter , that of polyvinyl chloride resin is 42 millinewtons per meter , that of PET resin is 45 millinewtons per meter , and that of nylon resin is 47 millinewtons per meter . Therefore, the surface tension of organic compounds is smaller than that of most solids. For this reason, the contact angle of the paste applied or dripped onto a solid substrate or part is small, and the paste is easily wetted by solids. Therefore, the paste wets substrates and parts of various materials, and when the paste is applied or dripped, a coating film or droplets are formed on the substrate or part without being restricted by the material.
In the fifth process, the crushed crystals of the metal compound are thermally decomposed to produce a paste in which metal nanoparticles are dispersed in the liquid organic compound in the container. That is, when the temperature at which the metal compound is thermally decomposed is reached, the crushed crystals of the metal compound surrounded by the liquid organic compound are first decomposed into inorganic or organic molecules and metal molecules. Next, the inorganic or organic molecules take the heat of vaporization and vaporize. At this time, the volume of the inorganic or organic gas expands explosively, and the gas molecules pass through the organic compound and are sequentially discharged to the outside world. That is, when one mole of inorganic or organic molecules is vaporized, the volume of the inorganic or organic gas occupies 22.4 liters. Therefore, when the vaporization of the inorganic or organic molecules begins, the inorganic or organic gas surrounded by the liquid organic compound expands explosively from a size of about 20 nm, and since the density of the inorganic or organic gas is two orders of magnitude smaller than the density of the organic compound, the gas molecules pass through the organic compound and are sequentially discharged to the outside world. Since the density of the inorganic or organic gas is two orders of magnitude smaller than the density of the organic compound, the inorganic or organic gas cannot remain in the liquid organic compound. Furthermore, at the moment when the vaporization of the inorganic or organic molecules is completed, a collection of metal molecules forms metal nanoparticles with a size of about 10 nm, and the metal nanoparticles are precipitated surrounded by the liquid organic compound, and a paste in which the metal nanoparticles are dispersed in the liquid organic compound is created. When the metal compound is thermally decomposed, all impurities such as moisture, organic matter, and hydroxides contained in the suspension, whose boiling point is lower than the thermal decomposition temperature of the metal compound, are vaporized from the suspension. Therefore, the metal nanoparticles are precipitated surrounded by an organic compound in a liquid that is free of impurities, and precipitate as true metal nanoparticles.
On the other hand, genuine metal nanoparticles are in an active state when precipitated, but do not undergo chemical reactions with liquid organic compounds, and after precipitation, they are surrounded by liquid organic compounds, becoming inactive and stable metal nanoparticles. The inorganic or organic gas vaporized from the container is collected by a recovery machine and reused as a raw material for organic compounds.
In the sixth process, the viscosity of the paste at 20° C. is preset to 20 mPascal seconds or less, and an organic solvent that dissolves or is mixed with the liquid organic compound and has a boiling point lower than that of the liquid organic compound is mixed into the paste at a different mixing ratio so as to obtain a preset viscosity. In other words, the viscosity of the paste is changed according to the application of the paste, and the thickness of the coating film formed by applying the paste is changed according to the application. Therefore, after the organic solvent and the organic compound are evaporated, the thickness of the conductive layer consisting of a collection of metallic nanoparticles bonded to each other changes according to the viscosity of the paste. This allows the thickness of the conductive layer to be freely changed depending on the application of the conductive layer. Alternatively, when the paste is dropped onto a substrate or a component and used as a brazing material in soldering or brazing, the viscosity of the paste is increased compared to when the paste is applied to form a conductive layer, and the viscosity of the paste is further increased according to the mass of the components to be brazed, so that the thickness and amount of the bonding layer made of a collection of metallic nanoparticles bonded to each other becomes thicker or larger according to the viscosity of the paste, and brazing is performed with a bonding layer having a large bonding force. Also, when the paste is applied or dropped onto a joint to bond substrates or components, or substrates and components to each other, the viscosity of the paste is increased according to the mass of the substrates or components to be bonded, so that the thickness and amount of the bonding layer made of a collection of metallic nanoparticles bonded to each other becomes thicker or larger according to the viscosity of the paste, and the substrates or components are bonded with a bonding layer having a large bonding force. In this way, the viscosity of the paste is preset according to the use of the paste and the mass of the other to which the paste is applied or dropped, and the thickness or amount of the bonding layer as a bonding agent is changed to change the bonding force of the bonding agent. This expands the range of applications for the paste. Furthermore, since the conductive layer or bonding layer formed using the paste is formed by simply heating the applied or dripped paste to the boiling point of the organic compound, the conductive layer or bonding layer can be formed on the substrate or component without being restricted by the material of the substrate or component. This expands the range of applications for forming the conductive layer or bonding layer using the paste.
The paste of the present invention is produced by successively carrying out the six extremely simple steps described above. The metal compounds, organic compounds, and organic solvents are all general-purpose industrial chemicals. Therefore, an inexpensive paste can be produced at low cost, and the produced paste can be used for various purposes.

A method for forming a conductive layer consisting of a collection of metallic nanoparticles bonded to each other on a surface of a substrate or a part using the paste produced by the method described in paragraph 6, comprising the steps of:
The paste produced by the above method is applied to a surface of a substrate or a part, and a coating film having a thickness corresponding to the viscosity of the paste is formed on the surface of the substrate or the part. Thereafter, the substrate or the part is heated to the boiling point of the organic compound of the liquid.
Through this treatment, first the organic solvent evaporates from the coating film, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was applied, and further, the clusters of overlapping and precipitated metal nanoparticles metal-bond at the sites where they come into contact with each other, and a conductive layer consisting of the clusters of metal nanoparticles that are metal-bonded is formed on the surface of the substrate or the part as a conductive layer having a thickness according to the viscosity of the paste.
A method for forming a conductive layer consisting of a collection of metallic nanoparticles bonded to each other on the surface of a substrate or part using a paste produced by the method described in paragraph 6.

That is, when the paste produced by the method described in paragraph 6 is applied to the surface of a substrate or a part, a coating film having a thickness according to the viscosity of the paste is formed. That is, the viscosity of the paste at 20°C is set to be 20 mPascal seconds or less, and the organic compound diluted with an organic solvent is adsorbed to the metal nanoparticles having a size of about 10 nm, which have almost no mass, with an adsorption force according to the viscosity. Therefore, when the paste is applied, the metal nanoparticles are not separated from the organic compound diluted with an organic solvent, and a coating film consisting of the paste in which the metal nanoparticles are dispersed in the organic compound diluted with an organic solvent is formed. In addition, the paste has an extremely small surface tension of 30 mN/m or less and a low viscosity of 20 mPascal seconds or less, and further, the metal nanoparticles are about 10 nm in size, which is two orders of magnitude smaller than the unevenness of the surface of the substrate or the part, so that the applied paste penetrates into the unevenness of the surface of the substrate or the part regardless of the material of the substrate or the part.
After this, the substrate or part on which the coating film is formed is heated to the boiling point of the organic compound. After the organic solvent evaporates, the organic compound evaporates. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, a collection of activated metal nanoparticles overlaps and precipitates, and the precipitated metal nanoparticles are metallically bonded at the contact portion, and a conductive layer consisting of a collection of metallically bonded metal nanoparticles is formed on the surface of the substrate or part with a thickness according to the viscosity of the paste. On the other hand, from the paste that has entered the unevenness of the surface of the substrate or part, after the organic solvent evaporates, the organic compound evaporates, and a collection of metallic nanoparticles overlaps and precipitates on the unevenness of the surface, and the precipitated metal nanoparticles are metallically bonded at the contact portion. Therefore, the collection of metallically bonded metal nanoparticles that fill the unevenness of the surface contacts the collection of metallically bonded metal nanoparticles that are precipitated just above the unevenness of the surface, and the contacted metal nanoparticles are metallically bonded. As a result, a collection of metallically bonded metal nanoparticles is formed continuously on the surface of the substrate or component and on the irregularities of the surface. Meanwhile, an anchor effect occurs in the collection of metallically bonded metal nanoparticles formed on the irregularities of the surface of the substrate or component. Therefore, the collection of metallically bonded metal nanoparticles precipitated on the surface of the substrate or component is bonded to the surface of the substrate or component with a certain degree of mechanical strength. As a result, a conductive layer consisting of the collection of metallically bonded metal nanoparticles is formed on the surface of the substrate or component, regardless of the material of the substrate or component.
When the substrate or part is heated to the boiling point of the organic compound, the moisture, hydrates, hydroxides, and organic matter adhering to the surface of the substrate or part are vaporized in order according to their respective boiling points. Therefore, a prior cleaning process to remove impurities adhering to the surface of the substrate or part is not necessary. In addition, the collection of metal nanoparticles penetrates into the unevenness of the surface of the substrate or part and fills in the unevenness of the surface, so that a conductive layer is formed on the surface of the substrate or part even if an oxide film or hydroxide film is formed on the surface of the substrate or part.
The conductive layer described above is formed by simply applying a paste having a preset viscosity and vaporizing the organic compound. Therefore, regardless of the size and shape of the substrate or part, a conductive layer having the required size and thickness is formed on the surface of the substrate or part, and has electrical conductivity and thermal conductivity equivalent to that of the metal constituting the metal nanoparticles. In addition, when the metal is a ferromagnetic metal made of iron, nickel, or cobalt, it has ferromagnetic properties in addition to electrical conductivity and thermal conductivity equivalent to that of the ferromagnetic metal. On the other hand, the surface of the conductive layer forms irregularities of about 10 nm, which are the size of the metal nanoparticles. Therefore, the surface of the conductive layer is extremely flat and has excellent smoothness. Therefore, when the sliding member slides on the surface of the conductive layer, the sliding member slides on the surface of the conductive layer. Therefore, the conductive layer acts as a lubricating coating with a small friction coefficient. Therefore, the conductive layer has the function of a lubricating coating with a remarkably slow wear rate and a long life. Furthermore, since the surface of the conductive layer is extremely flat, the surface of the conductive layer has water repellency and antifouling properties. For example, when the conductive layer is used as an electromagnetic shielding film or an antistatic film, foreign matter is less likely to adhere to the surface of the electromagnetic shielding film or the antistatic film. In this way, the paste produced by the present invention can form layers that have not only electrical conductivity and thermal conductivity but also various other functions according to various applications.

A method for bonding a component to a substrate or bonding components to each other using a bonding layer consisting of a collection of metallic nanoparticles bonded by metallurgical bonding using a paste produced by the method described in paragraph 6, comprising the steps of:
A part of a component is brought into contact with a surface of a substrate, and the paste produced by the above -mentioned method is dropped onto the portion where the part of the component comes into contact with the substrate. Then, both the substrate and the component are heated to the boiling point of the liquid organic compound.
By this process, first, the organic solvent evaporates from the dropped paste, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, and the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was dropped, and further, the clusters of overlapping and precipitated metal nanoparticles metal-bond with each other at the sites where they come into contact with each other, and a bonding layer consisting of the clusters of metal nanoparticles that are metal-bonded is formed at the site where a part of the component comes into contact with the base material as a bonding layer in an amount corresponding to the viscosity of the paste, and the part of the component is bonded to the surface of the base material by the bonding layer.
- a method for bonding a component to a substrate with a bonding layer consisting of a collection of metallic nanoparticles bonded together by using a paste produced according to the method according to paragraph 6,
Or,
The parts are brought into contact with each other, and the paste produced by the above- mentioned method is dripped onto the contacted portion of the parts. Thereafter, the parts are heated to the boiling point of the liquid organic compound.
By this process, first, the organic solvent evaporates from the dropped paste, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, and the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was dropped, and further, the clusters of overlapping and precipitated metal nanoparticles metal-bond at the sites where they come into contact with each other, and a bonding layer consisting of the clusters of metal nanoparticles that are metal-bonded is formed at the sites where the components come into contact as a bonding layer in an amount corresponding to the viscosity of the paste, and the components are bonded to each other by the bonding layer.
A method for joining components together using a paste produced by the method described in paragraph 6 with a joining layer consisting of a collection of metallically bonded metal nanoparticles.

That is, when a part of a component is brought into contact with the surface of a substrate and a paste produced by the method described in paragraph 6 is dropped onto the area where the component and the substrate are in contact, droplets are formed having a size and thickness according to the viscosity of the paste. Alternatively, when components are brought into contact with each other and a paste produced by the method described in paragraph 6 is dropped onto the area where the components are in contact, droplets are formed having a size and thickness according to the viscosity of the paste.
That is, the viscosity of the paste at 20°C is set to 20 mPascal seconds or less, and the organic compound diluted with an organic solvent is adsorbed to the metal nanoparticles having a size of about 10 nm, which have almost no mass, with an adsorption force according to the viscosity. Therefore, when the paste is dropped, the metal nanoparticles do not separate from the organic compound diluted with an organic solvent, and droplets are formed in which the metal nanoparticles are dispersed in the organic compound diluted with an organic solvent. In addition, the paste has an extremely small surface tension of 30 mN/m or less and a low viscosity of 20 mPascal seconds or less, and the metal nanoparticles are about 10 nm in size, which is two orders of magnitude smaller than the unevenness of the surface of the substrate or component. Therefore, the dropped paste covers the entire area where the component contacts the substrate, regardless of the material of the substrate or component, and enters the small gaps formed at the contact site and the unevenness of both surfaces where the component contacts the substrate. Furthermore, the dropped paste covers the entire area where the components come into contact with each other, and also penetrates into minute gaps at the contact site and into the irregularities on the surfaces of both components where they come into contact with each other.
After this, the substrate and the part on which the droplets are formed are heated to the boiling point of the organic compound. As a result, the organic solvent evaporates, and then the organic compound evaporates. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, a collection of activated metal nanoparticles overlaps and precipitates, and the precipitated metal nanoparticles are metallically bonded to each other at the contact area, and a bonding layer consisting of a collection of metallically bonded metal nanoparticles is formed with a size and thickness according to the viscosity of the paste, covering the entire area where the part contacts the substrate, and penetrating the gaps at the contact area and the unevenness of both surfaces where the part contacts the substrate. Meanwhile, the collection of metallically bonded metal nanoparticles that fills the unevenness of the substrate surface comes into contact with the collection of metallically bonded metal nanoparticles that have precipitated at the contact area with the part just above the unevenness of the surface, and the contacting metal nanoparticles are metallically bonded to each other. As a result, a group of metallically bonded metal nanoparticles is continuously formed at the portion where the part contacts the substrate, in the gaps at the contact portion, and in the unevenness of both surfaces where the part contacts the substrate. Therefore, a bonding layer consisting of a group of metallically bonded metal nanoparticles is formed at the portion where the part contacts the substrate, regardless of the material of the substrate or the part. Meanwhile, an anchor effect occurs in the group of metallically bonded metal nanoparticles formed in the gaps and in the unevenness of both surfaces where the part contacts the substrate. As a result, the group of metallically bonded metal nanoparticles bonds the part to the substrate with a certain mechanical strength.
Alternatively, the parts onto which the droplets are dropped are heated to the boiling point of the organic compound. As a result, the organic solvent evaporates, and then the organic compound evaporates. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the dropped paste is completed, the activated metal nanoparticles are deposited on top of each other, and the deposited metal nanoparticles are metallically bonded to each other at the contact portion, and a bonding layer consisting of the metal nanoparticles is formed in a size and thickness according to the viscosity of the paste, covering the entire contact portion between the parts, and in the gaps formed at the contact portion and the unevenness of the surfaces of both parts where the parts are in contact. Meanwhile, the metal nanoparticles deposited at the contact portion between the parts come into contact with the metal nanoparticles deposited in the gaps at the contact portion, and also come into contact with the metal nanoparticles deposited in the unevenness of the surfaces of both parts where the parts are in contact, and the contacting metal nanoparticles are metallically bonded to each other. As a result, a cluster of metallically bonded nanoparticles is continuously formed at the contact area between the components, in the gaps at the contact area, and in the unevenness of the surfaces of both components where the components are in contact. Meanwhile, an anchor effect occurs in the cluster of metallically bonded nanoparticles formed in the gaps and in the unevenness of the surfaces of both components where the components are in contact. As a result, a bonding layer made of a cluster of metallically bonded nanoparticles is formed at the contact area between the components, regardless of the materials of the components, and the components are bonded to each other by the bonding layer.
One example of the present invention in which a component is bonded to a substrate is manual soldering. Conventional soldering does not liquidize the solder, but utilizes the wetting phenomenon of the solder to bond the components, and therefore the adhesive strength is small. In contrast, in the present invention, the component is bonded to the substrate via the metallic bond of metal nanoparticles, and therefore the adhesive strength is greater than that of solder. Furthermore, compared to solder made of a three-component or two-component alloy, the paste can be produced at a lower cost. Thus, the paste is less expensive than conventional solder and has a higher bonding strength than conventional soldering. If a metal compound that decomposes at a temperature of about 180° C. is used, the thermal decomposition temperature is nearly 40° C. lower than the melting point of lead-free solder.
In addition, the method of joining a component to a substrate in the present invention is a process of bringing a part of the component into contact with the surface of the substrate, dripping a paste onto the area where the component comes into contact with the substrate, and heating the component and substrate to the boiling point of the organic compound. Therefore, examples of joining a component to a substrate are not limited to manual soldering.
In addition, brazing is one of the examples of joining parts together in the present invention. In conventional brazing, a brazing material with a melting point lower than that of the base material is melted, and the melted brazing material is dropped between the two base materials to be joined. The melted brazing material penetrates and diffuses between the base materials by capillary action, and the brazing material cools and solidifies to join the two base materials together. Brazing is performed by raising the temperature to a melting point of the brazing material higher than 450°C using a gas burner or industrial furnace. The brazing material to be used is limited depending on the material of the base material. In addition, in order to drop the melted brazing material between the base materials without taking a long time and to perform brazing while the base materials are fixed, brazing based on experience is required to achieve high quality brazing. Furthermore, in order to ensure the joining strength, foreign matter such as rust on the joint is removed in advance and then washed. After this, flux is added to the joint, and after the flux melts, a solder rod is inserted and the solder is poured in. The joint is then heated to diffuse the flux throughout the joint, and before the base material cools, the flux is removed. This is a complex process that is carried out in succession. Voids may occur in the brazed area, but they cannot be detected from the outside. On the other hand, brazing in a vacuum reduces the probability of voids occurring, but brazing in a vacuum is not practical from the perspective of processing costs.
In contrast, the present invention has no restrictions on the materials between the base materials. In addition, the process only involves dropping the paste and raising the temperature. Furthermore, the temperature at which the organic compound is vaporized is more than 200° C. lower than that of brazing. Furthermore, the process of dropping the paste and raising the temperature of the paste is extremely simple, and can be automated. Therefore, the base materials can be joined with the same joining strength. Therefore, the present invention can join base materials under the same conditions and with the same quality.
In addition, the method of joining parts together in the present invention is a process of contacting the parts together, dripping a paste onto the area where the parts contact, and raising the temperature of the parts to the boiling point of the organic compound, so the example of joining parts together is not limited to brazing.
As described above, in the present invention, by simply dripping paste onto the area where a component and a substrate come into contact, or onto the area where components come into contact with each other, and vaporizing the organic compound, it is possible to join a component to a substrate or join components to each other, even if the component and the substrate are made of different materials, or even if the components are made of different materials, the bonding range of the paste is wide.
Furthermore, by changing the viscosity of the paste according to the mass of the parts to be joined or according to the mass of the parts to be joined, the thickness and amount of the bonding layer that bonds the parts to the base material or the thickness and amount of the bonding layer that bonds the parts to each other can be changed, and the bonding strength of the bonding layer can be freely changed according to the mass of the parts or the mass of the parts to be joined. Therefore, when the mass of the parts is large and a large bonding strength is required, the viscosity of the paste is set to a relatively high viscosity.
Furthermore, when the substrate or part is heated to the boiling point of the organic compound, the moisture, hydrates, hydroxides, and organic substances attached to the surface of the substrate or part are vaporized in order according to their respective boiling points. Therefore, a pre-cleaning process to remove impurities attached to the surface of the substrate or part is not necessary. Also, since a collection of metal nanoparticles that is two orders of magnitude smaller than the unevenness of the surface of the substrate or part penetrates and precipitates in the unevenness of the surface of the substrate or part, even if an oxide film or hydroxide film is formed on the surface of the substrate or part, the collection of metal nanoparticles bonds the part to the substrate or bonds the parts to each other.

The method for joining a component to a substrate or joining components together described in paragraph 10 is a method for joining a component to a substrate or joining components together using a joining layer made of a collection of ferromagnetic metal nanoparticles that are joined together by magnetic attraction and metallic bonding, and the method for joining a component to a substrate or joining components together is as follows:
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of any one of iron, nickel, and cobalt upon thermal decomposition, and the metal compound is used as the metal compound to produce a paste consisting of a collection of nanoparticles consisting of the ferromagnetic metal dispersed in an organic compound according to the method for producing a paste described above , and the paste is dropped onto a portion of a part that is in contact with the surface of a substrate, and then both the substrate and the part are heated to the boiling point of the liquid organic compound described above .
By this treatment, first, the organic solvent evaporates from the dropped paste, then the organic compound in the liquid evaporates, and then the collection of ferromagnetic metal nanoparticles dispersed in the paste is activated, and the activated collection of ferromagnetic metal nanoparticles overlap and precipitate at the site where the paste was dropped, and further, the overlapping and precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and the magnetically attracted ferromagnetic metal nanoparticles are metallically bonded at the sites where they come into contact with each other, and a bonding layer consisting of the collection of metallically bonded ferromagnetic metal nanoparticles is formed as a bonding layer in an amount corresponding to the viscosity of the paste at the site where a part of the component comes into contact with the base material.
a method for bonding a component to a substrate, comprising: applying a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles to a portion of the component bonded to the substrate, thereby saturating the magnetization of the ferromagnetic metal nanoparticles; by this process, the metallically bonded ferromagnetic metal nanoparticles are magnetically attracted to each other due to the saturated magnetization, and the component is bonded to the substrate by a bonding layer made of a collection of the ferromagnetic metal nanoparticles in which the ferromagnetic metal nanoparticles are bonded to each other by magnetic attraction and metallic bonding ;
Or,
The metal compound that precipitates a metal upon thermal decomposition is a metal compound that precipitates a ferromagnetic metal consisting of iron, nickel, or cobalt upon thermal decomposition, and the metal compound is used as the metal compound to produce a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound according to the method for producing a paste described above , and the paste is dripped onto a portion where the components come into contact with each other, and then the components are heated to the boiling point of the liquid organic compound described above .
By this process, first, the organic solvent evaporates from the dropped paste, then the organic compound in the liquid evaporates, and then the clusters of ferromagnetic metal nanoparticles dispersed in the paste are activated, and the activated clusters of ferromagnetic metal nanoparticles overlap and precipitate at the site where the paste was dropped, and further, the overlapping and precipitated ferromagnetic metal nanoparticles magnetically attract each other, and the magnetically attracted ferromagnetic metal nanoparticles are metallically bonded at the sites where they come into contact with each other, and a bonding layer consisting of the clusters of metallically bonded ferromagnetic metal nanoparticles is formed at the sites where the components come into contact as a bonding layer in an amount corresponding to the viscosity of the paste.
A magnetic field is then applied to the areas where the parts come into contact, causing the magnetization of the ferromagnetic metal nanoparticles to saturate, and this process causes the metallically bonded ferromagnetic metal nanoparticles to be magnetically attracted to each other due to the saturated magnetization, and the parts are joined by a joining layer consisting of a collection of ferromagnetic metal nanoparticles bonded to each other by magnetic attraction and metallic bonding, in this method of joining parts.

That is, as the metal compound that precipitates a metal by thermal decomposition described in paragraph 6, a metal compound that precipitates a ferromagnetic metal consisting of iron, nickel, or cobalt by thermal decomposition is used, and a paste in which a collection of nanoparticles of the ferromagnetic metal is dispersed in an organic compound is manufactured according to the method for manufacturing a paste described in paragraph 6. When the paste is dropped onto a portion where a component contacts a substrate, droplets are formed at the contact portion. Also, when the paste is dropped onto a portion where components contact each other, droplets are formed at the contact portion.
That is, the viscosity of the paste at 20°C is set to 20 mPascal seconds or less, and the organic compound diluted with an organic solvent is adsorbed to the metal nanoparticles having a size of about 10 nm, which have almost no mass, with an adsorption force according to the viscosity. Therefore, when the paste is dropped, the metal nanoparticles do not separate from the organic compound diluted with an organic solvent, and droplets are formed in which the metal nanoparticles are dispersed in the organic compound diluted with an organic solvent. In addition, the paste has an extremely small surface tension of 30 mN/m or less and a low viscosity of 20 mPascal seconds or less, and further, the metal nanoparticles are about 10 nm in size, which is two orders of magnitude smaller than the unevenness of the surface of the substrate or component. Therefore, the dropped paste covers the entire area where the component contacts the substrate, regardless of the material of the substrate or component, and enters the small gaps formed at the contact area and the unevenness of both surfaces where the component contacts the substrate. Furthermore, the dropped paste not only covers the entire area where the components come into contact with each other, but also penetrates into any small gaps in the contact area and into the irregularities on the surfaces of both components where they come into contact with each other.
After this, the substrate and the part on which the droplets are formed are heated to the boiling point of the organic compound. As a result, the organic solvent evaporates, and then the organic compound evaporates. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, the activated ferromagnetic metal nanoparticles are precipitated by overlapping each other, the overlapping ferromagnetic metals are magnetically attracted to each other, the magnetically attracted ferromagnetic metal nanoparticles are metallically bonded to each other at the contact site, and the ferromagnetic metal nanoparticles joined by magnetic attraction and metallic bonding are formed in a size and thickness according to the viscosity of the paste, covering the entire part where the part contacts the substrate, and are formed in the gaps at the contact site and in the unevenness of both surfaces where the part contacts the substrate. Meanwhile, the ferromagnetic metal nanoparticles that fill the unevenness of the substrate surface are magnetically attracted to the ferromagnetic metal nanoparticles that are precipitated at the contact site with the part just above the unevenness of the surface, and the magnetically attracted ferromagnetic metal nanoparticles are metallically bonded to each other at the contact site. As a result, a group of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding is continuously formed at the part where the part contacts the substrate, in the gap at the contact part, and on the unevenness of both surfaces where the part contacts the substrate. Therefore, a bonding layer consisting of a group of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding is formed at the part where the part contacts the substrate, regardless of the material of the substrate or the part. On the other hand, an anchor effect occurs in the group of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed in the gap and the group of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed on the unevenness of both surfaces where the part contacts the substrate. As a result, the bonding layer consisting of a group of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding bonds the part to the substrate with a certain mechanical strength.
Furthermore, when a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is applied to a portion where a part of the component is joined to the substrate, the magnetization of all the ferromagnetic metal nanoparticles is saturated, and the magnetic attraction acting on all the ferromagnetic metal nanoparticles increases significantly. On the other hand, when a collection of ferromagnetic metal nanoparticles precipitates all at once, the bonding force that metal-bonds the ferromagnetic metal nanoparticles together is limited to the portion where the metal nanoparticles come into contact with each other. In contrast, the magnetic attraction acting on the magnetized ferromagnetic metal nanoparticles acts on the entire nanoparticles. Therefore, the magnetic attraction force is greater than the bonding force that metal-bonds the metal nanoparticles together. Furthermore, the ferromagnetic metal nanoparticles are extremely small, about 10 nm, and it is difficult to peel off the magnetic attraction between the ferromagnetic metal nanoparticles that are magnetically attracted by the saturated magnetization. This significantly increases the anchoring effect acting on the collections of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed in the gaps, and on the collections of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed in the irregularities on both surfaces where the component contacts the substrate.
Alternatively, the parts on which the droplets are formed are heated to the boiling point of the organic compound. As a result, the organic solvent evaporates, and then the organic compound evaporates. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, a collection of nanoparticles of the activated ferromagnetic metal overlaps and precipitates, the precipitated nanoparticles of the ferromagnetic metal are magnetically attracted, and the magnetically attracted nanoparticles of the ferromagnetic metal are metallically bonded at the contact site, and a bonding layer consisting of a collection of nanoparticles of the ferromagnetic metal bonded by magnetic attraction and metallic bonding is formed with a size and thickness according to the viscosity of the paste, covering the entire contact site between the parts, and is formed in the gaps at the contact site and in the unevenness of the surfaces of both parts where the parts contact each other. On the other hand, the ferromagnetic metal nanoparticles precipitated at the contact area of the parts are magnetically attracted to the ferromagnetic nanoparticles precipitated in the gaps at the contact area, and are also magnetically attracted to the ferromagnetic nanoparticles precipitated on the unevenness of the surfaces of both parts where the parts are in contact, and the magnetically attracted ferromagnetic metal nanoparticles are metallically bonded at the contact area. As a result, a collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding is continuously formed at the contact area of the parts, the gaps at the contact area, and the unevenness of the surfaces of both parts where the parts are in contact. On the other hand, an anchor effect occurs in the collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed in the gaps and the collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed on the unevenness of the surfaces of both parts where the parts are in contact. As a result, a bonding layer consisting of a collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding is formed at the contact area of the parts, regardless of the material of the parts. As a result, the bonding layer, which is made up of a collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding, bonds the components together with a certain degree of mechanical strength.
Furthermore, when a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is applied to the portion where the parts are joined, the magnetization of the ferromagnetic metal nanoparticles is saturated, and the magnetic attraction acting on all the ferromagnetic metal nanoparticles increases significantly. On the other hand, when a collection of metal nanoparticles precipitates all at once, the bonding force that metal bonds adjacent metal nanoparticles together is limited to the portion where the metal nanoparticles contact each other. In contrast, the magnetic attraction acting on the magnetized saturated ferromagnetic metal nanoparticles acts on the entire nanoparticles. Therefore, the magnetic attraction force is greater than the bonding force that metal nanoparticles bond together. Furthermore, the ferromagnetic metal nanoparticles are extremely small, about 10 nm, and it is difficult to peel off the magnetic attraction between the ferromagnetic metal nanoparticles that are magnetically attracted by the saturated magnetization. Therefore, the anchor effect acting on the collection of ferromagnetic metal nanoparticles that are bonded by magnetic attraction and metallic bonding formed in the gap and the collection of ferromagnetic metal nanoparticles that are bonded by magnetic attraction and metallic bonding formed on the unevenness of the surfaces of both parts where the parts are in contact with each other increases significantly.
Therefore, the component is more firmly bonded to the substrate, or the components are more firmly bonded to each other, than in the case where a part of the component described in paragraphs 10-11 is brought into contact with the surface of the substrate, a paste is then dripped onto the portion where the component is in contact with the substrate, clusters of activated metal nanoparticles are then precipitated in an overlapping state, and the precipitated metal nanoparticles are metallically bonded at the portions where they contact, and the component is joined to the substrate by the metallically bonded cluster of metal nanoparticles, or in the case where a paste is dripped onto the portion where the components are in contact with each other, a cluster of activated metal nanoparticles is then precipitated in an overlapping state, and the precipitated metal nanoparticles are metallically bonded at the portions where they contact, as described in paragraphs 10-11.
As a result, the bonding strength for bonding the component to the substrate or bonding the components together is greater than in the examples described in paragraphs 10 and 11. In addition, because the surface tension of the paste is small, droplets of the applied paste are formed on the surfaces of both the component and the substrate, regardless of the materials of the component and the substrate, and the component is bonded to the substrate or the components are bonded together by a collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding.
Furthermore, when the substrate or part is heated to the boiling point of the organic compound, the moisture, hydrates, hydroxides, and organic substances attached to the surface of the substrate or part are vaporized in order according to their respective boiling points. Therefore, a pre-cleaning process to remove impurities attached to the surface of the substrate or part is not necessary. Also, since a collection of metal nanoparticles that is two orders of magnitude smaller than the unevenness of the surface of the substrate or part penetrates and precipitates in the unevenness of the surface of the substrate or part, even if an oxide film or hydroxide film is formed on the surface of the substrate or part, the collection of metal nanoparticles bonds the part to the substrate or bonds the parts to each other.
In addition, the viscosity of the paste is changed according to the mass of the parts to be joined or according to the mass of the parts to be joined together. This allows the thickness and amount of the bonding layer that bonds the parts to the base material or the thickness and amount of the bonding layer that bonds the parts to each other to be changed, and the bonding strength of the bonding layer can be freely changed according to the mass of the parts or the mass of the parts to be joined together. Therefore, when the mass of the parts is large and a large bonding strength is required, the viscosity of the paste is set to a relatively high viscosity.
On the other hand, the magnetic Curie points of ferromagnetic metals are 770°C for iron, 358°C for nickel, and 1131°C for cobalt. Therefore, unless the magnetic Curie points of ferromagnetic metals are approached, the magnetic attractive force that bonds a component to a substrate or bonds components to each other does not change. For this reason, even if the component or substrate is exposed to high temperatures, the component continues to be bonded to the substrate or the components continue to be bonded to each other.

A method for joining a part to a substrate, or a method for joining substrates together, or a method for joining parts together, using a paste produced by the method described in paragraph 6, with a joining layer consisting of a collection of metal nanoparticles joined by frictional heat, comprises:
The paste produced by the above -mentioned method is applied to both joining portions where a component is to be joined to a substrate, the component to which the paste has been applied is placed on top of the substrate to which the paste has been applied, and a compressive load is applied to the surface of the component. Thereafter, both the component to which the compressive load has been applied and the substrate are heated to the boiling point of the liquid organic compound, and the application of the compressive load to the surface of the component is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the liquid organic compound evaporates, and then the collection of metal nanoparticles dispersed in the paste is activated, and the activated collection of metal nanoparticles overlap and precipitate at the site where the paste was applied, and further, compressive stress due to the compressive load is applied to the collection of metal nanoparticles that have precipitated and overlap, and the metal nanoparticles come into contact with each other due to the compressive stress, and further, frictional heat is generated at the site where the metal nanoparticles come into contact with each other due to the frictional heat, and the metal nanoparticles are bonded to each other by the frictional heat, and a bonding layer consisting of the collection of metal nanoparticles bonded by the frictional heat is formed at the bonding site as a bonding layer in an amount corresponding to the viscosity of the paste, and the part is bonded to the base material by the bonding layer.
A method for bonding a part to a substrate by means of a bonding layer consisting of a collection of nanoparticles of metal bonded by frictional heat, using a paste produced by the method according to paragraph 6;
Or,
The paste produced by the above -mentioned method is applied to both joining portions of the substrates to be joined, the joining portions to which the paste has been applied are overlapped, and a compressive load is applied to one of the overlapped substrates. Thereafter, the substrates to which the compressive load has been applied are heated to the boiling point of the liquid organic compound, and the application of the compressive load to the one of the substrates is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the liquid organic compound evaporates, and then the collection of metal nanoparticles dispersed in the paste is activated, and the activated collection of metal nanoparticles overlap and precipitate at the site where the paste was applied, and further, a compressive stress due to the compressive load is applied to the collection of metal nanoparticles that have precipitated and overlap, and the metal nanoparticles come into contact with each other due to the compressive stress, and further, frictional heat is generated at the site where the metal nanoparticles come into contact with each other, and the metal nanoparticles are bonded to each other by the frictional heat, and a bonding layer consisting of the collection of metal nanoparticles bonded by the frictional heat is formed at the bonding site as a bonding layer consisting of an amount corresponding to the viscosity of the paste, and the substrates are bonded to each other by the bonding layer.
A method for bonding substrates with a bonding layer made of a collection of metal nanoparticles bonded by frictional heat, using the paste produced by the method according to claim 1;
Or,
The paste produced by the above -mentioned method is applied to both joining portions of the components to be joined, the joining portions to which the paste has been applied are overlapped, and a compressive load is applied to one of the overlapped components. Thereafter, the components to which the compressive load has been applied are heated to the boiling point of the liquid organic compound, and the application of the compressive load to the one of the components is stopped.
By this process, first, the organic solvent evaporates from the applied paste, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, and the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was applied, and further, compressive stress due to the compressive load is applied to the clusters of metal nanoparticles that have precipitated and overlap, and the compressive stress causes the metal nanoparticles to come into contact with each other, and further, frictional heat is generated at the site where the metal nanoparticles come into contact with each other, and the metal nanoparticles are bonded together by the frictional heat, and a bonding layer consisting of the clusters of metal nanoparticles bonded together by the frictional heat is formed at the bonding site as a bonding layer in an amount corresponding to the viscosity of the paste, and the parts are bonded together by the bonding layer.
A method for joining parts together using a paste produced by the method described in paragraph 6, with a joining layer consisting of a collection of metal nanoparticles bonded by frictional heat.

First, a method for joining a component to a substrate using a joining layer made of a collection of nanoparticles of a metal, the nanoparticles being joined together by frictional heat, will be described.
When the paste produced by the method described in paragraph 6 is applied to a portion where a part is bonded to a substrate and a portion where a part is bonded to a substrate, a coating film is formed on both portions. That is, the viscosity of the paste at 20° C. is set to 20 mPascal seconds or less, and an organic compound diluted with an organic solvent is adsorbed to metal nanoparticles having a size of about 10 nm, which have almost no mass, with an adsorption force according to the viscosity. Therefore, when the paste is applied, a coating film is formed in which the metal nanoparticles are not separated from the organic compound diluted with an organic solvent, and the metal nanoparticles are dispersed in the organic compound diluted with an organic solvent. In addition, the paste has an extremely small surface tension of 30 mN/m or less, a low viscosity of 20 mPascal seconds or less, and the metal nanoparticles are about 10 nm in size, which is two orders of magnitude smaller than the unevenness of the surface of the substrate or the part, so that the applied paste covers the entire area where the part is bonded to the substrate, regardless of the material of the substrate or the part, and penetrates the unevenness of the surface of both portions where the part is superimposed on the substrate.
After this, the component coated with the paste is placed on the substrate coated with the paste, a compressive load is applied to the surface of the component, and the component and substrate are heated to the boiling point of the organic compound. This causes the organic solvent to evaporate, and then the organic compound to evaporate. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, a collection of activated metal nanoparticles overlaps and precipitates, and the precipitated metal nanoparticles are metallically bonded at the contact area, and a bonding layer consisting of a collection of metallic nanoparticles that is metallically bonded covers the entire area where the component is bonded to the substrate, with a thickness according to the viscosity of the paste, and penetrates into the unevenness of the surfaces of both parts where the component is placed on the substrate.
On the other hand, the collection of metallic nanoparticles that fills the surface irregularities of the substrate contacts the collection of metallic nanoparticles that are deposited on the contact area with the component immediately above the surface irregularities, and the contacting metallic nanoparticles are metallically bonded to each other. As a result, the collection of metallic nanoparticles is continuously formed in all areas where the component is bonded to the substrate and in the surface irregularities of both parts where the component is superimposed on the substrate. Therefore, a bonding layer made of a collection of metallic nanoparticles is formed in the part where the component is bonded to the substrate, regardless of the material of the substrate or the component. On the other hand, an anchor effect occurs in the collection of metallic nanoparticles that are formed on the surface irregularities of both parts where the component is superimposed on the substrate. As a result, the bonding layer made of a collection of metallic nanoparticles bonds the component to the substrate with a certain mechanical strength.
However, since the compressive stress is continuously applied to the part, the compressive stress is applied to the collection of metal nanoparticles formed at the part where the part is bonded to the substrate, and to the collection of metal nanoparticles formed on the unevenness of the surface of both parts where the part is superimposed on the substrate. As a result, the compressive stress is applied to the metal bond between the metal nanoparticles, and since the volume of the bond is small, the metal bond is destroyed first, and the metal nanoparticles that have been separated from the metal bond move slightly in the area filled with the metal nanoparticles, and the metal nanoparticles come into contact with each other again. Furthermore, the compressive stress is applied to the metal nanoparticles that have been separated from the metal bond, and the metal nanoparticles try to move, but the presence of the collection of contacting metal nanoparticles becomes an obstacle, preventing the movement of the metal nanoparticles, and the metal nanoparticles come into strong contact with each other. Therefore, the volume of the contact area between the metal nanoparticles is larger than the volume of the contact between the metal nanoparticles when the activated collection of metal nanoparticles precipitates. At this time, frictional heat is generated at the contact points between the metal nanoparticles, and adjacent metal nanoparticles are bonded together by the frictional heat. However, the bonding strength between the metal nanoparticles due to the frictional heat is greater than the bonding strength between the metal nanoparticles when a collection of activated metal nanoparticles precipitates.
As a result, regardless of the material of the substrate or part, the collection of metal nanoparticles bonded by frictional heat fills the area where the part is bonded to the substrate, and also fills the surface irregularities of both areas where the part is superimposed on the substrate, and the collections of metal nanoparticles of both are frictionally bonded at the areas where they come into contact with each other. In addition, the collection of metal nanoparticles bonded by frictional heat that fills the surface irregularities creates an anchor effect. As a result, the bonding layer made of the collection of metal nanoparticles bonded by frictional heat bonds the part to the substrate, regardless of the difference in material between the part and the substrate.
One example of joining the part of the present invention to a substrate is when the part and the substrate are made of different materials. That is, when the material combination of the part and the substrate is such that one is made of iron and the other is made of aluminum, or one is made of aluminum and the other is made of synthetic resin, or one is made of aluminum and the other is made of carbon fiber reinforced plastic, or one is made of synthetic resin and the other is made of ceramics, it is difficult to join the part to the substrate because the melting points or softening points of the two are significantly different, or the structures of the materials and the bonding structures between atoms are significantly different.
However, according to the method of joining a part to a substrate of the present invention, the part can be joined to the substrate by a bonding layer consisting of a collection of metal nanoparticles bonded by frictional heat, regardless of the combination of materials of the part and substrate.
Next, a method for joining substrates together or a method for joining parts together using a joining layer made of a collection of nanoparticles of a metal in which adjacent nanoparticles of the metal are joined by frictional heat will be described.
When the paste produced by the method described in paragraph 6 is applied to both joints between substrates or to both joints between parts, a coating film is formed at both joints. That is, the viscosity of the paste at 20°C is set to 20 mPascal seconds or less, and an organic compound diluted with an organic solvent is adsorbed to metal nanoparticles with a size of about 10 nm that have almost no mass with an adsorption force according to the viscosity. Therefore, when the paste is applied, the metal nanoparticles do not separate from the organic compound diluted with an organic solvent, and a coating film consisting of the paste is formed in which the metal nanoparticles are dispersed in the organic compound diluted with an organic solvent. In addition, the paste has an extremely low surface tension of 30 millinewtons per meter or less and a low viscosity of 20 millipascal seconds or less. Furthermore, the metal nanoparticles are about 10 nm in size, which is two orders of magnitude smaller than the irregularities on the surface of the substrate or component. Therefore, the applied paste covers the entire area where the substrates or components are joined, regardless of the material of the substrate or component, and penetrates into the irregularities on the surface of the overlapping substrates or overlapping components.
After this, the substrates coated with the paste are overlapped, or the parts coated with the paste are overlapped, a compressive load is applied to the surface of one of the substrates or one of the parts, and the substrate or part is heated to the boiling point of the organic compound. As a result, the organic solvent is evaporated, and then the organic compound is evaporated. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, a collection of activated metal nanoparticles overlaps and precipitates on the coating film, and the precipitated metal nanoparticles are metallically bonded at the contact area, and a bonding layer consisting of a collection of metallic nanoparticles is formed with a thickness according to the viscosity of the paste, covering the entire area where the substrates or parts are bonded, and penetrating the unevenness of the surface of the overlapped substrates or parts.
On the other hand, a collection of metal-bonded nanoparticles filling the unevenness of the surface of the substrate contacts a collection of metal-bonded nanoparticles deposited at the contact portion with the other substrate just above the unevenness of the surface, and the contacting metal nanoparticles are metal-bonded to each other. As a result, a collection of metal-bonded nanoparticles is continuously formed at the joining portion where the substrates are joined and on the unevenness of the surfaces of both substrates. Similarly, a collection of metal-bonded nanoparticles filling the unevenness of the surface of the part contacts a collection of metal-bonded nanoparticles deposited at the contact portion with the other substrate just above the unevenness of the surface, and the contacting metal nanoparticles are metal-bonded to each other. As a result, a collection of metal-bonded nanoparticles is continuously formed at all joining portions where the substrates are joined and on the unevenness of the surfaces of both substrates. Similarly, a collection of metal-bonded nanoparticles is continuously formed at all joining portions where the components are joined and on the unevenness of the surfaces of both components. As a result, a bonding layer consisting of a collection of metallic nanoparticles is formed at the site where the components or substrates are bonded together, regardless of the material of the substrate or component. Meanwhile, an anchor effect occurs in the collection of metallic nanoparticles formed on the unevenness of the surface of the overlapped substrates or components. As a result, the bonding layer consisting of a collection of metallic nanoparticles bonds the substrates or components together with a certain degree of mechanical strength.
However, since compressive stress is continuously applied to both substrates or both parts, compressive stress is applied to the collection of precipitated metal nanoparticles. Therefore, compressive stress is applied to the metal bond between the metal nanoparticles, and since the volume of the bond is small, the metal bond is preferentially destroyed, and the metal nanoparticles separated from the metal bond move slightly in the area filled with metal nanoparticles, and the metal nanoparticles contact each other again. Furthermore, compressive stress is applied to the metal nanoparticles separated from the metal bond, and the metal nanoparticles try to move, but the presence of the collection of contacting metal nanoparticles becomes an obstacle, preventing the movement of the metal nanoparticles, and the metal nanoparticles contact each other firmly. Therefore, the volume of the contact between the metal nanoparticles is larger than the volume of the contact between the metal nanoparticles when the activated metal nanoparticles are overlapped and precipitated. At this time, frictional heat is generated at the contact points between the metal nanoparticles, and the frictional heat bonds the metal nanoparticles together. However, the bonding strength between the metal nanoparticles due to the frictional heat is greater than the bonding strength between the metal nanoparticles when the activated metal nanoparticles overlap and precipitate.
As a result, the unevenness of the surfaces of the parts or substrates overlapping each other is filled with the collection of metal nanoparticles bonded by frictional heat, and the collection of metal nanoparticles of the parts or substrates overlapping each other is filled with the collection of metal nanoparticles bonded by frictional heat, and the collection of metal nanoparticles of the two metals are frictionally bonded at the contact points. In addition, an anchor effect occurs in the collection of metal nanoparticles bonded by frictional heat formed on the unevenness of the surfaces of the overlapping parts or substrates. Therefore, the bonding layer made of the collection of metal nanoparticles bonded by frictional heat firmly bonds the parts or substrates. In addition, the substrates or parts are bonded to each other regardless of the difference in material between the parts and substrates.
In one example of joining substrates or parts according to the present invention, the substrates or parts are made of different materials. According to the method for joining substrates or parts according to the present invention, the substrates or parts can be joined by a joining layer made of a collection of metal nanoparticles joined by frictional heat, regardless of the combination of materials of the substrates or parts.
As described above, the paste of the present invention is applied to a portion where a component is joined to a substrate, to a portion where substrates are joined, or to a portion where components are joined, and then the component is compressed to the substrate, or one of the substrates is compressed, or one of the components is compressed, and the organic compound is vaporized. Even if the component and the substrate, the substrates, or the components are made of different materials, the component is joined to the substrate, the substrates, or the components are joined by a bonding layer made of a collection of metal nanoparticles bonded by frictional heat, further expanding the range of application of the paste.
In addition, the bond between metal nanoparticles bonded by frictional heat has a larger volume of the bond than the bond between metal nanoparticles bonded by metallic bonding described in paragraphs 10-11, and therefore the bonding strength is greater than the bonding strength between metal nanoparticles bonded by metallic bonding described in paragraphs 10-11.
Furthermore, when the substrate or part is heated to the boiling point of the organic compound, the moisture, hydrates, hydroxides, and organic substances attached to the surface of the substrate or part are vaporized in order according to their respective boiling points. Therefore, a prior cleaning process to remove impurities attached to the surface of the substrate or part is not necessary. Also, since a collection of metal nanoparticles that is two orders of magnitude smaller than the unevenness of the surface of the substrate or part enters the unevenness of the surface of the substrate or part and precipitates, even if an oxide film or hydroxide film is formed on the surface of the substrate or part, the collection of metal nanoparticles bonds the part to the substrate, bonds the parts to each other, or bonds the substrates to each other.
In addition, the viscosity of the paste is changed according to the mass of the parts to be joined, or according to the mass of the base materials or parts to be joined, whereby the thickness of the joining layer that joins the parts to the base materials, or the thickness of the joining layer that joins the base materials or parts to each other, can be changed, and the joining strength of the joining layer can be freely changed according to the mass of the parts, or according to the mass of the base materials or parts to be joined. Therefore, when the mass of the base materials or parts is large and a large joining strength is required, the viscosity of the paste is set to a relatively high viscosity.

The method of joining a part to a substrate, or joining substrates together, or joining parts together described in paragraph 14 is a method of joining a part to a substrate, or joining substrates together, or joining parts together, by a joining layer made of a collection of ferromagnetic metal nanoparticles bonded together by magnetic attraction and frictional heat, and the method of joining a part to a substrate, or joining substrates together, or joining parts together is:
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of any one of iron, nickel, and cobalt upon thermal decomposition, and the metal compound is used as the metal compound, and a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound is produced according to the method for producing a paste described above , the paste is applied to both joining sites where a component is joined to a substrate, the joining site of the component to which the paste has been applied is overlapped with the joining site of the substrate to which the paste has been applied, and a compressive load is applied to the surface of the component, and then both the component to which the compressive load has been applied and the substrate are heated to the boiling point of the liquid organic compound, and further, the application of the compressive load applied to the surface of the component is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the organic compound in the liquid evaporates, and then the collection of ferromagnetic metal nanoparticles dispersed in the paste is activated, the activated collection of ferromagnetic metal nanoparticles overlaps and precipitates at the portion where the paste was applied, the overlapping and precipitated ferromagnetic metal nanoparticles magnetically attract each other, and further, a compressive stress due to the compressive load is applied to the magnetically attracted collection of ferromagnetic metal nanoparticles, and the compressive stress generates frictional heat at the magnetically attracted portions of the ferromagnetic metal nanoparticles, and the ferromagnetic metal nanoparticles are bonded together by the frictional heat, and a bonding layer consisting of the collection of ferromagnetic metal nanoparticles bonded by the frictional heat is formed at the bonding portion.
a method for bonding a component to a substrate, wherein a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is then applied to a portion where the component is superimposed on the substrate, thereby saturating the magnetization of the ferromagnetic metal nanoparticles; by this process, the ferromagnetic metal nanoparticles bonded by the frictional heat are magnetically attracted to each other due to the saturated magnetization, and the component is bonded to the substrate by a bonding layer made of a collection of the ferromagnetic metal nanoparticles that are bonded to each other by magnetic attraction and frictional heat;
Or,
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of iron, nickel, or cobalt upon thermal decomposition, and the metal compound is used as the metal compound, and a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound is produced according to the method for producing a paste described above , the paste is applied to both joining portions of substrates to be joined, the joining portions of the substrates to which the paste has been applied are overlapped, and a compressive load is applied to one of the overlapped substrates, and then the substrates to which the compressive load has been applied are heated to the boiling point of the liquid organic compound, and the application of the compressive load applied to the one of the substrates is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the organic compound in the liquid evaporates, and then the collection of ferromagnetic metal nanoparticles dispersed in the paste is activated, the activated collection of ferromagnetic metal nanoparticles overlaps and precipitates at the portion where the paste was applied, the overlapping and precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and further, a compressive stress due to the compressive load is applied to the magnetically attracted collection of ferromagnetic metal nanoparticles, and the compressive stress generates frictional heat at the magnetically attracted portions of the ferromagnetic metal nanoparticles, and the ferromagnetic metal nanoparticles are bonded to each other by the frictional heat, and a bonding layer consisting of the collection of ferromagnetic metal nanoparticles bonded by the frictional heat is formed at the bonding portion.
a method for joining substrates, comprising: applying a magnetic field to both joining sites of the substrates such that the magnetization of the ferromagnetic metal nanoparticles is saturated, and saturating the magnetization of the ferromagnetic metal nanoparticles; by this treatment, the ferromagnetic metal nanoparticles joined by the frictional heat are magnetically attracted to each other due to the saturated magnetization, and the substrates are joined by a joining layer made of an assembly of the ferromagnetic metal nanoparticles that are joined to each other by magnetic attraction and frictional heat;
Or,
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of any one of iron, nickel, and cobalt upon thermal decomposition, and the metal compound is used as the metal compound, and a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound is produced according to the method for producing a paste described above , the paste is applied to both joining sites where components are to be joined, the joining sites where the paste is applied are overlapped, and a compressive load is applied to one of the overlapped components, and then the temperature of the components to which the compressive load has been applied is raised to the boiling point of the liquid organic compound, and further, the application of the compressive load applied to the one of the components is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the organic compound in the liquid evaporates, and then the collection of ferromagnetic metal nanoparticles dispersed in the paste is activated, the activated collection of ferromagnetic metal nanoparticles overlaps and precipitates at the portion where the paste was applied, the overlapping and precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and further, a compressive stress due to the compressive load is applied to the magnetically attracted collection of ferromagnetic metal nanoparticles, and the compressive stress generates frictional heat at the magnetically attracted portions of the ferromagnetic metal nanoparticles, and the ferromagnetic metal nanoparticles are bonded to each other by the frictional heat, and a bonding layer consisting of the collection of ferromagnetic metal nanoparticles bonded by the frictional heat is formed at the bonding portion.
A magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is then applied to both joining sites where the parts are joined, thereby saturating the magnetization of the ferromagnetic metal nanoparticles; by this process, the ferromagnetic metal nanoparticles joined by the frictional heat are magnetically attracted to each other due to the saturated magnetization, and the parts are joined by a joining layer consisting of a collection of ferromagnetic metal nanoparticles that are joined to each other by magnetic attraction and frictional heat, in this method of joining parts.

First, a method for joining a component to a substrate using a joining layer made of a collection of ferromagnetic metal nanoparticles that are joined together by magnetic attraction and frictional heat will be described.
A paste in which ferromagnetic metal nanoparticles are dispersed in an organic compound is manufactured according to the method for manufacturing a paste described in paragraph 6, using a metal compound that precipitates a ferromagnetic metal consisting of iron, nickel, or cobalt by thermal decomposition as the metal compound that precipitates a metal by thermal decomposition described in paragraph 6. When the paste is applied to a portion where a part is joined to a substrate and a portion where the part is joined to the substrate, a coating film is formed at both joining portions. That is, the viscosity of the paste at 20°C is set to be 20 millipascal seconds or less, and the organic compound diluted with an organic solvent is adsorbed to the ferromagnetic metal nanoparticles having a size of about 10 nm and having almost no mass with an adsorption force according to the viscosity. Therefore, when the paste is applied, the ferromagnetic metal nanoparticles are not separated from the organic compound diluted with an organic solvent, and a coating film consisting of the paste is formed in which the ferromagnetic metal nanoparticles are dispersed in the organic compound diluted with an organic solvent. In addition, the paste has an extremely low surface tension of 30 millinewtons per meter or less and a low viscosity of 20 millipascal seconds or less. Furthermore, the metal nanoparticles are about 10 nm in size, which is two orders of magnitude smaller than the irregularities on the surface of the substrate or component. Therefore, the applied paste covers the entire area where the component is bonded to the substrate, regardless of the material of the substrate or component, and penetrates into the irregularities on the surfaces of both parts where the component is superimposed on the substrate.
After this, the component coated with the paste is placed on the substrate coated with the paste, a compressive load is applied to the surface of the component, and the component and substrate are heated to the boiling point of the organic compound. As a result, the organic solvent evaporates, and then the organic compound evaporates. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, a collection of nanoparticles of the activated ferromagnetic metal overlaps and precipitates, and the precipitated nanoparticles of the ferromagnetic metal are magnetically attracted to each other, and the magnetically attracted ferromagnetic metals are metallically bonded at the contact points, and a bonding layer consisting of a collection of nanoparticles of the ferromagnetic metal bonded by magnetic attraction and metallic bonding is formed on the bonding layer of the component and the substrate.
On the other hand, when the paste filling the unevenness of the surface of the substrate is heated, the activated ferromagnetic metal nanoparticles are precipitated by overlapping each other, and are magnetically attracted to the ferromagnetic nanoparticles precipitated at the contact portion with the component just above the unevenness of the surface of the substrate, and the contact portion of the magnetically attracted ferromagnetic metal is metallically bonded. As a result, the ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding are continuously formed in all areas where the component is bonded to the substrate and in the unevenness of the surface of the substrate with which the component is in contact. Therefore, a bonding layer consisting of the ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding is formed at the portion where the component is bonded to the substrate, regardless of the material of the substrate or the component. On the other hand, an anchor effect occurs in the ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed in the unevenness of the surfaces of both the portions where the component is superimposed on the substrate. As a result, the ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding bond the component to the substrate with a certain mechanical strength.
However, since the compressive stress is continuously applied to the part, the compressive stress is continuously applied to the collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed at the part where the part is bonded to the base material, and to the collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed on the unevenness of the surface of both parts where the part is superimposed on the base material. As a result, the compressive stress is concentrated at the joint between the ferromagnetic metal nanoparticles, and the ferromagnetic metal nanoparticles try to move by dissociating from the joint, but cannot move because they are filled with the bonded ferromagnetic metal nanoparticles. Furthermore, the compressive stress is applied to the ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding, and the compressive stress is applied to the joint. As a result, frictional heat is generated at the joint due to the compressive stress applied to the joint between the ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding, and the ferromagnetic metal nanoparticles are bonded to each other by the frictional heat. On the other hand, the contact volume between ferromagnetic metal nanoparticles at the joint where compressive stress is concentrated is larger than the contact volume between ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding. Therefore, the bonding force between nanoparticles due to frictional heat is greater than the bonding force between nanoparticles bonded by magnetic attraction and metallic bonding. As a result, ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding are firmly bonded by frictional heat.
As a result, the collection of ferromagnetic metal nanoparticles bonded by frictional heat fills the area where the part is bonded to the substrate, and also fills in the unevenness of the surface of the substrate where the part comes into contact, and the collection of ferromagnetic metal nanoparticles of both are frictionally bonded where they come into contact with each other. The collection of ferromagnetic metal nanoparticles that fills in the unevenness of the surface creates an anchor effect. As a result, the collection of ferromagnetic metal nanoparticles bonded by frictional heat bonds the part to the substrate, regardless of the difference in material between the part and the substrate.
Furthermore, when a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is applied to the portion where the part is bonded to the substrate, the magnetization of all the ferromagnetic metal nanoparticles is saturated, and the magnetic attraction acting on all the ferromagnetic metal nanoparticles increases significantly. On the other hand, the bonding force of the ferromagnetic metal nanoparticles bonded by frictional heat is limited to the portion where the ferromagnetic metal nanoparticles contact each other. In contrast, the magnetic attraction acting on the magnetized saturated ferromagnetic metal nanoparticles acts on the entire nanoparticles. Therefore, the magnetic attraction force is greater than the bonding force caused by frictional heat. Furthermore, the ferromagnetic metal nanoparticles are extremely small, about 10 nm, and it is difficult to peel off the magnetic attraction between the ferromagnetic metal nanoparticles magnetically attracted by the saturated magnetization. Therefore, the magnetic attraction acting on the collection of magnetized saturated ferromagnetic metal nanoparticles firmly bonds the part to the substrate, regardless of the difference in material between the part and the substrate. In addition, the anchor effect acting on the collection of ferromagnetic metal nanoparticles formed in the void increases significantly.
Therefore, compared to the case where the collection of metal nanoparticles bonded by frictional heat described in paragraphs 14-15 is used to bond a part to a substrate, the magnetic attraction force acting on the collection of ferromagnetic metal nanoparticles with saturated magnetization is added to the bonding force of the collection of ferromagnetic metal nanoparticles bonded by frictional heat, resulting in a stronger bond than the case where the part is bonded to the substrate described in paragraphs 14-15. This allows the part to be firmly bonded to the substrate regardless of the materials of the part and substrate.
Next, we will explain a method of joining substrates together or a method of joining parts together using a joining layer consisting of a collection of ferromagnetic metal nanoparticles that are bonded together by magnetic attraction and frictional heat.
A paste in which ferromagnetic metal nanoparticles are dispersed in an organic compound is manufactured according to the method for manufacturing a paste described in paragraph 6, using a metal compound that precipitates a ferromagnetic metal consisting of iron, nickel, or cobalt by thermal decomposition as the metal compound that precipitates a metal by thermal decomposition described in paragraph 6. When the paste is applied to both joint parts that join the substrates together, or to both joint parts that join the components together, a coating film is formed on both joint parts. That is, the viscosity of the paste at 20°C is set to be 20 millipascal seconds or less, and the organic compound diluted with an organic solvent is adsorbed to the ferromagnetic metal nanoparticles that have a size of about 10 nm and have almost no mass with an adsorption force according to the viscosity. Therefore, when the paste is applied, the ferromagnetic metal nanoparticles do not separate from the organic compound diluted with an organic solvent, and a coating film consisting of the paste is formed in which the ferromagnetic metal nanoparticles are dispersed in the organic compound diluted with an organic solvent. In addition, the paste has an extremely low surface tension of 30 millinewtons per meter or less and a low viscosity of 20 millipascal seconds or less. Furthermore, the ferromagnetic metal nanoparticles are approximately 10 nm in size, which is two orders of magnitude smaller than the irregularities on the surface of the substrate or component. Therefore, the applied paste covers the entire area to be joined, regardless of the material of the substrate or component, and penetrates into the irregularities on the surfaces of both parts where the component is layered on the substrate.
After this, the substrates coated with the paste are overlapped, or the parts coated with the paste are overlapped, a compressive load is applied to the surface of one of the substrates or one of the parts, and the substrates or parts are heated to the boiling point of the organic compound. As a result, the organic solvent is evaporated, and then the organic compound is evaporated. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, a collection of nanoparticles of the activated ferromagnetic metal is overlapped and precipitated, and the precipitated collection of nanoparticles of the ferromagnetic metal is magnetically attracted, and the magnetically attracted ferromagnetic metals are metallically bonded at the contact site, and a bonding layer consisting of a collection of nanoparticles of the ferromagnetic metal bonded by magnetic attraction and metallic bonding is formed at the site where the substrates or parts are overlapped.
On the other hand, when the paste filling the unevenness of the surface of the substrate or component is heated, the activated ferromagnetic metal nanoparticles are precipitated by overlapping each other, and the precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and the magnetically attracted ferromagnetic metals are metallically bonded at the contact points. Also, the ferromagnetic metals are magnetically attracted to the ferromagnetic nanoparticles precipitated at the contact points with the substrate or component immediately above the unevenness of the substrate or component surface, and the magnetically attracted ferromagnetic metals are metallically bonded to each other at the contact points. As a result, the ferromagnetic metal nanoparticles are continuously formed at the overlapping portions of the substrates or components and at the overlapping portions. As a result, a bonding layer consisting of the ferromagnetic metal nanoparticles are magnetically attracted to each other and at the contact points of the substrates or components, regardless of the material of the substrates or components. Meanwhile, an anchor effect occurs in the clusters of ferromagnetic metal nanoparticles that are bonded by magnetic attraction and metallic bonding and are formed on the uneven surfaces of the joints between the overlapping parts. As a result, the bonding layer, which is made up of clusters of ferromagnetic metal nanoparticles that are bonded by magnetic attraction and metallic bonding, bonds the substrates or parts together with a certain degree of mechanical strength.
However, since the compressive stress is continuously applied between the substrates or between the parts, the compressive stress is continuously applied to the collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed at the portion where the substrates or the parts are overlapped, and to the collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding formed on the unevenness of the surfaces of both of the overlapped portions. As a result, the compressive stress is concentrated at the joint between the ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding, and the ferromagnetic metal nanoparticles try to dissociate from the joint and move, but cannot move because they are filled with the bonded ferromagnetic metal nanoparticles. Furthermore, the compressive stress is applied to the ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding, and the compressive stress is applied to the joint. As a result, the compressive stress applied to the joint between the ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding generates frictional heat at the joint, and the ferromagnetic metal nanoparticles are bonded to each other by the frictional heat. On the other hand, the volume of contact between ferromagnetic metal nanoparticles at the joint where compressive stress is concentrated is larger than the volume of contact between ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding. Therefore, the bonding strength between ferromagnetic metal nanoparticles due to frictional heat is greater than the bonding strength between nanoparticles due to magnetic attraction and metallic bonding. As a result, the ferromagnetic metal nanoparticles are firmly bonded together by frictional heat.
As a result, the collection of ferromagnetic metal nanoparticles bonded by frictional heat fills in the areas where the substrates or parts are overlapped, and also fills in the unevenness on both surfaces of the overlapped areas, and the collection of ferromagnetic metal nanoparticles of both are frictionally bonded at the areas where they come into contact with each other. In addition, the collection of ferromagnetic metal nanoparticles bonded by frictional heat that fills in the unevenness on the surfaces creates an anchor effect. As a result, the collection of ferromagnetic metal nanoparticles bonded by frictional heat bonds the substrates or parts together, regardless of the difference in material between the parts and the substrate.
Furthermore, when a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is applied to the portion where the substrates or parts are overlapped, the magnetization of all the ferromagnetic metal nanoparticles is saturated, and the magnetic attraction acting on all the ferromagnetic metal nanoparticles increases significantly. On the other hand, the joint of the ferromagnetic metal nanoparticles joined by frictional heat is limited to the portion where the ferromagnetic metal nanoparticles are in contact with each other. In contrast, the magnetic attraction acting on the magnetized saturated ferromagnetic metal nanoparticles acts on the entire nanoparticles. Therefore, the magnetic attraction is greater than the joining force caused by frictional heat. Furthermore, the ferromagnetic metal nanoparticles are extremely small, about 10 nm, and it is difficult to peel off the magnetic attraction between the ferromagnetic metal nanoparticles magnetically attracted by the saturated magnetization. Therefore, the magnetic attraction acting on the collection of magnetized saturated ferromagnetic metal nanoparticles firmly joins the substrates or parts together, regardless of the difference in material between the parts and the substrate. In addition, the anchor effect acting on the collection of ferromagnetic metal nanoparticles formed on the unevenness of the surfaces of both of the overlapping portions is significantly increased.
Therefore, compared to the case where a group of metal nanoparticles bonded by frictional heat described in paragraphs 14-15 is used to bond substrates or components, the magnetic attraction force acting on the group of nanoparticles of a ferromagnetic metal with saturated magnetization is added to the bonding force of the group of nanoparticles bonded by frictional heat, resulting in a stronger bond than when substrates or components are bonded together as described in paragraphs 14-15. As a result, regardless of the materials of the components and substrates, substrates or components are bonded together more strongly.
Furthermore, when the substrate or part is heated to the boiling point of the organic compound, the moisture, hydrates, hydroxides, and organic substances attached to the surface of the substrate or part are vaporized in order according to their respective boiling points. Therefore, a prior cleaning process to remove impurities attached to the surface of the substrate or part is not necessary. Also, since a collection of metal nanoparticles that is two orders of magnitude smaller than the unevenness of the surface of the substrate or part enters the unevenness of the surface of the substrate or part and precipitates, even if an oxide film or hydroxide film is formed on the surface of the substrate or part, the collection of metal nanoparticles bonds the part to the substrate, bonds the parts to each other, or bonds the substrates to each other.
In addition, the viscosity of the paste is changed according to the masses of the substrates or parts to be joined, and the thickness of the joining layer joining the substrates or parts can be changed, and the joining strength of the joining layer can be freely changed according to the masses of the substrates or parts to be joined. Therefore, when the mass of the substrates or parts is large and a large joining strength is required, the viscosity of the paste is set to a relatively high viscosity.
The magnetic Curie points of ferromagnetic metals are 770°C for iron, 358°C for nickel, and 1131°C for cobalt. Therefore, unless the magnetic Curie points of the ferromagnetic metals are approached, the magnetic attraction force that bonds the substrates or components together does not change. Therefore, even if the components or substrates are exposed to high temperatures, the substrates or components continue to be bonded together.

A method for joining parts together by a joining layer consisting of a collection of metal nanoparticles joined by frictional heat using a paste produced by the method described in paragraph 6, comprising:
Both joining portions of the parts to be joined are processed into a gap fit, the paste produced by the above- mentioned method is applied to both joining portions processed into the gap fit, one of the parts to which the paste has been applied is inserted into the other part to which the paste has been applied, and the two joining portions to which the paste has been applied are overlapped.
Thereafter, the temperature of the overlapped parts is raised to the boiling point of the liquid organic compound, and one of the overlapped parts is fixed and the other of the overlapped parts is rotated.
By this process, first, the organic solvent evaporates from the applied paste, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, and the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was applied, and then the overlapping and precipitated metal nanoparticles are metallically bonded at the sites where they come into contact with each other, and then shear stress generated by rotating the other part is applied to the clusters of metallically bonded metal nanoparticles, and frictional heat is generated at the joints between the metallically bonded metal nanoparticles due to the shear stress, and the metallically bonded metal nanoparticles are bonded together due to the frictional heat, and the parts are bonded together by a bonding layer consisting of the clusters of metallic nanoparticles bonded by the frictional heat.
A method for joining parts together using a paste produced by the method described in paragraph 6, with a joining layer consisting of a collection of metal nanoparticles bonded by frictional heat.

That is, when both joints for joining parts are processed into a gap fit and the paste manufactured by the method described in paragraph 6 is applied to both joints, a coating film is formed on both joints. That is, the viscosity of the paste at 20°C is set to 20 mPascal seconds or less, and the organic compound diluted with an organic solvent is adsorbed to the metal nanoparticles having a size of about 10 nm and having almost no mass with an adsorption force according to the viscosity. Therefore, when the paste is applied, the metal nanoparticles do not separate from the organic compound diluted with an organic solvent, and a coating film consisting of the paste is formed in which the metal nanoparticles are dispersed in the organic compound diluted with an organic solvent. In addition, the paste has an extremely low surface tension of 30 millinewtons per meter or less and a low viscosity of 20 millipascal seconds or less.Furthermore, the metal nanoparticles are about 10 nm in size, which is nearly three orders of magnitude smaller than the surface irregularities of the joints between the two parts that join the two parts.Therefore, the applied paste covers the entire joint areas of both parts, regardless of the materials of the two parts, and penetrates into the surface irregularities of both joints.
After this, one part coated with paste is inserted into the other part coated with paste, and the joint parts coated with paste are overlapped. At this time, when the parts start to be inserted into the joint part processed into a gap fit, the paste coating comes into contact with each other, and the coating film formed on the part to be inserted moves in the opposite direction to the insertion direction, but when the insertion of the part is completed, the movement of the coating film stops. As a result, the coating film of the paste formed on the joint part of the gap fit moves more and the thickness of the coating film becomes thinner toward the tip of the gap fit. In contrast, the movement of the coating film becomes less and the thickness of the coating film becomes thicker toward the rear end of the gap fit. As a result, the gap near the rear end of the gap fit is filled with the coating film.
Furthermore, the overlapped parts are heated to the boiling point of the organic compound. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, the activated metal nanoparticles are deposited on the coating film, and the deposited metal nanoparticles are metallically bonded at the contact portion, and a bonding layer consisting of a collection of metallically bonded metal nanoparticles covers the entire bonding portion between the parts with a thickness according to the viscosity of the paste and penetrates into the unevenness of the surfaces of both bonding portions. At this time, due to the movement of the coating film when the parts are inserted, the thickness of the bonding layer consisting of a collection of metallically bonded metal nanoparticles becomes thinner toward the tip of the gap fit, and conversely, the thickness of the bonding layer consisting of a collection of metallically bonded metal nanoparticles becomes thicker toward the rear end of the gap fit. For this reason, the gap near the rear end of the gap fit is filled with a collection of metallically bonded metal nanoparticles.
On the other hand, the collection of metallic nanoparticles that fills the unevenness of the surfaces of the joints of both parts comes into contact with the collection of metallic nanoparticles that are deposited on the joints just above the unevenness of the surfaces, and the metallic nanoparticles are metallically bonded at the contact area. As a result, the collection of metallic nanoparticles that are metallically bonded is continuously formed over the entire joints of the parts and the uneven surfaces of both joints. Therefore, a bonding layer made of the collection of metallic nanoparticles that are metallically bonded covers the entire joints of both parts, regardless of the materials of both parts. On the other hand, an anchor effect occurs in the collection of nanoparticles that are formed on the uneven surfaces of both joints. As a result, the collection of metallic nanoparticles that are metallically bonded bonds the joints of the parts with a certain mechanical strength. Therefore, the closer the gap is to the rear end of the joint of the clearance fit, the greater the bonding force that bonds the parts together. This bonds the parts together.
Furthermore, one of the overlapping parts is fixed, and the other part is rotated. As a result, shear stress is applied to the collection of metallic nanoparticles formed at the joint, and since the volume of the metallic bond is small, the metallic bond is preferentially destroyed, and the metallic nanoparticles separated from the metallic bond move slightly in the area filled with metallic nanoparticles, and the metallic nanoparticles contact each other again. Furthermore, stress is applied to the metallic nanoparticles separated from the metallic bond, and the metallic nanoparticles try to move, but the presence of the collection of metallic nanoparticles becomes an obstacle, suppressing the movement of the metallic nanoparticles, and the metallic nanoparticles contact each other firmly. Therefore, the volume where the metallic nanoparticles contact each other is larger than the volume where the metallic nanoparticles contact each other when the activated metallic nanoparticles are precipitated. At this time, frictional heat is generated at the contact portion between the metallic nanoparticles, and the metallic nanoparticles are bonded to each other by the frictional heat, but the bonding force between the metallic nanoparticles is larger than the bonding force between the metallic nanoparticles when the activated metallic nanoparticles are precipitated. Therefore, the closer the gap is to the rear end of the gap fit, the greater the joining force due to the frictional heat that joins the parts together. This allows the parts to be firmly joined together.
Furthermore, when the other part is rotated, the bonding by the frictional heat of the metal nanoparticles increases. As a result, the gap near the rear end of the gap fit is gradually filled with the metal nanoparticles bonded by the frictional heat. On the other hand, as the number of metal nanoparticles bonded by the frictional heat increases, the movement of the metal nanoparticles becomes more difficult, and the bonding force of the collection of metal nanoparticles bonded by the frictional heat increases. This makes it difficult to rotate the other part, and the rotation of the part stops. Therefore, the collection of metal nanoparticles bonded by the frictional heat cannot move at the joint between the parts, and the collection of metal nanoparticles bonded by the frictional heat firmly bonds the joints. As a result, the bonding layer consisting of the collection of metal nanoparticles bonded by the frictional heat firmly bonds the joints.
Therefore, the aggregation of metal nanoparticles bonded by frictional heat formed in the narrow joint area is bonded so strongly that it becomes difficult to move, and the bonding strength between the parts is stronger than when parts are bonded with the aggregation of metal nanoparticles bonded by frictional heat described in paragraphs 14 and 15. As a result, the parts are bonded more strongly regardless of the difference in materials between the parts.
One example of the joining of parts according to the present invention is a case where the parts are made of different materials. In other words, the joint processed by a clearance fit is joined with a joining layer made of a collection of metal nanoparticles joined by frictional heat, so the parts can be joined regardless of the combination of materials of the parts. This makes it possible to join metal and synthetic resin, and synthetic resin and ceramics, which have significantly different melting points and softening points. It is also possible to join metals with significantly different melting points.
As explained above, the paste of the present invention is applied to the joints of both parts processed into a gap fit, and activated metal nanoparticles are precipitated at the joints of both parts, and one part is fixed and the other part is rotated, and the parts are firmly joined by the joints of the metal nanoparticles that are joined by frictional heat. Therefore, even if the joints processed into a gap fit are made of different materials, the paste of the present invention can be used as a paste to join parts, further expanding the range of application of the paste.
Furthermore, when the parts are heated to the boiling point of the organic compounds, the moisture, hydrates, hydroxides, and organic substances adhering to the surfaces of the parts are vaporized in order according to their respective boiling points. Therefore, a pre-cleaning process to remove impurities adhering to the surfaces of the parts is not necessary. Also, because the clusters of metal nanoparticles, which are nearly three orders of magnitude smaller than the unevenness of the surfaces of the parts, penetrate into the unevenness of the surfaces of the parts and precipitate, the clusters of metal nanoparticles bond the parts together even if an oxide or hydroxide film is formed on the surfaces of the parts.
In addition, the viscosity of the paste is changed according to the mass of the parts to be joined, and the thickness of the joining layer at the joint where the parts are joined can be changed, and the joining strength of the joining layer can be freely changed according to the mass of the parts to be joined. Therefore, when the mass of the parts is large and a large joining strength is required, the viscosity of the paste is set to a relatively high viscosity.

The method for joining parts described in paragraph 18 is a method for joining parts by a joining layer made of a collection of ferromagnetic metal nanoparticles that are joined together by magnetic attraction and frictional heat, and the method for joining parts includes:
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of any one of iron, nickel, and cobalt upon thermal decomposition, and the metal compound is used as the metal compound, and a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound is produced according to the method for producing a paste described above , and the paste is applied to both joining portions of parts that are joined together and processed into a gap fit, one of the parts to which the paste has been applied is inserted into the other part to which the paste has been applied, and the two joining portions to which the paste has been applied are overlapped.
Thereafter, the temperature of the overlapped parts is raised to the boiling point of the liquid organic compound, and one of the overlapped parts is fixed and the other of the overlapped parts is rotated.
By this treatment, first, the organic solvent evaporates from the applied paste, then the organic compound in the liquid evaporates, and then the clusters of ferromagnetic metal nanoparticles dispersed in the paste are activated, the activated clusters of ferromagnetic metal nanoparticles overlap and precipitate at the site where the paste was applied, the overlapping and precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and further, a shear stress generated by rotating the other part is applied to the magnetically attracted clusters of ferromagnetic metal nanoparticles, and the shear stress generates frictional heat at the magnetic attraction sites where the ferromagnetic metal nanoparticles are magnetically attracted to each other, and the frictional heat further bonds the magnetically attracted ferromagnetic metal nanoparticles to each other.
Thereafter, a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is applied to both joining sites where the parts are joined, and the magnetization of the ferromagnetic metal nanoparticles is saturated. Through this process, the ferromagnetic metal nanoparticles joined by the frictional heat are magnetically attracted to each other due to the saturated magnetization, and the parts are joined by a joining layer made of an assembly of the ferromagnetic metal nanoparticles that are joined to each other by magnetic attraction and frictional heat.
A method for joining parts together using a paste produced by the method described in paragraph 6, with a joining layer consisting of a collection of ferromagnetic metal nanoparticles bonded together by magnetic attraction and frictional heat .

That is, as the metal compound that precipitates a metal by thermal decomposition described in paragraph 6, a metal compound that precipitates a ferromagnetic metal consisting of iron, nickel, or cobalt by thermal decomposition is used, and a paste in which a collection of ferromagnetic metal nanoparticles is dispersed in an organic compound is manufactured according to the method for manufacturing a paste described in paragraph 6. Meanwhile, both joint parts that join the parts are processed into a gap fit, and the paste is applied to both joint parts to form a coating film on both joint parts. That is, the viscosity of the paste at 20°C is set to be 20 millipascal seconds or less, and the organic compound diluted with an organic solvent is adsorbed to the metal nanoparticles that have a size of about 10 nm and have almost no mass with an adsorption force according to the viscosity. Therefore, when the paste is applied, the ferromagnetic metal nanoparticles do not separate from the organic compound diluted with an organic solvent, and a coating film consisting of the paste is formed in which the ferromagnetic metal nanoparticles are dispersed in the organic compound diluted with an organic solvent. In addition, the paste has an extremely low surface tension of 30 millinewtons per meter or less and a low viscosity of 20 millipascal seconds or less.Furthermore, the ferromagnetic metal nanoparticles are about 10 nm in size, which is nearly three orders of magnitude smaller than the surface irregularities of the joining points between the two components.Therefore, the applied paste covers the entirety of both joining points, regardless of the materials of the two components, and penetrates into the surface irregularities of both joining points.
After this, one part coated with paste is inserted into the other part coated with paste, and the joint parts coated with paste are overlapped. At this time, when the parts start to be inserted into the joint part processed into a gap fit, the paste coating comes into contact with each other, and the coating film formed on the part to be inserted moves in the opposite direction to the insertion direction, but when the insertion of the part is completed, the movement of the coating film stops. As a result, the coating film of the paste formed on the joint part of the gap fit moves more and the thickness of the coating film becomes thinner toward the tip of the gap fit. In contrast, the movement of the coating film becomes less and the thickness of the coating film becomes thicker toward the rear end of the gap fit. As a result, the gap near the rear end of the gap fit is filled with the coating film.
Furthermore, the overlapped parts are heated to the boiling point of the organic compound. Since the boiling point of the organic compound is higher than the thermal decomposition temperature of the metal compound, when the evaporation of the organic compound from the applied paste is completed, the activated ferromagnetic metal nanoparticles are precipitated by overlapping each other, and the precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and further, the magnetically attracted ferromagnetic metal nanoparticles are metallically bonded at the contact points, and a bonding layer consisting of a collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding covers the entire bonding area between the parts with a thickness according to the viscosity of the paste and penetrates into the unevenness of the surfaces of both bonding areas. At this time, due to the movement of the coating film when the parts are inserted, the thickness of the bonding layer consisting of a collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding becomes thinner toward the tip of the gap fit, and conversely, the thickness of the bonding layer consisting of a collection of ferromagnetic metal nanoparticles bonded by magnetic attraction and metallic bonding becomes thicker toward the rear end of the gap fit. As a result, the gap near the rear end of the gap fit is filled with a mass of ferromagnetic metal joined by magnetic attraction and metallic bonding.
After this, one of the overlapping parts is fixed, and the other overlapping part is rotated. As a result, shear stress is applied to the joint between the ferromagnetic metal nanoparticles bonded by magnetic attraction and metal bonding, and since the volume of the joint is small, the joint is destroyed first, and the ferromagnetic metal nanoparticles that have been separated from the joint between the nanoparticles move slightly in the area filled with ferromagnetic metal nanoparticles, and the ferromagnetic metal nanoparticles come into contact with each other again. Furthermore, stress is applied to the ferromagnetic metal nanoparticles that have been separated from the joint between the nanoparticles, and the nanoparticles try to move, but the presence of the ferromagnetic metal nanoparticle clusters acts as an obstacle, suppressing the movement of the nanoparticles, and the nanoparticles come into firm contact with each other, generating frictional heat at the contact area. On the other hand, the nanoparticles that were forcibly pulled away from the joints between the nanoparticles were moved and contacted the nanoparticles in a state where it was difficult for the nanoparticles to move, so that the volume of the contact area was larger than the volume of the joint where the nanoparticles were joined by magnetic attraction and metallic bonding when the activated ferromagnetic metal nanoparticles were piled up and precipitated, and the bonding force between the nanoparticles due to frictional heat was greater than the bonding force between the nanoparticles joined by magnetic attraction and metallic bonding. Therefore, the closer the gap is to the rear end of the gap fit, the greater the bonding force that bonds the parts together. This bonds the parts together.
Furthermore, when the parts are rotated, the bonding between the nanoparticles caused by the nanoparticles that are separated from the magnetic attraction increases. Therefore, the gap near the rear end of the gap fit is gradually filled with nanoparticles bonded by frictional heat. On the other hand, the more nanoparticles bonded by frictional heat, the greater the bonding force due to frictional heat, making it difficult for the bonded nanoparticles to move, which makes it difficult to rotate the parts and stops the rotation of the parts. Therefore, the collection of nanoparticles bonded by frictional heat cannot move at the joint between the parts, and the collection of nanoparticles bonded by frictional heat bonds the joints. Therefore, the closer the gap is to the rear end of the gap fit, the greater the bonding force that bonds the parts. As a result, the collection of nanoparticles bonded by frictional heat firmly bonds the joints. Furthermore, the paste has low surface tension and low viscosity, and the ferromagnetic metal nanoparticles are approximately 10 nm in size, so regardless of the materials of the two parts, the collection of nanoparticles bonded by frictional heat covers the entire joining area of both parts and penetrates into the uneven surfaces of both joining areas, joining the parts together regardless of the materials of the parts.
Furthermore, when a magnetic field that saturates the magnetization of ferromagnetic metal nanoparticles is applied to the portion where the parts are joined, the magnetization of all ferromagnetic metal nanoparticles is saturated, and the magnetic attraction acting on all nanoparticles increases significantly. On the other hand, the joining force of nanoparticles joined together by frictional heat is limited to the portion where the nanoparticles come into contact with each other due to friction. In contrast, the magnetic attraction acting on nanoparticles with saturated magnetization acts on the entire nanoparticle. Therefore, the magnetic attraction force is greater than the binding force caused by frictional heat. Furthermore, since the nanoparticles are small, around 10 nm, it is difficult to separate the magnetic attraction between ferromagnetic metal nanoparticles that are magnetically attracted by saturated magnetization.
Therefore, in the joint between parts described in paragraphs 18-19, the magnetic attraction force of the collection of nanoparticles of a ferromagnetic metal with saturated magnetization is added to the joining force of the collection of nanoparticles joined by frictional heat, compared to the case where the collection of nanoparticles joined by frictional heat joins the parts at the joint between parts described in paragraphs 18-19, so the parts are joined more strongly than in the example described in paragraphs 18-19. As a result, the parts are joined even more strongly regardless of the difference in materials between the parts.
The magnetic Curie points of ferromagnetic metals are 770°C for iron, 358°C for nickel, and 1131°C for cobalt. Therefore, unless the temperature approaches the magnetic Curie point of the ferromagnetic metal, the magnetic attraction force that bonds the parts together does not change. Therefore, even if the parts are exposed to high temperatures, they will continue to be bonded together.
Furthermore, when the parts are heated to the boiling point of the organic compounds, the moisture, hydrates, hydroxides, and organic substances adhering to the surfaces of the parts are vaporized in order according to their respective boiling points. Therefore, there is no need for a pre-cleaning process to remove impurities adhering to the surfaces of the parts. Also, because the clusters of metal nanoparticles, which are nearly three orders of magnitude smaller than the unevenness of the surfaces of the parts, penetrate into the unevenness of the surfaces of the parts and precipitate, the clusters of metal nanoparticles bond the parts together even if an oxide or hydroxide film is formed on the surfaces of the parts.
In addition, the viscosity of the paste is changed according to the mass of the parts to be joined, and the thickness of the joining layer at the joint where the parts are joined can be changed, and the joining strength of the joining layer can be freely changed according to the mass of the parts to be joined. Therefore, when the mass of the parts is large and a large joining strength is required, the viscosity of the paste is set to a relatively high viscosity.

The method for producing a paste in which a collection of metal nanoparticles is dispersed in an organic compound as described in paragraph 6 includes the steps of:
the metal compound which precipitates a metal by thermal decomposition is an inorganic metal compound composed of an inorganic salt having a metal complex ion in which an inorganic molecule or an inorganic ion acts as a ligand and is coordinately bonded to a metal ion, the liquid organic compound is an organic compound belonging to a primary alcohol having 8 to 10 carbon atoms, and the organic solvent is diethyl ether, acetone, or ethanol,
a paste is produced according to the method for producing a paste, using the inorganic metal compound as the metal compound that precipitates a metal by thermal decomposition, using the organic compound belonging to the primary alcohol having 8 to 10 carbon atoms as the liquid organic compound, and using the diethyl ether, acetone, or ethanol as the organic solvent;
A method for producing a paste in which a collection of metal nanoparticles as described in paragraph 6 is dispersed in an organic compound.

First, when an inorganic metal compound made of an inorganic salt having a metal complex ion coordinated to a metal ion, in which an inorganic molecule or an inorganic ion acts as a ligand, is heat-treated in a reducing atmosphere, the coordinate bond is first broken and the compound is decomposed into the inorganic substance and the metal. When the temperature is further increased, the inorganic substance absorbs the heat of vaporization and vaporizes, and the vaporization of the inorganic substance is completed in the temperature range of 180-220°C, and the metal is precipitated.
That is, among the ions constituting the inorganic metal compound, the metal ion located at the center of the molecule is the largest, and the distance between the metal ion and the ligand is the longest. When this inorganic metal compound is heat-treated in a reducing atmosphere, the coordinate bond where the metal ion is bonded to the ligand is first broken, and the compound is decomposed into the metal and the inorganic substance. When the temperature is further increased, the inorganic substance absorbs the heat of vaporization and vaporizes, and when the vaporization of the inorganic substance is completed, the metal precipitates, and the thermal decomposition is completed. The temperature at which the metal precipitates is the lowest among the temperatures at which metal precipitates in the thermal decomposition of metal compounds. In addition, the inorganic metal compound is dispersed in methanol at nearly 10% by weight, and is not dissolved in methanol. For this reason, the inorganic metal compound made of an inorganic salt having a metal complex ion can be used as the metal compound described in paragraph 6.
That is, metal complex ions in which molecules of inorganic substances or ions of inorganic substances become ligands and are coordinated to metal ions are easier to synthesize than other metal complex ions. Examples of such metal complex ions include ammine metal complex ions in which ammonia NH ₃ becomes ligands and is coordinated to metal ions, aqua metal complex ions in which water H ₂ O becomes ligands and is coordinated to metal ions, hydroxo metal complex ions in which hydroxyl groups OH ^- become ligands and are coordinated to metal ions, and chloro metal complex ions in which chlorine ions Cl ^- or chlorine ions Cl ^- and ammonia NH ₃ become ligands and are coordinated to metal ions. Furthermore, inorganic metal compounds made of inorganic salts such as chlorides, sulfates, and nitrates having such metal complex ions are easy to synthesize, and since the molecular weight of the inorganic salt is small, the inorganic substances are vaporized and the metal is precipitated in a temperature range of 180-220°C. The temperature at which the metal precipitates is the lowest among the temperatures at which metals are precipitated by thermal decomposition of metal compounds. These inorganic metal compounds are common industrial chemicals.
Next, an organic compound belonging to primary alcohols having 8-10 carbon atoms has five properties described in paragraph 6, namely, a first property of having a melting point lower than 15°C, a second property of not dissolving or dispersing the inorganic metal compound, a third property of having a boiling point higher than the thermal decomposition temperature of the inorganic metal compound, a fourth property of not chemically reacting with metal nanoparticles precipitated by thermal decomposition of the inorganic metal compound, and a fifth property of having a surface tension of 30 millinewtons per meter or less at 20°C.
That is, the primary alcohol having 8 carbon atoms is n-octane having the rational formula CH ₃ (CH ₂ ) ₇ OH, which is an organic compound having a melting point of −16° C., a boiling point of 195° C., a viscosity of 7.3 mPascal seconds at 20° C., a surface tension of 27.5 millinewtons per meter at 20° C., a density of 0.83 g/cm ³ and a molecular weight of 130 g/mol. n-Octane does not dissolve or disperse in the inorganic metal compound, and does not chemically react with the metal nanoparticles precipitated by the thermal decomposition of the inorganic metal compound. Thus, n-octane is an organic compound that has all five properties described in paragraph 6.
Furthermore, the primary alcohol having 9 carbon atoms is n-nonane having the rational formula CH ₃ (CH ₂ ) ₈ OH, which is an organic compound having a melting point of −7° C., a boiling point of 215° C., a viscosity of 10.8 mPascal seconds at 20° C., a surface tension of 28 millinewtons per meter at 24° C., a density of 0.83 g/cm ³ and a molecular weight of 144 g/mol. n-nonane does not dissolve or disperse in the inorganic metal compound, and does not chemically react with the metal nanoparticles precipitated by thermal decomposition of the inorganic metal compound. Thus, n-nonane is an organic compound that has all five properties described in paragraph 6.
Furthermore, the primary alcohol having 10 carbon atoms is n-decane having the rational formula CH ₃ (CH ₂ ) ₁₀ OH, which is an organic compound having a melting point of 6.4° C., a boiling point of 233° C., a viscosity at 20° C. of 14.5 mPascal seconds, a surface tension at 20° C. of 29 mN/ m, a density of 0.83 g/cm ³ and a molecular weight of 158 g/mol. n-Decane does not dissolve or disperse in the inorganic metal compound, and does not chemically react with the metal nanoparticles precipitated by the thermal decomposition of the inorganic metal compound. Thus, n-decane is an organic compound having the five properties described in paragraph 6.
On the other hand, diethyl ether, acetone, or ethanol dissolves or is miscible with organic compounds belonging to primary alcohols having 8-10 carbon atoms, and has a boiling point lower than that of the organic compounds belonging to the primary alcohols. Therefore, it is an organic solvent that has the two properties described in paragraph 6, that is, dissolves or is miscible with liquid organic compounds and has a boiling point lower than that of liquid organic compounds. Note that all primary alcohols having 8-10 carbon atoms have a viscosity of 20 mPascal seconds or less at 20°C, but dissolving or mixing them in diethyl ether, acetone, or ethanol makes them into organic compounds with even lower viscosity.
The inorganic metal compound described above, the primary alcohol having 8-10 carbon atoms, and diethyl ether, acetone, or ethanol are all general-purpose industrial chemicals. The method for producing the paste described in paragraph 6 is carried out by continuously carrying out six very simple steps. Therefore, by using inexpensive industrial chemicals and continuously carrying out six very simple steps, an inexpensive paste can be produced.

The method for producing a paste in which a collection of metal nanoparticles is dispersed in an organic compound as described in paragraph 6 includes the steps of:
the metal compound that precipitates a metal by thermal decomposition is a metal octylate compound, the liquid organic compound is tetraethylene glycol, and the organic solvent is either ethanol or acetone;
a paste is produced according to the method for producing a paste, using the metal octylate compound as the metal compound that precipitates a metal by thermal decomposition, using the tetraethylene glycol as the liquid organic compound, and using either the ethanol or the acetone as the organic solvent;
A method for producing a paste in which a collection of metal nanoparticles as described in paragraph 6 is dispersed in an organic compound.

First, in the octylic acid metal compound in which the oxygen ion constituting the carboxyl group of octylic acid is covalently bonded to the metal ion, the metal ion is the largest ion, and the distance between the oxygen ion constituting the carboxyl group and the metal ion is longer than the distance between other ions. When the octylic acid metal compound having such molecular structure characteristics is heat-treated in an air atmosphere, the bond between the oxygen ion constituting the carboxyl group and the metal ion is first broken when the boiling point of octylic acid is exceeded, and it is separated into octylic acid and metal. Since octylic acid is composed of saturated fatty acid and does not have an unsaturated structure in which carbon atoms are in excess of hydrogen atoms, octyl takes the heat of vaporization and vaporizes, and when vaporization is completed, the metal precipitates. In addition, the octylic acid metal compound is dispersed in methanol at nearly 10% by weight, and is not dissolved in methanol. Therefore, the octylic acid metal compound having both characteristics can be used as the metal compound described in paragraph 6.
The octylic acid metal compound is an organometallic compound belonging to the carboxylic acid metal compound, which has a first characteristic that the oxygen ion constituting the carboxyl group of the carboxylic acid is covalently bonded to the metal ion, and a second characteristic that the carboxylic acid is a saturated fatty acid. Among the carboxylic acid metal compounds having both characteristics, the boiling point of octylic acid is the lowest at 228°C, so that the thermal decomposition is completed at 290°C in the air atmosphere, and the metal is precipitated. In addition to the octylic acid metal compound, other carboxylic acid metal compounds having both characteristics include a lauric acid metal compound and a stearic acid metal compound. The boiling points of lauric acid and stearic acid are 296°C and 376°C, respectively, which are higher than the boiling point of octylic acid, so that the temperature at which the thermal decomposition is completed and the metal is precipitated is higher than that of the octylic acid metal compound. Therefore, the octylic acid metal compound precipitates the metal at the lowest thermal decomposition temperature among the organometallic compounds.
That is, octylic acid is a branched saturated fatty acid with the rational formula _CH3 ( _{CH2 ) 3CH} ( _C2H5 )COOH, branched at CH to alkanes _CH3 ( _CH2 ) ₃ and _C2H5 , and a _carboxyl group COOH is bonded to CH. Branched saturated fatty acids have a shorter chain length than linear saturated fatty acids and a low boiling point of 228°C. In contrast, lauric acid and stearic acid are linear saturated fatty acids with higher boiling points than branched saturated fatty acids.
In addition, octyl acid and caprylic acid (also called octanoic acid) have the same molecular formula C ₈ H ₁₆ O ₂ , but are isomers with different molecular structures. That is, octyl acid is a fatty acid with a branched structure as described above. On the other hand, caprylic acid is a fatty acid with a straight chain structure, and its rational formula is CH ₃ (CH ₂ ) ₆ COOH. Therefore, although the octyl acid metal compound and the caprylic acid metal compound have the same molecular formula, the molecular structures of octyl acid and caprylic acid are different, so that the molecular structures of octyl acid and caprylic acid metal compounds are different. That is, in the caprylic acid metal compound, a metal ion is coordinated to a carboxylate anion, which is an anion generated by ionization of caprylic acid, so that the caprylic acid metal compound precipitates a metal oxide by thermal decomposition in an air atmosphere. In other words, in the case of a metal caprylic acid compound, the carboxylate ion approaches the metal ion, which is the largest ion, and forms a coordinate bond, so the distance between the metal ion and the oxygen ion that constitutes the carboxylate ion becomes shorter. This results in the longest distance between the ion that the oxygen ion is covalently bonded to on the opposite side of the metal ion. When the temperature of a metal caprylic acid compound with such molecular structure exceeds the boiling point of caprylic acid, the bond between the oxygen ion and the ion that is covalently bonded on the opposite side of the metal ion is broken, and the compound is decomposed into a metal oxide, which is a compound of a metal ion and an oxygen ion, and caprylic acid. When the temperature is further increased, the caprylic acid absorbs the heat of vaporization and vaporizes, and immediately after the vaporization of caprylic acid is completed, the metal oxide precipitates.
Moreover, metal octylate compounds are inexpensive industrial chemicals that can be easily synthesized. That is, when octylic acid, which is the most widely used organic acid, is reacted with a strong alkali, an alkali metal octylate compound is produced, and when an alkali metal octylate compound is reacted with an inorganic metal compound, an octylate metal compound made of various metals is synthesized. Therefore, metal octylate compounds are the cheapest organic metal compounds. For this reason, although the heat treatment temperature is higher than that of the inorganic metal compounds described in paragraphs 23-24, they are organic metal compounds that are cheaper than inorganic metal compounds.
Next, tetraethylene glycol is an organic compound having a rational formula of HO(CH ₂ CH ₂ O) ₃ CH ₂ CH ₂ OH, a melting point of -9.4°C, a boiling point of 328°C, a viscosity of 58 mPascal seconds at 20°C, a surface tension of 18.8 millinewtons per meter at 20°C, a density of 1.12 g/cm ³ , and a molecular weight of 194 g/mol. In addition, tetraethylene glycol does not dissolve or disperse in octyl metal compounds, and does not chemically react with metal nanoparticles precipitated by thermal decomposition of octylate metal compounds. Therefore, tetraethylene glycol is an organic compound that has the five properties described in paragraph 6.
On the other hand, ethanol or acetone dissolves or is miscible with tetraethylene glycol and has a boiling point lower than that of tetraethylene glycol. Therefore, it is an organic solvent that has the two properties described in paragraph 6, that is, dissolves or is miscible with liquid organic compounds and has a boiling point lower than that of liquid organic compounds. Tetraethylene glycol has a viscosity of 58 mPascal seconds at 20°C, which is higher than the viscosity of primary alcohols with 8-10 carbon atoms, but by dissolving or miscible with ethanol or acetone, the viscosity at 20°C can be reduced to 20 mPascal seconds or less.
The metal octylate compound, tetraethylene glycol, ethanol, and acetone described above are all general-purpose industrial chemicals. The method for producing the paste described in paragraph 6 is a method for continuously carrying out six very simple steps. Therefore, by using inexpensive industrial chemicals and continuously carrying out six very simple steps, an inexpensive paste can be produced.

FIG. 2 is an explanatory diagram showing an enlarged view of a paste in which clusters of copper nanoparticles are dispersed in n-octane.

EMBODIMENT 1
This embodiment relates to the inorganic metal compound described in paragraphs 22-23. The metal compound described in paragraph 6 has both a first property of being dispersed in methanol and not dissolved in methanol, and a second property of precipitating a metal by thermal decomposition. Here, the metal is copper, and a copper compound is used as an example for explanation.
First, copper compounds having the first property of dispersing in methanol will be described. Inorganic copper compounds such as copper chloride, copper sulfate, and copper nitrate dissolve in methanol, and copper ions are eluted, so that many of the copper ions cannot participate in the precipitation of copper particles. In addition, inorganic copper compounds such as copper oxide, copper chloride, and copper sulfide do not disperse in methanol, which is the most commonly used solvent. For this reason, these inorganic copper compounds are not copper compounds having the property of dispersing in methanol.
On the other hand, copper compounds have a second property of precipitating copper. Among the chemical reactions by which copper is produced from copper compounds, the simplest chemical reaction is a thermal decomposition reaction. Furthermore, if the thermal decomposition temperature of a copper compound is low, copper is precipitated inexpensively. Therefore, copper compounds with low thermal decomposition temperatures can be used as raw materials for copper microparticles. Among such copper compounds, there are inorganic copper compounds made of inorganic salts having copper complex ions in which molecules of inorganic substances or ions of inorganic substances act as ligands and are coordinately bonded to copper ions. In other words, the ligands have low molecular weights, the number of ligands is small, and the molecular weight of the inorganic substances that form the inorganic copper compounds is small, so the thermal decomposition temperature is low. Furthermore, such inorganic copper compounds have small molecular weights, so they are easier and less expensive to synthesize than other copper compounds made of copper complex ions.
Among the molecules that make up inorganic copper compounds, copper ions are the largest. Incidentally, the covalent bond radius of the double bond of the copper atom is 115 pm, the covalent bond radius of the single bond of the nitrogen atom is 71 pm, and the covalent bond radius of the single bond of the oxygen atom is 63 pm. Therefore, the distance of the coordinate bond part where the ligand is coordinated to the copper ion is the longest. Therefore, in heat treatment in a reducing atmosphere, the coordinate bond part is first broken, decomposing into copper and inorganic matter, and copper is precipitated after the evaporation of the inorganic matter is completed.
As copper complex salts made of such inorganic copper compounds, copper complex salts having tetraammine copper ion [Cu(NH ₃ ) ₄ ] ²⁺ or hexaammine copper ion [Cu(NH ₃ ) ₆ ] ²⁺ in which ammonia NH ₃ acts as a ligand and is coordinated to the copper ion, and copper complex salts having tetrachloro copper ion [CuCl ₄ ] ^2- in which chlorine ion Cl ^- acts as a ligand and is coordinated to the copper ion, are easy to synthesize and inexpensive compared to complexes having other copper complex ions, because the ligands have low molecular weights and a small number of ligands. When copper complex salts made of inorganic copper compounds having such copper complex ions are heat-treated in a reducing atmosphere, the coordinate bond site is first broken and thermal decomposition is completed at 180-200°C. Furthermore, they are dispersed in methanol to a dispersion concentration of nearly 10% by weight. Such copper complexes include tetraamminecopper nitrate [Cu(NH ₃ ) ₄ ](NO ₃ ) ₂ and tetraamminecopper sulfate [Cu(NH ₃ ) ₄ ]SO ₄ .
Furthermore, as a nickel complex made of an inorganic nickel compound that precipitates nickel by thermal decomposition, a nickel complex made of hexaamminenickel ion [Ni(NH ₃ ) ₆ ] ²⁺ in which ammonia NH ₃ acts as a ligand and is coordinated to the nickel ion is easy to synthesize and inexpensive compared to other complexes having nickel complex ions, since the ligand has a low molecular weight and the number of ligands is small. When heat-treated in a reducing atmosphere, the coordinate bond site of such a complex salt made of an inorganic metal compound having a nickel complex ion is first broken because the molecular weight of the inorganic substance is small, and thermal decomposition is completed at 180-200°C. In addition, it disperses in methanol to a dispersion concentration of nearly 10% by weight. An example of such a nickel complex salt is hexaamminenickel chloride [Ni(NH ₃ ) ₆ ]Cl ₂ .
In addition, as silver complexes made of inorganic gold compounds, a silver complex having a diamine silver ion [Ag(NH ₃ ) ₂ ] ⁺ in which ammonia NH ₃ acts as a ligand and is coordinated to the silver ion, and a silver complex having a dicyano silver ion [Ag(CN) ₂ ] ^- in which cyanide ion CN ^- acts as a ligand and is coordinated to the silver ion, are easy to synthesize and inexpensive to manufacture compared to silver complexes having other silver complex ions, because the ligands have low molecular weights and a small number of ligands. When such complex salts made of inorganic metal compounds having silver complex ions are heat-treated in a reducing atmosphere, the coordinate bond site is first broken, and thermal decomposition is completed at 180-200°C, because the molecular weight of the inorganic substance is small. In addition, they can be dispersed in methanol to a dispersion concentration of nearly 10% by weight. Examples of such silver complex salts include tetraammine copper nitrate [Ag(NH ₃ ) ₂ ]Cl, diammine silver sulfate [Ag(NH ₃ ) ₂ ] ₂ SO ₄ , and diammine silver nitrate [Ag(NH ₃ ) ₂ ]NO ₃ .
Furthermore, inorganic platinum compounds having platinum complex ions that precipitate platinum by thermal decomposition include ammine complexes such as diammine platinum chloride [Pt(NH ₃ ) ₂ ]Cl ₂ , tetraammine platinum chloride [Pt(NH ₃ ) ₄ ]Cl ₂ , tetraammine platinum acetate [Pt(NH ₃ ) ₄ ](CH ₃ COO) ₂ , tetraammine platinum sulfate [Pt(NH ₃ ) ₄ ](SO ₄ ) ₂ , and pentaammine chloroplatinum chloride [PtCl(NH ₃ ) ₅ ]Cl ₃ , as well as chloro complexes such as ammonium tetrachloroplatinate (NH ₄ ) ₂ [PtCl ₄ ] and diammine dichloroplatinum [PtCl ₂ (NH ₃ ) ₂ ]. Thermal decomposition is complete at 180-200°C. When these inorganic platinum compounds are heat-treated in a reducing atmosphere, the coordinate bond sites are first broken and the thermal decomposition is completed at 180-200° C. Also, they disperse in methanol up to a dispersion concentration of nearly 10% by weight.
Inorganic rhodium compounds having rhodium complex ions that precipitate rhodium upon thermal decomposition include ammine complexes such as pentaamminechlororhodium chloride [RhCl( _NH3 ) ₅ ] _Cl2 , hexaamminerhodium chloride [Rh( _NH3 ) ₆ ] _Cl3 , and hexaamminerhodium nitrate [Rh( _NH3 ) ₆ ]( _NO3 ) ₃ , as well as rhodium complex salts such as chloro complexes such as ammonium hexachlororhodate ( _NH4 ) ₃ [ _RhCl6 ]. When these inorganic rhodium compounds are heat-treated in a reducing atmosphere, the coordinate bond sites are first broken and thermal decomposition is completed at 180-200°C. They also disperse in methanol to a dispersion concentration of nearly 10% by weight.
Furthermore, inorganic ruthenium compounds having ruthenium complex ions that precipitate ruthenium by thermal decomposition include ruthenium salts such as ammine complex hexaammineruthenium chloride [Ru(NH ₃ ) ₆ ]Cl ₃ , hexaammineruthenium sulfate [Ru(NH ₃ ) ₆ ](SO ₄ ) ₃ , hexaammineruthenium nitrate [Ru(NH ₃ ) ₆ ](NO ₃ ) ₃ , and chloropentaammineruthenium chloride [Ru(NH ₃ ) ₅ Cl]Cl _2. When these inorganic ruthenium compounds are heat-treated in a reducing atmosphere, the coordinate bond site is first broken, and thermal decomposition is completed at 180-200° C. Also, they disperse in methanol to a dispersion concentration of nearly 10% by weight.
As explained above, the complex salts of inorganic metal compounds have the lowest thermal decomposition temperature, are easy to synthesize, and are the cheapest metal complex salts because the ligands have low molecular weights, the number of ligands is small, and the molecular weights of the inorganic substances that form the inorganic metal compounds are small. Therefore, the complex salts of inorganic metal compounds can be used as raw materials for metal nanoparticles.

EMBODIMENT 2
This embodiment relates to the carboxylate metal compound described in paragraphs 24-25. The metal compound described in paragraph 6 has both a first property of being dispersed in methanol and not dissolved in methanol, and a second property of precipitating a metal by thermal decomposition. Here, the metal is nickel, and a nickel compound is used as an example for explanation.
First, we will explain nickel compounds that have the first property of dispersing in methanol. Nickel sulfate and nickel chloride dissolve in methanol, and nickel ions are dissolved, so many nickel ions cannot participate in nickel precipitation. In addition, nickel hydroxide and nickel oxide do not disperse in methanol. For this reason, inorganic nickel compounds do not disperse in methanol.
Organonickel compounds precipitate nickel through thermal decomposition. Among the chemical reactions by which nickel precipitates from organonickel compounds, the simplest is the thermal decomposition reaction. In other words, nickel precipitates through thermal decomposition simply by raising the temperature of the organonickel compound. Furthermore, if organonickel compounds are easy to synthesize, they can be produced inexpensively. One organonickel compound that has both of these properties is nickel carboxylate compound.
That is, the composition formula of the nickel carboxylate compound is expressed as RCOO-Ni-COOR. R is a hydrocarbon, and the composition formula is C _m H _n (where m and n are integers). Among the substances that compose the nickel carboxylate compound, the nickel ion Ni ²⁺ located at the center of the composition formula is the largest substance. Therefore, when the nickel ion Ni ²⁺ and the oxygen ion O ^- that constitutes the carboxyl group are covalently bonded, the distance between the nickel ion Ni ²⁺ and the oxygen ion O ^- is the largest. This is because the covalent bond radius of nickel is 110 pm, the covalent bond radius of the oxygen single bond is 63 pm, and the covalent bond radius of the carbon double bond is 67 pm. Therefore, in the nickel carboxylate compound in which the nickel ion and the oxygen ion that constitutes the carboxyl group are covalently bonded, the bond between the nickel ion with the longest bond distance and the oxygen ion that constitutes the carboxyl group is first broken at the boiling point of the carboxylic acid, and the nickel and the carboxylic acid are separated. When the temperature is further increased, if the carboxylic acid is a saturated fatty acid, the carboxylic acid will absorb the heat of vaporization and vaporize, and nickel will precipitate after the vaporization of the carboxylic acid is complete. Examples of such nickel carboxylate compounds include nickel octylate, nickel laurate, and nickel stearate.
Furthermore, the lower the boiling point of the saturated fatty acid, the lower the temperature at which thermal decomposition begins, and the smaller the molecular weight of the saturated fatty acid, the more the saturated fatty acid vaporizes, and the lower the temperature at which nickel precipitates. When the hydrocarbons constituting the saturated fatty acid have a long chain structure, the longer the long chain, that is, the larger the molecular weight of the saturated fatty acid, the higher the boiling point of the saturated fatty acid. Incidentally, the boiling point of lauric acid, which has a molecular weight of 200.3, at atmospheric pressure is 296°C, and the boiling point of stearic acid, which has a molecular weight of 284.5, at atmospheric pressure is 361°C. Therefore, nickel carboxylate compounds made of saturated fatty acids with relatively small molecular weights of long-chain structure have relatively low thermal decomposition temperatures. Note that the thermal decomposition of nickel laurate is completed at 360°C in the air, and the thermal decomposition of nickel stearate is completed at 430°C in the air.
On the other hand, when the saturated fatty acid is a branched-chain saturated fatty acid, the chain length is shorter than that of a straight-chain saturated fatty acid, the boiling point is lower, and the temperature at which nickel precipitates is also lower. Furthermore, branched-chain saturated fatty acids have polarity, and nickel carboxylate compounds made of branched-chain saturated fatty acids also have polarity and disperse in alcohol, which is a polar substance, at a relatively high rate. Octylic acid is one such branched-chain saturated fatty acid. Octylic acid has a rational formula of CH ₃ (CH ₂ ) ₃ CH (C ₂ H ₅ ) COOH, and is branched at CH to alkanes CH ₃ (CH ₂ ) ₃ and C ₂ H ₅ , with a carboxyl group COOH bonded to CH. The boiling point of octylic acid at atmospheric pressure is 228°C, which is 68°C lower than that of lauric acid. For this reason, nickel octylate thermally decomposes at the lowest temperature among nickel carboxylate compounds. Incidentally, nickel octylate undergoes complete thermal decomposition at 290° C. in an air atmosphere, whereby nickel precipitates and disperses in methanol to a concentration of nearly 10% by weight.
As explained above, nickel octylate, which has the first feature that the oxygen ions constituting the carboxyl group are covalently bonded to nickel ions and the second feature that it is composed of carboxylic acids made of saturated fatty acids, is an inexpensive industrial chemical that precipitates nickel by thermal decomposition.
In addition, copper octylate Cu( _C7H15COO ) ₂ precipitates copper upon thermal decomposition, aluminum _octylate Al( _C7H15COO ) ₃ precipitates aluminum upon thermal decomposition, iron _{octylate Fe(C7H15COO ) 3} precipitates iron upon thermal decomposition, zinc octylate Zn( _C7H15COO ) ₂ precipitates zinc upon thermal decomposition, cobalt _octylate Co( _C7H15COO ) ₂ precipitates cobalt upon thermal decomposition, manganese _octylate Mn( _C7H15COO ) ₂ precipitates manganese upon thermal decomposition, tin _{octylate Sn(C7H15COO ) 2} precipitates tin upon thermal decomposition, _{and calcium octylate} Ca( _C7H15COO ) _When thermally decomposed, potassium octylate K (C ₇ H ₁₅ COO) precipitates potassium, and when thermally decomposed, lithium octylate Li (C ₇ H ₁₅ COO) precipitates lithium.

Example 1
In this example, a paste was prepared in which copper nanoparticles were dispersed in n-octane as described in paragraph 23. Tetraammine copper nitrate as described in paragraph 27 was used as the raw material for the copper nanoparticles.
250 g (corresponding to 1 mole) of tetraamine copper nitrate (e.g., a product of Mitsuwa Chemical Co., Ltd.) was dispersed in 3.3 L of methanol and stirred to prepare a methanol dispersion of tetraamine copper nitrate. After this, the methanol dispersion of tetraamine copper nitrate was heated to 65° C., methanol was evaporated from the methanol dispersion, and crystals of tetraamine copper nitrate were precipitated. After this, the collection of tetraamine copper nitrate crystals was filled into a container of 10 cm×10 cm×3 cm, and a plate of 10 cm×10 cm×1 cm was placed on the collection of tetraamine copper nitrate crystals, and a weight of 10 kg was placed on the plate. After this, the weight was once removed from the plate, and an impact acceleration of 0.4 G was applied to the container in three directions, front and back, left and right, and up and down, five times in turn. The weight was placed on the plate again, and then the impact acceleration in the three directions was applied again. After repeating this pair of treatments consisting of applying a compressive load by a weight and applying an impact acceleration three times, a weight was placed on the plate again, but since the plate did not sink at all, it was determined that the crushing of the tetraammine copper nitrate crystals by the compressive load was completed, and the pair of treatments was stopped and the plate was removed from the container.
Furthermore, 430 cc of n-octane (e.g., a product of Fujifilm Wako Pure Chemical Industries, Ltd.) was filled into the container and stirred to prepare a paste in which clusters of tetraammine copper nitrate crystals were dispersed in n-octane. After this, the container was placed in a heat treatment device in an ammonia atmosphere and left at 180°C for 5 minutes, after which the container was removed from the heat treatment device.
After this, a part of the sample was taken out from the container and observed under an electron microscope. An extremely low accelerating voltage SEM owned by JFE Techno Research Corporation was used as the electron microscope. This device allows surface observation at extremely low accelerating voltages starting from 100 volts , and allows the surface to be observed directly without forming a conductive coating.
The secondary electron beam between 900-1000 volts was extracted from the reflected electron beam from the surface of the sample and image processing was performed. Granular nanoparticles with a size of about 10 nm were dispersed in the sample. Next, the energy between 900-1000 volts of the reflected electron beam was extracted and image processing was performed, and the material of the nanoparticles was observed based on the shading of the image. Since no shading was observed, it was found that the nanoparticles were formed from the same element. Furthermore, the energy and intensity of the characteristic X-rays were image processed, and the elements that make up the nanoparticles were analyzed. Since only copper atoms are present, the nanoparticles are copper nanoparticles. Therefore, the paste created is a paste in which a collection of copper nanoparticles is dispersed in n-octane. Figure 1 shows an enlarged view of the paste in which a collection of copper nanoparticles is dispersed in n-octane. 1 is copper nanoparticles and 2 is n-octane.

Example 2
In this example, the paste prepared in Example 1 was diluted with ethanol to reduce the viscosity at 20° C. to 6.0 mPa sec. For this purpose, 114 cc of ethanol was added to the paste prepared in Example 1, and the paste prepared in Example 1 was diluted with ethanol.

Example 3
In this example, the paste prepared in Example 1 was diluted with ethanol to reduce the viscosity at 20° C. to 7.0 mPa sec. For this purpose, 23 cc of ethanol was added to the paste prepared in Example 1, and the paste prepared in Example 1 was diluted with ethanol.

Example 4
In this example, a coating consisting of an aggregate of copper nanoparticles is formed using the paste prepared in Example 2. For this purpose, the paste prepared in Example 2 is applied to the surface of a glass epoxy substrate (a product of Tokiwa Corporation) to which no copper foil is attached, and the glass epoxy substrate is heated to 195° C. in an air atmosphere to vaporize ethanol and n-octane from the paste.
Thereafter, the surface resistance of the coating formed on the surface of the glass epoxy substrate was measured at multiple locations using a surface resistance meter (for example, a surface resistance meter ST-4 manufactured by SIMCO Japan Co., Ltd.) The surface resistance was 1×10 ³ Ω/□, which was close to that of a metal.
Furthermore, the static and dynamic coefficients of friction were measured at multiple points on the coating using a friction coefficient measuring device (a friction coefficient measuring device consisting of a Shimadzu Corporation tabletop precision universal testing machine Autograph AGS-X). The static friction coefficient was 0.09±0.01, and the dynamic friction coefficient was 0.08±0.01. Both friction coefficients were extremely small. Furthermore, the bonding strength between the coating and the glass epoxy substrate was measured based on the adhesive strength test method specified in JIS Z0237, and the result was that it withstood a load of 400 g. Therefore, the coating was bonded to the substrate with a constant bonding strength.
Furthermore, the surface of the coating was observed with the electron microscope used in Example 1. The surface was formed with a collection of copper nanoparticles consisting of 8-12 nm, and adjacent nanoparticles were bonded to each other at the contact sites. In addition, the side of the coating was observed with the electron microscope. Approximately 20 copper nanoparticles were stacked on top of each other to form a coating with a thickness of approximately 0.2 μm.

Example 5
In this example, a coating consisting of an aggregate of copper nanoparticles is formed using the paste prepared in Example 3. For this purpose, the paste prepared in Example 3 is applied to the surface of the glass epoxy substrate to which the copper foil used in Example 4 is not attached, and the glass epoxy substrate is heated to 195° C. in an air atmosphere to vaporize the ethanol and n-octane from the paste.
Thereafter, the surface resistance of the coating film formed on the surface of the glass epoxy substrate was measured at multiple points using a surface resistance meter in the same manner as in Example 4. The surface resistance value was smaller than that in Example 4.
Furthermore, the static and dynamic friction coefficients were measured at multiple points on the coating in the same manner as in Example 4. Both the static and dynamic friction coefficients were close to those in Example 4.
Furthermore, the surface of the coating was observed with the electron microscope used in Example 1. As in Example 4, the surface was formed with a collection of copper nanoparticles consisting of 8-12 nm, and adjacent copper nanoparticles were bonded to each other at the contact sites. In addition, the side of the coating was laminated with about 24 copper nanoparticles overlapping each other to form a coating with a thickness of about 0.24 μm, which was thicker than that of Example 4.
From the results of Examples 4 and 5, it was found that the thickness of the coating consisting of an aggregate of copper nanoparticles increases according to the viscosity of the paste, and as a result, the conductivity of the coating increases.

Example 6
In this example, a copper terminal plate is joined to a copper conductor at the tip of a 600- volt cross-linked polyethylene-insulated vinyl sheathed cable for wiring, using the paste prepared in Example 2. For this purpose, the copper terminal plate and the copper conductor are brought into contact with each other, the paste prepared in Example 2 is dripped onto the contact portion, and the copper terminal plate and the copper conductor are heated to 195° C. in a nitrogen atmosphere, and the ethanol and n-octane are vaporized from the paste.
After this, the bonding strength between the copper terminal plate and the copper conductor was measured with a tensile tester (a product of Imada Co., Ltd.), and the result was a bonding strength of 200 N. Therefore, a bonding layer consisting of an aggregate of metallically bonded copper nanoparticles was formed at the contact portion between the copper terminal plate and the copper conductor, and the copper terminal plate and the copper conductor were bonded by this bonding layer.
This embodiment is an example of joining parts together. For joining electric wires together or an electric wire to various terminal plates, paste is dropped onto the joining portion, and then an organic compound that disperses copper nanoparticles is evaporated from the paste, causing clusters of activated copper nanoparticles to precipitate, and the copper nanoparticles form metallic bonds at the contact portions, resulting in joining via a joining layer made of the clusters of copper nanoparticles.

Example 7
In this example, the paste prepared in Example 2 is used to bond copper foil to the glass epoxy substrate to which the copper foil used in Example 4 is not attached, via a collection of metallically bonded copper nanoparticles. The copper foil used is 12 μm thick and has a maximum surface roughness Rz of 4.5 μm on the laminate surface (Mitsui Kinzoku Co., Ltd. product 3EC-3).
The paste prepared in Example 2 was applied to the surface of the glass epoxy substrate, and the paste prepared in Example 2 was also applied to the laminated surface of the copper foil, and the applied surfaces were overlapped. Furthermore, a plate material having the same shape as the copper foil was placed on the copper foil, and a weight of 20 kg was also placed on the plate material. The sample was heated to 195°C in the air atmosphere, and ethanol and n-octane were vaporized from the paste.
After that, the bonding strength between the glass epoxy board and the copper foil was measured based on the adhesive strength test method used in Example 4, and it was found to withstand a load of 600 g, which was a larger adhesive strength than in Example 4. Therefore, the bonding layer made of a collection of copper nanoparticles was bonded to the plate material with a certain bonding strength.
The reason why the bonding strength between the glass epoxy board and the copper foil in Example 7 was greater than that in Example 4 is because a compressive load was applied in Example 7 to bond the glass epoxy board and the copper foil.
On the other hand, in a method of joining the synthetic resin and the metal by a method other than bonding them with an adhesive, the melting point of the metal is significantly higher than the softening point of the synthetic resin. For example, even aluminum, which has a low melting point, has a high melting point of 660°C. Therefore, the metal surface is roughened by chemical treatment such as oxidation treatment or alkali treatment, or physical treatment such as laser treatment or plasma treatment, and then the synthetic resin is injection molded or insert molded to join the metal and the synthetic resin. In this embodiment, the treatment of roughening the metal surface is not necessary. Furthermore, there is no restriction on the combination of materials of the metal and the synthetic resin. Therefore, the metal and the synthetic resin can be joined generally at low cost.
This embodiment is also an example of bonding substrates together. In most processes for bonding substrates together, foreign matter on the bonding surfaces is removed, and then the bonding surfaces are cleaned and activated by chemical or physical treatment, and the activated bonding surfaces are bonded together. Examples of such bonding methods include chemical bonding, in which the bonding surfaces are activated by CB (Chemical Bonding) treatment and then bonded together, and room temperature bonding, in which the bonding surfaces are activated by sputtering or ion beam irradiation and then bonded together. In this embodiment, such special pre-treatment of the bonding surfaces is not required.

Example 8
In this example, a paste was prepared by dispersing nickel nanoparticles in n-nonane as described in paragraph 23. Hexaamminenickel chloride as described in paragraph 27 was used as the raw material for the nickel nanoparticles.
232 g (corresponding to 1 mole) of hexaamminenickel chloride (e.g., a product of Fujifilm Wako Pure Chemical Industries, Ltd.) was dispersed in 3.3 L of methanol and stirred to prepare a methanol dispersion of hexaamminenickel chloride. After that, the methanol dispersion of hexaamminenickel chloride was heated to 65° C., methanol was evaporated from the methanol dispersion, and crystals of hexaamminenickel chloride were precipitated. After that, the collection of hexaamminenickel chloride crystals was filled into a container of 10 cm×10 cm×3 cm, and a plate material of 10 cm×10 cm×1 cm was placed on the collection of hexaamminenickel chloride crystals, and a weight of 10 kg was placed on the plate material. After that, the weight was once removed from the plate material, and an impact acceleration of 0.4 G was applied to the container in three directions, front and back, left and right, and up and down, five times in order. The weight was placed on the plate material again, and then the impact acceleration in the three directions was applied again. After repeating this pair of treatments consisting of a treatment of applying a compressive load by a weight and a treatment of applying an impact acceleration three times, a weight was placed on the plate material again, but since the plate material did not sink at all, it was determined that the crushing of the hexaamminenickel chloride crystals by the compressive load had been completed, and the pair of treatments was stopped and the plate material was removed from the container.
Furthermore, 430 cc of n-nonane (e.g., a product of Fujifilm Wako Pure Chemical Industries, Ltd.) was charged into the container and stirred to prepare a paste in which clusters of tetraamine copper nitrate crystals were dispersed in n-nonane. After this, the container was placed in a heat treatment device in a hydrogen atmosphere and left at 200°C for 5 minutes, and then the container was removed from the heat treatment device.
After this, a part of the sample in the container was taken out, and the sample was observed with the electron microscope used in Example 1. A secondary electron beam between 900-1000 volts was taken out of the reflected electron beam from the surface of the sample, and image processing was performed. Granular nanoparticles with a size of 10 nm were dispersed. Next, the energy between 900-1000 volts of the reflected electron beam was extracted and image processing was performed, and the material of the nanoparticles was observed based on the shading of the image. Since no shading was observed, it was found that the nanoparticle clusters were formed from the same element. Furthermore, the energy and intensity of the characteristic X-rays were image processed, and the elements that make up the nanoparticles were analyzed. Since only nickel atoms were present, the nanoparticles were nickel nanoparticles. Therefore, the paste created was a paste in which a cluster of nickel nanoparticles was dispersed in n-nonane.

Example 9
In this example, the paste prepared in Example 8 was diluted with ethanol to reduce the viscosity at 20° C. to 6.0 mPa sec. For this purpose, 430 cc of ethanol was added to the paste prepared in Example 8, and the paste prepared in Example 7 was diluted with ethanol.

Example 10
In this example, a copper terminal plate is joined to a copper conductor at the tip of a 600- volt cross-linked polyethylene-insulated vinyl sheathed cable for wiring, in the same manner as in Example 6, using the paste prepared in Example 9. For this purpose, the paste prepared in Example 9 is dropped onto the contact portion between the copper terminal plate and the copper conductor, and the copper terminal plate and the copper conductor are heated to 215° C. in a nitrogen atmosphere, and ethanol and n-nonane are vaporized from the paste.
After this, the bonding strength between the copper terminal plate and the copper conductor was measured using the tensile tester used in Example 6, and the result was a bonding strength of 200 N, similar to Example 6. In other words, since the viscosity of the paste used in Example 10 is equivalent to that of the paste used in Example 6, even if the material of the metal nanoparticles is different, the thickness of the bonding layer bonding the copper terminal plate and the copper conductor does not change, and since the size of the metal nanoparticles is equivalent, the bonding strength between the copper terminal plate and the copper conductor in Example 10 became equivalent to the bonding strength between the copper terminal plate and the copper conductor in Example 6.
Furthermore, a DC magnetic field was applied to the contact portion between the copper terminal plate and the copper conductor by a Helmholtz coil/magnetic field generator (e.g., a product of Nippon Universal Electric Co., Ltd.). After this, the bonding strength between the copper terminal plate and the copper conductor was measured again by a tensile tester, and the tensile strength was found to have increased to 400N.
These results show that saturating the magnetization of the nickel nanoparticles precipitated in the joint doubled the joint strength between the copper terminal plate and the copper conductor. In other words, by saturating the magnetization of the nickel nanoparticles, the magnetic attraction force between the magnetized saturated nickel nanoparticles was added to the metallic bonding force between the nickel nanoparticles, increasing the bonding strength between the copper terminal plate and the copper conductor.
This embodiment is an example of joining parts together, in which a paste containing dispersed clusters of ferromagnetic metal nanoparticles is used, an organic compound is vaporized from the dropped paste, and then the magnetization of the ferromagnetic metal nanoparticles is saturated, thereby increasing the joining strength between the parts.

Example 11
In this example, the paste of Example 9 was used to bond copper foil to a glass epoxy substrate in the same manner as in Example 7. For this purpose, the paste prepared in Example 9 was applied to the surface of the glass epoxy substrate, and the paste prepared in Example 9 was also applied to the laminate surface of the copper foil, and the coated surfaces were overlapped. Furthermore, a plate material having the same shape as the copper foil was placed on the copper foil, and a weight of 20 kg was placed on the plate material. The sample was heated to 215°C in the air atmosphere, and ethanol and n-nonane were vaporized from the paste.
After that, the bonding strength between the glass epoxy board and the copper foil was measured based on the adhesive strength test method used in Example 4, and the result showed that it withstood a load of 600 g, which was the same as in Example 7. In other words, even though the material of the metal nanoparticles was changed from copper to nickel, the viscosity of the paste was the same, and furthermore, the applied compressive load was also the same, and furthermore, the size of the metal nanoparticles was the same, so the bonding strength of the bonding layer consisting of an assembly of metal nanoparticles did not change.
Furthermore, a direct current magnetic field was applied to the portion where the copper foil was bonded to the glass epoxy substrate by the Helmholtz coil/magnetic field generator used in Example 10. After this, the bonding force between the glass epoxy substrate and the copper foil was measured again based on the adhesive strength test method, and the bonding force increased to 1 kg. From this result, when the magnetization of the nickel nanoparticles precipitated at the bonding portion was saturated, the bonding force between the glass epoxy substrate and the copper foil increased. In other words, the magnetization of the nickel nanoparticles was saturated, and the magnetic adsorption force between the magnetized nickel nanoparticles was added to the bonding force of the nickel nanoparticles metallically bonded to each other, and the bonding force between the glass epoxy substrate and the copper foil increased.
This embodiment is an example of joining substrates together, and similarly to embodiment 10, a paste in which clusters of ferromagnetic metal nanoparticles are dispersed is used, an organic compound is evaporated from the dropped paste, and then the magnetization of the ferromagnetic metal nanoparticles is saturated, thereby increasing the joining strength between the substrates.

Example 12
In this example, the paste prepared in Example 9 is used to bond copper foil to both sides of a polyimide film via a collection of metallically bonded nickel nanoparticles. The polyimide film used is one with a thickness of 12.5 μm (e.g., Kapton 50H/V, a product of Toray DuPont Co., Ltd.). The polyimide film has a heat resistance of nearly 400° C. in air. The copper foil used in Example 7 is the same as that used in Example 7.
The paste prepared in Example 9 was applied to both sides of a polyimide film and to the laminated surfaces of two copper foils, and the applied surfaces were placed together. A plate having the same shape as the copper foil was placed on one of the copper foils, and a weight of 20 kg was placed on the plate. The sample was heated to 215° C. in an air atmosphere, and ethanol and n-nonane were vaporized from the paste.
After this, the bonding strength between the polyimide film and the copper foil was measured based on the adhesive strength test method performed in Example 2, and the result was that it withstood a load of 600 g. Therefore, the polyimide film and the copper foil were bonded via a collection of nickel nanoparticles. In addition, in Examples 7 and 11, when the glass epoxy board and the copper foil were bonded, the adhesive strength was the same as in Example 12, that is, a load of 600 g. In other words, even if the materials of the substrates to be bonded were different, and even if the materials of the nanoparticles, which are the bonding medium, were different, the viscosity of the paste was the same, and further, the compressive load applied during bonding was the same, and the size of the nanoparticles was the same, so that the adhesive strength was the same.
Furthermore, a DC magnetic field was applied to the entire area where the copper foil laminated surfaces were bonded to both sides of the polyimide film using the Helmholtz coil/magnetic field generator used in Example 10. The adhesive strength was measured again based on the adhesive strength test method, and the adhesive strength increased to 1000 g. Therefore, when the magnetization of the nickel nanoparticles precipitated at the joint was saturated, the bonding strength between the polyimide film and the copper foil increased significantly.
This embodiment is another example of bonding substrates together, and similarly to embodiment 11, a paste in which clusters of ferromagnetic metal nanoparticles are dispersed is used, an organic compound is vaporized from the dropped paste, and then the magnetization of the ferromagnetic metal nanoparticles is saturated, thereby increasing the bonding strength for bonding the substrates together.

Example 13
In this example, 100 cc of ethanol was added to the paste prepared in Example 8 so that the viscosity of the paste prepared in Example 8 was 9.0 mPascal seconds at 20°C.

Example 14
In this example, a copper terminal plate is joined to a copper conductor at the tip of a 600- volt cross-linked polyethylene-insulated vinyl sheathed cable for wiring, in the same manner as in Example 10, using the paste prepared in Example 13. For this purpose, the paste prepared in Example 13 is dropped onto the contact portion between the copper terminal plate and the copper conductor, and the copper terminal plate and the copper conductor are heated to 215° C. in a nitrogen atmosphere, and ethanol and n-nonane are vaporized from the paste.
Thereafter, the bonding strength between the copper terminal plate and the copper conductor was measured using the tensile tester used in Example 10, and the result was a bonding strength of 300 N. In other words, since the viscosity of the paste used in this example was higher than that of the paste in Example 10, the volume of the joint between the copper terminal plate and the copper conductor increased with the increase in the viscosity of the paste, and the bonding strength between the copper terminal plate and the copper conductor increased.
Furthermore, a DC magnetic field was applied to the contact portion between the copper terminal plate and the copper conductor, as in Example 10. After this, the bonding strength between the copper terminal plate and the copper conductor was measured again with a tensile tester, and the tensile strength increased to 600 N. In other words, the magnetization of the nickel nanoparticles was saturated, and the magnetic attraction force between the magnetized nickel nanoparticles was added to the bonding force between the nickel nanoparticles metallically bonded to each other, and the bonding strength between the copper terminal plate and the copper conductor increased by two times.
This embodiment is an example of an embodiment for joining components together, and by using a paste in which clusters of ferromagnetic metal nanoparticles are dispersed and further increasing the viscosity of the paste used, the joining strength for joining the components together can be increased.

Example 15
In this example, a paste is prepared in which copper nanoparticles are dispersed in the tetraethylene glycol described in paragraph 24. Copper octylate described in paragraph 28 is used as the raw material for the copper nanoparticles.
350 g (corresponding to 1 mole) of copper octylate (e.g., a product of Mitsuwa Chemical Co., Ltd.) was dispersed in 5 L of methanol and stirred to prepare a methanol dispersion of copper octylate. After that, the temperature of the methanol dispersion of copper octylate was raised to 65° C., methanol was evaporated from the methanol dispersion, and crystals of copper octylate were precipitated. After that, the collection of copper octylate crystals was filled into a 10 cm×10 cm×3 cm container, and a 10 cm×10 cm×1 cm plate material was placed on the collection of copper octylate crystals, and a 10 kg weight was placed on the plate material. After that, the weight was once removed from the plate material, and an impact acceleration of 0.4 G was applied to the container in three directions, front and back, left and right, and up and down, five times in order. The weight was placed on the plate material again, and then the impact acceleration in the three directions was applied again. After repeating this pair of treatments consisting of applying a compressive load by a weight and applying an impact acceleration three times, a weight was placed on the plate again, but since the plate did not sink at all, it was determined that the crushing of the copper octylate crystals by the compressive load was completed, and the pair of treatments was stopped and the plate was removed from the container.
Furthermore, 400 cc of tetraethylene glycol (e.g., a product of Fujifilm Wako Pure Chemical Industries, Ltd.) was filled into the container and stirred to prepare a paste in which the copper octylate crystal clusters were dispersed in tetraethylene glycol. After this, the container was placed in a heat treatment device in an air atmosphere and left at 290°C for 1 minute, after which the container was removed from the heat treatment device.
After this, a part of the sample in the container was taken out, and the sample was observed with the electron microscope used in Example 1. A secondary electron beam between 900-1000 volts was taken out of the reflected electron beam from the surface of the sample, and image processing was performed. Granular nanoparticles with a size of about 10 nm were dispersed in the sample. Next, the energy between 900-1000 volts of the reflected electron beam was extracted and image processing was performed, and the material of the nanoparticles was observed based on the shading of the image. Since no shading was observed, it was found that the nanoparticle clusters were formed from the same element. Furthermore, the energy and intensity of the characteristic X-rays were image processed, and the elements that make up the nanoparticles were analyzed. Since only copper atoms were present, the nanoparticles were copper nanoparticles. Therefore, the sample created was a paste in which a cluster of copper nanoparticles was dispersed in tetraethylene glycol.

Example 16
In this example, 4,306 cc of ethanol was added to the paste prepared in Example 15 so that the viscosity of the paste prepared in Example 15 was 6.0 mPa-sec at 20°C, and a paste in which copper nanoparticles were dispersed in an ethanol diluted solution of tetraethylene glycol was prepared.

Example 17
In this example, 2100 cc of ethanol was added to the paste prepared in Example 15 so that the viscosity of the paste prepared in Example 15 was 10.0 mPa-sec at 20°C, and a paste in which copper nanoparticles were dispersed in an ethanol diluted solution of tetraethylene glycol was prepared.

Example 18
In this example, a coating consisting of an aggregate of copper nanoparticles is formed using the paste prepared in Example 16. For this purpose, the paste prepared in Example 16 is applied to the surface of the glass epoxy substrate to which the copper foil used in Example 4 is not attached, and the glass epoxy substrate is heated to 330° C. in a nitrogen atmosphere to vaporize the ethanol and tetraethylene glycol from the paste.
Thereafter, the surface resistance of the coating film formed on the surface of the glass epoxy substrate was measured at a number of points using a surface resistance meter in the same manner as in Example 4. The surface resistance values were close to those in Example 4.
Furthermore, the static and dynamic friction coefficients were measured at multiple points on the coating in the same manner as in Example 4. Both the static and dynamic friction coefficients were close to those in Example 4.
Furthermore, the surface of the coating was observed with the electron microscope used in Example 1. As in Example 4, the surface was formed with a collection of copper nanoparticles consisting of 8-12 nm, and adjacent nanoparticles were bonded to each other at the contact sites. In addition, the side of the coating was observed with the electron microscope. Approximately 20 copper nanoparticles were stacked on top of each other to form a coating with a thickness of approximately 0.2 μm.
From the results of Examples 4 and 18, it was found that even if the organic compounds used to disperse the copper nanoparticles were different, as long as the viscosity of the paste was the same, the size of the copper nanoparticles was equivalent, and therefore a copper coating with equivalent properties was formed.

Example 19
In this example, a copper terminal plate is joined to a copper conductor at the tip of a 600- volt cross-linked polyethylene-insulated vinyl sheathed cable for wiring, using the paste prepared in Example 17, in the same manner as in Example 14. For this purpose, the paste prepared in Example 17 is dropped onto the contact portion between the copper terminal plate and the copper conductor, and the copper terminal plate and the copper conductor are heated to 330° C. in a nitrogen atmosphere, and the ethanol and tetraethylene glycol are vaporized from the paste.
Thereafter, the bonding strength between the copper terminal plate and the copper conductor was measured using the tensile tester used in Example 10, and the result was a bonding strength of 400 N. In other words, since the viscosity of the paste used in this example was higher than that of the paste in Example 14, the volume of the joint between the copper terminal plate and the copper conductor increased with the increase in the viscosity of the paste, and the bonding strength between the copper terminal plate and the copper conductor increased.
This embodiment is an embodiment in which components are bonded together, and by increasing the viscosity of the paste used, the thickness of the bonding layer bonding the components together becomes thicker, thereby increasing the bonding strength between the components.

Example 20
In this example, the paste prepared in Example 17 is used to bond the copper foil used in Example 7 to a glass epoxy substrate to which the copper foil used in Example 4 is not attached, via a collection of metallically bonded copper nanoparticles, in the same manner as in Example 7.
The paste prepared in Example 17 was applied to the surface of the glass epoxy substrate, and the paste prepared in Example 17 was also applied to the laminate surface of the copper foil, and the applied surfaces were overlapped. Furthermore, a plate material having the same shape as the copper foil was placed on the copper foil, and a weight of 20 kg was also placed on the plate material. The sample was heated to 330° C. in a nitrogen atmosphere, and the ethanol and tetraethylene glycol were vaporized from the paste.
After that, the bonding strength between the glass epoxy substrate and the copper foil was measured based on the adhesive strength test method performed in Example 4, and the result was that the bonding strength withstood a load of 900 g. This value of bonding strength was 1.5 times that of the bonding strength between the glass epoxy substrate and the copper foil in Example 7. That is, the viscosity of the paste in which the clusters of copper nanoparticles were dispersed in the organic compound at 20° C. was 6.0 mPascal seconds in Example 7, whereas it was 10.0 mPascal seconds in this example. Therefore, the thickness of the bonding layer consisting of the clusters of copper nanoparticles bonded by frictional heat increased according to the viscosity of the paste, and as a result, the bonding strength between the glass epoxy substrate and the copper foil increased.
This embodiment is an embodiment in which substrates are bonded to each other, and by increasing the viscosity of the paste used, the thickness of the bonding layer bonding the substrates to each other becomes thicker, thereby increasing the bonding strength between the substrates.

Example 21
In this example, two copper foils are bonded to both sides of a polyimide film using the paste of Example 17, in the same manner as in Example 12. For this purpose, the paste prepared in Example 17 is applied to both sides of a polyimide film and to the laminated surfaces of two copper foils, and the applied surfaces are overlapped. Furthermore, a plate material having the same shape as the copper foil is placed on one of the copper foils, and a weight of 20 kg is placed on the plate material. The sample is heated to 330° C. in an air atmosphere, and ethanol and tetraethylene glycol are vaporized from the paste.
After this, the bonding strength between the polyimide film and the copper foil was measured based on the adhesive strength test method performed in Example 2, and the result was that it withstood a load of 1 kg. Therefore, the polyimide film and the copper foil were bonded through the aggregation of copper nanoparticles. That is, in Example 12, the viscosity of the paste in which the aggregation of nickel nanoparticles is dispersed in an organic compound is 6.0 mPascal seconds at 20°C. In contrast, in this example, the viscosity of the paste in which the aggregation of copper nanoparticles is dispersed in an organic compound is 10.0 mPascal seconds at 20°C. Therefore, the thickness of the bonding layer consisting of the aggregation of metal nanoparticles bonded by frictional heat increases according to the viscosity of the paste, and as a result, the bonding strength between the polyimide film and the copper foil increases.

Example 22
In this example, an aluminum pipe having the same outer diameter as the inner diameter of a socket made of SUS304, which joins a metal pipe, is joined to the socket through a collection of copper nanoparticles. The inner diameter of the SUS304 socket and the outer diameter of the aluminum pipe were previously processed to fit together with a clearance fit.
For this purpose, the paste of Example 16 was applied to the inner surface of a SUS304 socket and the surface to which the aluminum pipe was to be joined, and the aluminum pipe was inserted into the SUS304 socket. The sample was heated to 330° C. in an air atmosphere, and the ethanol and tetraethylene glycol were vaporized from the paste. After this, the socket was fixed with a jig, and the pipe was rotated until the repulsive force became strong.
After this, the bonding strength between the socket and the pipe was measured with the tensile tester used in Example 4, and the result was a bonding strength of 500 N. Therefore, the collection of copper nanoparticles bonded the socket and the pipe with a certain bonding strength. In other words, when the socket was fixed and the pipe was rotated, frictional heat was generated at the site where adjacent copper nanoparticles contacted each other in the collection of copper nanoparticles precipitated at the joints of both, and the adjacent copper nanoparticles were metallically bonded at the contact points by the frictional heat, and the joints of both were bonded by the collection of metallically bonded copper nanoparticles.
The melting point of SUS304 is 1400-1450°C, and the melting point of aluminum is 660°C. The thermal conductivity of SUS304 is 16.7 W/mK, and the thermal conductivity of aluminum is 204 W/mK. Thus, it is difficult to join materials with significantly different melting points and thermal conductivities by welding. However, according to this embodiment, adjacent copper nanoparticles are metallically bonded at the contact points by frictional heat, and the joining parts of both are joined by a collection of metallically bonded copper nanoparticles, making it possible to join dissimilar metals with significantly different melting points and thermal conductivities. In addition, since dissimilar metals are joined by a collection of metallically bonded copper nanoparticles, pre-treatment to remove the oxide film at the joint, as in conventional welding, is not required.

Example 23
In this example, a paste is prepared by dispersing nickel nanoparticles in the tetraethylene glycol described in paragraph 24. Nickel octylate described in paragraph 28 is used as the raw material for the nickel nanoparticles.
345 g (corresponding to 1 mole) of nickel octylate (for example, a product of Nippon Kagaku Sangyo Co., Ltd.) was dispersed in 5 L of methanol and stirred to prepare a methanol dispersion of nickel octylate. After this, the temperature of the methanol dispersion of nickel octylate was raised to 65° C., methanol was evaporated from the methanol dispersion, and crystals of nickel octylate were precipitated. After this, the collection of nickel octylate crystals was filled into a container of 10 cm x 10 cm x 3 cm, and a plate material of 10 cm x 10 cm x 1 cm was placed on the collection of nickel octylate crystals, and a weight of 10 kg was placed on the plate material. After this, the weight was once removed from the plate material, and an impact acceleration of 0.4 G was applied to the container in three directions, front and back, left and right, and up and down, five times in order. The weight was placed on the plate material again, and then the impact acceleration in the three directions was applied again. After repeating this pair of treatments consisting of a treatment of applying a compressive load by a weight and a treatment of applying an impact acceleration three times, a weight was placed on the plate material again, but since the plate material did not sink at all, it was determined that the crushing of the nickel octoate crystals by the compressive load had been completed, and the pair of treatments was stopped and the plate material was removed from the container.
Furthermore, 400 cc of tetraethylene glycol (e.g., a product of Fujifilm Wako Pure Chemical Industries, Ltd.) was filled into the container and stirred to prepare a paste in which agglomerations of nickel octylate crystals were dispersed in tetraethylene glycol. After this, the container was placed in a heat treatment device in an air atmosphere and left at 290°C for 1 minute, and then the container was removed from the heat treatment device.
After this, a part of the sample in the container was taken out, and the sample was observed with the electron microscope used in Example 1. A secondary electron beam between 900-1000 volts was taken out of the reflected electron beam from the surface of the sample, and image processing was performed. Granular nanoparticles with a size of about 10 nm were dispersed in the sample. Next, the energy between 900-1000 volts of the reflected electron beam was extracted and image processing was performed, and the material of the nanoparticles was observed based on the shading of the image. Since no shading was observed, it was found that the collection of nanoparticles was formed from the same element. Furthermore, the energy and intensity of the characteristic X-rays were image processed, and the elements that make up the nanoparticles were analyzed. Since only nickel atoms were present, the nanoparticles were nickel nanoparticles.

Example 24
In this example, 4,306 cc of ethanol was added to the paste prepared in Example 23 so that the viscosity of the paste prepared in Example 23 was 6.0 mPa-sec at 20°C, and a paste in which nickel nanoparticles were dispersed in an ethanol diluted solution of tetraethylene glycol was prepared.

Example 25
In this example, 2100 cc of ethanol was added to the paste prepared in Example 23 so that the viscosity of the paste prepared in Example 23 was 10.0 mPa-sec at 20°C, and a paste in which nickel nanoparticles were dispersed in an ethanol diluted solution of tetraethylene glycol was prepared.

Example 26
In this example, a copper terminal plate is joined to a copper conductor at the tip of a 600- volt cross-linked polyethylene-insulated vinyl-sheathed cable for wiring, in the same manner as in Example 10, using the paste of Example 24. For this purpose, the paste prepared in Example 24 is dropped onto the contact portion between the copper terminal plate and the copper conductor, and the copper terminal plate and the copper conductor are heated to 330° C. in a nitrogen atmosphere, and the ethanol and tetraethylene glycol are vaporized from the paste.
After this, the bonding strength between the copper terminal plate and the copper conductor was measured using the tensile tester used in Example 6, and as a result, it had a bonding strength of 200 N, similar to Examples 6 and 10. The bonding strength between the copper terminal plate and the copper conductor was the same as in Examples 6 and 10. In other words, even if the organic compound that disperses the metal nanoparticles is different, and even if the metal material of the nanoparticles is different, if the viscosity of the paste is the same, the thickness of the bonding layer consisting of a collection of metal nanoparticles bonded to each other is the same, and the size of the metal nanoparticles is the same, so the copper terminal plate and the copper conductor are bonded with the same bonding strength.
Furthermore, a DC magnetic field was applied to the contact portion between the copper terminal plate and the copper conductor by the Helmholtz coil/magnetic field generator used in Example 10. After this, the bonding strength between the copper terminal plate and the copper conductor was measured again by the tensile tester, and the tensile strength was found to have increased to 400 N.
From this result, when the magnetization of the nickel nanoparticles precipitated at the joint was saturated, the bonding strength between the copper terminal plate and the copper conductor was doubled. In other words, the magnetic attraction force between the nickel nanoparticles whose magnetization was saturated was added to the bonding force of the nickel nanoparticles metallically bonded to each other, and the bonding force between the copper terminal plate and the copper conductor was increased. This bonding force is also the same value as the bonding force in Example 10. In other words, even if the organic compound that disperses the nickel nanoparticles is different, if the viscosity of the paste is the same, the thickness of the bonding layer consisting of a collection of metallically bonded nickel nanoparticles is the same, and also the size of the nickel nanoparticles is the same, so the magnetic attraction force between the nickel nanoparticles is also the same.

Example 27
In this example, the paste of Example 24 is used to bond copper foil to a glass epoxy substrate in the same manner as in Example 11. For this purpose, the paste prepared in Example 24 is applied to the surface of the glass epoxy substrate, and the paste prepared in Example 24 is also applied to the laminate surface of the copper foil, and the applied surfaces are overlapped. Furthermore, a plate material having the same shape as the copper foil is placed on the copper foil, and a weight of 20 kg is also placed on the plate material. The sample is heated to 330° C. in a nitrogen atmosphere, and ethanol and tetraethylene glycol are vaporized from the paste.
Thereafter, the bonding strength between the glass epoxy board and the copper foil was measured based on the adhesive strength test method used in Example 4, and it was found to withstand a load of 600 g, which was equivalent to that of Example 11. In other words, even if the organic compound dispersing the nickel nanoparticles is different, if the viscosity of the paste is the same, the thickness of the bonding layer consisting of a collection of metallically bonded nickel nanoparticles is equivalent, and also, the size of the nickel nanoparticles is equivalent, so that the glass epoxy board is bonded to the copper foil with the same bonding strength.
Furthermore, a direct current magnetic field was applied to the portion where the copper foil was bonded to the glass epoxy substrate by the Helmholtz coil/magnetic field generator used in Example 10. After this, the bonding force between the glass epoxy substrate and the copper foil was measured again based on the adhesive strength test method, and the bonding force increased to 1 kg. From this result, when the magnetization of the nickel nanoparticles precipitated at the bonding portion was saturated, the bonding force between the glass epoxy substrate and the copper foil increased. In other words, the magnetization of the nickel nanoparticles was saturated, and the magnetic adsorption force between the magnetized nickel nanoparticles was added to the bonding force of the nickel nanoparticles metallically bonded to each other, and the bonding force between the glass epoxy substrate and the copper foil increased.
This bonding strength is also equivalent to the bonding strength in Example 11. In other words, even if the organic compound dispersing the nickel nanoparticles is different, if the viscosity of the paste is the same, the thickness of the bonding layer made of a collection of metallically bonded nickel nanoparticles is equivalent, and since the size of the nickel nanoparticles is equivalent, the magnetic adsorption force between the nickel nanoparticles is also equivalent.

Example 28
In this example, the paste of Example 24 is used, and similarly to Example 12, two copper foils are bonded to both sides of a polyimide film via clusters of metallically bonded nickel nanoparticles.
The paste prepared in Example 24 was applied to both sides of a polyimide film and to the laminated surfaces of two copper foils, and the applied surfaces were placed together. A plate material having the same shape as the copper foil was placed on one of the copper foils, and a weight of 20 kg was placed on the plate material. The sample was heated to 330° C. in an air atmosphere, and ethanol and tetraethylene glycol were vaporized from the paste.
Thereafter, the bonding strength between the polyimide film and the copper foil was measured based on the adhesive strength test method used in Example 2, and the result showed that the polyimide film could withstand a load of 600 g, which was equivalent to that of Example 12. In other words, even if the organic compound dispersing the nickel nanoparticles was different, if the viscosity of the paste was the same, the thickness of the bonding layer consisting of a collection of metallically bonded nickel nanoparticles was equivalent, and also, the size of the nickel nanoparticles was equivalent, so that the polyimide film was bonded to the copper foil with the same bonding strength.
Furthermore, a direct current magnetic field was applied to the entire area where the laminated surfaces of the copper foil were bonded to both sides of the polyimide film by the Helmholtz coil/magnetic field generator used in Example 10. The adhesive strength was measured again based on the adhesive strength test method, and the adhesive strength withstood a load of 1 kg, which was the same as in Example 12. Therefore, when the magnetization of the nickel nanoparticles precipitated at the joint was saturated, the bonding strength between the polyimide film and the copper foil increased significantly. In other words, even if the organic compound that disperses the nickel nanoparticles is different, if the viscosity of the paste is the same, the thickness of the bonding layer consisting of a collection of metallically bonded nickel nanoparticles is the same, and since the size of the nickel nanoparticles is the same, the magnetic adsorption force between the nickel nanoparticles is also the same.

Example 29
In this example, the paste of Example 24 is used, and a socket and a pipe having the same dimensions and processing conditions as those of the socket and the pipe used in Example 22 are used, and an aluminum pipe is joined to a socket made of SUS304 via a collection of nickel nanoparticles, as in Example 22. For this purpose, the paste of Example 24 is applied to the inner surface of the SUS304 socket and the surface to which the aluminum pipe is joined, and the aluminum pipe is inserted into the SUS304 socket. Furthermore, the temperature is raised to 330°C in an air atmosphere, and ethanol and tetraethylene glycol are vaporized from the paste. After this, the socket is fixed with a jig, and the pipe is rotated until the repulsive force becomes strong.
After this, the bonding strength between the socket and the pipe was measured with the tensile tester used in Example 4, and the bonding strength was 500N, which was equivalent to that of Example 22. Therefore, the collection of nickel nanoparticles bonded the socket and the pipe with a constant bonding strength. In other words, the viscosity of the paste was equivalent to that of Example 22, and the thickness of the bonding layer bonding the socket and the pipe did not change, and further, the dimensions and processing conditions of the joint between the socket and the pipe were equivalent to those of Example 22, and the conditions for stopping the socket and rotating the pipe were equivalent, so that the same shear force was generated in the collection of nickel nanoparticles at the joint between the socket and the pipe, and the size of the metal nanoparticles was equivalent, so that even if the material of the nanoparticles was different, the bonding strength was equivalent to that of Example 22.
Furthermore, a direct current magnetic field was applied to the joint between the SUS304 socket and the aluminum pipe by the Helmholtz coil/magnetic field generator used in Example 10. After this, the bonding force between the socket and the pipe was measured again by the tensile tester, and the bonding force increased to 1000 N. From this result, when the magnetization of the nickel nanoparticles precipitated at the joint was saturated, the bonding force between the SUS304 socket and the aluminum pipe was doubled. In other words, the magnetic attraction force between the nickel nanoparticles, which were saturated with the magnetization of the nickel nanoparticles, was added to the bonding force between the nickel nanoparticles bonded by metal bonding, and the bonding force between the SUS304 socket and the aluminum pipe was increased. Therefore, in the bonding between the parts, a paste in which ferromagnetic metal nanoparticles are dispersed is used, the magnetization of the ferromagnetic metal nanoparticles is saturated, and the magnetic attraction force between the nanoparticles is expressed, thereby increasing the bonding force between the parts.

Example 30
In this example, a copper terminal plate is joined to a copper conductor at the tip of a 600- volt cross-linked polyethylene-insulated vinyl sheathed cable for wiring, in the same manner as in Example 14, using the paste of Example 25. For this purpose, the paste prepared in Example 25 was dropped onto the contact portion between the copper terminal plate and the copper conductor, and the copper terminal plate and the copper conductor were heated to 330° C. in a nitrogen atmosphere, and the ethanol and tetraethylene glycol were vaporized from the paste.
Thereafter, the bonding strength between the copper terminal plate and the copper conductor was measured using the tensile tester used in Example 10, and the result was a bonding strength of 400 N, which was greater than that of Example 14. In other words, since the viscosity of the paste used in this example was greater than that of the paste in Example 14, the volume of the joint between the copper terminal plate and the copper conductor increased with the increase in the viscosity of the paste, and the bonding strength between the copper terminal plate and the copper conductor increased.
Further, as in Example 14, a direct current magnetic field was applied to the contact portion between the copper terminal plate and the copper conductor. After this, the bonding force between the copper terminal plate and the copper conductor was measured again with a tensile tester, and the tensile strength increased to 800 N. That is, the magnetization of the nickel nanoparticles was saturated, and the magnetic adsorption force between the magnetized nickel nanoparticles was added to the bonding force of the nickel nanoparticles metallically bonded to each other, and the bonding force between the copper terminal plate and the copper conductor was doubled. Therefore, in the bonding between parts, it is effective to use a paste in which ferromagnetic metal nanoparticles are dispersed, to saturate the magnetization of the ferromagnetic metal nanoparticles, and to add the magnetic adsorption force between the nanoparticles to the metallic bonding force between the nanoparticles.

Example 31
In this example, the paste of Example 25 is used, and in the same manner as in Example 7, the copper foil used in Example 7 is bonded to a glass epoxy substrate to which the copper foil used in Example 4 is not attached, via a collection of metallically bonded nickel nanoparticles.
The paste prepared in Example 25 was applied to the surface of the glass epoxy substrate, and the paste prepared in Example 25 was also applied to the laminate surface of the copper foil, and the applied surfaces were overlapped. Furthermore, a plate material having the same shape as the copper foil was placed on the copper foil, and a weight of 20 kg was placed on the plate material. The sample was heated to 330° C. in a nitrogen atmosphere, and ethanol and tetraethylene glycol were vaporized from the paste.
After that, the bonding strength between the glass epoxy substrate and the copper foil was measured based on the adhesive strength test method performed in Example 4, and the result was that the substrate withstood a load of 900 g. This value of bonding strength is equivalent to the bonding strength between the glass epoxy substrate and the copper foil in Example 20. That is, since the viscosity of the paste used in this example is equivalent to the viscosity of the paste used in Example 20, even if the material of the metal nanoparticles is different, the thickness of the bonding layer bonding the glass epoxy substrate and the copper foil does not change, and since the size of the metal nanoparticles is equivalent, the bonding strength between the glass epoxy substrate and the copper foil in this example is equivalent to the bonding strength in Example 20.
Furthermore, a direct current magnetic field was applied to the portion where the copper foil was bonded to the glass epoxy substrate by the Helmholtz coil/magnetic field generator used in Example 10. After this, the bonding strength between the glass epoxy substrate and the copper foil was measured again based on the adhesive strength test method, and the bonding strength withstood a load of 1.4 kg. From this result, when the magnetization of the nickel nanoparticles precipitated at the bonding portion was saturated, the bonding strength between the glass epoxy substrate and the copper foil increased. In other words, the magnetization of the nickel nanoparticles was saturated, and the magnetic adsorption force between the magnetized nickel nanoparticles was added to the bonding force of the nickel nanoparticles metallically bonded to each other, and the bonding strength between the glass epoxy substrate and the copper foil increased. Therefore, as a means for further firmly bonding the substrates to each other, it is effective to use a paste in which ferromagnetic metal nanoparticles are dispersed, saturate the magnetization of the ferromagnetic metal nanoparticles, and add the magnetic adsorption force between the nanoparticles to the metallic bonding force between the nanoparticles.

Example 32
In this example, the paste of Example 25 is used to bond two copper foils to both sides of a polyimide film in the same manner as in Example 12. For this purpose, the paste prepared in Example 25 is applied to both sides of a polyimide film and to the laminated surfaces of two copper foils, and the applied surfaces are overlapped. Furthermore, a plate material having the same shape as the copper foil is placed on one of the copper foils, and a weight of 20 kg is placed on the plate material. The sample is heated to 330° C. in an air atmosphere, and ethanol and tetraethylene glycol are vaporized from the paste.
After that, the bonding strength between the polyimide film and the copper foil was measured based on the adhesive strength test method performed in Example 2, and the result was that it withstood a load of 1 kg. Therefore, the polyimide film and the copper foil were bonded via the collection of copper nanoparticles. This bonding strength is equivalent to the bonding strength in Example 21. In other words, even if the material of the metal nanoparticles was changed from copper to nickel, the viscosity of the paste was the same, and further, the applied compressive load was also the same, and the size of the metal nanoparticles was the same, so the bonding strength of the bonding layer consisting of the collection of metal nanoparticles did not change.
Furthermore, a DC magnetic field was applied to the entire area where the copper foil laminated surfaces were bonded to both sides of the polyimide film using the Helmholtz coil/magnetic field generator used in Example 10. The adhesive strength was measured again based on the adhesive strength test method, and the adhesive strength withstood a load of 1500 g. In other words, when the magnetization of the nickel nanoparticles precipitated at the joint was saturated, the adhesive strength between the polyimide film and the copper foil increased by 1.5 times.
In contrast, in Example 28, after ethanol and tetraethylene glycol were evaporated from the paste from the coating surface, the adhesive strength between the polyimide film and the copper foil withstood a load of 600 g, and when the magnetization of the nickel nanoparticles precipitated at the joint was saturated, it withstood a load of 1000 g. Therefore, in order to increase the adhesive strength between the substrates, the viscosity of the paste used is increased, and the thickness of the bonding layer consisting of a collection of metal nanoparticles bonded by metal bonding is increased, thereby increasing the adhesive strength between the substrates. Furthermore, if the bonding layer is formed by a collection of nanoparticles made of ferromagnetic metal, the magnetization of the ferromagnetic metal nanoparticles is saturated, and the magnetic adsorption force between the ferromagnetic metal nanoparticles whose magnetization is saturated is added to the bonding force of the collection of metal nanoparticles bonded by metal bonding, thereby further increasing the adhesive strength between the substrates.

Although the embodiment for preparing the paste consisting of 12 has been described above, the preparation of the paste is not limited to these 12 embodiments. That is, the metal of the nanoparticles is not limited to copper and nickel, and by using various metal compounds described in paragraphs 27 and 28, nanoparticles consisting of metals other than copper and nickel can be precipitated. In addition, the organic compound for dispersing the nanoparticles is not limited to n-octane, n-nonane, or tetraethylene glycol, and a primary alcohol having 8-10 carbon atoms described in paragraph 23 can be used. In addition, the viscosity of the paste at 20° C. is not limited to 6, 7, or 10 millipascal seconds, and if diethyl ether, acetone, ethanol, or an organic solvent belonging to aromatic hydrocarbons described in paragraphs 22 and 24 is mixed with a primary alcohol having 8-10 carbon atoms, the viscosity of the paste can be changed according to the mixing ratio of the organic solvent. Therefore, the preparation of the paste is not limited to the embodiment of 12.
In addition, as an example of forming a coating made of a collection of metal nanoparticles, the formation of three coatings made of a collection of copper nanoparticles has been described in the examples. The formation of a coating made of a collection of metal nanoparticles is not limited to these examples. That is, by using various metal compounds described in paragraphs 27 and 28, a coating made of a metal other than copper can be formed. In addition, by changing the viscosity of the paste used to form the coating, the thickness of the coating made of a collection of metal nanoparticles can be freely changed. Therefore, the formation of a coating made of a collection of metal nanoparticles is not limited to the three examples made of a collection of copper nanoparticles.
Furthermore, as an example of joining parts together by a joining layer made of a collection of metallic nanoparticles bonded to each other, an example of joining a copper terminal plate to a copper conductor at the tip of a wiring wire made of a cross-linked polyethylene insulated vinyl sheath cable for 600 volts has been described. Also, an example of joining an aluminum pipe having an outer diameter equal to the inner diameter of a socket made of SUS304 has been described. Examples of joining parts together are not limited to these examples. That is, by bringing parts into contact with each other, dripping a paste onto the contact area, and then vaporizing the organic solvent and organic compound that make up the paste, the parts are joined together by a joining layer made of a collection of metallic nanoparticles bonded to each other. Therefore, examples of joining parts together are not limited to these examples.
In addition, as examples of bonding substrates to each other by a bonding layer consisting of a collection of metallic nanoparticles, a case where copper foil is bonded to a glass epoxy substrate and a case where two sheets of copper foil are bonded to both sides of a polyimide film have been described as examples, but the bonding of substrates to each other is not limited to these examples. That is, a paste is applied to the bonding surface where the substrates are bonded to each other, the bonding portions where the paste is applied are overlapped, and a compressive load is applied to one of the substrates, and then the substrates are heated to the boiling point of the liquid organic compound, and the application of the compressive load applied to one of the substrates is stopped, whereby the substrates are bonded to each other by a bonding layer consisting of a collection of metallic nanoparticles. Therefore, the bonding of substrates to each other is not limited to these examples.
Furthermore, as the metal nanoparticles, nickel nanoparticles, which are ferromagnetic metals, are used, and when joining parts together or joining base materials together, a magnetic field that saturates the magnetization of the nickel nanoparticles is applied to the joint where the nickel nanoparticles are metallically bonded together, and the magnetic attraction force between the magnetized nickel nanoparticles is added to the metallic bond between the nickel nanoparticles, increasing the bonding force of the joint. Similarly, by using ferromagnetic metal nanoparticles made of iron or cobalt, the magnetic attraction force between the magnetized ferromagnetic metal nanoparticles is added to the metallic bond between the ferromagnetic metal nanoparticles, increasing the bonding force of the joint.

1. Copper nanoparticles 2. n-octane

Claims (10)

A method for producing a paste in which a collection of metal nanoparticles is dispersed in an organic compound includes the steps of:
A metal compound having both a first property of being dispersed in methanol but not dissolved in methanol and a second property of precipitating a metal by thermal decomposition is dispersed in methanol to prepare a methanol dispersion of the metal compound; and further, methanol is evaporated from the methanol dispersion of the metal compound to precipitate a crystal cluster of the metal compound.
Then, the collection of crystals of the metal compound is filled into a container, a plate material that covers the entire surface of the collection of crystals of the metal compound in the container is placed on the surface of the collection of crystals of the metal compound, and a compressive load is applied to the entire surface of the plate material to crush the collection of crystals of the metal compound in the container. After the process of applying the compressive load to the plate material is stopped, impact acceleration is applied to the container in three directions, namely, front-back, left-right, and up-down, to move the crushed crystals of the metal compound to the gaps in the container formed by the crushing of the crystals of the metal compound, and rearrange the crushed collection of crystals of the metal compound in the container. Then, the compressive load is applied again to the entire surface of the plate material, and after the process of applying the compressive load to the plate material is stopped, impact acceleration is applied again to the container in the three directions. Such a pair of processes consisting of the process of applying the compressive load and the process of applying the impact acceleration are repeated, and when a repulsive force against the compressive load is generated in the plate material when the compressive load is applied to the plate material, it is determined that the crushing of the crystals of the metal compound is completed, and the pair of processes is stopped, and the plate material is removed from the container.
Then, a liquid organic compound having five properties, namely, a first property of a melting point lower than 15°C, a second property of the metal compound not dissolving or dispersing therein, a third property of a boiling point higher than the thermal decomposition temperature of the metal compound, a fourth property of not reacting chemically with metal nanoparticles precipitated by thermal decomposition of the metal compound, and a fifth property of a surface tension of 30 millinewtons per meter or less at 20°C, is weighed out in a weight greater than the weight of the aggregate of crystals of the metal compound, and the weighed liquid organic compound is filled into the container and stirred to create a suspension in the container in which the aggregate of crushed crystals of the metal compound is dispersed in the liquid organic compound.
Thereafter, the container is placed in an atmosphere in which the crushed metal compound crystals are thermally decomposed, and the temperature is raised to a temperature at which the crushed metal compound crystals are thermally decomposed. Through this process, metal nanoparticles are precipitated surrounded by the liquid organic compound, and a paste consisting of a collection of the metal nanoparticles dispersed in the liquid organic compound is produced in the container.
Then, an organic solvent having a first property of dissolving or being mixed in the liquid organic compound and a second property of having a boiling point lower than the boiling point of the liquid organic compound is mixed into the paste at varying mixing ratios so that the viscosity of the paste at 20°C becomes a preset viscosity of 20 millipascal seconds or less, thereby producing a paste having the preset viscosity in the container. A method for forming a conductive layer consisting of a collection of metallic nanoparticles bonded to each other on the surface of a substrate or a part using the paste produced by the method according to claim 1 is as follows:
The paste produced by the above method is applied to a surface of a substrate or a part, and a coating film having a thickness corresponding to the viscosity of the paste is formed on the surface of the substrate or the part. Thereafter, the substrate or the part is heated to the boiling point of the organic compound of the liquid.
Through this treatment, first the organic solvent evaporates from the coating film, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was applied, and further, the clusters of overlapping and precipitated metal nanoparticles metal-bond at the sites where they come into contact with each other, and a conductive layer consisting of the clusters of metal nanoparticles that are metal-bonded is formed on the surface of the substrate or the part as a conductive layer having a thickness according to the viscosity of the paste.
2. A method for forming a conductive layer consisting of a collection of metallic nanoparticles bonded to each other on the surface of a substrate or part, using the paste produced by the method according to claim 1. A method for bonding a component to a substrate or bonding components to each other using a bonding layer made of a collection of metallic nanoparticles bonded by metallurgical bonding using a paste produced by the method according to claim 1, comprising the steps of:
A part of a component is brought into contact with a surface of a substrate, and the paste produced by the above -mentioned method is dropped onto the portion where the part of the component comes into contact with the substrate. Then, both the substrate and the component are heated to the boiling point of the liquid organic compound.
By this process, first, the organic solvent evaporates from the dropped paste, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, and the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was dropped, and further, the clusters of overlapping and precipitated metal nanoparticles metal-bond with each other at the sites where they come into contact with each other, and a bonding layer consisting of the clusters of metal nanoparticles that are metal-bonded is formed at the site where a part of the component comes into contact with the base material as a bonding layer in an amount corresponding to the viscosity of the paste, and the part of the component is bonded to the surface of the base material by the bonding layer.
A method for bonding a component to a substrate with a bonding layer consisting of a collection of metallic nanoparticles bonded together by using a paste produced by the method according to claim 1,
Or,
The components are brought into contact with each other, and the paste produced by the above- mentioned method is dripped onto the contacted portion of the components. Thereafter, the components are heated to the boiling point of the liquid organic compound.
By this process, first, the organic solvent evaporates from the dropped paste, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, and the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was dropped, and further, the clusters of overlapping and precipitated metal nanoparticles metal-bond at the sites where they come into contact with each other, and a bonding layer consisting of the clusters of metal nanoparticles that are metal-bonded is formed at the sites where the components come into contact as a bonding layer in an amount corresponding to the viscosity of the paste, and the components are bonded to each other by the bonding layer.
A method for bonding components together with a bonding layer comprising an assembly of metallic nanoparticles bonded together, using a paste produced by the method according to claim 1. The method for joining a component to a substrate or joining components together according to claim 3 is a method for joining a component to a substrate or joining components together using a joining layer made of an assembly of ferromagnetic metal nanoparticles that are joined together by magnetic attraction and metallic bonding, and the method for joining a component to a substrate or joining components together comprises:
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of any one of iron, nickel, and cobalt upon thermal decomposition, and the metal compound is used as the metal compound to produce a paste consisting of a collection of nanoparticles consisting of the ferromagnetic metal dispersed in an organic compound according to the method for producing a paste described above , and the paste is dropped onto a portion of a part that is in contact with the surface of a substrate, and then both the substrate and the part are heated to the boiling point of the liquid organic compound described above .
By this treatment, first, the organic solvent evaporates from the dropped paste, then the organic compound in the liquid evaporates, and then the collection of ferromagnetic metal nanoparticles dispersed in the paste is activated, and the activated collection of ferromagnetic metal nanoparticles overlap and precipitate at the site where the paste was dropped, and further, the overlapping and precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and the magnetically attracted ferromagnetic metal nanoparticles are metallically bonded at the sites where they come into contact with each other, and a bonding layer consisting of the collection of metallically bonded ferromagnetic metal nanoparticles is formed as a bonding layer in an amount corresponding to the viscosity of the paste at the site where a part of the component comes into contact with the base material.
a method for bonding a component to a substrate, comprising: applying a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles to a portion of the component bonded to the substrate, thereby saturating the magnetization of the ferromagnetic metal nanoparticles; by this process, the metallically bonded ferromagnetic metal nanoparticles are magnetically attracted to each other due to the saturated magnetization, and the component is bonded to the substrate by a bonding layer made of a collection of the ferromagnetic metal nanoparticles in which the ferromagnetic metal nanoparticles are bonded to each other by magnetic attraction and metallic bonding ;
Or,
The metal compound that precipitates a metal upon thermal decomposition is a metal compound that precipitates a ferromagnetic metal consisting of iron, nickel, or cobalt upon thermal decomposition, and the metal compound is used as the metal compound to produce a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound according to the method for producing a paste described above , and the paste is dripped onto a portion where the components come into contact with each other, and then the components are heated to the boiling point of the liquid organic compound described above .
By this process, first, the organic solvent evaporates from the dropped paste, then the organic compound in the liquid evaporates, and then the clusters of ferromagnetic metal nanoparticles dispersed in the paste are activated, and the activated clusters of ferromagnetic metal nanoparticles overlap and precipitate at the site where the paste was dropped, and further, the overlapping and precipitated ferromagnetic metal nanoparticles magnetically attract each other, and the magnetically attracted ferromagnetic metal nanoparticles are metallically bonded at the sites where they come into contact with each other, and a bonding layer consisting of the clusters of metallically bonded ferromagnetic metal nanoparticles is formed at the sites where the components come into contact as a bonding layer in an amount corresponding to the viscosity of the paste.
A magnetic field is then applied to the areas where the parts come into contact, causing the magnetization of the ferromagnetic metal nanoparticles to saturate, and this process causes the metallically bonded ferromagnetic metal nanoparticles to be magnetically attracted to each other due to the saturated magnetization, and the parts are joined by a joining layer consisting of a collection of ferromagnetic metal nanoparticles bonded to each other by magnetic attraction and metallic bonding, in this method of joining parts. A method for joining a part to a substrate, or a method for joining substrates together, or a method for joining parts together, using a paste produced by the method according to claim 1 and a joining layer made of a collection of metal nanoparticles joined by frictional heat, comprises the steps of:
The paste produced by the above -mentioned method is applied to both joining portions where a component is to be joined to a substrate, the component to which the paste has been applied is placed on top of the substrate to which the paste has been applied, and a compressive load is applied to the surface of the component. Thereafter, both the component to which the compressive load has been applied and the substrate are heated to the boiling point of the liquid organic compound, and the application of the compressive load to the surface of the component is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the liquid organic compound evaporates, and then the collection of metal nanoparticles dispersed in the paste is activated, and the activated collection of metal nanoparticles overlap and precipitate at the site where the paste was applied, and further, compressive stress due to the compressive load is applied to the collection of metal nanoparticles that have precipitated and overlap, and the metal nanoparticles come into contact with each other due to the compressive stress, and further, frictional heat is generated at the site where the metal nanoparticles come into contact with each other due to the frictional heat, and the metal nanoparticles are bonded to each other by the frictional heat, and a bonding layer consisting of the collection of metal nanoparticles bonded by the frictional heat is formed at the bonding site as a bonding layer in an amount corresponding to the viscosity of the paste, and the part is bonded to the base material by the bonding layer.
A method for bonding a component to a substrate by means of a bonding layer consisting of a collection of nanoparticles of metal bonded by frictional heat, using a paste produced by the method according to claim 1;
Or,
The paste produced by the above -mentioned method is applied to both joining portions of the substrates to be joined, the joining portions to which the paste has been applied are overlapped, and a compressive load is applied to one of the overlapped substrates. Thereafter, the substrates to which the compressive load has been applied are heated to the boiling point of the liquid organic compound, and the application of the compressive load to the one of the substrates is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the liquid organic compound evaporates, and then the collection of metal nanoparticles dispersed in the paste is activated, and the activated collection of metal nanoparticles overlap and precipitate at the site where the paste was applied, and further, a compressive stress due to the compressive load is applied to the collection of metal nanoparticles that have precipitated and overlap, and the metal nanoparticles come into contact with each other due to the compressive stress, and further, frictional heat is generated at the site where the metal nanoparticles come into contact with each other, and the metal nanoparticles are bonded to each other by the frictional heat, and a bonding layer consisting of the collection of metal nanoparticles bonded by the frictional heat is formed at the bonding site as a bonding layer consisting of an amount corresponding to the viscosity of the paste, and the substrates are bonded to each other by the bonding layer.
A method for bonding substrates with a bonding layer made of a collection of metal nanoparticles bonded by frictional heat, using the paste produced by the method according to claim 1;
Or,
The paste produced by the above -mentioned method is applied to both joining portions of the components to be joined, the joining portions to which the paste has been applied are overlapped, and a compressive load is applied to one of the overlapped components. Thereafter, the components to which the compressive load has been applied are heated to the boiling point of the liquid organic compound, and the application of the compressive load to the one of the components is stopped.
By this process, first, the organic solvent evaporates from the applied paste, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, and the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was applied, and further, compressive stress due to the compressive load is applied to the clusters of metal nanoparticles that have precipitated and overlap, and the compressive stress causes the metal nanoparticles to come into contact with each other, and further, frictional heat is generated at the site where the metal nanoparticles come into contact with each other, and the metal nanoparticles are bonded together by the frictional heat, and a bonding layer consisting of the clusters of metal nanoparticles bonded together by the frictional heat is formed at the bonding site as a bonding layer in an amount corresponding to the viscosity of the paste, and the parts are bonded together by the bonding layer.
A method for joining parts together by using a paste produced by the method according to claim 1, with a joining layer consisting of a collection of metal nanoparticles joined by frictional heat. The method for joining a component to a substrate, or joining substrates together, or joining components together as set forth in claim 5 is a method for joining a component to a substrate, or joining substrates together, or joining components together, by a joining layer made of an assembly of ferromagnetic metal nanoparticles bonded together by magnetic attraction and frictional heat, and the method for joining a component to a substrate, the method for joining substrates together, or the method for joining components together is as follows:
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of any one of iron, nickel, and cobalt upon thermal decomposition, and the metal compound is used as the metal compound, and a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound is produced according to the method for producing a paste described above , the paste is applied to both joining sites where a component is joined to a substrate, the joining site of the component to which the paste has been applied is overlapped with the joining site of the substrate to which the paste has been applied, and a compressive load is applied to the surface of the component, and then both the component to which the compressive load has been applied and the substrate are heated to the boiling point of the liquid organic compound, and further, the application of the compressive load applied to the surface of the component is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the organic compound in the liquid evaporates, and then the collection of ferromagnetic metal nanoparticles dispersed in the paste is activated, the activated collection of ferromagnetic metal nanoparticles overlaps and precipitates at the portion where the paste was applied, the overlapping and precipitated ferromagnetic metal nanoparticles magnetically attract each other, and further, a compressive stress due to the compressive load is applied to the magnetically attracted collection of ferromagnetic metal nanoparticles, and the compressive stress generates frictional heat at the magnetically attracted portions of the ferromagnetic metal nanoparticles, and the ferromagnetic metal nanoparticles are bonded together by the frictional heat, and a bonding layer consisting of the collection of ferromagnetic metal nanoparticles bonded by the frictional heat is formed at the bonding portion.
a method for bonding a component to a substrate, wherein a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is then applied to a portion where the component is superimposed on the substrate, thereby saturating the magnetization of the ferromagnetic metal nanoparticles; by this process, the ferromagnetic metal nanoparticles bonded by the frictional heat are magnetically attracted to each other due to the saturated magnetization, and the component is bonded to the substrate by a bonding layer made of a collection of the ferromagnetic metal nanoparticles that are bonded to each other by magnetic attraction and frictional heat;
Or,
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of iron, nickel, or cobalt upon thermal decomposition, and the metal compound is used as the metal compound, and a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound is produced according to the method for producing a paste described above , the paste is applied to both joining portions of substrates to be joined, the joining portions of the substrates to which the paste has been applied are overlapped, and a compressive load is applied to one of the overlapped substrates, and then the substrates to which the compressive load has been applied are heated to the boiling point of the liquid organic compound, and the application of the compressive load applied to the one of the substrates is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the organic compound in the liquid evaporates, and then the collection of ferromagnetic metal nanoparticles dispersed in the paste is activated, the activated collection of ferromagnetic metal nanoparticles overlaps and precipitates at the portion where the paste was applied, the overlapping and precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and further, a compressive stress due to the compressive load is applied to the magnetically attracted collection of ferromagnetic metal nanoparticles, and the compressive stress generates frictional heat at the magnetically attracted portions of the ferromagnetic metal nanoparticles, and the ferromagnetic metal nanoparticles are bonded to each other by the frictional heat, and a bonding layer consisting of the collection of ferromagnetic metal nanoparticles bonded by the frictional heat is formed at the bonding portion.
a method for joining substrates, comprising: applying a magnetic field to both joining sites of the substrates such that the magnetization of the ferromagnetic metal nanoparticles is saturated, and saturating the magnetization of the ferromagnetic metal nanoparticles; by this treatment, the ferromagnetic metal nanoparticles joined by the frictional heat are magnetically attracted to each other due to the saturated magnetization, and the substrates are joined by a joining layer made of an assembly of the ferromagnetic metal nanoparticles that are joined to each other by magnetic attraction and frictional heat;
Or,
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of any one of iron, nickel, and cobalt upon thermal decomposition, and the metal compound is used as the metal compound, and a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound is produced according to the method for producing a paste described above , the paste is applied to both joining sites where components are to be joined, the joining sites where the paste is applied are overlapped, and a compressive load is applied to one of the overlapped components, and then the temperature of the components to which the compressive load has been applied is raised to the boiling point of the liquid organic compound, and further, the application of the compressive load applied to the one of the components is stopped.
By this treatment, first, the organic solvent evaporates from the applied paste, then the organic compound in the liquid evaporates, and then the collection of ferromagnetic metal nanoparticles dispersed in the paste is activated, the activated collection of ferromagnetic metal nanoparticles overlaps and precipitates at the portion where the paste was applied, the overlapping and precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and further, a compressive stress due to the compressive load is applied to the magnetically attracted collection of ferromagnetic metal nanoparticles, and the compressive stress generates frictional heat at the magnetically attracted portions of the ferromagnetic metal nanoparticles, and the ferromagnetic metal nanoparticles are bonded to each other by the frictional heat, and a bonding layer consisting of the collection of ferromagnetic metal nanoparticles bonded by the frictional heat is formed at the bonding portion.
A magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is then applied to both joining sites where the parts are joined, thereby saturating the magnetization of the ferromagnetic metal nanoparticles; by this process, the ferromagnetic metal nanoparticles joined by the frictional heat are magnetically attracted to each other due to the saturated magnetization, and the parts are joined by a joining layer consisting of a collection of ferromagnetic metal nanoparticles that are joined to each other by magnetic attraction and frictional heat, in this method of joining parts. A method for joining parts together using a paste produced by the method according to claim 1 with a joining layer made of a collection of metal nanoparticles joined by frictional heat, comprising the steps of:
Both joining portions of the parts to be joined are processed into a gap fit, the paste produced by the above- mentioned method is applied to both joining portions processed into the gap fit, one of the parts to which the paste has been applied is inserted into the other part to which the paste has been applied, and the two joining portions to which the paste has been applied are overlapped.
Thereafter, the temperature of the overlapped parts is raised to the boiling point of the liquid organic compound, and one of the overlapped parts is fixed and the other of the overlapped parts is rotated.
By this process, first, the organic solvent evaporates from the applied paste, then the liquid organic compound evaporates, and then the clusters of metal nanoparticles dispersed in the paste are activated, and the activated clusters of metal nanoparticles overlap and precipitate at the site where the paste was applied, and then the overlapping and precipitated metal nanoparticles are metallically bonded at the sites where they come into contact with each other, and then shear stress generated by rotating the other part is applied to the clusters of metallically bonded metal nanoparticles, and frictional heat is generated at the joints between the metallically bonded metal nanoparticles due to the shear stress, and the metallically bonded metal nanoparticles are bonded together due to the frictional heat, and the parts are bonded together by a bonding layer consisting of the clusters of metallic nanoparticles bonded by the frictional heat.
A method for joining parts together by using a paste produced by the method according to claim 1, with a joining layer consisting of a collection of metal nanoparticles joined by frictional heat. The method for joining components according to claim 7 is a method for joining components by a joining layer made of a collection of ferromagnetic metal nanoparticles joined together by magnetic attraction and frictional heat, and the method for joining components comprises:
The metal compound is a metal compound that precipitates a ferromagnetic metal consisting of any one of iron, nickel, and cobalt upon thermal decomposition, and the metal compound is used as the metal compound, and a paste consisting of a collection of nanoparticles consisting of a ferromagnetic metal dispersed in an organic compound is produced according to the method for producing a paste described above , and the paste is applied to both joining portions of parts that are joined together and processed into a gap fit, one of the parts to which the paste has been applied is inserted into the other part to which the paste has been applied, and the two joining portions to which the paste has been applied are overlapped.
Thereafter, the temperature of the overlapped parts is raised to the boiling point of the liquid organic compound, and one of the overlapped parts is fixed and the other of the overlapped parts is rotated.
By this treatment, first, the organic solvent evaporates from the applied paste, then the organic compound in the liquid evaporates, and then the clusters of ferromagnetic metal nanoparticles dispersed in the paste are activated, the activated clusters of ferromagnetic metal nanoparticles overlap and precipitate at the site where the paste was applied, the overlapping and precipitated ferromagnetic metal nanoparticles are magnetically attracted to each other, and further, a shear stress generated by rotating the other part is applied to the magnetically attracted clusters of ferromagnetic metal nanoparticles, and the shear stress generates frictional heat at the magnetic attraction sites where the ferromagnetic metal nanoparticles are magnetically attracted to each other, and the frictional heat further bonds the magnetically attracted ferromagnetic metal nanoparticles to each other.
Thereafter, a magnetic field that saturates the magnetization of the ferromagnetic metal nanoparticles is applied to both joining sites where the parts are joined, and the magnetization of the ferromagnetic metal nanoparticles is saturated. Through this process, the ferromagnetic metal nanoparticles joined by the frictional heat are magnetically attracted to each other due to the saturated magnetization, and the parts are joined by a joining layer made of an assembly of the ferromagnetic metal nanoparticles that are joined to each other by magnetic attraction and frictional heat.
A method for joining parts together using a paste produced by the method described in claim 1, with a joining layer consisting of a collection of ferromagnetic metal nanoparticles bonded together by magnetic attraction and frictional heat . The method for producing the paste in which a collection of metal nanoparticles is dispersed in an organic compound according to claim 1 includes the steps of:
the metal compound which precipitates a metal by thermal decomposition is an inorganic metal compound composed of an inorganic salt having a metal complex ion in which an inorganic molecule or an inorganic ion acts as a ligand and is coordinately bonded to a metal ion, the liquid organic compound is an organic compound belonging to a primary alcohol having 8 to 10 carbon atoms, and the organic solvent is diethyl ether, acetone, or ethanol,
a paste is produced according to the method for producing a paste, using the inorganic metal compound as the metal compound that precipitates a metal by thermal decomposition, using the organic compound belonging to the primary alcohol having 8 to 10 carbon atoms as the liquid organic compound, and using the diethyl ether, acetone, or ethanol as the organic solvent;
A method for producing a paste in which the collection of metal nanoparticles according to claim 1 is dispersed in an organic compound. The method for producing the paste in which a collection of metal nanoparticles is dispersed in an organic compound according to claim 1 includes the steps of:
the metal compound that precipitates a metal by thermal decomposition is a metal octylate compound, the liquid organic compound is tetraethylene glycol, and the organic solvent is either ethanol or acetone;
a paste is produced according to the method for producing a paste, using the metal octylate compound as the metal compound that precipitates a metal by thermal decomposition, using the tetraethylene glycol as the liquid organic compound, and using either the ethanol or the acetone as the organic solvent;
A method for producing a paste in which the collection of metal nanoparticles according to claim 1 is dispersed in an organic compound.