JP7574773B2 - Metal particle-containing composition, joining paste, joined body, and method for producing joined body - Google Patents

Description

The present invention relates to a metal particle-containing composition, a bonding paste, a bonded body, and a method for manufacturing the bonded body.

Conventionally, solder has been used as a bonding material for bonding metal members together, between metal members and semiconductor elements, between metal members and light-emitting diode (LED) elements, etc. In recent years, in the field of next-generation power electronics technology, there has been a demand for devices such as SiC that can operate at high temperatures. As a bonding material for manufacturing such devices, there is a demand for alternative materials to solder from the viewpoint of high-temperature operating reliability. For example, bonding materials such as bonding pastes using sinterable metal particles as shown in Patent Documents 1 to 4 have been proposed.

Patent Document 1 discloses a bonding material that contains metal submicron particles with an average primary particle size of 0.5 to 3.0 μm and metal nanoparticles with an average primary particle size of 1 to 200 nm that are coated with an organic compound with 6 to 8 carbon atoms. However, there is a problem in that the bonding strength at the bonded portion is poor, and the bonding strength decreases with thermal cycles.

Patent Document 2 discloses a bonding material that contains silver nanoparticles with an average primary particle size of 1 to 200 nm that are coated with an organic substance having 8 or less carbon atoms, and a flux component that has at least two carboxyl groups. In addition, Patent Document 3 discloses a bonding material that contains silver fine particles with an average primary particle size of 130 nm or less, and a cross-linked interparticle distance maintaining agent that maintains the distance between the silver fine particles.

Patent Document 4 discloses a bonding material that contains metal particles including metal nanoparticles with an average particle size of 2 to 200 nm, a specific polyamide having a phenolic hydroxyl group on the side chain and a hydrocarbon group with 20 to 60 carbon atoms, and a trifunctional or higher compound that can react with the phenolic hydroxyl group.

However, the bonding materials described in Patent Documents 1 to 4 have the problem that defects such as voids (air gaps) are formed in the bonded portion, resulting in poor strength at the bonded portion and a decrease in bond strength with thermal cycles. Furthermore, when a bonding paste containing a high concentration of silver nanoparticles is created to achieve a dense and strong bond, it has the drawback of significantly poor fluidity. As a result, in the process of printing the bonding paste on the bonded portion, there are problems such as fading of the printed portion and the occurrence of portions that cannot be coated (the formation of uncoated portions).

JP 2011-80147 A JP 2011-240406 A JP 2018-109232 A JP 2017-137375 A

The problem that the present invention aims to solve is to provide a metal particle-containing composition that provides high bonding strength at the bonded portion and suppresses a decrease in bonding strength due to thermal cycling. In addition to the above characteristics, the present invention also aims to provide a bonding paste that has excellent printability for the bonded portion even if it contains a high concentration of metal particles. Furthermore, the present invention aims to provide a bonded body that does not deteriorate due to long-term thermal cycling of 1,000 cycles or more.

The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention.
That is, the present invention relates to a metal particle-containing composition comprising metal particles (A) having an average particle size of 1 nm to 1000 nm, a polyvalent fatty acid (B), and a polyamine (C).

The present invention also relates to the above metal particle-containing composition, in which the polyvalent fatty acid (B) has 20 to 80 carbon atoms and the polyamine (C) has 20 to 80 carbon atoms.

The present invention also relates to the above metal particle-containing composition, in which the polyvalent fatty acid (B) contains a divalent and/or trivalent fatty acid.

The present invention also relates to the above metal particle-containing composition, in which the polyamine (C) contains a diamine and/or a triamine.

The present invention also relates to the above metal particle-containing composition, in which the polyvalent fatty acid (B) and/or the polyamine (C) have a branched and/or cyclic structure.

The present invention also relates to the above metal particle-containing composition, in which the polyvalent fatty acid (B) has an m-valent hydrocarbon group (D) or the polyamine (C) has an n-valent hydrocarbon group (E), where the valence of the polyvalent fatty acid (B) is m and the valence of the polyamine (C) is n.

The present invention also relates to the above metal particle-containing composition, in which the carbon number of the m-valent hydrocarbon group (D) and/or the carbon number of the n-valent hydrocarbon group (E) is 30 to 60.

The present invention also relates to the above metal particle-containing composition, which contains 0.05 to 1 part by mass of polyvalent fatty acid (B) and/or 0.05 to 1 part by mass of polyamine (C) per 100 parts by mass of metal particles (A).

The present invention also relates to the above metal particle-containing composition, which contains 0.1 to 0.5 parts by mass of polyvalent fatty acid (B) and/or 0.1 to 0.5 parts by mass of polyamine (C) per 100 parts by mass of metal particles (A).

The present invention also relates to the above metal particle-containing composition, in which the average particle size of the metal particles (A) is 180 nm to 400 nm.

The present invention also relates to the above metal particle-containing composition, in which the average particle size of the metal particles (A) is 200 nm to 300 nm.

The present invention also relates to a joining paste containing the above metal particle-containing composition and a dispersion medium (F).

The present invention also relates to the above-mentioned joining paste, in which the mass ratio of the metal particles (A) to the sum of the masses of the metal particles (A), the polyvalent fatty acid (B), the polyamine (C), and the dispersion medium (F) is 80% by mass to 95% by mass.

The present invention also relates to a bonded body in which a first bonded part and a second bonded part are bonded via a bonding layer, the bonding layer being a layer formed from the bonding paste.

The present invention also relates to a method for producing a bonded body in which a first bonded part and a second bonded part are bonded via a bonding layer, the method comprising the steps of applying a bonding paste containing metal particles (A) having an average particle size of 1 nm to 1000 nm, a polyvalent fatty acid (B), a polyamine (C), and a dispersion medium (F) to the first bonded part, placing the second bonded part on the paste, and sintering the bonded part.

The present invention makes it possible to provide a metal particle-containing composition that provides high bonding strength at the bonded portion and that does not decrease with long-term thermal cycles, and a bonding paste that, in addition to these effects, also has excellent printability. It also makes it possible to provide a bonded body that does not deteriorate with thermal cycles.

The metal particle-containing composition of the present invention contains metal particles (A) having an average particle size of 1 nm to 1000 nm, a polyvalent fatty acid (B), and a polyamine (C). The bonding paste of the present invention contains a dispersion medium (F) in addition to the metal particle-containing composition. The metal particle-containing composition may be formed by volatilizing a part or all of the dispersion medium (F) from the bonding paste during the bonding process.
In this specification, "metal particles (A) having an average particle size of 1 nm to 1000 nm" may be abbreviated as "metal particles (A)".

The metal particles (A) are within a specific average particle size range, so that when heated or sintered, the particles melt or bond together (hereinafter also referred to as sintering), turning into bulk metal. As a result, the parts to be joined can be joined together. Hereinafter, the area formed by sintering the metal particle-containing composition present between the parts to be joined will be referred to as the joining layer.

In addition, since the joining paste of the present invention contains polyhydric fatty acid (B) and polyamine (C), a joining layer with fewer defects such as voids (gaps) is obtained during sintering, so it is presumed that the joining strength of the joined parts is high and that the decrease in the joining strength is suppressed even after long-term thermal cycles.

There are no particular limitations on the temperature at which the metal particle-containing composition or bonding paste is sintered, but it is generally sintered at 200°C to 350°C. Sintering causes dehydration condensation of the polyvalent fatty acid (B) and polyamine (C), and in the later stages of the sintering time, polyamide is formed in the bonding layer by dehydration condensation of the polyvalent fatty acid (B) and polyamine (C). Therefore, even if organic matter remains in the bonding layer produced, it is believed that volatilization is suppressed by polymerization, and heat resistance is improved. As a result, it is believed that the decrease in bonding strength due to long-term thermal cycle testing is suppressed.

<Metal Particles (A)>
Examples of the metal in the metal particles (A) include gold, silver, copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molybdenum, platinum, and alloys thereof. In addition, fine particles coated with a core and a material different from the core material, specifically, for example, silver-coated copper powder in which copper is used as the core and its surface is coated with silver, can be mentioned. In addition, powders of metal oxides such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, ITO (tin-doped indium oxide), AZO (aluminum-doped zinc oxide), and GZO (gallium-doped zinc oxide), as well as powders surface-coated with these metal oxides, can be mentioned. The type of metal used may be one type, or two or more types may be used in combination.

The metal particles (A) are preferably selected from copper or silver, since a bonded body having particularly excellent strength can be obtained. Furthermore, the metal particles (A) are more preferably silver, since it can be used at a wide range of firing temperatures and in various firing environments such as atmospheric pressure, a nitrogen atmosphere, a vacuum, or a reducing atmosphere.

In the present invention, it is important to use metal particles (A) having a specific average particle size. In this specification, "average particle size" means the 50% cumulative particle size distribution particle size (d50) on a volume basis determined by the measurement method described in the Examples. The d50 of metal particles (A) is 1 to 1000 nm, preferably 180 to 400 nm, and more preferably 200 to 300 nm.

The metal particles (A) are preferably coated on the surface with an organic component (a). Coating with the organic component (a) is expected to increase the storage stability of the metal particle-containing composition and the bonding paste. Examples of the organic component (a) include fatty acids, aliphatic amines, and aliphatic alcohols, and are preferably saturated or unsaturated fatty acids, more preferably saturated or unsaturated fatty acids having 3 to 18 carbon atoms, and even more preferably saturated or unsaturated fatty acids having 6 to 18 carbon atoms. The organic component (a) may contain one or more types.

Metal particles (A) may be used alone or in combination. If necessary, metal particles other than metal particles (A) may be used in combination. In that case, it is preferable to use a combination of metal particles having an average particle size of more than 1000 nm.

<Polyvalent fatty acids (B)>
Next, the polyvalent fatty acid (B) will be described. The polyvalent fatty acid (B) refers to a compound having a plurality of carboxy groups in the molecule and having a hydrocarbon as a basic skeleton. The number of carbon atoms in the polyvalent fatty acid (B) is preferably 20 to 80. The number of carbon atoms in the polyvalent fatty acid (B) includes the carboxy carbon in the molecule as the number of carbon atoms in the polyvalent fatty acid (B).

The polyvalent fatty acid (B) is thought to have the effect of maintaining the metal particle-containing composition in a fluid liquid state during sintering, and is presumed to increase the wettability at the bonding interface with the parts to be bonded. Therefore, even if voids occur in the bonding layer, it is thought that the liquid will flow into the defective parts, making it possible to obtain a bonding layer with few defects and high bonding strength.

The properties of the polyvalent fatty acid (B) are not particularly limited, but it is preferably liquid at 200°C to 350°C, which is the normal temperature range in which the metal particle-containing composition of the present invention is fired. The polyvalent fatty acid (B) may be solid or liquid at room temperature (25°C), but it is more preferably liquid at room temperature, so that it can be uniformly dispersed in the metal particle-containing composition and act effectively.

The valence of the polyvalent fatty acid (B), i.e., the number of carboxy groups, is preferably 2 or 3.

The polyvalent fatty acid (B) may have a linear structure or a branched and/or cyclic structure, but preferably has a branched and/or cyclic structure. If it has a branched and/or cyclic structure, it is preferable because it tends to be a liquid with low crystallinity and good fluidity. In addition, a branched and/or cyclic structure is preferable because the flexibility of the polyamide formed from the polyvalent fatty acid (B) and the polyamine (C) is increased, which leads to an improvement in bonding strength and suppression of a decrease in strength.

When the valence of the polyvalent fatty acid (B) is m, it is preferable that the polyvalent fatty acid (B) has a hydrocarbon group (D) with a valence of m. It is more preferable that the skeleton of the polyvalent fatty acid (B) excluding the carboxyl group consists only of hydrocarbons with a valence of m.

When the m-valent hydrocarbon group (D) has 30 to 60 carbon atoms, this is more preferable since the initial and post-cycle bond strengths are particularly high.

Specific examples of polyvalent fatty acids (B) with a linear structure include, but are not limited to, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosane dioic acid, heneicosane dioic acid, docosane dioic acid, tetracosane dioic acid, triacontanedioic acid, dotriacontanedioic acid, tetracontanedioic acid, pentacontanedioic acid, and hexacontanedioic acid.

In addition, examples of branched and/or cyclic structures include, but are not limited to, methylmalonic acid, dimer acid, trimer acid, tetramer acid, etc.

Among these specific examples, it is more preferable that the polyvalent fatty acid (B) contains a dimer acid and/or a trimer acid.

Dimer acid, trimer acid and tetramer acid can be produced by a polymerization reaction of unsaturated fatty acids. For example, they can be produced by a Diels-Alder reaction between oleic acid (having 18 carbon atoms) and linoleic acid (having 18 carbon atoms) or a radical reaction. The dimer acid, trimer acid and tetramer acid preferably have 36, 44, 54 and 72 carbon atoms, respectively. In addition, by appropriately changing the carbon number of the unsaturated fatty acid used as the raw material, it is possible to produce a polyvalent fatty acid (B) having a carbon number other than the above.
In this specification, dimers, trimers and tetramers of unsaturated fatty acids having 12 or more carbon atoms are referred to as dimer acid, trimer acid and tetramer acid, respectively.

Due to the manufacturing process, polyvalent fatty acid (B) may be a mixture of compounds with different degrees of polymerization, but it may be used as a mixture of different polymers or as a specific single compound.

<Polyamine (C)>
Next, polyamine (C) will be described. Polyamine (C) means a compound having a plurality of amino groups ( _-NH2 groups) in the molecule. The number of carbon atoms of polyamine (C) is preferably 20 to 80.

In the polyamine (C), the skeleton (partial structure) excluding the amino group is an organic residue, but is preferably a hydrocarbon group or a group in which the hydrocarbon group is bonded via a linking group which may contain a heteroatom. Examples of linking groups containing such heteroatoms include -O- group (ether group), -C(=O)- group (carbonyl group), -C(=O)-O- group (also called ester group or oxycarbonyl group), and -C(=O)-NH- group (also called amide group or iminocarbonyl group). Arylene groups such as phenylene group and naphthylene group are also included in the linking group.

Like the polyvalent fatty acid (B), the polyamine (C) is thought to have the effect of maintaining the metal particle-containing composition in a fluid liquid state during sintering, and is presumed to increase the wettability at the bonding interface with the parts to be bonded. Therefore, even if voids occur in the bonding layer, the metal particles will flow into the defective parts, making it possible to obtain a bonding layer with few defects and high bonding strength.

The properties of the polyamine (C) are not particularly limited, but it is preferably liquid at 200°C to 350°C, which is the normal temperature range in which the metal particle-containing composition of the present invention is fired. The polyamine (C) may be solid or liquid at room temperature (25°C), but it is more preferably liquid at room temperature, so that it can be uniformly dispersed in the metal particle-containing composition and act effectively.

The number of amino groups (-NH ₂ ) in the polyamine (C) is preferably 2 or 3. The polyamine (C) preferably contains a diamine and/or a triamine.

The polyamine (C) may have a linear structure or a branched and/or cyclic structure, but preferably has a branched and/or cyclic structure. If it has a branched and/or cyclic structure, it is preferable in that it has low crystallinity and tends to become a liquid with good fluidity.

When the number of amino groups (-NH ₂ ) in polyamine (C) is n, polyamine (C) preferably has an n-valent hydrocarbon group (E). In polyamine (C), the skeleton excluding the amino groups (-NH ₂ ) is more preferably composed of only n-valent hydrocarbons. It is more preferable that the carbon number of the n-valent hydrocarbon group (E) is 30 to 60, since this particularly increases the initial bonding strength and the bonding strength after the cycle test.

Among the polyamines (C), examples of polyamines having a linear structure include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,9-nonanediamine, and 1,12-diaminododecane, and examples of polyamines having a branched and/or cyclic structure include metaxylenediamine, isophoronediamine, norbornanediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 4,4'-diaminodicyclohexylmethane, and piperazine. In addition, dimer diamine, trimer triamine, and tetramer tetramine are also included in the polyamines (C). Among these specific examples, it is more preferable that the polyamine (C) contains dimer diamine and/or trimer triamine.

In addition, dimer diamine has a structure in which the carboxy group of dimer acid, trimer triamine has a structure in which the carboxy group of trimer acid, and tetramer tetramine has a structure in which the carboxy group of tetramer acid are converted to an amino group. It is preferable that the carbon numbers of dimer diamine, trimer triamine, and tetramer tetramine are 36, 54, and 72, respectively.

The combination of polyvalent fatty acid (B) and polyamine (C) is not limited, but it is more preferable that the polyvalent fatty acid (B) contains a dimer acid and/or a trimer acid, and the polyamine (C) contains a dimer diamine and/or a trimer triamine.

In the metal particle-containing composition of the present invention, the amount of polyvalent fatty acid (B) is preferably 0.05 parts by mass to 1 part by mass, and more preferably 0.1 parts by mass to 0.5 parts by mass, per 100 parts by mass of metal particles (A). The amount of polyamine (C) is preferably 0.05 parts by mass to 1 part by mass, and more preferably 0.1 parts by mass to 0.5 parts by mass, per 100 parts by mass of metal particles (A). This range of amounts is preferable in that it is expected that the fluidity during sintering will increase, making it easier to obtain a bonded body with excellent initial and long-term cycle resistance.

The blending ratio of polyhydric fatty acid (B) and polyamine (C) is not limited, but in terms of facilitating the formation of polyamide, the mass ratio of polyhydric fatty acid (B)/polyamine (C) is preferably 0.1/0.9 to 0.9/0.1, and more preferably 0.3/0.7 to 0.7/0.3.

<Dispersion medium (F)>
The bonding paste of the present invention contains a dispersion medium (F). The dispersion medium (F) serves to disperse the metal particles (A), the polyvalent fatty acid (B), and the polyamine (C).
The dispersion medium (F) may be any medium capable of dispersing the metal particles (A), polyvalent fatty acid (B), and polyamine (C). Specific examples include terpineol, dihydroterpineol, dihydroterpinyl acetate, Tersolve MTPH (manufactured by Nippon Terpene Co., Ltd.), Texanol (2,2,4-trimethylpentane-1,3-diol monoisobutyrate), carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyl lactone, dipropylene glycol monomethyl ether, dipropylene glycol methyl-n-propyl ether, 3-methoxy-3-methylbutyl acetate, ethylene glycol, hexanoic acid, propylene glycol diacetate, dipropylene glycol methyl ether acetate, 1,3-butylene glycol, and isoparaffin-based solvents contained in hydrocarbon-based solvents, but are not limited thereto.

Of these dispersion media (F), terpineol, dihydroterpineol, tersolve MTPH, texanol, carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyrolactone, dipropylene glycol monomethyl ether, and isoparaffin-based solvents are more preferably used. These dispersion media (F) can be used alone or in combination.

The joining paste of the present invention contains polyvalent fatty acid (B) and polyamine (C) and is therefore capable of forming a joining interface with good adhesion to the parts to be joined even after some or all of the dispersion medium (F) has evaporated.

The bonding paste of the present invention uses a combination of metal particles (A), polyvalent fatty acid (B), and polyamine (C), and has excellent fluidity even when it contains a high concentration of metal particles (A), i.e., when the content ratio of dispersion medium (F) is low, so it has excellent printability for the parts to be bonded. Furthermore, compared to the case where polyamide resin is added, the bonding paste of the present invention does not have the risk of the compatibility of the components decreasing, resulting in non-uniformity, or loss of fluidity. As a result, it is possible to obtain a stronger bonded body with fewer defects.

In the bonding paste, the mass ratio of the metal particles (A) to the sum of the masses of the metal particles (A), polyvalent fatty acid (B), polyamine (C), and dispersion medium (F) is preferably 80% by mass to 95% by mass, and more preferably 85% by mass to 94% by mass. By including the above range, good printability of the bonding paste can be ensured. Furthermore, by including the above range, the residual dispersion medium (F) in the bonded body can be suppressed, and voids originating from the dispersion medium (F) are less likely to occur, so that good bonding strength can be achieved.

<Other ingredients>
The bonding paste of the present invention may further contain other components such as additives, etc. Examples of the other components include a sintering accelerator, a binder resin, and a dispersant such as a low molecular weight dispersant or a resin type dispersant.
The dispersant that may be contained in the bonding paste of the present invention is preferably a low molecular weight dispersant having a molecular weight of 150 to 600, and more preferably an unsaturated fatty acid having 18 to 22 carbon atoms or an unsaturated fatty acid amide having 18 to 22 carbon atoms. The unsaturated fatty acid is a monovalent fatty acid having an unsaturated bond, and specific examples thereof include oleic acid, elaidic acid, linoleic acid, linolenic acid, ricinoleic acid, erucic acid, and the like. The unsaturated fatty acid amide is a monovalent fatty acid amide having an unsaturated bond, and specific examples thereof include oleamide (oleic acid amide), erucic acid amide, and the like. By containing these dispersants, the metal particles (A) in the bonding paste are more uniformly loosened, and a strong bonded body with less void bias can be obtained, which is preferable.
The amount of the low molecular weight dispersant is not limited, but in order to achieve both good dispersion of the metal particles (A) and densification of the bonding layer, the amount is preferably 0.1 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, and even more preferably 0.2 to 2 parts by mass, relative to 100 parts by mass of the metal particles (A).

Examples of devices for preparing a joining paste from metal particles (A), compound (B), and dispersion medium (C) include a disperser, a three-roll mill, a bead mill, an ultrasonic disperser, and a self-rotating mixer.

<Joint>
The bonding paste of the present invention can bond a first bonded part and a second bonded part to obtain a bonded body. In detail, the bonded body of the present invention is a bonded body in which a first bonded part and a second bonded part are bonded via a bonding layer, and the bonded body can be produced by a production method including a step of applying a bonding paste containing metal particles (A) having an average particle size of 1 nm to 1000 nm, a polyvalent fatty acid (B), a polyamine (C), and a dispersion medium (F) to the first bonded part, placing the second bonded part on the bonding paste, and sintering the applied paste.
The method of applying the bonding paste to the bonded portion is not particularly limited as long as it can be applied uniformly to the member. For example, various printing methods such as screen printing, flexographic printing, offset printing, gravure printing, metal mask printing, gravure offset printing, and the like, and a discharge method using a dispenser, etc. are included. Since the bonding paste of the present invention has excellent fluidity even when it contains metal particles at a high concentration, it is particularly preferable to use it in combination with metal mask printing.

When placing the second part to be joined on the first part to be joined coated with the joining paste of the present invention, pressure can be applied during the placement. The pressure is set appropriately depending on the viscosity of the joining paste and the drying state of the paste, but is preferably 0.1 to 40 MPa, and more preferably 0.3 to 30 MPa.

The sintering conditions for joining a laminate in which a second bonded portion is placed on a first bonded portion may be changed as appropriate, but may include, for example, conditions such as atmospheric pressure, a nitrogen atmosphere, a vacuum, or a reducing atmosphere at 200 to 350°C. As the sintering device, a hot air oven, an infrared oven, a reflow oven, a microwave oven, a hot plate, an optical sintering device, etc. may be used alone or in combination as appropriate. Pressure may also be applied during sintering. The pressure is set as appropriate depending on the viscosity of the bonding paste and the drying state of the paste, but is preferably 0.1 to 40 MPa, more preferably 0.3 to 30 MPa.

Before the firing process, a preliminary drying process can be carried out as appropriate to remove organic components from the bonded coating film. For example, a pre-drying process can be carried out using a device similar to the firing device under conditions ranging from 60 to 220°C.

A preferred method for joining two parts to be joined is to apply the joining paste of the present invention to the first part to be joined, place the second part to be joined on it, and heat it up to about 300°C at a heating rate of about 2°C/min to perform sintering. After the heating is complete, it is preferable to maintain the temperature higher than the temperature at the end of the heating for about 10 minutes to 2 hours.

The type of the parts to be joined is not particularly limited, and examples include metal materials, semiconductor materials, plastic materials, ceramic materials, etc. Also included are electronic elements.

Examples of the metal include copper, gold, and aluminum.
Examples of semiconductor materials include silicon, germanium, gallium arsenide, gallium phosphide, cadmium sulfide, silicon nitride, graphite, yttrium oxide, magnesium oxide, silicon carbide, gallium nitride, and gallium oxide.
Examples of the plastic material include polyimide, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, and polyethylene naphthalate.
Examples of the ceramic material include glass and silicon.
Examples of the electronic element include a semiconductor element, an LED element, and a power device element.

The first and second joined parts may be of different types, not just the same type. The surfaces of the joined parts may be corona-treated, plated, or otherwise treated to increase the joining strength of the joined parts.

There is no limit to the thickness of the bonding layer formed when bonding parts using the metal particle-containing composition or bonding paste of the present invention, but it is preferably 3 μm to 500 μm, more preferably 10 μm to 200 μm, and even more preferably 20 μm to 100 μm.

The present invention will be described in detail below using examples and comparative examples, but the technical scope of the present invention is not limited thereto. In the examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass", and the numerical values in the tables mean "parts" unless otherwise specified.

<Production of Metal Particles>
(Production Example 1) Metal particles A1
Under a nitrogen atmosphere, 200 parts of toluene and 22.3 parts of silver hexanoate were mixed while stirring at 25 ° C. to obtain a 0.5 M solution, and then 1.6 parts of diethylaminoethanol and 0.28 parts of oleic acid were added as a dispersant and dissolved. Then, 73.1 parts of a 20% aqueous solution of succinic acid dihydrazide (hereinafter, SUDH) was dropped as a reducing agent, and the liquid color changed from light yellow to dark brown. In order to further promote the reaction, the temperature was raised to 40 ° C., and the reaction was allowed to proceed. After standing and separating, the aqueous phase was removed to remove excess reducing agent and impurities, and distilled water was added to the toluene layer several times, washing and separation were repeated, and then the process of adding toluene, centrifuging, and removing the supernatant was repeated twice. The precipitate was dried to obtain metal particles A1 in which silver particles were coated with hexanoic acid and oleic acid. The particle size of metal particles A1 was determined by the method described below, and d50 was 210 nm.

(Production Example 2) Metal particles A2
Metal particles A2 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 1.8 parts and the amount of oleic acid was 0.31 parts. The d50 was 185 nm.
(Production example 3) Metal particles A3
Metal particles A3 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 1.2 parts and the amount of oleic acid was 0.18 parts. The d50 was 290 nm.
(Production Example 4) Metal particles A4
Metal particles A4 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 1.0 part and the amount of oleic acid was 0.14 part. The d50 was 390 nm.
(Production Example 5) Metal particles A5
Metal particles A5 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 2.1 parts and the amount of oleic acid was 0.71 parts. The d50 was 85 nm.
(Production Example 6) Metal particles A6
Metal particles A6 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 0.6 parts and the amount of oleic acid was 0.070 parts. The d50 was 1100 nm.
Among the metal particles produced by the above method, metal particles A1 to A5 correspond to metal particles (A), and metal particle A6 corresponds to metal particles other than metal particles (A).

[Measurement of particle size]
Isopropyl alcohol was added to each metal particle (A) and dispersed in an ultrasonic disperser to obtain a 0.5% by mass dispersion. The particle size of the metal particle (A) in the obtained dispersion was measured using Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.) to determine the average particle size (d50).

[Fatty acids, amines and other components]
The fatty acids, amines, and other materials used in the examples and comparative examples are as follows. The number of carbon atoms, material name, and properties at 25°C are shown in parentheses. Of the following, Pripol and Priamine were manufactured by Croda Japan Co., Ltd., oleic acid amide was a reagent manufactured by Tokyo Chemical Industry Co., Ltd., and the other materials were reagents manufactured by Sigma-Aldrich. Fatty acids B1 to B3, B5, and B6 correspond to polyvalent fatty acids (B), and amines C1 to C3 correspond to polyamines (C). Fatty acid B4 and fatty acid amide G1 correspond to dispersants that may be added to the present invention.

Fatty acid B1: Pripol 1009 (a hydrogenated dimer acid having 36 carbon atoms, consisting of two carboxyl groups and a divalent hydrocarbon group having a branched and cyclic structure. A liquid polyvalent fatty acid)
Fatty acid B2: Pripol 1040 (a trimer acid having 54 carbon atoms, consisting of three carboxyl groups and a trivalent hydrocarbon group having a branched and cyclic structure. A liquid polyvalent fatty acid)
Fatty acid B3: Straight-chain dibasic acid (22 carbon atoms, docosane diacid, consisting of two carboxy groups and a divalent hydrocarbon having a straight-chain structure. A solid polyvalent fatty acid)
Fatty acid B4: Oleic acid (a monovalent straight-chain fatty acid with 18 carbon atoms. A liquid monounsaturated fatty acid)
Fatty acid B5: Malonic acid (a straight-chain dibasic acid having 3 carbon atoms. A solid polyvalent fatty acid)
Fatty acid B6: Pripol 1004 (a hydrogenated dimer acid having 44 carbon atoms, consisting of two carboxyl groups and a divalent hydrocarbon group having a branched and cyclic structure. A liquid polyvalent fatty acid)
Amine C1: Priamine 1071 [a mixture of a dimer diamine having 36 carbon atoms (a liquid polyamine consisting of two amino groups and a divalent hydrocarbon group having a branched and cyclic structure) and a trimer triamine having 54 carbon atoms (a liquid polyamine consisting of three amino groups and a trivalent hydrocarbon group having a branched and cyclic structure)]
Amine C2: Priamine 1075 (a dimer diamine having 36 carbon atoms, consisting of two amino groups and a divalent hydrocarbon group having a branched and cyclic structure. A liquid polyamine)
Amine C3: 1,12-diaminododecane (a solid polyamine having 12 carbon atoms, two amino groups, and a divalent hydrocarbon group having a linear structure)
Amine C4: Oleylamine (a monovalent linear monoamine having 18 carbon atoms; liquid)
Fatty acid amide G1: Oleic acid amide (solid monounsaturated fatty acid amide)

(Production Example 7) Polyamide containing phenolic hydroxyl groups (Polyamide P1)
Polyamide P1 was synthesized as follows with reference to JP 2017-137375 A. A four-neck flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, inlet tube, and thermometer was charged with 202.9 g of Pripol 1009 (0.35 mol in terms of dibasic acid), 25.7 g (0.14 mol) of 5-hydroxyisophthalic acid, 35.1 g (0.21 mol) of terephthalic acid, 313.9 g (0.59 mol in terms of diamine) of Priamine 1074 (manufactured by Croda Japan Co., Ltd.) as a polyamine compound having 36 carbon atoms, and 100 g of water, and stirred until the temperature of the heat generation became constant. When the temperature stabilized, the temperature was raised to 110 ° C., and after confirming the outflow of water, the temperature was raised to 120 ° C. after 30 minutes, and the dehydration reaction was continued while raising the temperature by 10 ° C. every 30 minutes. When the temperature reached 230° C., the reaction was continued at that temperature for 3 hours, and then the mixture was held under a vacuum of about 2 kPa for 1 hour and then allowed to cool, yielding polyamide P1 containing phenolic hydroxyl groups and having a weight average molecular weight of 9,800.

(Production Example 8) Polyamide containing phenolic hydroxyl groups (Polyamide P2)
A polyamide P2 containing a phenolic hydroxyl group and having a weight average molecular weight of 11,700 was obtained in the same manner as in Production Example 7, except that 202.9 g of Pripol 1009 (0.35 mol in terms of dibasic acid) was replaced with 243.1 g of Pripol 1004 (0.35 mol in terms of dibasic acid).

[Dispersion medium (F)]
The following materials were used as the dispersion medium (F). The manufacturer's name and supplementary information are given in parentheses.
Dispersion medium F1: Dihydroterpineol (manufactured by Nippon Terpene Chemical Co., Ltd.)
Dispersion medium F2: Isobornylcyclohexanol (manufactured by Nippon Terpene Chemical Co., Ltd.)
Dispersion medium F3: Isopar L (manufactured by Ando Parachemie Co., Ltd.)
Dispersion medium F4: Texanol (manufactured by Tokyo Chemical Industry Co., Ltd., reagent)

<Production of bonding paste>
[Example 1]
Metal particles A1 (92 parts), dihydroterpineol (8 parts), fatty acid B1 (0.15 parts), and amine C2 (0.15 parts) were mixed using a rotary stirrer to prepare a bonding paste. Then, a bonded body was produced and evaluated by the method described below. The results are shown in Table 1.

[Examples 2 to 39], [Comparative Examples 1 to 8]
A bonding paste and a bonded body were obtained and then evaluated in the same manner as in Example 1, except that the types and amounts of materials were changed according to the compositions shown in Table 1. The results are shown in Table 1.

<Evaluation of bonding paste>
[Preparation of Joint]
Each joining paste was printed once on the plated surface of the joining part 1 described below under the printing conditions described below, and then the plated surface of the joining part 2 (chip) described below was placed facing the joining paste surface and heated under the sintering conditions described below to obtain each joining body.
<Jointed part 1>
Gold-plated copper substrate: 20 x 20 x 3 mm
<Jointed part 2>
・Gold-plated SiC chip: 5 x 5 x 0.3 mm
<Printing conditions (metal mask printing)>
Metal mask: opening 4 mm square, plate thickness 50 μm (manufactured by Ceria Corporation)
Metal squeegee: 40 mm x 250 mm, thickness 1 mm (manufactured by Ceria Corporation) <Sintering conditions>
The unsintered bonded body was placed in a hot air oven, and the temperature was raised from 25° C. to 300° C. at a rate of 2° C./min. After reaching 300° C., the bonded body was held at 300° C. for 2 hours.
[Evaluation criteria (printability)]
◯: Printing was possible on the bonded portion 1.
×: Printing on the bonded portion 1 was not possible.

[Bonding strength (initial, after thermal cycle test)
The bond strength (die shear strength) of the obtained bonded body was measured using the following measuring device and test conditions. Note that an asterisk (*) in Table 1 indicates that this evaluation was not performed because printing was not possible.
Measurement equipment: Universal bond tester (4000 series, manufactured by Daisy Japan Co., Ltd.)
<Test conditions>
Measurement height: 100 μm
Measurement speed: 500 μm/s

Specifically, the bonded body was fixed at the site of the bonded part 1, and pushed from the interface between the bonded part 1 and the bonding layer toward the bonded part 2 at a height of 100 μm at a speed of 500 μm/s to determine the bond strength at which the bond was destroyed. The bond strength (initial strength) immediately after the bonded body was made and the bond strength after the cycle test described below were measured and evaluated based on the following evaluation criteria. The higher the adhesive strength value, the better, and a value of 15 MPa or more is within the practical range. The higher the evaluation criterion value, the better, and an evaluation criterion value of 2 or less indicates poor quality.

6: 40 MPa or more 5: 30 MPa or more but less than 40 MPa 4: 20 MPa or more but less than 30 MPa 3: 15 MPa or more but less than 20 MPa 2: 5 MPa or more but less than 15 MPa 1: Less than 5 MPa

<Cold-heat cycle test>
The bonded body was stored for 500 cycles, with one cycle being a process of holding the bonded body at -40°C for 30 minutes, then holding the bonded body at 25°C for 15 minutes, and then holding the bonded body at 150°C for 30 minutes. Thereafter, the bonded body was evaluated according to the same procedures and criteria as the above-mentioned bond strength evaluation method. Furthermore, as a long-term durability test, a similar evaluation was performed after 1000 cycles.

The bonding pastes of the comparative examples could not be printed when they contained high concentrations of metal particles (Comparative Examples 1, 5, and 7). By reducing the metal particle concentration, printing became possible, but the bonding strength of the resulting bonded body was extremely low, and when a sample that had been broken after a die shear test was observed, it was found that the bond was broken at the interface between the gold-plated SiC chip and the bonding layer.
On the other hand, it was confirmed that the bonding paste of the examples has excellent printability even when it contains a high concentration of metal particles, the bonding strength of the resulting bonded body is very high, and even after a thermal cycle test, the decrease in bonding strength is suppressed. In addition, in Examples 1 to 39, when the samples after the evaluation of bonding strength were immersed in toluene to extract and concentrate the remaining organic matter, and IR was measured, a peak attributable to an amide bond was detected in each sample, and it was confirmed that a polyamide formed in the bonded body by condensation of a polyvalent fatty acid (B) and a polyamine (C) was produced.

Claims (15)

The present invention comprises metal particles (A) having an average particle size of 1 nm to 1000 nm, a polyvalent fatty acid (B), and a polyamine (C) ,
A metal particle-containing composition comprising 0.05 to 0.98 parts by mass of the polyvalent fatty acid (B) and 0.05 to 0.98 parts by mass of the polyamine (C) relative to 100 parts by mass of the metal particles (A) . The metal particle-containing composition according to claim 1, characterized in that the polyvalent fatty acid (B) has 20 to 80 carbon atoms, and the polyamine (C) has 20 to 80 carbon atoms. The metal particle-containing composition according to claim 1 or 2, characterized in that the polyvalent fatty acid (B) contains a divalent and/or trivalent fatty acid. The metal particle-containing composition according to any one of claims 1 to 3, characterized in that the polyamine (C) contains a diamine and/or a triamine. The metal particle-containing composition according to any one of claims 1 to 4, characterized in that the polyvalent fatty acid (B) and/or the polyamine (C) have a branched and/or cyclic structure. The metal particle-containing composition according to any one of claims 1 to 5, characterized in that, when the valence of the polyvalent fatty acid (B) is m and the valence of the polyamine (C) is n, the polyvalent fatty acid (B) has a hydrocarbon group (D) with a valence of m, or the polyamine (C) has a hydrocarbon group (E) with a valence of n. The metal particle-containing composition according to claim 6, characterized in that the carbon number of the m-valent hydrocarbon group (D) and/or the carbon number of the n-valent hydrocarbon group (E) is 30 to 60. 8. The metal particle-containing composition according to claim 1, further comprising 0.1 to 0.5 parts by mass of the polyvalent fatty acid (B) per 100 parts by mass of the metal particles (A). 9. The metal particle-containing composition according to claim 1 , comprising 0.1 to 0.5 parts by mass of polyamine (C) per 100 parts by mass of metal particles (A). The metal particle-containing composition according to any one of claims 1 to 9, characterized in that the average particle size of the metal particles (A) is 180 nm to 400 nm. The metal particle-containing composition according to any one of claims 1 to 10, characterized in that the average particle size of the metal particles (A) is 200 nm to 300 nm. A joining paste containing the metal particle-containing composition according to any one of claims 1 to 11 and a dispersion medium (F). The joining paste according to claim 12, wherein the mass ratio of the metal particles (A) to the sum of the masses of the metal particles (A), the polyvalent fatty acid (B), the polyamine (C), and the dispersion medium (F) is 80% by mass to 95% by mass. A bonded body in which a first bonded part and a second bonded part are bonded via a bonding layer, the bonding layer being a layer formed from the bonding paste according to claim 12 or 13. A method for manufacturing a bonded body in which a first bonded part and a second bonded part are bonded via a bonding layer, the method comprising the steps of applying a bonding paste containing metal particles (A) having an average particle size of 1 nm to 1000 nm, a polyvalent fatty acid (B), a polyamine (C), and a dispersion medium (F) to the first bonded part, placing the second bonded part on the paste, and sintering the bonded part.