JP6649840B2 - Conductor forming paste - Google Patents

Description

  The present invention relates to a conductor forming paste. In particular, the present invention relates to a conductor forming paste used for forming a conductive film (such as an internal electrode) on a multilayer ceramic capacitor and other ceramic electronic components (including various circuit elements).

  2. Description of the Related Art In recent years, as electronic devices have become smaller and more sophisticated, ceramic electronic components such as multilayer ceramic capacitors (MLCC), which are smaller and have higher capacitance than other capacitors, have been widely used. For example, a multilayer ceramic capacitor is formed by alternately laminating an internal electrode layer (conductive film) containing a conductive metal powder and a dielectric layer (ceramic layer), and such a dielectric layer and / or an internal electrode is formed. There is a strong demand for multilayer and thin layers.

  The above-mentioned multilayer ceramic capacitor is made of a conductive powder prepared in the form of a paste for forming a conductor film (internal electrode layer) on an unfired ceramic green sheet mainly composed of a ceramic powder typified by barium titanate or the like and a binder. A conductive material (hereinafter, referred to as "conductor forming paste") is applied, a plurality of these are laminated, then simultaneously fired and integrally sintered, and finally, an external electrode can be formed to manufacture. As the conductor forming paste for forming the conductor film, for example, a paste obtained by dispersing nickel powder (conductive powder material) in an organic vehicle (dispersion medium) is used. Further, in addition to the nickel powder, a common material made of barium titanate (ceramic powder) is added to the conductor forming paste. By adding barium titanate to the conductor forming paste, heat shrinkage (sintering) during firing is suppressed, and the continuity of the conductor film is improved. Documents that disclose this type of conventional technology include Patent Documents 1 to 3.

JP 2015-216244 A JP 2004-330247 A JP 2007-157563 A

  However, when barium titanate is added to the conductor-forming paste, although the continuity of the conductor film can be improved, a reaction between barium titanate and the ceramic particles forming the dielectric layer occurs, resulting in a composition shift in the dielectric layer. Occurs. Such a composition deviation becomes more remarkable when the thickness of the dielectric layer is reduced as the multilayer ceramic capacitor is miniaturized and multi-layered. As a result, the quality of the ceramic electronic component becomes unstable, which may be a factor of reducing reliability. From the viewpoint of quality stability, it is desired to reduce the amount of barium titanate added to the conductor forming paste. On the other hand, in order to reduce the size and increase the number of layers of the multilayer ceramic capacitor, it is necessary to reduce the thickness of the conductive film. For that purpose, it is required that the nickel powder to be mixed with the conductor forming paste be finely divided. However, when the above-mentioned addition amount of barium titanate is further reduced when small-diameter nickel particles are used, thermal contraction occurs due to insufficient heat resistance of the nickel particles, and continuity of the conductor film is reduced. There is a need for a technique that can achieve good continuity of a conductive film with a small amount of barium titanate (co-material).

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a conductor-forming paste capable of realizing good continuity of a conductor film with a small amount of barium titanate (co-material). It is to be. Another related object is to provide a multilayer ceramic capacitor including an internal electrode layer formed using the conductor forming paste.

  According to the present invention, there is provided a conductor-forming paste used for forming a conductor film. The conductor forming paste includes nickel particles, barium titanate particles, and a dispersion medium. The content of the barium titanate particles is 10 parts by mass or less based on 100 parts by mass of the nickel particles. In the analysis of the surface of the nickel particles by X-ray photoelectron spectroscopy (XPS), the ratio (B / A) of the molar fraction B of nickel hydroxide to the molar fraction A of nickel oxide is 0.2 ≦ (B / A). A) <1. By using nickel particles containing nickel oxide and nickel hydroxide at a specific mole fraction ratio, good continuity of the conductor film can be realized with a small amount of barium titanate.

  In a preferred embodiment of the conductor forming paste disclosed herein, the ratio (B / A) satisfies 0.3 ≦ (B / A) ≦ 0.8. When the molar fraction ratio of nickel oxide and nickel hydroxide is within the range (B / A), the above-described effects can be more effectively exerted.

  In a preferred embodiment of the conductor forming paste disclosed herein, the molar fraction A of the nickel oxide is greater than the molar fraction B of the nickel hydroxide by 12 mol% or more. This makes it possible to more appropriately exert the effect (for example, the effect of improving the heat resistance of the nickel particles) by making the molar fraction A of nickel oxide larger than the molar fraction B of nickel hydroxide.

  In a preferred embodiment of the conductor forming paste disclosed herein, a value (AB) obtained by subtracting the molar fraction B of the nickel hydroxide from the molar fraction A of the nickel oxide is 30 mol% or less. . According to such a configuration, compatibility between the heat resistance and the dispersibility of the nickel particles can be realized at a high level.

  In a preferred embodiment of the conductor forming paste disclosed herein, the nickel particles have an average particle diameter of 10 nm to 500 nm. According to such a paste for forming a conductor, the continuity of the conductor film can be further improved while realizing a thinner conductor film.

  In a preferred embodiment of the conductor forming paste disclosed herein, the paste is used for forming an internal electrode layer in a multilayer ceramic electronic component. In the field of multilayer ceramic electronic components, more continuous internal electrode layers (conductor films) are required for higher capacity and higher reliability. Therefore, the internal electrode layer of the multilayer ceramic electronic component can be a preferable application target of the technology disclosed herein.

  According to this specification, a multilayer ceramic capacitor is also provided. This multilayer ceramic capacitor includes an internal electrode layer made of a fired body of any of the conductor forming pastes disclosed herein. According to such a configuration, it is possible to provide a high-performance multilayer ceramic capacitor having good continuity of the internal electrode layers and excellent quality stability.

FIG. 1 is a partial cross-sectional view schematically illustrating a multilayer ceramic capacitor according to an embodiment of the present invention. It is a graph which shows the relationship between the molar fraction ratio (B / A) of nickel oxide and nickel hydroxide, and a coverage. 4 is a cross-sectional SEM image of the laminate sheet of Example 2. 9 is a cross-sectional SEM image of the laminate sheet of Example 3. 13 is a cross-sectional SEM image of the laminate sheet of Example 4.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters specifically mentioned in the present specification and necessary for carrying out the present invention (such as a manufacturing process of a multilayer ceramic capacitor) are design matters of a person skilled in the art based on conventional technology in the relevant field. Can be grasped. The present invention can be implemented based on the contents disclosed in this specification and common technical knowledge in the field.

<Conductor forming paste>
(Nickel particles)
The conductor forming paste disclosed herein is a conductor forming paste used for forming a conductive film (for example, an internal electrode layer of a multilayer ceramic electronic component), and includes nickel particles, barium titanate particles, and a dispersion medium. Contains. This conductor forming paste has a content of barium titanate particles of 10 parts by mass or less based on 100 parts by mass of the nickel particles. Then, in the analysis of the surface of the nickel particles by X-ray photoelectron spectroscopy (XPS), the ratio (B / A) of the molar fraction B of nickel hydroxide to the molar fraction A of nickel oxide is 0.2 ≦ (B / A). ) <1. By including nickel particles containing nickel oxide and nickel hydroxide at a specific molar fraction ratio in this manner, good continuity of the conductor film can be realized with a small amount of barium titanate (co-material).

The reason why such an effect is obtained is not particularly limited, but is considered as follows, for example. That is, the surface of the nickel particles is generally composed of nickel oxide (typically NiO), nickel hydroxide (typically Ni (OH) ₂ ) and nickel metal (simple). Of these, nickel oxide has a higher melting point than metallic nickel and contributes to improving the heat resistance of nickel particles, while nickel hydroxide is a basic substance and contributes to improving the dispersibility of nickel particles. In the case of a conductive paste containing a large amount of barium titanate particles, the molar fraction ratio (B / A) is large (that is, the molar fraction B of nickel hydroxide is large with respect to the molar fraction A of nickel oxide). The use of nickel particles improves the dispersibility of the nickel particles, and the nickel particles and the barium titanate particles are uniformly mixed. Therefore, the effect of suppressing heat shrinkage (sintering) by the barium titanate particles is more appropriately exhibited, and good continuity of the conductive film is easily realized. On the other hand, in the conductor forming paste having a low content of barium titanate particles, since the effect of the barium titanate particles on the effect of suppressing heat shrinkage is small, the heat resistance of the particles themselves is higher than that of enhancing the dispersibility of nickel particles. Is advantageous from the viewpoint of suppressing heat shrinkage. That is, the use of nickel particles having a small molar fraction ratio (B / A) (that is, a small molar fraction B of nickel hydroxide with respect to a molar fraction A of nickel oxide) results in a higher thermal shrinkage during firing. It is considered that (sintering) is suppressed and the continuity of the conductor film is improved.

  According to the study of the present inventors, the improvement of the continuity of the conductor film by specifying the molar fraction ratio (B / A) on the surface of the nickel particles in the preferable range disclosed herein is considered as nickel. Test examples described later confirmed that the same effect could not be obtained in the case of a conductor forming paste in which the content of barium titanate particles was more than 10 parts by mass with respect to 100 parts by mass of the particles. Therefore, by combining the above-mentioned regulation of the molar fraction ratio (B / A) on the surface of the nickel particles with the barium titanate particles having a low content, a synergistic effect of such a combination can be obtained with a small amount of barium titanate. A paste for forming a conductor that can greatly improve the continuity of the conductor film can be provided.

  The ratio (B / A) of the molar fraction B of nickel hydroxide to the molar fraction A of nickel oxide may be generally less than 1, preferably 0.95 or less, more preferably 0.85 or less. It is more preferably at most 0.8, further preferably at most 0.75, particularly preferably at most 0.7. The conductor forming paste having the above molar fraction ratio (B / A) equal to or less than a predetermined value effectively increases the heat resistance of the nickel particles themselves. Therefore, the application effects of the technology disclosed herein can be appropriately exerted. The molar fraction ratio (B / A) is usually appropriate to be 0.2 or more, preferably 0.24 or more, more preferably 0.28 or more, and still more preferably 0.3 or more. (For example, 0.32 or more). If the molar fraction ratio (B / A) is too small, the viscosity stability of the paste decreases. Therefore, the stability, handling property, and coating property when applying the paste to a ceramic green sheet or the like are deteriorated, and as a result, the continuity of the conductive film may tend to decrease. In the technology disclosed herein, for example, the ratio (B / A) of the molar fraction B of nickel hydroxide to the molar fraction A of nickel oxide on the surface of nickel particles is 0.25 or more and 0.95 or less (preferably 0.1% or less). 3 or more and 0.8 or less).

  From the viewpoint of improving the continuity of the conductive film, the molar fraction A of the nickel oxide is preferably at least 10 mol%, more preferably at least 12 mol%, than the molar fraction B of the nickel hydroxide. More preferably, it is more preferably at least 15 mol%, particularly preferably at least 20 mol%. The value obtained by subtracting the molar fraction B of nickel hydroxide from the molar fraction A of nickel oxide (that is, AB) is preferably 60 mol% or less, more preferably 50 mol% or less, and still more preferably 40 mol% or less. Mol% or less, particularly preferably 30 mol% or less. For example, AB may be 25 mol% or less. Thereby, the above-described effects can be more effectively exerted.

  The molar fraction A of nickel oxide on the surface of the nickel particles is not particularly limited as long as the ratio (B / A) to the molar fraction B of nickel hydroxide satisfies the above relationship. The molar fraction A of the nickel oxide can be, for example, 30 mol% or more. From the viewpoint of improving the heat resistance of the nickel particles, the molar fraction A of the nickel oxide is preferably at least 32 mol%, more preferably at least 35 mol%. Although the upper limit of the molar fraction A of nickel oxide is not particularly limited, it can be generally 85 mol% or less. From the viewpoint of viscosity stability and the like, the molar fraction A of the nickel oxide is preferably 75 mol% or less, more preferably 65 mol% or less (typically 60 mol% or less). The technology disclosed herein can be preferably implemented in a mode in which the molar fraction A of nickel oxide in nickel particles is 35 mol% or more and 75 mol% or less (preferably 35 mol% or more and 60 mol% or less).

  The molar fraction B of nickel hydroxide on the surface of the nickel particles is not particularly limited as long as the value (B / A) of the ratio to the molar fraction A of nickel oxide satisfies the above relationship. The molar fraction B of the nickel hydroxide can be, for example, less than 30 mol%. From the viewpoint of enhancing the heat resistance of the nickel particles, the molar fraction B of the nickel hydroxide is preferably 28 mol% or less, more preferably 25 mol% or less. Further, the lower limit of the molar fraction B of nickel hydroxide is not particularly limited, but may be usually 10 mol% or more. From the viewpoint of the dispersibility of the nickel particles, the molar fraction B of the nickel hydroxide is preferably 15 mol% or more, more preferably 20 mol% or more, and still more preferably 25 mol% or more. The technology disclosed herein can be preferably implemented in a mode in which the molar fraction B of nickel hydroxide in the nickel particles is 15 mol% or more and less than 30 mol% (preferably 20 mol% or more and 28 mol% or less).

  The molar fraction C of metallic nickel (Si alone) on the surface of the nickel particles is such that the value of the ratio (B / A) of the molar fraction A of nickel oxide to the molar fraction B of nickel hydroxide satisfies the above relationship. Is not particularly limited. The molar fraction C of metallic nickel can be usually at least 5 mol%, preferably at least 10 mol%, more preferably at least 15 mol%. The molar fraction C of metallic nickel is preferably 50 mol% or less, more preferably 45 mol% or less, and further preferably 40 mol% or less. The technology disclosed herein can be preferably implemented in a mode in which the molar fraction C of metallic nickel in nickel particles is 5 mol% or more and 50 mol% or less (preferably 15 mol% or more and 40 mol% or less).

  From the viewpoint of enhancing the heat resistance of the nickel particles, the molar fraction C of metallic nickel on the surface of the nickel particles is preferably smaller than the molar fraction A of nickel oxide (C <A), and 0.4 mol%. More preferably, it is smaller. The molar fraction C of metallic nickel may be smaller than the molar fraction A of nickel oxide by 10 mol% or more, or may be smaller by 30 mol% or more. The value obtained by subtracting the molar fraction C of metallic nickel from the molar fraction A of nickel oxide (that is, AC) is preferably 70 mol% or less, more preferably 60 mol% or less, and still more preferably 50 mol% or less. % Or less. For example, AC may be 45 mol% or less.

  In a preferred embodiment, the molar fraction C of metallic nickel on the surface of the nickel particles is larger than the molar fraction B of nickel hydroxide (B <C). For example, the molar fraction C of metallic nickel may be greater than the molar fraction B of nickel hydroxide by 5 mol% or more, or may be greater than 10 mol%. The value obtained by subtracting the molar fraction B of nickel hydroxide from the molar fraction C of metallic nickel (that is, CB) may be, for example, 20 mol% or less, or 15 mol% or less. Good.

  In another preferred embodiment, the molar fraction C of metallic nickel on the surface of the nickel particles is smaller than the molar fraction B of nickel hydroxide (C <B). For example, the molar fraction C of metallic nickel may be smaller than the molar fraction B of nickel hydroxide by 5 mol% or more, or may be smaller by 10 mol% or more. Further, the value obtained by subtracting the molar fraction C of metallic nickel from the molar fraction B of nickel hydroxide (that is, BC) may be 25 mol% or less, or may be 20 mol% or less. , 15 mol% or less.

In the technology disclosed herein, the molar fraction of nickel oxide, nickel hydroxide, and metallic nickel can be determined by analyzing the surface of nickel particles by X-ray photoelectron spectroscopy (XPS). Here, X-ray photoelectron spectroscopy (XPS) is a method of irradiating a sample surface with X-rays and measuring the energy of emitted photoelectrons to analyze constituent elements on the sample surface and their electronic states. Since the spectrum obtained by XPS shows a pattern peculiar to the substance and a peak intensity proportional to the amount of the substance, qualitative and quantitative analysis of the substance is possible. In the analysis of the chemical bonding state of nickel on the surface of the nickel particles using the XPS, the molar fraction A of nickel oxide was calculated from the area ratio of the peak attributed to the bonding state of nickel and oxygen to the entire Ni2P3 _{/ 2} spectrum. The mole fraction B of nickel hydroxide is determined from the area ratio of the peak attributed to the bonding state of the metal and the hydroxyl group to the entire Ni2P _3/2 spectrum, and the mole fraction of nickel metal is determined from the area ratio of the peak of the metal nickel to the entire Ni2P _3/2 spectrum. The fraction C can be determined. As the X-ray photoelectron spectroscopy device, XPS PHI-5000 VersaProbeII manufactured by ULVAC-PHI, Inc. can be used.

  The molar fraction ratio (B / A) of nickel oxide and nickel hydroxide on the surface of the nickel particles can be adjusted by subjecting the nickel particles to an oxidation treatment. That is, by appropriately selecting the oxidation treatment conditions for the nickel particles, it is possible to adjust the molar fraction ratio (B / A) of nickel oxide and nickel hydroxide on the surface of the nickel particles to an appropriate range disclosed herein. it can. As a specific method of the oxidation treatment, for example, a heat treatment (for example, 140 ° C. to 250 ° C.) is performed in an air atmosphere or an atmosphere in which an oxidizing gas (for example, oxygen gas or ozone gas) is mixed with an inert gas such as nitrogen. , Typically, a heat treatment at 160 ° C to 230 ° C).

  The type and properties of the nickel particles disclosed herein are not particularly limited as long as the molar fraction ratio (B / A) of nickel oxide and nickel hydroxide on the surface of the nickel particles satisfies the above relationship. For example, the shape (outer shape) of the nickel particles may be spherical or non-spherical. Further, the nickel particles may be various kinds of nickel particles containing nickel as a main component. Here, nickel particles containing nickel as a main component are particles in which 80% by mass or more (usually 90% by mass or more, typically 95% by mass or more, for example, 98% by mass or more) of the particles is nickel. Say. Examples of the nickel particles that can be used include, but are not particularly limited to, vapor-phase nickel and liquid-phase nickel. Examples of the vapor phase nickel mentioned here include nickel obtained by a vapor phase reduction method in which nickel powder is produced by contacting a nickel chloride gas with a reducing gas. Alternatively, nickel obtained by a spray pyrolysis method in which a pyrolytic nickel compound is sprayed and pyrolyzed may be used.

  As the nickel particles, those having an average particle diameter of 500 nm or less can be preferably used. From the viewpoint of reducing the thickness of the conductor film, the average particle diameter of the nickel particles is preferably 400 nm or less, more preferably 300 nm or less, further preferably 250 nm or less, and particularly preferably 200 nm or less. Although the lower limit of the average particle diameter of the nickel particles is not particularly limited, it is suitably about 10 nm or more, and is preferably 30 nm or more, more preferably 50 nm or more, from the viewpoint of heat resistance and handleability. For example, the average particle size of the nickel particles may be 80 nm or more, typically 100 nm or more. The technology disclosed herein can be preferably implemented in a mode in which the average particle size of the nickel particles is 10 nm or more and 500 nm or less (preferably 50 nm or more and 250 nm or less). In the present specification, the “average particle size” of the particle powder means a particle size D50 (median particle size) at an integrated value of 50% in a particle size distribution estimated based on scanning electron microscope (SEM) observation. I do.

  It is preferable that the content of the nickel particles in the conductor forming paste is 30 to 90% by mass (more preferably, about 40 to 60% by mass) with the whole paste being 100% by mass.

(Barium titanate particles)
The conductor forming paste disclosed herein contains barium titanate particles. Barium titanate particles are components that suppress thermal shrinkage (sintering) during firing as described above. The barium titanate particles may be various barium titanate particles containing barium titanate as a main component. Here, barium titanate particles containing barium titanate as a main component means that 80% by mass or more (normally 90% by mass or more, typically 95% by mass or more, for example, 98% by mass or more) of the particles is titanium. Refers to particles that are barium acid.

  The barium titanate particles preferably have an average particle diameter of 100 nm or less. From the viewpoints of barium titanate particle dispersibility and filling properties, the average particle size of the barium titanate particles is preferably 80 nm or less, more preferably 50 nm or less (for example, 40 nm or less). Although the lower limit of the average particle diameter of the barium titanate particles is not particularly limited, it is appropriate to set the average particle diameter to approximately 1 nm. The average particle diameter of the barium titanate particles is preferably 10 nm or more, more preferably 20 nm or more, from the viewpoints of suppressing aggregation of the barium titanate particles and handling properties. For example, barium titanate particles having an average particle diameter of 10 nm or more and 100 nm or less are preferable, and those having a mean particle diameter of 20 nm or more and 40 nm or less are particularly preferable from the viewpoint of achieving a higher level of the filling property and the suppression of aggregation.

  The content of the barium titanate particles in the conductor forming paste is 10 parts by mass or less based on 100 parts by mass of the nickel particles. From the viewpoint of quality stability (for example, suppressing adverse effects on the dielectric layer (composition deviation of the dielectric layer)), the content of the barium titanate particles is 9 parts by mass or less based on 100 parts by mass of the nickel particles. The amount is preferably 7 parts by mass or less, more preferably 5 parts by mass or less. The lower limit of the content of barium titanate particles is not particularly limited as long as it is larger than 0 (zero), but it is appropriate that the lower limit is approximately 0.5 parts by mass or more with respect to 100 parts by mass of the nickel particles. Is at least 1 part by mass, more preferably at least 1.5 parts by mass, further preferably at least 2 parts by mass, particularly preferably at least 3 parts by mass. For example, the content of the barium titanate particles is preferably 5 parts by mass with respect to 100 parts by mass of the nickel particles from the viewpoint of better exerting the effect of adding the barium titanate particles (the effect of suppressing firing shrinkage). It is at least 7 parts by mass, more preferably at least 7 parts by mass, even more preferably at least 9 parts by mass. For example, the content of barium titanate particles is 1 part by mass or more and 10 parts by mass or less (more preferably 2.5 parts by mass or more and 9 parts by mass or less, for example, 2.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of nickel particles). Is preferable from the viewpoint of achieving a high level of both the quality stability and the effect of suppressing firing shrinkage at a high level.

(Dispersion medium)
The dispersion medium used for the conductor-forming paste is not particularly limited as long as it can disperse the nickel particles and barium titanate particles. As the dispersion medium, those used in conventional pastes for forming conductors can be used without any particular limitation. For example, a cellulose-based polymer such as ethylcellulose, ethylene glycol and diethylene glycol derivatives, toluene, xylene, mineral spirit, butyl carbitol, high boiling organic solvents such as terpineol or an organic vehicle containing as a component a combination of two or more thereof. Can be used. Although not particularly limited, it is appropriate that the content of the organic vehicle is about 10 to 60% by mass of the whole paste.

  The organic vehicle disclosed herein may further include an organic binder. Any organic binder may be used as long as it can be removed by evaporation (degreasing) in binder removal treatment during baking (typically, heat treatment at 250 to 500 ° C. in an oxidizing atmosphere). Any resin that has been contained in the paste for use can be used without particular limitation. Suitable organic binders from this viewpoint include, for example, cellulose polymers such as ethyl cellulose and hydroxyethyl cellulose, acrylic resins such as polybutyl methacrylate, polymethyl methacrylate, and polyethyl methacrylate, epoxy resins, phenol resins, alkyd resins, and polyvinyl alcohol. And an organic binder based on polyvinyl butyral and the like.

(Other components)
The paste for forming a conductor disclosed herein may contain various organic additives similar to those of the conventional paste for forming a conductor, if necessary. Examples of such an organic additive include various organic binders (which may overlap with the above-mentioned vehicle, or different binders may be added separately), or a silicon-based material for the purpose of improving adhesion to a ceramic substrate. And various coupling agents such as titanates and aluminums. Examples of the organic binder include those based on acrylic resin, epoxy resin, phenol resin, alkyd resin, cellulosic polymer, polyvinyl alcohol, polyvinyl butyral, and the like. It is preferable that the paste for forming a conductor of the present invention can impart good viscosity and ability to form a coating film (adhesion film to a substrate). When it is desired to impart photocurability (photosensitivity) to the conductive paste, various photopolymerizable compounds and a photopolymerization initiator may be appropriately added.

  The conductor forming paste disclosed herein is a polymerization initiator, a surfactant, an antifoaming agent, a plasticizer, a thickener, an antioxidant, a dispersant, and a polymerization inhibitor within a range not to impair the effects of the present invention. A known additive that can be used in a conductor forming paste (for example, an internal electrode layer forming paste) may be further contained as necessary. The content of the above-mentioned additives may be appropriately set according to the purpose of the addition, and does not characterize the present invention, and therefore detailed description is omitted.

<Preparation of conductor forming paste>
The method for producing the conductor-forming paste disclosed herein is not particularly limited. For example, the components contained in the conductor forming paste may be mixed using a ball mill, a three-roll mill, or another known mixing device. The manner in which these components are mixed is not particularly limited. For example, all components may be mixed at once, or may be mixed in an appropriately set order.

<Application>
The conductor-forming paste disclosed herein can improve the continuity of the conductive film to a high degree, and is therefore preferably used for forming a conductive film requiring good continuity, for example, an internal electrode layer in a multilayer ceramic electronic component. Can be applied. For example, it is particularly suitable for use in forming an internal electrode layer of a multilayer ceramic capacitor. As shown in FIG. 1, the multilayer ceramic capacitor 200 includes a conductor film (an internal electrode layer made of a sintered body of a conductor forming paste) 220 containing nickel particles and barium titanate particles, and a ceramic layer (dielectric layer) 210. May be alternately laminated. It is suitable as a paste for forming an internal electrode layer of such a multilayer ceramic capacitor 200. In such an application, since the barium titanate particles can reduce the amount of barium titanate used to suppress the dielectric layer from adversely affecting (eg, change in composition), it is particularly preferable to apply the technology disclosed herein. It is significant.

<Construction of multilayer ceramic capacitor>
The conductor forming paste disclosed herein can be used for constructing the multilayer ceramic capacitor 200, for example, in an aspect including the following steps.
That is, the conductor forming paste disclosed herein is prepared. The conductor forming paste is formed into a desired shape and thickness by a screen printing method, a dispenser coating method, or the like, and a green sheet made of a dielectric material (for example, a ceramic material such as barium titanate or strontium titanate) (fired) It is applied to an unfired dielectric sheet which will later become a dielectric film. A plurality of green sheets on which the unsintered conductor film is formed are prepared, stacked, and pressed. Thus, an unfired laminated chip in which the unfired conductor film and the dielectric film are laminated is obtained.
Next, the laminated chip is dried, and then in a heater under appropriate heating conditions (the maximum firing temperature is generally 800 to 1400 ° C., preferably 1000 to 1400 ° C., particularly preferably 1200 to 1300 ° C.) for a predetermined time (maximum). The chip is baked (baked) and cured by heating (for example, a time maintained at the sintering temperature for about 10 minutes to 2 hours). In a preferred embodiment, the method includes a step of raising the temperature at a rate of 600 to 20000 ° C./hour (for example, 1000 to 15000 ° C./hour) from predetermined high-temperature firing conditions (ie, normal temperature (typically room temperature) to the maximum firing temperature). Firing conditions). By performing this series of processes, a main body 250 of an electronic component such as a capacitor in which the target conductor film (internal electrode layer) 220 and the dielectric film 210 are laminated is obtained.
Finally, an external electrode 230 is formed by applying a paste for forming an external electrode (which may be the same as the conductor forming paste) to a predetermined portion of the electronic component body 250 and firing the paste. Thus, a multilayer ceramic electronic component can be constructed. Since the construction method itself does not particularly characterize the present invention, a detailed description thereof will be omitted.
Although not intended to limit the use, as described above, by using the conductor forming paste disclosed herein, compared to the conventional conductor forming paste, even when the nickel particles are finer, The heat shrinkage at the time is suppressed, the heat resistance is improved, and a dense conductor film in which the thickness is further reduced can be preferably formed. Therefore, according to the paste for forming a conductor of the present invention, a conductor thin film having a film thickness of 10 μm or less (for example, 0.3 μm to 3 μm) can be suitably formed.

<Production method of multilayer ceramic capacitor>
The technology disclosed herein may include a method for manufacturing a multilayer ceramic capacitor including a step of forming an internal electrode layer using the above-described paste for forming a conductor, and providing a multilayer ceramic capacitor manufactured by the method. That is, according to the technology disclosed herein, there is provided a method of manufacturing a multilayer ceramic capacitor including forming an internal electrode layer using the conductor forming paste, and a multilayer ceramic capacitor manufactured by the method. According to the above manufacturing method, a high-performance (for example, large-capacity) multilayer ceramic capacitor having internal electrode layers with good continuity can be provided.

  Hereinafter, some embodiments of the present invention will be described, but it is not intended to limit the present invention to those shown in the embodiments.

<Preparation of conductor forming paste>
A plurality of types of nickel powders having different mole fractions of nickel oxide (NiO), nickel hydroxide (Ni (OH) ₂ ) and metallic nickel (Ni) on the surface of nickel particles were prepared. These nickel powders (average particle diameter of about 180 nm) and barium titanate powders (average particle diameter of about 30 nm) were weighed, stirred and mixed to prepare a conductor-forming powder material. Next, a Ni paste was prepared using the powder material for forming a conductor. That is, each material was weighed so that the composition (mass ratio) of the final paste was 57.5% by mass of the powder material for forming a conductor and the remainder was a vehicle (40.5% by mass of a solvent and 2% by mass of a binder component). Using a three-roll mill. Here, as shown in Table 1, the amount of the barium titanate powder used per 100 parts by mass of the Ni powder was varied between 0 and 15 parts by mass to prepare a Ni paste. Thus, the Ni paste according to each example was prepared.

For the Ni paste according to each example, the molar fraction of NiO, the molar fraction of Ni (OH) ₂ , the molar fraction of Ni, the molar fraction of NiO and Ni (OH) _{2 on} the surface of the nickel particles used. Table 1 summarizes the ratio (B / A) and the amount of barium titanate added. In each example, the molar fraction A of NiO, the molar fraction B of Ni (OH) ₂ , and the molar fraction C of Ni on the surface of the nickel particles were determined in accordance with the above-described method based on XPS.

<Formation of conductive film>
A conductor film was manufactured using the Ni paste according to each example. That is, a Ni paste was applied onto a ceramic green sheet mainly composed of BaTiO ₃ so that the application amount based on the mass of the Ni powder was 0.5 mg / cm ^2, and dried. A plurality of green sheets on which the unsintered conductive film was formed were produced, and these were laminated and pressed. Thereafter, firing treatment in a mixed gas (reducing) atmosphere containing 1% hydrogen gas and 99% nitrogen (heating rate 200 ° C./hour, cooling rate 200 ° C./hour, maximum firing temperature maintained at 1250 ° C. for 10 minutes) ). In this way, a fired laminate sheet in which the conductor films and the ceramic base material (fired ceramic base material) were alternately formed was obtained.

  An image obtained by observing the cross section of the obtained fired laminated sheet with a scanning electron microscope (SEM) at a magnification of 5000 times was analyzed, and the length of a portion where the conductor forming paste was applied to the ceramic green sheet in the cross section was analyzed. The coverage (= [L2 / L1] × 100) is calculated from (L1) and the length (L2) of the portion of the fired product where the conductor film covers the dielectric film (the fired ceramic substrate). did. This coverage can be grasped as an index of the continuity of the conductor film (and the effect of suppressing the firing shrinkage). In other words, it can be said that the higher the coverage, the better the continuity of the conductor film and the greater the effect of suppressing firing shrinkage. The results are shown in Table 1 and FIG. FIG. 2 is a graph showing the relationship between the molar fraction ratio (B / A) of nickel oxide and nickel hydroxide and the coverage (continuity of the conductive film). 3 to 5 show cross-sectional SEM images of the fired laminate sheet when the addition amount of barium titanate is 5 parts by mass in Examples 2 to 4.

  As shown in Table 1 and FIG. 2, when the addition amount of barium titanate is 10 parts by mass or less, when the molar fraction ratio (B / A) of nickel oxide and nickel hydroxide increases from 0 (zero), the coating rate increases. (Continuity of the conductive film) once showed an increasing tendency, and after having reached a maximum value in the middle, turned to a decreasing tendency again. That is, it was confirmed that the covering ratio tends to decrease when the molar fraction ratio (B / A) is too large or too small. Further, when the added amount of barium titanate is the same, a better coverage is realized in a region where the molar fraction ratio (B / A) of nickel oxide and nickel hydroxide is 0.2 ≦ (B / A) <1. It was completed (Examples 3 to 5). On the other hand, when the added amount of barium titanate was 15 parts by mass or more, the above tendency was not observed, and the coverage increased as the molar fraction ratio (B / A) increased. From this, regarding the improvement of the coverage (continuity of the conductive film) by defining the molar fraction ratio (B / A) within the preferred range disclosed herein, the addition amount of barium titanate was 10 parts by mass. It has been confirmed that it is particularly effective in the following cases.

  As described above, the specific examples of the present invention have been described in detail. However, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples illustrated above.

200 multilayer ceramic capacitor 210 dielectric film 230 external electrode 250 electronic component body

Claims (7)

A conductor forming paste used for forming a conductive film,
Nickel particles, barium titanate particles, including a dispersion medium,
The content of the barium titanate particles is 2 parts by mass or more and 10 parts by mass or less based on 100 parts by mass of the nickel particles,
In the analysis of the surface of the nickel particles by X-ray photoelectron spectroscopy (XPS), the ratio (B / A) of the molar fraction B of nickel hydroxide to the molar fraction A of nickel oxide is 0.2 ≦ (B / A). <1. Conductor forming paste.   The conductor forming paste according to claim 1, wherein the ratio (B / A) satisfies 0.3 ≦ (B / A) ≦ 0.7.   3. The conductor forming paste according to claim 1, wherein the molar fraction A of the nickel oxide is greater than the molar fraction B of the nickel hydroxide by 12 mol% or more. 4.   The conductor according to any one of claims 1 to 3, wherein a value (AB) obtained by subtracting the molar fraction B of the nickel hydroxide from the molar fraction A of the nickel oxide is 30 mol% or less. Forming paste.   The paste for forming a conductor according to claim 1, wherein the average particle diameter of the nickel particles is 10 nm to 500 nm.   The conductor forming paste according to any one of claims 1 to 5, which is used for forming an internal electrode layer in the multilayer ceramic electronic component.   A multilayer ceramic capacitor comprising an internal electrode layer made of a sintered body of the paste for forming a conductor according to claim 1.