TWI734769B - Paste and multilayer ceramic capacitors for conductor formation - Google Patents

Abstract

The present invention provides a conductor forming paste capable of achieving good continuity of a conductor film with a small amount of barium titanate. According to the present invention, there is provided a conductor forming paste containing nickel particles, barium titanate particles, and a dispersion medium. In this conductor-forming paste, the content of barium titanate particles is 10 parts by mass or less with respect to 100 parts by mass of nickel particles. In addition, in the analysis of the surface of nickel particles by X-ray photoelectron spectroscopy (XPS), the ratio of the molar fraction B of nickel hydroxide to the molar fraction A of nickel oxide (B/A) is 0.2≦(B/ A)<1.

Description

Paste and multilayer ceramic capacitors for conductor formation

The present invention relates to a paste for forming a conductor. In particular, it relates to a conductor forming paste used for the purpose of forming conductor films (internal electrodes, etc.) in ceramic electronic parts (including various circuit elements) such as multilayer ceramic capacitors.

In recent years, with the miniaturization and higher functionality of electrical equipment, compared with other capacitors, ceramic electronic components such as multi-layer ceramic capacitors (MLCC), which are small and high-capacity, are commonly used. For example, multilayer ceramic capacitors are formed by alternately laminating internal electrode layers (conductor films) and dielectric layers (ceramic layers) containing conductive metal powder, and there is a strong demand for multilayering of the dielectric layers and/or internal electrode layers , Thin layer.

The multilayer ceramic capacitor can be manufactured by applying ceramic powders represented by barium titanate and the like on an unfired ceramic green sheet containing a binder as the main components, and providing a conductive film (internal electrode layer). A paste-like conductive material (hereinafter referred to as "conductor-forming paste") is prepared, and these are laminated in multiple layers, and then calcined at the same time for integral sintering, and finally an external electrode is formed. As the conductor formation paste for forming the conductor film, for example, a paste obtained by dispersing nickel powder (conductive powder material) in an organic vehicle (dispersion medium) can be used. In addition, in addition to the nickel powder, a coexisting material containing barium titanate (ceramic powder) is added to the conductor forming paste. By adding barium titanate to the paste for forming the conductor, the heat shrinkage during firing (firing The junction) is suppressed, and the continuity of the conductor film is improved. As a document that discloses such a prior art, Patent Document 1 to Patent Document 3 can be cited.

[Patent Document 1] Japanese Patent Laid-Open No. 2015-216244

[Patent Document 2] Japanese Patent Laid-Open No. 2004-330247

[Patent Document 3] Japanese Patent Laid-Open No. 2007-157563

However, if barium titanate is added to the conductor forming paste, although the continuity of the conductor film can be improved, it will cause a reaction between the barium titanate and the ceramic particles forming the dielectric layer, and cause compositional unevenness in the dielectric layer. In the case where the dielectric layer is thinned along with the miniaturization and multi-layer build-up of the multilayer ceramic capacitor, the composition unevenness becomes more noticeable. As a result, the quality of ceramic electronic components becomes unstable, which may become a main cause of a decrease in 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 miniaturize and multiply multilayer ceramic capacitors, the conductor film must also be thinned. Therefore, the nickel powder blended in the conductor forming paste is required to be finely divided. However, when nickel particles with a small diameter are used, if the addition amount of barium titanate is further reduced, thermal shrinkage occurs due to insufficient heat resistance of the nickel particles, and the continuity of the conductor film is reduced. There is a need for a technique capable of achieving good continuity of the conductor film with a small amount of barium titanate (coexisting material).

The present invention was made in view of the above circumstances, and its main purpose is to provide a conductive film that can achieve good continuity of the conductor film with a small amount of barium titanate (coexisting material) The conductor is formed with paste. 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 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 with respect to 100 parts by mass of the nickel particles. Furthermore, in the analysis of the surface of the nickel particles by X-ray Photoelectron Spectroscopy (XPS), the ratio of the molar fraction B of nickel hydroxide to the molar fraction A of nickel oxide (B/ A) is 0.2≦(B/A)<1. By using nickel particles containing nickel oxide and nickel hydroxide at a specific molar fraction ratio as described above, it is possible to achieve good conductor film continuity with a small amount of barium titanate.

In a preferred form of the conductor forming paste disclosed herein, the ratio (B/A) is 0.3≦(B/A)≦0.8. If it is in the range of the molar fraction ratio (B/A) of such nickel oxide and nickel hydroxide, the effect can be exhibited more satisfactorily.

In a preferred form 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 more than 12 mol%. If so, the effect (for example, the heat resistance improvement effect of nickel particles) produced by making the molar fraction A of nickel oxide larger than the molar fraction B of nickel hydroxide can be exhibited more suitably.

In a preferred form of the conductor forming paste disclosed herein, the value (AB) obtained by subtracting the mole fraction B of the nickel hydroxide from the mole fraction A of the nickel oxide is 30 moles Less than ear%. According to the structure, nickel can be realized at a high level The heat resistance and dispersibility of the particles coexist.

In a preferred form of the conductor forming paste disclosed herein, the average particle diameter of the nickel particles is 10 nm to 500 nm. According to such a paste for conductor formation, the thickness of the conductor film can be reduced, and the continuity of the conductor film can be improved more satisfactorily.

In a preferred form of the conductor forming paste disclosed herein, it is used to form an internal electrode layer in a multilayer ceramic electronic component. In the field of multilayer ceramic electronic parts, in order to increase the capacity or the reliability, an internal electrode layer (conductor film) with higher continuity is required. Therefore, the internal electrode layer of the multilayer ceramic electronic component can be a better application target of the technology disclosed herein.

According to this specification, a multilayer ceramic capacitor is additionally provided. This multilayer ceramic capacitor is equipped with the internal electrode layer containing the sintered body of any conductor-forming paste disclosed herein. According to the above configuration, it is possible to provide a high-performance multilayer ceramic capacitor with good continuity of the internal electrode layer and excellent quality stability.

200: Multilayer ceramic capacitor

210: Dielectric film

220: Conductor film

230: External electrode

250: Electronic component body

Fig. 1 is a partial cross-sectional view schematically showing a multilayer ceramic capacitor according to an embodiment of the present invention.

Fig. 2 is a graph showing the relationship between the molar fraction ratio (B/A) of nickel oxide and nickel hydroxide and the coverage.

3 is a scanning electron microscope (Scanning Electron Microscope, SEM) image of a cross-section of the laminate sheet of Example 2. FIG.

4 is a cross-sectional SEM image of the laminate sheet of Example 3. FIG.

5 is a cross-sectional SEM image of the laminate sheet of Example 4. FIG.

Hereinafter, suitable embodiments of the present invention will be described. Furthermore, matters other than the matters specifically mentioned in this specification and which are required in the implementation of the present invention (the manufacturing process of multilayer ceramic capacitors, etc.) can be used as the basis for practitioners based on the prior art in the field. Design matters to master. The present invention can be implemented based on the content disclosed in this specification and common technical knowledge in the field.

<Paste for Conductor Formation>

(Nickel particles)

The conductor-forming paste disclosed herein is a conductor-forming paste for forming a conductor film (for example, an internal electrode layer of a multilayer ceramic electronic component), and includes nickel particles, barium titanate particles, and a dispersion medium. In this conductor-forming paste, the content of barium titanate particles is 10 parts by mass or less with respect to 100 parts by mass of nickel particles. Furthermore, in the analysis of the surface of 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 was 0.2≦(B/ A)<1. By containing nickel particles containing nickel oxide and nickel hydroxide at a specific molar fraction ratio as described above, it is possible to achieve good continuity of the conductor film with a small amount of barium titanate (coexisting material).

The reason for obtaining such an effect is not particularly limitedly interpreted, and it can be considered as follows, for example. That is, the surface of the nickel particles usually contains nickel oxide (typically NiO), nickel hydroxide (typically Ni(OH) ₂ ), and metallic nickel (single body). Among them, the melting point of nickel oxide is higher than that of metallic nickel, which helps to improve the heat resistance of nickel particles. On the other hand, nickel hydroxide is an alkaline substance and helps to improve the dispersibility of nickel particles. In the case of a conductor-forming paste with a large content of barium titanate particles, the molar fraction ratio (B/A) is larger (that is, the molar fraction A relative to nickel oxide, and the molar fraction A of nickel hydroxide is used. The nickel particles with a large fraction B) will improve the dispersibility of the nickel particles, and the nickel particles and the barium titanate particles will be uniformly mixed. Therefore, the thermal shrinkage (sintering) suppression effect by the barium titanate particles is more appropriately exerted, and it is easy to achieve good continuity of the conductor film. In contrast, in a conductor-forming paste with a small content of barium titanate particles, the effect of suppressing heat shrinkage by barium titanate particles is small. Therefore, from the viewpoint of suppressing heat shrinkage, the particle itself is improved. Heat resistance is more advantageous than improving the dispersibility of nickel particles. That is, it can be considered that the use of nickel particles with a molar fraction ratio (B/A) smaller (that is, the molar fraction A of nickel oxide and the molar fraction B of nickel hydroxide are small) will suppress the heat during sintering. Shrinking (sintering) and improving the continuity of the conductor film.

Furthermore, according to the research of the inventors, regarding the continuity of the conductor film caused by the molar fraction ratio (B/A) on the surface of the nickel particles specified in the preferred range disclosed in the text As an improvement, it was confirmed by the test example described later that in the case of the conductor-forming paste in which the content of barium titanate particles per 100 parts by mass of nickel particles exceeds 10 parts by mass, the same effect cannot be obtained. Therefore, by combining the requirements of the molar fraction ratio (B/A) on the surface of the nickel particles and the low content of barium titanate particles, as a synergistic effect produced by the combination, it is possible to provide A conductor forming paste capable of greatly improving the continuity of a conductor film with a small amount of barium titanate.

The ratio (B/A) of the molar fraction B of the nickel hydroxide to the molar fraction A of nickel oxide (B/A) is usually less than 1, preferably 0.95 or less, more preferably 0.85 Below, it is more preferably 0.8 or less, still more preferably 0.75 or less, and particularly preferably 0.7 or less. The conductor-forming paste having the molar fraction ratio (B/A) below a predetermined value effectively improves the heat resistance of the nickel particles themselves. Therefore, the application effect of the technology disclosed herein can be appropriately exerted. In addition, the molar fraction ratio (B/A) is usually suitably 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 will decrease. Therefore, when the paste is applied to a ceramic green sheet or the like, the stability, handleability, and applicability deteriorate, and as a result, the continuity of the conductor film may tend to decrease. The technology disclosed herein can be based on, for example, that the ratio (B/A) of the molar fraction B of nickel hydroxide on the surface of nickel particles to the molar fraction A of nickel oxide is 0.25 or more and 0.95 or less (preferably 0.3 or more) , 0.8 or less).

From the viewpoint of improving the continuity of the conductor film, etc., the molar fraction A of nickel oxide is preferably 10 mol% or more larger than the molar fraction B of nickel hydroxide, and more preferably 12 molar%. Ear% or more, more preferably 15 mol% or more, particularly preferably 20 mol% or more. In addition, the value obtained by subtracting the mole fraction B of nickel hydroxide from the mole fraction A of nickel oxide (ie, AB) is preferably 60 mole% or less, more preferably 50 mole% or less, and still more Preferably, it is 40 mol% or less, and particularly preferably, it is 30 mol% or less. For example, A-B may be 25 mol% or less. Thereby, the above-mentioned effect can be exhibited more satisfactorily.

The mole fraction A of nickel oxide on the surface of the nickel particles is not particularly limited as long as the ratio (B/A) of the ratio of the mole fraction B of nickel hydroxide to the mole fraction B of nickel hydroxide satisfies the above relationship. Certainly. The mole fraction A of nickel oxide may be 30 mole% or more, for example. From the viewpoint of improving the heat resistance of the nickel particles, etc., the molar fraction A of the nickel oxide is preferably 32 mol% or more, and more preferably 35 mol% or more. In addition, the upper limit of the mole fraction A of the nickel oxide is not particularly limited, but it can usually be 85 mole% or less. From the viewpoint of viscosity stability and the like, the molar fraction A of 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 in a form where 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). Better implementation.

The molar fraction B of nickel hydroxide on the surface of the nickel particles is not particularly limited as long as the ratio (B/A) of the ratio of the molar fraction A of nickel oxide to the molar fraction A of nickel oxide satisfies the above-mentioned relationship. The mole fraction B of nickel hydroxide may be less than 30 mole%, for example. From the viewpoint of improving the heat resistance of nickel particles, etc., the molar fraction B of nickel hydroxide is preferably 28 mol% or less, and more preferably 25 mol% or less. In addition, the lower limit of the molar fraction B of nickel hydroxide is not particularly limited, and it can usually be 10 mol% or more. From the viewpoint of the dispersibility of nickel particles, etc., the molar fraction B of 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 in this paper can use the molar fraction B of the nickel hydroxide in the nickel particles to be 15 mol% or more and less than 30 mol% (preferably 20 mol% or more, 28 mol% or less). The form is preferably implemented.

The molar fraction C of metallic nickel (Ni monomer) on the surface of the nickel particles as long as the ratio of the molar fraction A of nickel oxide to the molar fraction B of nickel hydroxide (B/A) satisfies the requirements The relationship is not particularly limited. The mole fraction of nickel metal C Generally, it can be 5 mol% or more, preferably 10 mol% or more, and more preferably 15 mol% or more. In addition, the molar fraction C of metallic nickel is preferably 50 mol% or less, more preferably 45 mol% or less, and still more preferably 40 mol% or less. The technology disclosed herein can be in a form 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). Better implementation.

From the viewpoint of improving the heat resistance of nickel particles, etc., it is preferable that the molar fraction C of metallic nickel on the surface of the nickel particles is smaller than the molar fraction A of nickel oxide (C<A), and it is more preferable to Smaller than 0.4 mol%. The molar fraction C of metallic nickel can be less than 10 mol% or more than 30 mol% less than the molar fraction A of nickel oxide. In addition, the value obtained by subtracting the molar fraction C of metallic nickel from the molar fraction A of nickel oxide (ie AC) is preferably 70 mol% or less, more preferably 60 mol% or less, and still more preferably It is less than 50 mol%. For example, A-C may be 45 mol% or less.

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

In another preferred aspect, 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 can be less than 5 mol% or more than the molar fraction B of nickel hydroxide, or Less than 10 mol%. In addition, the value obtained by subtracting the mole fraction C of metallic nickel from the mole fraction B of nickel hydroxide (ie, BC) may be 25 mole% or less, 20 mole% or less, or 15 mol% or less.

In the technique disclosed herein, the molar fraction of nickel oxide, nickel hydroxide, and metallic nickel can be grasped by analyzing the surface of nickel particles by X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy). Here, X-ray photoelectron spectroscopy (XPS) is a method of irradiating the surface of a sample with X-rays and measuring the energy of the emitted photoelectrons to analyze the constituent elements on the surface of the sample and their electronic states. The spectrum obtained by XPS shows the inherent pattern of the substance and the peak intensity proportional to the amount of the substance, so the qualitative and quantitative analysis of the substance can be carried out. In the analysis of the chemical bonding state of nickel on the surface of nickel particles using XPS, the molar ratio of nickel oxide can be obtained from the area ratio _{of the peak attributable to the bonding state of nickel and oxygen to the entire spectrum of Ni2P 3/2.} Fraction A, the molar fraction B of nickel hydroxide is calculated based on the area ratio of the peak attributable to the bonding state of nickel and hydroxyl to the entire _{spectrum of Ni2P 3/2 , and the peak value of metallic nickel is relative to the Ni2P 3/2} spectrum. The molar fraction C of metallic nickel is calculated from the overall area ratio. As an X-ray photoelectron spectrometer, the XPS PHI-5000 VersaProbe II manufactured by ULVAC‧PHI Co., Ltd. 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 performing oxidation treatment on the nickel particles. That is, by appropriately selecting the oxidation treatment conditions for the nickel particles, the molar fraction ratio (B/A) of nickel oxide and nickel hydroxide on the surface of the nickel particles can be adjusted to an appropriate range as disclosed in the article. Surrounding. As a specific method of the oxidation treatment, for example, heat treatment (for example, 140°C to 250°C, in an air environment or an environment where an oxidizing gas (for example, oxygen or ozone gas) is mixed with an inert gas such as nitrogen, etc. A typical method is heat treatment at 160°C to 230°C.

The types or 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-mentioned relationship. For example, the shape (outer shape) of the nickel particles may be spherical or non-spherical. In addition, the nickel particles may be various nickel particles containing nickel as a main component. Here, the term "nickel particles containing nickel as a main component" refers to 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 are nickel. It does not specifically limit as an example of the nickel particle which can be used, A vapor-phase method nickel, a liquid-phase method nickel, etc. are mentioned. Examples of the gas-phase method nickel described here include nickel obtained by a gas-phase reduction method that produces nickel powder by contacting nickel chloride gas with a reducing gas. Alternatively, nickel obtained by a spray thermal decomposition method in which a thermally decomposable nickel compound is sprayed and thermally decomposed can also 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 thinning of the conductive film, etc., the average particle diameter of the nickel particles is preferably 400 nm or less, more preferably 300 nm or less, still more preferably 250 nm or less, and particularly preferably 200 nm or less. The lower limit of the average particle diameter of the nickel particles is not particularly limited, but it is suitably approximately 10 nm or more. From the viewpoint of heat resistance, handling properties, etc., it is preferably 30 nm or more, and more preferably 50 nm or more. For example, the average particle diameter of nickel particles may be 80 nm or more, and typically it may be 100 nm or more. The technology disclosed in this article It can be preferably implemented in a form in which the average particle diameter of the nickel particles is 10 nm or more and 500 nm or less (preferably 50 nm or more and 250 nm or less). Furthermore, in this specification, the "average particle size" of the particle powder refers to the particle size D50 (median particle size) at 50% of the cumulative value of the particle size distribution estimated by scanning electron microscope (SEM) observations. ).

The entire paste is set to 100% by mass, and the content of nickel particles in the conductor forming paste is preferably 30% to 90% by mass (more preferably about 40% to 60% by mass) of the entire paste .

(Barium titanate particles)

The conductor forming paste disclosed herein contains barium titanate particles. As described above, the barium titanate particles are a component that suppresses thermal shrinkage (sintering) during firing. The barium titanate particles may be various barium titanate particles having barium titanate as a main component. Here, the so-called barium titanate particles containing barium titanate as the main component means that 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 are titanium. Particles of barium acid.

The barium titanate particles preferably have an average particle diameter of 100 nm or less. From the viewpoints of the dispersibility and filling properties of the barium titanate particles, the average particle diameter of the barium titanate particles is preferably 80 nm or less, and more preferably 50 nm or less (for example, 40 nm or less). In addition, the lower limit of the average particle diameter of the barium titanate particles is not particularly limited, and it is appropriately set to approximately 1 nm. From the viewpoint of suppressing aggregation of barium titanate particles, handling properties, etc., the average particle diameter of the barium titanate particles is preferably 10 nm or more, and more preferably 20 nm or more. For example, from the viewpoint of coexisting filling properties and suppressing aggregation at a higher level In other words, barium titanate particles having an average particle diameter of 10 nm or more and 100 nm or less are preferable, and barium titanate particles having an average particle diameter of 20 nm or more and 40 nm or less are particularly preferable.

The content of barium titanate particles in the conductor forming paste is 10 parts by mass or less with respect to 100 parts by mass of nickel particles. From the viewpoint of quality stability (for example, suppression of adverse effects on the dielectric layer (uneven composition of the dielectric layer)), etc., the content of barium titanate particles is preferably 9 parts by mass or less relative to 100 parts by mass of nickel particles. It is more preferably 7 parts by mass or less, and still more preferably 5 parts by mass or less. In addition, the lower limit of the content of the barium titanate particles is not particularly limited as long as it is greater than 0 (zero), but it is appropriately set to approximately 0.5 parts by mass or more, preferably 1 part by mass or more with respect to 100 parts by mass of nickel particles. , More preferably 1.5 parts by mass or more, still more preferably 2 parts by mass or more, particularly preferably 3 parts by mass or more. For example, from the viewpoint of making the addition effect of the barium titanate particles (effect of suppressing firing shrinkage) more satisfactory, the content of the barium titanate particles is preferably 5 parts by mass or more relative to 100 parts by mass of the nickel particles. , More preferably 7 parts by mass or more, and still more preferably 9 parts by mass or more. For example, from the viewpoint of coexisting quality stability and firing shrinkage suppression effect at a high level, it is suitable that the content of barium titanate particles is 1 part by mass or more and 10 parts by mass or less (more It is 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) of the conductor-forming paste.

(Dispersion medium)

The dispersion medium used in 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 the conventional paste for conductor formation can be used without particular limitation. For example, you can use: There are cellulose polymers such as ethyl cellulose, ethylene glycol and diethylene glycol derivatives, toluene, xylene, mineral spirits, butyl carbitol, pinoresinol and other high-boiling organic solvents or these organic solvents A combination of two or more of the organic vehicles as constituent components. Although it is not particularly limited, the content of the organic vehicle is suitably an amount that becomes approximately 10% by mass to 60% by mass of the entire paste.

The organic vehicle disclosed herein may further include an organic binder. As the organic binder, any one that can be evaporated and removed (degreased) in the debinding treatment (typically heat treatment at 250°C to 500°C in an oxidizing environment) during calcination (degreasing) is sufficient, and as long as it is the same as the previous one. The resin contained in the conductor forming paste for the same purpose can be used without particular limitation. Suitable organic binders from the above viewpoints include, for example, cellulose polymers such as ethyl cellulose and hydroxyethyl cellulose, polybutyl methacrylate, polymethyl methacrylate, and poly(methyl methacrylate). Acrylic resins such as ethyl methacrylate, epoxy resins, phenol resins, alkyd resins, polyvinyl alcohol, polyvinyl butyral, etc. are used as basic organic adhesives.

(Other ingredients)

In the conductor formation paste disclosed herein, the same various organic additives as the previous conductor formation paste may be contained as necessary. Examples of the organic additives include: various organic adhesives (which can be repeated with the vehicle, or a different adhesive may be added separately), or silicon-based, Various coupling agents such as titanate series and aluminum series. Examples of the organic binder include those based on acrylic resins, epoxy resins, phenol resins, alkyd resins, cellulosic polymers, polyvinyl alcohol, polyvinyl butyral, and the like. Suitable is Those capable of imparting good adhesiveness and coating film (adhesion film to the substrate) forming performance to the conductor forming paste of the present invention. In addition, when it is desired to impart photocurability (photosensitivity) to the conductor forming paste, various photopolymerizable compounds and photopolymerization initiators can also be suitably added.

The conductor forming paste disclosed herein may further contain polymerization initiators, surfactants, defoamers, plasticizers, tackifiers, antioxidants, dispersants, A polymerization inhibitor or the like can be used as a well-known additive for the paste for forming a conductor (for example, the paste for forming an internal electrode layer). The content of the additive may be appropriately set in accordance with the purpose of the addition, and since it does not characterize the present invention, detailed description is omitted.

<Preparation of Paste for Conductor Formation>

The manufacturing method of the paste for conductor formation disclosed herein is not particularly limited. For example, a well-known mixing device such as a ball mill or a three-roll mill can be used to mix the components contained in the conductor forming paste. The form in which these components are mixed is not particularly limited, and, for example, all the components may be mixed at once or may be mixed in an appropriately set order.

<Use>

Since the conductor forming paste disclosed herein can highly improve the continuity of the conductor film, it can be preferably applied to conductor films that require good continuity, such as the formation of internal electrode layers in multilayer ceramic electronic parts. For example, it is particularly suitable for the application of forming the internal electrode layer of a multilayer ceramic capacitor. As shown in FIG. 1, the multilayer ceramic capacitor 200 may be a conductive film (including a conductive film containing nickel particles and barium titanate particles). The internal electrode layer 220 and the ceramic layer (dielectric layer) 210 of the calcined body of the paste used are alternately laminated and formed. It is suitable as a paste for forming the internal electrode layer of the multilayer ceramic capacitor 200. In the application, by reducing the amount of barium titanate used, the barium titanate particles can inhibit the adverse effects (such as composition changes) on the dielectric layer. Therefore, it is particularly meaningful to apply the technology disclosed herein.

<Construction of Multilayer Ceramic Capacitors>

The conductor forming paste disclosed herein can be used for the construction of the multilayer ceramic capacitor 200 in a form including the following steps, for example.

That is, the conductor forming paste disclosed herein is prepared. The conductor forming paste is applied to a dielectric material (for example, ceramic materials such as barium titanate or strontium titanate) in a manner that becomes the desired shape and thickness by screen printing or dispenser coating method. On the green sheet (the unfired dielectric sheet that becomes the dielectric film after firing). A plurality of green sheets in which the unfired conductor film is formed as described above is produced, and the green sheets are laminated and pressure-bonded. In this way, an unfired laminated wafer in which an unfired conductor film and a dielectric film are laminated is obtained.

Then, the laminated wafer is dried, and thereafter, it is heated in a heater under appropriate heating conditions (the highest calcination temperature is about 800°C to 1400°C, preferably 1000°C to 1400°C, particularly preferably 1200°C to 1300°C ) Heating for a predetermined time (as the time to maintain at the highest calcination temperature, for example, about 10 minutes to 2 hours), thereby sintering (sintering) and hardening the wafer. In a preferred form, the prescribed high-speed calcination conditions (that is, from room temperature (typically room temperature) to the maximum calcination temperature, 600°C/hour to 20000°C/hour (e.g., 1000°C/hour~ 15000℃/hour) The calcination conditions of the process of heating up at the rate of calcination. By performing this series of processes, a target electronic component body 250 such as a capacitor in which a conductor film (internal electrode layer) 220 and a dielectric film 210 are laminated can be obtained.

Finally, a paste for forming an external electrode (which may be the same as the paste for forming a conductor) is applied to a predetermined portion of the electronic component body 250 and fired, thereby forming the external electrode 230. In this way, multilayer ceramic electronic parts can be constructed. In addition, the construction method itself does not particularly characterize the present invention, so a detailed description is omitted.

Furthermore, although it is not intended to limit the use, as described above, by using the conductor forming paste disclosed in this article, compared with the previous conductor forming paste, even when nickel particles are micronized, It is possible to preferably form a fine conductor film in which thermal shrinkage during firing is suppressed, heat resistance is improved, and further thinning is achieved. Therefore, according to the conductor forming paste 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 also be suitably formed.

<Method of Manufacturing Multilayer Ceramic Capacitors>

The technology disclosed herein may include providing a method for manufacturing a multilayer ceramic capacitor including a step of forming an internal electrode layer using the conductor forming paste, and a multilayer ceramic capacitor manufactured by the method. That is, according to the technology disclosed herein, a method for manufacturing a multilayer ceramic capacitor including the formation of an internal electrode layer using the conductor forming paste and a multilayer ceramic capacitor manufactured by the method are provided. According to the manufacturing method, it is possible to provide a high-performance (for example, large-capacity) multilayer ceramic capacitor having an internal electrode layer with good continuity.

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

<Preparation of Paste for Conductor Formation>

A variety of nickel powders with different molar fractions of nickel oxide (NiO), nickel hydroxide (Ni(OH) _{2 ), and metallic nickel (Ni) on the surface of nickel particles are prepared.} Weigh the nickel powder (average particle size about 180nm) and barium titanate powder (average particle size about 30nm), and stir and mix them to prepare a powder material for conductor formation. Then, this powder material for conductor formation was used to prepare a Ni paste. That is, the final paste composition (mass ratio) becomes 57.5 mass% of the powder material for conductor formation and the remaining part is the vehicle (solvent is 40.5 mass%, binder component is 2 mass%), and each material is weighed and used Three-roll mill for mixing. Here, as shown in Table 1, the usage amount of the barium titanate powder with respect to 100 parts by mass of Ni powder was varied between 0 parts by mass and 15 parts by mass to prepare Ni paste. In this way, the Ni paste of each example was prepared.

Regarding the Ni paste of each example, the molar fraction A of NiO on the surface of the nickel particles used, the molar fraction B of Ni(OH) _{2 and} the molar fraction C of Ni, NiO and Ni(OH) ₂ mole fraction ratio (B / a), the addition amount of barium titanate are summarized and shown in table 1. In addition, 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 of each example were obtained by the above-mentioned method based on XPS.

<Formation of Conductor Film>

The Ni paste of each example was used to produce a conductor film. That is, the Ni paste was applied to a ceramic green sheet _{mainly composed of BaTiO 3} and dried so that the coating amount based on the mass of the Ni powder became 0.5 mg/cm ^2. A plurality of green sheets having an unfired conductor film formed as described above are produced, and the green sheets are laminated and pressure-bonded. After that, the calcination process is carried out in a mixed gas (reducing) environment containing 1% hydrogen and 99% nitrogen (the temperature rise rate is 200°C/hour, the temperature drop rate is 200°C/hour, and the maximum calcination temperature is 1250°C. 10 minutes). In this way, a fired laminated body sheet in which a conductor film and a ceramic base material (fired ceramic base material) are alternately formed is obtained.

The image obtained by observing the cross section of the calcined laminate sheet obtained by SEM (Scanning Electron Microscope) at 5000 times magnification was analyzed. The length (L1) and the length (L2) of the portion where the conductor film covers the dielectric film (ceramic substrate after sintering) in the sintered product were calculated to calculate the coverage rate (=[L2/L1]×100). This coverage rate can be grasped as an index of the continuity of the conductor film (and further, the effect of suppressing firing shrinkage). That is, it can be said that the higher the coverage, the better the continuity of the conductor film, and the greater the firing shrinkage suppression effect. The results are shown in Table 1 and Fig. 2. Fig. 2 is a graph showing the relationship between the molar fraction ratio (B/A) of nickel oxide and nickel hydroxide and the coverage (conductor film continuity). In addition, regarding Examples 2 to 4, the cross-sectional SEM images of the fired laminate sheet when the addition amount of barium titanate is 5 parts by mass is shown in FIGS. 3 to 5.

As shown in Table 1 and Figure 2, when the addition amount of barium titanate is less than 10 parts by mass When the mole fraction ratio (B/A) of nickel oxide and nickel hydroxide increases from 0 (zero), the coverage rate (continuity of the conductor film) temporarily shows a tendency to increase, and it is extremely large in the middle. After the value, it turns into a decreasing tendency again. That is, it was confirmed that the coverage rate showed a tendency to decrease regardless of whether the molar fraction ratio (B/A) was too large or too small. In addition, when the addition amount of barium titanate is the same, in the region where the molar fraction ratio (B/A) of nickel oxide and nickel hydroxide (B/A) is 0.2≦(B/A)<1, a better coverage rate can be achieved (Example 3~Example 5). On the other hand, when the addition amount of barium titanate is 15 parts by mass or more, the tendency is not seen, and the more the molar fraction ratio (B/A) increases, the more the coverage rate shows a tendency to increase. Therefore, it was confirmed that the increase in the coverage rate (continuity of the conductor film) caused by the molar fraction ratio (B/A) being specified in the preferred range disclosed in the text, the addition amount of barium titanate is It is particularly effective when it is 10 parts by mass or less.

The specific examples of the present invention have been described in detail above, but these are only examples and do not limit the scope of the patent application. The technology described in the scope of the patent application includes various modifications and changes to the specific examples exemplified above.

Claims (7)

A conductor forming paste for forming a conductor film, comprising: nickel particles, barium titanate particles, and a dispersion medium, relative to 100 parts by mass of the nickel particles, the content of the barium titanate particles is 10 parts by mass or less , And 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. The conductor forming paste described in the first item of the scope of patent application, wherein the ratio (B/A) is 0.3≦(B/A)≦0.7. The conductor-forming paste described in item 1 or item 2 of the scope of patent application, wherein the mole fraction A of the nickel oxide is greater than the mole fraction B of the nickel hydroxide by 12 mole% or more. The conductor-forming paste described in item 1 or item 2 of the scope of patent application, wherein the value obtained by subtracting the molar fraction B of the nickel hydroxide from the molar fraction A of the nickel oxide (A- B) Less than 30 mol%. The conductor forming paste described in item 1 or item 2 of the scope of patent application, wherein the average particle diameter of the nickel particles is 10 nm to 500 nm. The conductor-forming paste described in item 1 or item 2 of the scope of the patent application is used to form internal electrode layers in multilayer ceramic electronic parts. A multilayer ceramic capacitor includes an internal electrode layer including a calcined body of the conductor-forming paste described in the first or second patent application.

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