TWI819190B - Conductive paste, electronic components, and laminated ceramic capacitors - Google Patents

Abstract

The present invention provides a conductive slurry in which the dispersibility of conductive powder is excellent, the viscosity stability is further excellent, and the amount of gas generated is small at low temperatures at the beginning of firing. It is a conductive slurry containing conductive powder, ceramic powder, dispersant, binder resin and organic solvent. It is characterized in that the dispersant contains an amino acid dispersant, an amine dispersant and an alkyl phosphate compound. 0.03% by mass or more and 0.3% by mass or less of an amino acid-based dispersant, 0.2% by mass or more of an amine-based dispersant, 0.05% by mass or more of an alkyl phosphate compound, an amino acid-based dispersant and the above-mentioned amine-based dispersant The total content of the dispersant is 0.5% by mass or less, and the total content of the amino acid dispersant, amine dispersant and alkyl phosphate compound is 0.7% by mass or less.

Description

Conductive paste, electronic components, and laminated ceramic capacitors

The present invention relates to a conductive paste, an electronic component, and a multilayer ceramic capacitor.

As electronic devices such as mobile phones and digital devices become smaller and have higher performance, electronic components including multilayer ceramic capacitors are also expected to be smaller and have higher capacities. The laminated ceramic capacitor has a structure in which a plurality of dielectric layers and a plurality of internal electrode layers are alternately laminated. By thinning the dielectric layers and internal electrode layers, it is possible to achieve miniaturization and high capacity.

For example, a multilayer ceramic capacitor can be manufactured in the following manner. First, conductive paste for internal electrodes is printed (coated) in a predetermined electrode pattern on the surface of a green sheet containing dielectric powder such as barium titanate (BaTiO ₃ ) and a binder resin, and is dried to form a dry membrane. Next, the dry film and the green sheet are laminated so as to alternately overlap each other, and are heat-pressed and bonded to form an integrated laminated body. The laminated body is cut, subjected to an organic binder removal treatment in an oxidizing gas or an inert gas, and then fired to obtain a fired wafer. Next, the paste for external electrodes is applied to both ends of the fired wafer, and after firing, the surface of the external electrodes is plated with nickel or the like to obtain a multilayer ceramic capacitor.

Generally, the conductive slurry used to form the internal electrode layer contains conductive powder, ceramic powder, binder resin, and organic solvent. In order to improve the dispersibility of conductive powder and the like, the conductive slurry may contain a dispersant. As internal electrode layers become thinner in recent years, conductive powders also tend to have smaller particle diameters. When the particle size of the conductive powder is small, the specific surface area of the particle surface becomes large, so the surface activity of the conductive powder (metal powder) becomes high, which may cause a decrease in dispersibility and a decrease in viscosity characteristics.

Therefore, attempts have been made to improve the viscosity characteristics of the conductive slurry over time. For example, Patent Document 1 describes a conductive slurry that contains at least a metal component, an oxide, a dispersant, and a binder resin. The metal component is Ni powder whose surface composition has a specific composition ratio. The acid points of the dispersant are The amount is 500~2000μmol/g, and the acid point amount of the binder resin is 15~100μmol/g. Furthermore, according to Patent Document 1, this conductive slurry has good dispersibility and viscosity stability.

In addition, Patent Document 2 describes a conductive slurry for internal electrodes, which is composed of a common material of conductive powder, resin, organic solvent, ceramic powder mainly composed of TiBaO ₃ , and an aggregation inhibitor, wherein the aggregation inhibitor is The content of the agent is 0.1% by weight or more and 5% by weight or less. The aggregation inhibitor is a tertiary amine or a secondary amine represented by a specific structural formula. According to Patent Document 2, this conductive paste for internal electrodes suppresses aggregation of common material components, has excellent long-term storage properties, and can achieve thinning of multilayer ceramic capacitors.

On the other hand, when thinning the internal electrode layer, it is required that the dry film obtained by printing the conductive paste for the internal electrode on the surface of the green sheet and drying it has a high density. For example, Patent Document 3 proposes a metal ultrafine powder slurry that contains an organic solvent, a surfactant, and metal ultrafine particles, wherein the surfactant is oleyl sarcosine, and The above-mentioned ultrafine metal powder slurry contains not less than 70% by mass and not more than 95% by mass of the above-mentioned ultrafine metal powder, and contains more than 0.05 parts by mass and less than 2.0 parts by mass of the above-mentioned surfactant based on 100 parts by mass of the above-mentioned ultrafine metal powder. According to Patent Document 3, by preventing aggregation of ultrafine particles, it is possible to obtain a metal ultrafine powder slurry that has no agglomerated particles and is excellent in dispersibility and dry film density.

[Previous technical literature]

【Patent Document】

[Patent Document 1] Japanese Patent Application Publication No. 2015-216244

[Patent document 2] Japanese Patent Application Publication No. 2013-149457

[Patent Document 3] Japanese Patent Application Publication No. 2006-063441

However, as electrode patterns become thinner in recent years, there is a demand for further improvement in viscosity characteristics over time and improvement in surface smoothness of the dried film after application. In addition, due to the thinning of the electrode pattern, shrinkage mismatch occurs at the interface between the internal electrode layer and the dielectric layer when the laminated body is fired, making it easier to generate structural defects such as cracks and delamination.

The inventors of the present invention have discovered that the generation of decomposition gas derived from components contained in the conductive slurry at a low temperature at the start of firing of the laminated body is one of the causes of cracks and delamination. That is, it is considered that when the laminated body is fired, the dielectric layer (green sheet) starts firing When a certain amount of gas is generated from the dry film at a temperature where the junction temperature is low, the gas remains between the dielectric layers and voids are generated, thereby causing cracks and interlayer delamination.

Even in conductive pastes in which problems such as cracks and interlayer delamination have not been reported in the past, when the electrode pattern is further thinned, the generation of a trace amount of gas at low temperature at the beginning of firing may cause cracks and interlayer delamination. Reason for stripping.

In view of such a situation, an object of the present invention is to provide a conductive slurry that has high dry film surface smoothness and high dry film density, has excellent dispersibility of conductive powder, and has very good viscosity changes over time. Small, more excellent viscosity stability, and less gas generation at low temperatures at the beginning of firing.

In a first aspect of the present invention, a conductive slurry is provided, which includes conductive powder, ceramic powder, dispersant, binder resin and organic solvent, wherein the dispersant contains the following general formula (1) The amino acid-based dispersant, the amine-based dispersant represented by the following general formula (2), and the phosphate alkyl ester compound contain 0.03 mass % or more and 0.3 mass % or less of the amino acid based on the entire conductive slurry. A dispersant containing 0.2% by mass or more of an amine dispersant relative to the entire conductive slurry and 0.05% by mass or more of an alkyl phosphate compound relative to the entire conductive slurry. , the total content of the amino acid dispersant and the amine dispersant is 0.5% by mass or less, and the total content of the amino acid dispersant, the amine dispersant and the alkyl phosphate compound relative to the entire conductive slurry is 0.7% by mass or less.

【Chemical 1】

(Wherein, in formula (1), R ₁ represents a chain hydrocarbon group having 10 to 20 carbon atoms.)

(Wherein, in formula (2), R ₂ represents an alkyl group, alkenyl group or alkynyl group with 8 to 16 carbon atoms, R ₃ represents an oxyethylene group, an oxypropenyl group or a methylene group, and R ₄ represents an oxyethylene group. group or oxypropenyl group, R ₃ and R ₄ may be the same or different. In addition, the N atom in formula (2) is not directly bonded to the O atom in R ₃ and R ₄ , and Y is 0~2 Numerical value, Z is a numerical value from 1 to 2.)

In addition, in the general formula (1), R ₁ ideally represents a linear hydrocarbon group having 10 to 20 carbon atoms. In addition, the conductive powder preferably contains at least one metal powder selected from the group consisting of Ni, Pd, Pt, Au, Ag, Cu and alloys thereof. In addition, the conductive powder is preferably contained in an amount of not less than 40% by mass and not more than 60% by mass relative to the entire conductive slurry. In addition, the average particle diameter of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less. In addition, the ceramic powder preferably contains a perovskite type oxide. In addition, the average particle diameter of the ceramic powder is preferably 0.01 μm or more and 0.5 μm or less. In addition, the binder resin preferably contains at least one kind of cellulose-based resin, acrylic resin, and butyral-based resin. Moreover, it is preferable to contain 0.05 mass % or more and 0.3 mass % or less of an amino acid-type dispersing agent with respect to the whole conductive paste. In addition, the above-mentioned conductive paste is preferably used for internal electrodes of multilayer ceramic capacitors.

In a second aspect of the present invention, there is provided an electronic component formed using the above-mentioned conductive paste.

In a third aspect of the present invention, there is provided a laminated ceramic capacitor having a laminated body in which an internal electrode layer formed using the conductive slurry and a dielectric layer are laminated.

The conductive slurry of the present invention has very small viscosity changes over time and more excellent viscosity stability. At the same time, it has excellent dispersibility of conductive powder, and has high surface smoothness and high stability in the dried film after coating. dry film density. In addition, the conductive paste of the present invention can suppress the occurrence of cracks and delamination because the amount of gas generated is small at a low temperature at the beginning of firing.

The electrode patterns of electronic components such as laminated ceramic capacitors formed using the conductive paste of the present invention also have excellent adhesion to the conductive paste when forming thin electrodes, and have highly accurate and uniform widths and thicknesses.

1: Multilayer ceramic capacitor

10: Ceramic laminated body

11: Internal electrode layer

12: Dielectric layer

20:External electrode

21:External electrode layer

22:Electroplating layer

[Fig. 1] is a perspective view and a cross-sectional view showing the multilayer ceramic capacitor according to this embodiment.

[Conductive paste]

The conductive slurry of this embodiment contains conductive powder, ceramic powder, dispersant, binder resin, and organic solvent. Each component is described in detail below.

(Conductive powder)

The conductive powder is not particularly limited, and metal powder may be used. For example, one or more powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof may be used. Among them, from the viewpoint of electrical conductivity, corrosion resistance, and cost, powder of Ni or its alloy is ideal. As the Ni alloy, for example, an alloy (Ni alloy) of at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd and Ni can be used. The Ni content in the Ni alloy is, for example, 50 mass% or more, and ideally is 80 mass% or more. In addition, in order to suppress severe gas generation due to partial thermal decomposition of the binder resin during the binder removal process, the Ni powder may contain S on the order of several hundred ppm.

The average particle diameter of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. When the average particle diameter of the conductive powder is within the above range, it can be suitably used as a slurry for internal electrodes of thinned multilayer ceramic capacitors. For example, the smoothness and dry film density of the dry film can be improved. The average particle diameter is a value determined based on observation with a scanning electron microscope (SEM), and is obtained by measuring the particle diameters of a plurality of particles one by one from an image obtained by observing with a SEM at a magnification of 10,000 times. average value.

The content of the conductive powder is preferably 30 mass % or more and less than 70 mass % with respect to the entire conductive slurry, and more preferably 40 mass % or more and 60 mass % or less. in conductivity When the content of the powder is within the above range, conductivity and dispersibility are excellent.

(ceramic powder)

The ceramic powder is not particularly limited. For example, in the case of a slurry for internal electrodes of a multilayer ceramic capacitor, a conventional ceramic powder can be appropriately selected depending on the type of multilayer ceramic capacitor to be used. Examples of the ceramic powder include perovskite-type oxides containing Ba and Ti, and preferably barium titanate (BaTiO ₃ ).

As the ceramic powder, a ceramic powder containing barium titanate as a main component and an oxide as a sub-component can be used. Examples of oxides include Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and oxides of one or more rare earth elements. Such ceramic powders include, for example, perovskite-type oxide ferroelectric ceramic powders in which Ba atoms and Ti atoms of barium titanate (BaTiO ₃ ) are substituted with other atoms such as Sn, Pb, and Zr.

As the internal electrode slurry, powder having the same composition as the dielectric ceramic powder constituting the green sheet of the multilayer ceramic capacitor can be used. This can suppress the occurrence of cracks due to shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer in the sintering process. In addition to the above, examples of such ceramic powder include ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , R (rare earth element) ₂ O ₃ , TiO ₂ , and Nd ₂ O ₃ and other oxides. In addition, one type of ceramic powder may be used, or two or more types may be used.

The average particle diameter of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, preferably in the range of 0.01 μm or more and 0.3 μm or less. By setting the average particle diameter of the ceramic powder within the above range, when used as a slurry for internal electrodes, sufficiently thin and uniform internal electrodes can be formed. The average particle diameter is a value determined based on observation with a scanning electron microscope (SEM), and is obtained step by step from an image obtained by observing the SEM at a magnification of 50,000 times. The average value obtained by measuring the particle diameters of multiple particles.

The content of the ceramic powder is preferably not less than 1 part by mass and not more than 30 parts by mass based on 100 parts by mass of the conductive powder, and more preferably not less than 3 parts by mass and not more than 30 parts by mass.

The content of the ceramic powder is preferably not less than 1% by mass and not more than 20% by mass, and more preferably not less than 5% by mass and not more than 20% by mass, relative to the entire conductive slurry. When the content of the ceramic powder is within the above range, conductivity and dispersibility are excellent.

(Binder resin)

The binder resin is not particularly limited, and conventional resins can be used. Examples of the binder resin include cellulose-based resins such as methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, and nitrocellulose, acrylic resins, and butyral resins such as polyvinyl butyral. Aldehyde resin, etc. Among these, it is preferable to contain ethyl cellulose from the viewpoint of solubility in a solvent, combustion decomposability, etc. In addition, when used as a slurry for internal electrodes, a butyral-based resin may be included from the viewpoint of improving the bonding strength with the green sheet, or the butyral-based resin may be used alone. One type of binder resin may be used, or two or more types may be used. Examples of the binder resin include cellulose resin and butyral resin. In addition, the molecular weight of the binder resin is, for example, 20,000 to 200,000.

The content of the binder resin is preferably not less than 1 part by mass and not more than 10 parts by mass based on 100 parts by mass of the conductive powder, and more preferably not less than 1 part by mass and not more than 8 parts by mass.

The content of the binder resin is preferably not less than 0.5% by mass and not more than 10% by mass, and more preferably not less than 1% by mass and not more than 6% by mass relative to the entire conductive slurry. When the content of the binder resin is within the above range, conductivity and dispersibility are excellent.

(organic solvent)

The organic solvent is not particularly limited, and a conventional organic solvent that can dissolve the above-mentioned binder resin can be used. Examples of the organic solvent include dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, and ethylene glycol monobutyl ether acetate. , acetate solvents such as dipropylene glycol methyl ether acetate, terpene solvents such as terpineol and dihydroterpineol, hydrocarbon solvents such as tridecane, nonane, and cyclohexane, etc. In addition, one type of organic solvent may be used, or two or more types of organic solvents may be used.

The content of the organic solvent is preferably not less than 40 parts by mass and not more than 100 parts by mass based on 100 parts by mass of the conductive powder, and more preferably not less than 65 parts by mass and not more than 95 parts by mass. When the content of the organic solvent is within the above range, conductivity and dispersibility are excellent.

The content of the organic solvent is preferably not less than 20% by mass and not more than 60% by mass, and more preferably not less than 35% by mass and not more than 55% by mass, based on the entire conductive slurry. When the content of the organic solvent is within the above range, conductivity and dispersibility are excellent.

(dispersant)

The conductive slurry of this embodiment contains a dispersant. The dispersant includes an amino acid dispersant (amino acid surfactant) represented by the general formula (1), an amine dispersant represented by the general formula (2), and an alkyl phosphate compound. The alkyl phosphate compound is an acid dispersant. In addition, the dispersant may contain dispersants other than the above three types.

The inventors of the present invention conducted research on various dispersants used in conductive slurries and found that by combining the above three dispersants in specific blending amounts, the viscosity stability of the conductive slurry can be improved. It is very excellent. The dried film after coating has high surface smoothness and high dry film density. The dispersibility of the conductive powder is excellent, and the amount of gas generation is small at the low temperature at the beginning of firing. , can inhibit the occurrence of cracks and interlayer delamination. born. Hereinafter, the dispersant used in this embodiment will be described.

The amino acid-based dispersant used in this embodiment has an N-acyl amino acid skeleton as represented by the following general formula (1) and a chain hydrocarbon group having a carbon number of 10 to 20.

(Wherein, in formula (1), R ₁ represents a chain hydrocarbon group having 10 to 20 carbon atoms.)

In the above formula (1), R ₁ represents a chain hydrocarbon group having 10 to 20 carbon atoms. The number of carbon atoms in R ₁ is preferably 15 or more and 20 or less. In addition, the chain hydrocarbon group may be a linear hydrocarbon group or a branched hydrocarbon group. In addition, the chain hydrocarbon group may be an alkyl group, an alkenyl group or an alkynyl group. R ₁ is preferably a linear hydrocarbon group, more preferably a linear alkenyl group having a double bond.

As the amino acid dispersant represented by the above formula (1), for example, an amino acid dispersant satisfying the above characteristics among commercially available products can be selected and used. In addition, the above-mentioned amino acid-based dispersant may be produced using conventionally known production methods to satisfy the above-mentioned characteristics.

The amine dispersant used in this embodiment is represented by the following general formula (2), and is a tertiary amine or a secondary amine, and has a structure in which an amine group is bonded to one or two oxyalkylene groups.

【Chemical 4】

(Wherein, in formula (2), R ₂ represents an alkyl group, alkenyl group or alkynyl group with 8 to 16 carbon atoms, R ₃ represents an oxyethylene group, an oxypropenyl group or a methylene group, and R ₄ represents an oxyethylene group. group or oxypropylene group, R ₃ and R ₄ may be the same or different. In addition, the N atom in formula (2) is not directly bonded to the O atom in R ₃ and R ₄ , and Y is a value between 0 and 2 , Z is a value from 1 to 2.)

In the above formula (2), R ₂ represents an alkyl group, alkenyl group or alkynyl group having 8 to 16 carbon atoms. When the number of carbon atoms of R ₂ is within the above range, the powder in the conductive slurry has sufficient dispersibility and has excellent solubility in the solvent. In addition, R ₂ is preferably a linear hydrocarbon group.

In the above formula (2), R ₃ represents an oxyethylene group, an oxypropylene group or a methylene group, and R ₄ represents an oxyethylene group or an oxypropylene group. R ₃ and R ₄ may be the same or different. In addition, the N atom in the formula (2) is not directly bonded to the O atom in R ₃ and R ₄ , Y is a numerical value from 0 to 2, and Z is a numerical value from 1 to 2.

For example, in the above formula (2), R ₃ is an oxyalkylene group represented by -AO-. When Y is 1 to 2, the O atom in the terminal oxyalkylene group and (R ₃ ) _Y Adjacent H atoms bond. In addition, when R ₃ is a methylene group, (R ₃ ) _Y is represented by -(CH ₂ ) _Y -. When Y is 1 to 2, it is bonded with the adjacent H element to form a methyl group. (-CH ₃ ) or ethyl (-CH ₂ -CH ₃ ). In addition, when R ₄ is an oxyalkylene group represented by -AO-, the O atom in the oxyalkylene group at the terminal portion and the H atom adjacent to (R ₄ ) _Z are bonded.

In the above formula (2), when Y is 0, the above-mentioned amine dispersant is a secondary amine having -R ₂ , one hydrogen group and -(R ₄ ) _z H. For example, when Y is 0 and Z is 2, the above-mentioned amine dispersant is composed of an alkyl group, alkenyl group or alkynyl group with 8 to 16 carbon atoms, one hydrogen group, and -(R ₄ ) ₂ H. In the secondary amine that constitutes the above-mentioned -(R ₄ ) ₂ H, it is -(AO) ₂ H formed by bonding either an vinyl dioxide group or a propylene dioxide group to an H element.

In addition, in the above formula (2), when Y is 1, the above-mentioned amine dispersant is a tertiary amine having -R ₂ , -R ₃ H and -(R ₄ ) _z H. Moreover, when Y is 2, the above-mentioned amine-based dispersant is a tertiary amine having -R ₂ , -(R ₃ ) ₂ H, and -(R ₄ ) _z H. The above-mentioned -(R ₃ ) ₂ H is It is -(AO) ₂ H or -C ₂ H ₅ in which any one of an ethylene dioxide group, a propenyl dioxide group or an ethylene group is bonded to an H element.

As the amine-based dispersant represented by the above formula (2), for example, an amine-based dispersant satisfying the above characteristics among commercially available products can be selected and used. In addition, the above-mentioned amine-based dispersant may be produced using conventionally known production methods to satisfy the above-mentioned characteristics.

Furthermore, in this embodiment, an alkyl phosphate compound is used as an acid-based dispersant. The alkyl phosphate compound is a phosphate ester having an alkyl group, preferably has a polyoxyalkylene structure, and may be an alkyl phosphate polyoxyalkylene compound.

The inventors of the present invention conducted research on various dispersants used in conductive slurries. As a result, they found that by using the dispersants used in conductive slurries in addition to the above-mentioned amino acid-based dispersants and amines, The system contains an alkyl phosphate compound in addition to the dispersant, and when the laminated body is fired, the generation of decomposition gas derived from the components contained in the conductive slurry is delayed, thereby suppressing structural defects such as cracks and delamination. produce. The content of each component used as a dispersant will be described below.

The above-mentioned amino acid dispersant is contained in an amount of not less than 0.03% by mass and not more than 0.3% by mass relative to the entire conductive slurry. When the amount of the amino acid-based dispersant is less than 0.03% by mass, sufficient dispersibility of the conductive slurry may not be obtained. When the content of the above-mentioned amino acid-based dispersant exceeds 0.3% by mass, the amount of decomposition gas generated from the conductive slurry at the beginning of firing is large, and the dispersant removability may be insufficient. In addition, from the viewpoint of further improving dispersibility, the amino acid-based dispersant may be contained in an amount of 0.05% by mass or more and 0.3% by mass or less, or 0.10% by mass or more and 0.3% by mass or less, based on the entire conductive slurry.

The above-mentioned amine dispersant is contained in an amount of 0.2% by mass or more relative to the entire conductive slurry. When the amine dispersant is less than 0.2% by mass, the conductive slurry may not have sufficient viscosity stability and may have insufficient dispersibility.

Contains 0.05% by mass or more of alkyl phosphate compound relative to the entire conductive slurry. When the content of the alkyl phosphate compound is less than 0.05% by mass, the conductive paste cannot obtain sufficient viscosity stability, and decomposition gas may be generated at the low temperature at the beginning of sintering, which may cause cracks and interlayer delamination. .

In addition, the total content of the above-mentioned amine-based dispersant and the above-mentioned amino acid-based dispersant is 0.5 mass % or less with respect to the entire conductive slurry. When the total amount of the two dispersants exceeds the above range, decomposition gas originating from components contained in the conductive slurry may be generated at a lower temperature when the laminated body is fired. , causing voids and poor peeling of the green sheet.

In addition, the total content of the above-mentioned amino acid-based dispersant, the above-mentioned amine-based dispersant, and the alkyl phosphate compound is 0.7 mass % or less with respect to the entire conductive slurry. When the content of the above three kinds of dispersants exceeds 0.7% by mass, when the laminated body is fired, the dispersion If the agent is not fully removed and a part of it remains, structural defects such as cracks, voids, poor peeling of the green sheet, and sheet erosion may occur.

In addition, the conductive slurry may contain a dispersant other than the above-mentioned amino acid-based dispersant, amine-based dispersant, and alkyl phosphate compound within a range that does not inhibit the effects of the present invention. Examples of dispersants other than the above include acid-based dispersants including higher fatty acids, polymeric surfactants, and the like, cationic dispersants other than acid-based dispersants, nonionic dispersants, amphoteric surfactants, and polymeric surfactants. Molecular dispersants, etc. In addition, these dispersants may be used alone or in combination of two or more.

(Conductive paste)

The manufacturing method of the conductive paste of this embodiment is not particularly limited, and conventionally known methods can be used. For example, the conductive slurry can be produced by stirring and kneading the above-mentioned components using a three-roll mill, a ball mill, or a mixer. At this time, if a dispersant is applied to the surface of the conductive powder in advance, the conductive powder will not agglomerate and can be fully dispersed. The surface of the conductive powder will be dispersed with the dispersant, making it easy to obtain a uniform conductive slurry. Alternatively, the binder resin may be dissolved in an organic solvent for the carrier to prepare an organic carrier, and the conductive powder, ceramic powder, organic carrier, and dispersant may be added to the organic solvent for the slurry, and then stirred and mixed. Refining to prepare conductive slurry.

When the viscosity 24 hours after the production of the conductive slurry is used as a reference (0%), the viscosity of the conductive slurry after it has been left to stand for 28 days from the reference date is ideally within ±10%. In addition, the viscosity of the above-mentioned conductive slurry can be measured, for example, by the method described in the Examples (a method of measuring using a B-type viscometer manufactured by Brookfield Corporation under the conditions of 10 rpm (shear rate = 4 sec ^-1 )). Determination.

In addition, the surface smoothness of the dry film formed by printing the conductive paste can be evaluated by surface roughness. The surface roughness of the conductive slurry can be measured using a surface roughness meter, for example. Specifically, after applying the conductive slurry on the glass substrate using an applicator (the gap thickness is 10 μm), it can be dried in the air at 120° C. for 5 minutes, and the resulting dry film with a film thickness of 3 μm can be obtained. , use a surface roughness meter to measure the surface roughness of the dried film. Such surface roughness is preferably 0.05 μm or less, and more preferably 0.04 μm or less.

In addition, the dry film density (DFD) of the dry film obtained by drying the conductive paste after printing is preferably 5.45 g/cm ³ or more, more preferably more than 5.45 g/cm ³ , and further preferably more than 5.5 g/cm 3 cm ³ .

In addition, the mass change amount (ΔTG) at 250°C when the conductive slurry is heated in nitrogen gas at a temperature increase rate of 5°C/min and thermogravimetry (TG) is performed is preferably less than 0.0020%/s. More ideally, it is 0.0015%/s or less. When the amount of mass change is within the above range, the dispersant removability during firing can be improved.

The conductive paste can be suitably used in electronic components such as multilayer ceramic capacitors. The multilayer ceramic capacitor has a dielectric layer formed using a green sheet and an internal electrode layer formed using a conductive paste.

In a multilayer ceramic capacitor, the dielectric ceramic powder contained in the green sheet and the ceramic powder contained in the conductive slurry are preferably powders of the same composition. The multilayer ceramic capacitor manufactured using the conductive slurry of this embodiment can suppress sheet erosion and peeling failure of the green sheet even when the thickness of the green sheet is, for example, 3 μm or less.

[Electronic parts]

Hereinafter, embodiments of electronic components and the like of the present invention will be described with reference to the drawings. In the drawings, the figures may be represented in a schematic manner or the scale may be changed as appropriate. In addition, the position, direction, etc. of a component are demonstrated suitably with reference to the XYZ orthogonal coordinate system shown in FIG. 1 etc. In this XYZ orthogonal coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is the vertical direction (up and down direction).

A in FIG. 1 and B in FIG. 1 are diagrams showing a multilayer ceramic capacitor 1 as an example of an electronic component according to the embodiment. The multilayer ceramic capacitor 1 has a multilayer body 10 in which dielectric layers 12 and internal electrode layers 11 are alternately laminated, and external electrodes 20 .

Hereinafter, a method of manufacturing a multilayer ceramic capacitor using the above-mentioned conductive slurry will be described. First, conductive paste is printed on a dielectric layer made of a green sheet and dried to form a dry film. A laminated body is obtained by laminating and press-bonding a plurality of dielectric layers having the dry film on the upper surface, and then firing the laminated body to integrate it, whereby the internal electrode layer 11 and the dielectric layer 12 are alternately prepared. The ceramic laminated body 10 is made of ground layers. Thereafter, the laminated ceramic capacitor 1 is manufactured by forming a pair of external electrodes 20 at both ends of the ceramic laminated body 10 . Below, a more detailed description is provided.

First, a green sheet, which is an unfired ceramic sheet using a dielectric material, is prepared. Examples of the green sheet include a PET film and a slurry for a dielectric layer obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a predetermined ceramic raw material powder such as barium titanate. A green sheet formed by coating a supporting film into a sheet and drying to remove the solvent. In addition, the thickness of the dielectric layer composed of the green sheet is not particularly limited, but from the viewpoint of the requirement for miniaturization of the multilayer ceramic capacitor, it is preferably 0.05 μm or more and 3 μm or less.

Next, a plurality of sheets in which dry films are formed by printing (coating) the above-mentioned conductive paste on one surface of the green sheet by a known method such as screen printing and drying are prepared. In addition, from the viewpoint of the requirement for thinning the internal electrode layer 11, the thickness of the conductive paste after printing is preferably such that the thickness of the dried film after drying is 1 μm or less.

Next, the green sheet is peeled off from the support film and laminated so that the dielectric layer composed of the green sheet and the dry film formed on one surface of the dielectric layer are alternately laminated, and then processed by heating and pressure A laminated body is obtained. Furthermore, it is also possible to adopt a configuration in which protective green sheets to which conductive paste is not applied are further disposed on both sides of the laminated body.

Next, the laminated body is cut into a predetermined size to form a green wafer, and then the green wafer is subjected to a binder removal process and fired under reducing gas, thereby manufacturing the ceramic laminated body 10 . In addition, the gas in the debinder treatment is preferably atmospheric air or N ₂ gas. The temperature during the binder removal treatment is, for example, 200°C or more and 400°C or less. In addition, the holding time at the above-mentioned temperature during the binder removal treatment is preferably from 0.5 hours to 24 hours. In addition, in order to suppress the oxidation of the metal used in the internal electrode layer, the firing is performed under a reducing gas. In addition, the temperature during firing of the laminated body is, for example, 1000°C or more and 1350°C or less. The holding time is, for example, from 0.5 hours to 8 hours.

By firing the green wafer, the organic binder in the green wafer is completely removed, and the ceramic raw material powder is fired to form the ceramic dielectric layer 12 . In addition, the organic carrier in the dry film is removed, and the nickel powder or the alloy powder containing nickel as the main component is sintered or melted to integrate, thereby forming the internal electrode layer 11, and further forming a multi-layer alternation of the dielectric layer 12 and the internal electrode layer 11. A laminated ceramic fired body made of layers of ground. In addition, from the viewpoint of bringing oxygen into the interior of the dielectric layer to improve reliability and suppress re-oxidation of the internal electrodes, it is possible to The fired laminated ceramic fired body is subjected to annealing treatment.

Then, a pair of external electrodes 20 is provided on the prepared laminated ceramic fired body, thereby manufacturing the laminated ceramic capacitor 1 . For example, the external electrode 20 includes an external electrode layer 21 and a plating layer 22 . The external electrode layer 21 is electrically connected to the internal electrode layer 11 . In addition, as a material of the external electrode 20, for example, copper, nickel, or alloys thereof can be suitably used. In addition, the electronic components are not limited to the laminated ceramic capacitors, and may be electronic components other than the laminated ceramic capacitors.

[Example]

Hereinafter, the present invention will be described in detail based on Examples and Comparative Examples, but the present invention is not limited by the Examples in any way.

[Materials used]

(Conductive powder)

As the conductive powder, Ni powder (SEM average particle diameter: 0.2 μm) was used.

(ceramic powder)

As the ceramic powder, barium titanate (BaTiO ₃ ; SEM average particle size: 0.05 μm) was used.

(Binder resin)

As the binder resin, ethyl cellulose resin and polyvinyl butyral resin (PVB resin) are used. In addition, a binder resin prepared as a carrier dissolved in terpineol was used.

(dispersant)

(1) As the amino acid-based dispersant, dispersant A represented by R ₁ =C ₁₇ H ₃₃ (linear hydrocarbon group) in the above general formula (1) is used.

(2) As the amine dispersant, use R ₂ =C ₁₂ H ₂₅ , R ₃ =C ₂ H ₄ O, R ₄ =C ₂ H ₄ O, Y=1, Z= in the above general formula (2). Dispersant B shown in 1.

(3) As the alkyl phosphate compound, a dispersant C composed of an alkyl phosphate polyoxyalkylene compound is used.

(organic solvent)

As organic solvent, terpineol is used.

[Example 1]

48% by mass of Ni powder, 5% by mass of ceramic powder, and a total of 3% by mass of binder resin (composed of ethyl cellulose resin and polyvinyl butyral) in the carrier are mixed so that the total amount is 100% by mass. resin composition), 0.10 mass% of amino acid dispersants, 0.26 mass% of amine dispersants, 0.10 mass% of alkyl phosphate compounds, and the balance of terpineol (organic solvent), and these materials Mix to prepare conductive slurry. The viscosity stability, dispersibility (dry film density, dry film surface roughness), and dispersant removability of the prepared conductive slurry were evaluated by the following methods. The evaluation results are shown in Table 1.

[Evaluation method]

(1) Viscosity stability: change in viscosity of conductive slurry

Using 24 hours after the production of the conductive slurry as the reference time, the viscosity of each sample after standing at room temperature (25°C) for 28 days from the reference time was measured by the following method. Determination. Then, using the viscosity after 24 hours after production (reference time) as the reference (0%), the value expressed as a percentage (%) is the change in the viscosity of the sample after it was left to stand for 28 days ( [(viscosity after 28 days of standing - viscosity after 24 hours from production)/viscosity after 24 hours from production] × 100), and used as the change in viscosity. The viscosity of the conductive slurry was measured using a Brookfield type B viscometer under conditions of 10 rpm (shear rate = 4 sec ^-1 ). In addition, it is more preferable that the change amount of the viscosity of the conductive slurry is smaller. The change in viscosity of the conductive paste after standing for 28 days is marked as "○" if it is 10% or less, and "△" is if it exceeds 10% and less than 40%, and it is 40% or more. The situation is marked as "×" to evaluate the viscosity stability of the conductive paste.

(2) Dispersion: surface roughness of dry film, density of dry film

<Surface roughness>

The prepared conductive paste was screen-printed on a 2.54 cm (1 inch) square piece of heat-resistant tempered glass and dried in the air at 120° C. for 1 hour, thereby preparing a 20 mm square dry film with a film thickness of approximately 3 μm. When the dispersibility of the conductive slurry is good, the surface of the dried film becomes a smooth film. In the case of poor dispersion, aggregation occurs in the conductive slurry, making the surface of the dry film rough and reducing surface smoothness. Here, the protrusions on the surface of the dried film were measured with a contact-type surface roughness meter. Specifically, the surface roughness Ra of the dried film was measured using a surface roughness measuring device (SURFCOM480 manufactured by Tokyo Precision Co., Ltd.). The smaller the value of surface roughness Ra, the smoother the surface of the dry film.

<Dry Film Density (DFD: Dry Film Density)>

The prepared conductive slurry was placed on the PET film and extended to a length of approximately 100 mm using an applicator with a width of 50 mm and a gap of 125 μm. The obtained PET film was dried at 120°C for 40 minutes to form a dried body. The dried body was cut into four 2.54cm (1 inch) squares. After peeling off the PET film, the four dry films were The thickness and mass were measured separately, and the dry film density (average value) was calculated. If the dispersion of the conductive paste is relatively If it is low and the conductive powder agglomerates, the dry film density may be reduced, resulting in poor electrical properties. The higher the dry film density, the better the dispersion.

<Evaluation of dispersion>

The case where the surface roughness Ra of the dry film is 0.04 μm or less and the dry film density DFD is 5.45 g/cm ³ or more is recorded as “○”, and the surface roughness Ra (arithmetic mean height) of the dry film exceeds 0.04 μm. When the surface roughness Ra of the dry film exceeds 0.05 μm, or the dry film density DFD is less than 5.45 g/ ^cm3 , it is recorded as "△". In the case of either cm ³ , it was recorded as "×" to evaluate the dispersibility.

(3) Evaluation of dispersant removability

The prepared conductive slurry was heated in nitrogen gas at a temperature increase rate of 5°C/min to perform thermogravimetry (TG), and the decomposition behavior caused by the difference in dispersants was analyzed to evaluate the dispersant removability. Evaluation. Specifically, a curve of mass change (ΔTG) with respect to temperature was prepared, and evaluation was performed based on the mass change (ΔTG) at 250°C. The greater the mass change amount (ΔTG) at 250°C, the greater the amount of decomposition gas generated from the conductive slurry at the start of firing.

250°C is the temperature at which sintering of the dielectric layer begins. When the dielectric layer starts to be sintered, a gap is formed in the dielectric layer, and a certain amount of decomposition gas generated from the components contained in the conductive paste can be discharged from the gap. On the other hand, when a certain amount of decomposition gas is generated before starting the firing of the dielectric layer, since there are no gaps in the dielectric layer, it is not discharged to the outside and easily accumulates between the dielectric layers to create gaps. Therefore, by measuring the mass change of the conductive slurry during heat treatment at 250° C., it is possible to determine the start of firing of the laminated body Whether the gas generated due to decomposition can be discharged through the dielectric layer (good dispersant removability), or whether it remains between the dielectric layers and becomes a cause of voids (poor dispersant removability).

In the evaluation of dispersant removability, when the mass change amount is 0.0015%/s or less, the gas generation amount is sufficiently small, so it is recorded as "○" (very good), and when the mass change amount is greater than 0.0015%/s and When it is less than 0.0020%/s, a certain amount of gas is generated, but it is an amount that can be discharged through the dielectric layer, so it is recorded as "△" (good). When the mass change amount is 0.0020%/s or more , a large amount of generated gas may not be discharged to the outside and may remain, so it is marked as "×" (defective).

[Examples 2 to 6, Comparative Examples 1 to 9]

A conductive slurry was prepared under the same conditions as in Example 1, except that the contents of dispersant A, dispersant B, and dispersant C were set to the amounts shown in Table 1 and the mixing ratio of the dispersant was changed. The viscosity stability, dispersibility (dry film density, dry film surface roughness) and dispersant removability of the prepared conductive slurry were evaluated by the above method. The evaluation results are shown in Table 1.

[Evaluation results]

As shown in Table 1, the conductive slurry of the Example has good viscosity stability. In addition, the conductive slurry of the Example has a dry film density of 5.45 g/cm ³ or more, a surface roughness Ra of 0.05 μm or less, and shows good dispersibility. Furthermore, the conductive slurry of the Example has a small weight change at 250° C., and at a low temperature at the beginning of firing, the amount of decomposition gas generated is small, and there is no concern that voids will be generated due to residual decomposition gas.

On the other hand, it was found that the conductive slurry of the comparative example in which the content of the dispersant was outside the range of the present invention had poor viscosity stability and low dispersibility.

【Industrial Applicability】

The conductive slurry according to this embodiment has excellent viscosity stability over time and excellent dispersibility. Therefore, the smoothness and dry film density of the dried film after application are excellent. Furthermore, the conductive paste according to this embodiment can suppress the generation of decomposition gas at 250° C., thereby suppressing the generation of cracks and delamination caused by the generation of voids and the like. Therefore, the conductive paste according to the present embodiment can be particularly suitably used as a raw material for internal electrodes of laminated ceramic capacitors that are chip components (electronic components) of electronic devices such as mobile phones and digital devices.

In addition, the technical scope of the present invention is not limited to the modes described in the above embodiments and the like. One or more of the requirements described in the above-mentioned embodiments and the like may be omitted. In addition, the requirements described in the above embodiments and the like can be combined appropriately. In addition, as long as permitted by law, the disclosure contents of all documents cited in the above-described embodiments, etc. are cited as part of the description of this specification. In addition, whenever permitted by law, citing Japanese patent application as a Japanese patent application The contents of 2019-022906 are not included in this manual.

Claims (11)

A conductive slurry containing conductive powder, ceramic powder, a dispersant, a binder resin and an organic solvent, wherein the dispersant contains an amino acid dispersant represented by the following general formula (1), The amine-based dispersant and the phosphate alkyl ester compound represented by the following general formula (2) contain 0.03 mass % or more and 0.3 mass % or less of the aforementioned amino acid-based dispersant with respect to the entire conductive slurry. The whole conductive slurry contains 0.2 mass % or more of the aforementioned amine dispersant, and the whole conductive slurry contains 0.05 mass % or more of the above-mentioned alkyl phosphate compound, and the whole conductive slurry contains the above-mentioned amino acid. The total content of the above-mentioned amino acid-based dispersant and the aforementioned amine-based dispersant is 0.5% by mass or less, and the total content of the aforementioned amino acid-based dispersant, the aforementioned amine-based dispersant, and the aforementioned alkyl phosphate compound relative to the entire conductive slurry is 0.7% by mass or less,

Among them, in formula (1), R ₁ represents a chain hydrocarbon group with 10 to 20 carbon atoms, [Chemical 2]

Among them, in formula (2), R ₂ represents an alkyl group, alkenyl group or alkynyl group with 8 to 16 carbon atoms, R ₃ represents an oxyethylene group, an oxypropenyl group or a methylene group, and R ₄ represents an oxyethylene group. or oxypropenyl group, R ₃ and R ₄ may be the same or different. In addition, the N atom in formula (2) is not directly bonded to the O atom in R ₃ and R ₄ , and Y is a value between 0 and 2. , Z is a numerical value of 1 to 2; the content of the aforementioned conductive powder is not less than 40% by mass and not more than 60% by mass relative to the entire conductive slurry; the content of the aforementioned ceramic powder is not less than 1% by mass and not more than 20% by mass relative to the entire conductive slurry. mass % or less; the content of the aforementioned binder resin is 0.5 mass % or more and 10 mass % or less relative to the entire conductive slurry. The conductive paste described in claim 1, wherein in the general formula (1), R ₁ represents a linear hydrocarbon group having 10 to 20 carbon atoms. The conductive slurry as described in claim 1 or 2, wherein the conductive powder contains at least one metal powder selected from the group consisting of Ni, Pd, Pt, Au, Ag, Cu and alloys thereof. The conductive slurry described in claim 1 or 2, wherein the conductive powder has an average particle size of 0.05 μm or more and 1.0 μm or less. The conductive slurry described in item 1 or 2 of the patent application, wherein the aforementioned ceramic powder Contains perovskite oxide at the end. The conductive slurry described in claim 1 or 2, wherein the average particle size of the ceramic powder is 0.01 μm or more and 0.5 μm or less. The conductive slurry described in claim 1 or 2, wherein the binder resin contains at least one of a cellulose resin, an acrylic resin, and a butyral resin. The conductive slurry described in claim 1 or 2, which contains 0.05% by mass or more and 0.3% by mass or less of the above-mentioned amino acid-based dispersant relative to the entire conductive slurry. The conductive paste described in claim 1 or 2, wherein the conductive paste is used for internal electrodes of multilayer ceramic capacitors. An electronic component characterized by being formed using the conductive paste described in any one of items 1 to 8 of the patent application. A laminated ceramic capacitor characterized by having a laminated body in which an internal electrode layer and a dielectric layer formed using the conductive slurry described in claim 9 are laminated.

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