KR20240135633A - Challenger paste, electronic components, and multilayer ceramic capacitors - Google Patents

Abstract

(단, R¹, R², R³ 은, 각각 독립적으로, 탄소수 2 ∼ 12 의 포화 또는 불포화의 지방족 탄화수소기를 나타내고, 상기 지방족 탄화수소기는, 직사슬형 또는 분기 사슬형이어도 되고, 상기 지방족 탄화수소기에 포함되는 1 이상의 메틸렌 (-CH₂-) 이 산소 (-O-) 로 치환되어도 된다.)A conductive paste capable of further improving adhesion to a substrate is provided. A conductive paste comprising a conductive powder, a binder resin, an additive, and an organic solvent, and comprising, as an additive, a compound having a structure represented by the following structural formula (1) or the following structural formula (2).

(However, R ¹ , R ² , and R ³ each independently represent a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched, and one or more methylene (-CH ₂ -) contained in the aliphatic hydrocarbon group may be replaced with oxygen (-O-).)

Description

Challenger paste, electronic components, and multilayer 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 more powerful, electronic components including multilayer ceramic capacitors are also required to be smaller and have higher capacitance. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately laminated, and by thinning these dielectric layers and internal electrode layers, miniaturization and higher capacitance can be achieved.

A multilayer ceramic capacitor is manufactured, for example, as follows. First, a conductive paste for internal electrodes is printed in a predetermined electrode pattern on the surface of a green sheet containing a dielectric powder such as barium titanate (BaTiO ₃ ) and a binder resin, and dried to form a dry film (conductive film). Next, the dry film and the green sheet are alternately overlapped and laminated to obtain a laminate. Next, this laminate is heat-pressed to integrate it, and a press body is formed. This press body is cut, and after performing a deorganizing binder treatment in an oxidizing atmosphere or an inert atmosphere, firing is performed to obtain a fired chip. Next, a paste for external electrodes is applied to both ends of the fired chip, and after firing, nickel plating or the like is performed on the surfaces of the external electrodes, to obtain a multilayer ceramic capacitor.

In the process of heating, pressing, and cutting a laminate formed by overlapping a dry film and a green sheet, if the adhesion between the dry film and the green sheet (substrate) is insufficient, the dry film (conductive film) may peel off from the green sheet (substrate) or the layer structure may be misaligned, and the resulting laminated ceramic capacitor may not have the desired electrical characteristics.

For example, in Patent Document 1, for the purpose of improving the adhesion of the conductive paste including a (meth)acrylic resin as a binder resin to a ceramic green sheet, a conductive paste including a (meth)acrylic resin as a binder resin, an organic solvent, and a metal powder is disclosed, wherein the (meth)acrylic resin has a glass transition point Tg in a range of -60°C to 120°C, a hydroxyl group in a molecule in a range of 0.01 mass% to 5 mass%, an acid value in a range of 1 mgKOH/g to 50 mgKOH/g, and a weight average molecular weight in a range of 10,000 Mv to 350,000 Mv.

In addition, Patent Document 2 discloses a conductive paste for forming an electrode layer on a substrate, the conductive paste comprising a conductive powder, a resin binder, an organic additive, and an organic solvent, wherein the organic additive comprises a (meth)acrylate compound having two or more (meth)acryloyl groups per molecule and a number average molecular weight of 1000 or less, for the purpose of providing a conductive paste capable of forming a conductive film having excellent adhesion to a substrate.

In addition, Patent Document 3 discloses a dry film for an internal electrode of a multilayer ceramic capacitor, which is formed from a composition containing a conductive powder and an organic binder resin, and is characterized in that the dry film has a Vickers hardness of 47 Hv or more and 51 Hv or less, with the aim of providing a dry film for an internal electrode capable of forming an internal electrode having excellent adhesion to a dielectric layer and not significantly changing shape before and after heat treatment.

International Publication No. 2013/187183 Japanese Patent Publication No. 2018-055933 Japanese Patent Publication No. 2019-121744

Recently, from the viewpoint of improving productivity or reducing costs, in the manufacturing process of a multilayer ceramic capacitor, there are cases where the pressing time during pressing is shortened or the pressure is lowered when heat-pressing a laminate obtained by alternately laminating dry films and ceramic green sheets.

However, when the pressing time is shortened or the pressure is lowered during pressing, conventional conductive pastes do not provide sufficient adhesion between the dry film and the substrate, and the position of the dry film may be misaligned, resulting in a decrease in yield. Therefore, a conductive paste that can further improve adhesion with the substrate when the dry film is formed is desired.

The present invention, taking such circumstances into consideration, aims to provide a conductive paste capable of further improving adhesion to a substrate.

In a first aspect of the present invention, a conductive paste is provided, which comprises a conductive powder, a binder resin, an additive, and an organic solvent, and which comprises, as an additive, a compound having a structure represented by the following structural formula (1) or the following structural formula (2).

[Chemical Formula 1]

(However, R ¹ , R ² , and R ³ each independently represent a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched, and one or more methylenes (-CH ₂ -) contained in the aliphatic hydrocarbon group may be replaced with oxygen (-O-).)

In addition, it is preferable that the compound is contained in an amount of 0.01 mass% or more and 2.0 mass% or less with respect to the entire conductive paste. In addition, it is preferable that the compound has a temperature of 200° C. or more at which the weight reduction rate in thermogravimetric analysis becomes maximum. In addition, it is preferable that the molecular weight of the compound is 250 or more and 3000 or less. The conductive paste further preferably contains an acid dispersant and/or a base dispersant. In addition, it is preferable that the conductive powder contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. In addition, it is preferable that the conductive powder has an average particle diameter of 0.05 µm or more and 1.0 µm or less. In addition, it is preferable that the binder resin contains a butyral resin. In addition, it is preferable that the conductive paste further contains a ceramic powder. In addition, it is preferable that the ceramic powder contains barium titanate. In addition, it is preferable that the ceramic powder has an average particle size of 0.01 ㎛ or more and 0.5 ㎛ or less. In addition, it is preferable that the ceramic powder is included in an amount of 1 mass% or more and 20 mass% or less with respect to the entire conductive paste. In addition, it is preferable that the conductive paste is for internal electrodes of a laminated ceramic component.

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

In a third aspect of the present invention, a laminated ceramic capacitor is provided, which has at least a laminated body in which a dielectric layer and an internal electrode layer are laminated, wherein the internal electrode layer is formed using the conductive paste.

The conductive paste of the present invention can further improve adhesion with a substrate. In addition, in the manufacturing process of a multilayer ceramic capacitor, a dry film (inner electrode layer) formed using the conductive paste of the present invention has high adhesion with a green sheet (dielectric layer).

FIG. 1 is a perspective view and a cross-sectional view showing a laminated ceramic capacitor related to an embodiment.

[Challenge Paste]

The conductive paste of the present embodiment includes a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent. Hereinafter, each component will be described in detail.

(challenging powder)

As the conductive powder, there is no particular limitation, and a metal powder can be used, and for example, one or more powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof can be used. Among these, from the viewpoints of conductivity, corrosion resistance, and cost, a powder of Ni or an alloy thereof (hereinafter sometimes referred to as "Ni powder") is preferable. As the Ni alloy, for example, an alloy of Ni with at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd can be used. The Ni content in the Ni alloy is, for example, 50 mass% or more, preferably 80 mass% or more. In addition, the Ni powder may contain about several hundred ppm of element S in order to suppress rapid gas generation due to partial thermal decomposition of the binder resin during the debinding treatment.

The average particle size of the conductive powder is preferably 0.05 ㎛ or more and 1.0 ㎛ or less, more preferably 0.1 ㎛ or more and 0.5 ㎛ or less. When the average particle size of the conductive powder is within the above range, it can be suitably used as a paste for an internal electrode of a thin-film multilayer ceramic capacitor (multilayer ceramic component). The average particle size is a value obtained from observation with a scanning electron microscope (SEM), and is an average value (SEM average particle size) obtained by measuring the particle sizes of individual particles from an image observed at a magnification of 10,000 times with a SEM.

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

(ceramic powder)

As the ceramic powder, there is no particular limitation, and for example, in the case of paste for internal electrodes of a multilayer ceramic capacitor, an appropriately known ceramic powder is selected depending on the type of the multilayer ceramic capacitor to be applied. As the ceramic powder, for example, a perovskite-type oxide containing Ba and Ti can be used, and preferably barium titanate (BaTiO ₃ ) is included.

As the ceramic powder, a ceramic powder containing barium titanate as a main component and an oxide as a secondary component may be used. As the oxide, oxides of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and one or more rare earth elements may be used. In addition, as the ceramic powder, a perovskite-type oxide ferroelectric ceramic powder in which Ba atoms or Ti atoms of barium titanate (BaTiO ₃ ) are replaced with other atoms, such as Sn, Pb, Zr, etc. may be used.

When used as a conductive paste for internal electrodes, the ceramic powder may have the same composition as the dielectric ceramic powder constituting the green sheet of the multilayer ceramic capacitor (electronic component). This suppresses the occurrence of cracks due to mismatch in shrinkage 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 oxides such as 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 . In addition, the ceramic powder may be used alone or in combination of two or more.

The average particle size of the ceramic powder is, for example, 0.01 ㎛ or more and 0.5 ㎛ or less, and preferably 0.01 ㎛ or more and 0.3 ㎛ or less. Since the average particle size of the ceramic powder is in the above range, when used as an internal electrode paste, a sufficiently fine and thin uniform internal electrode can be formed. The average particle size is a value obtained from observation with a scanning electron microscope (SEM), and is an average value (SEM average particle size) obtained by measuring the particle sizes of individual multiple particles from an image observed with a SEM at a magnification of 50,000 times.

The content of the ceramic powder is preferably 1 mass% or more and 20 mass% or less, and more preferably 3 mass% or more and 15 mass% or less, relative to the entire conductive paste. When the content of the ceramic powder is within the above range, the dispersibility and sinterability are excellent.

In addition, the content of the ceramic powder is preferably 1 part by mass or more and 30 parts by mass or less, and more preferably 3 parts by mass or more and 30 parts by mass or less, per 100 parts by mass of the conductive powder.

(Binder resin)

As the binder resin, it is preferable to include a butyral resin. In addition, when used as an internal electrode paste, from the viewpoint of improving the adhesive strength with the green sheet, a butyral resin may be included, or a butyral resin may be used alone. As the butyral resin, polyvinyl butyral (PVB) can be mentioned. When the conductive paste includes a butyral resin, the adhesive strength with the green sheet can be further improved.

The content of the butyral resin may be, for example, 20 mass% or more, 40 mass% or more, or 60 mass% or more, relative to the entire binder resin. When the content of the butyral resin is within the above range, the adhesiveness is further improved, and the adhesive strength between the dry film and the green sheet (substrate) is improved.

In addition, the upper limit of the content of the butyral resin is not particularly limited, but may be, for example, 90 mass% or less, or 80 mass% or less, relative to the entire binder resin. When the content of the butyral resin is within the above range, since the conductive paste has an appropriate hardness, problems such as the printing film not being peeled off from the support film or the electrode being crushed during heat compression are less likely to occur.

In addition, the weight average molecular weight (Mw) of the butyral resin may be 30,000 or more and 300,000 or less, 50,000 or more and 200,000 or less, or 100,000 or more and 150,000 or less. In addition, the glass transition point Tg of the butyral resin may be 50°C or more and 90°C or less, or 60°C or more and 80°C or less. By including the butyral resin having the above characteristics and the additive described below, a conductive paste having further improved adhesion can be obtained. In addition, the butyral resin may be used alone, or two or more types may be used in combination.

In addition, a resin other than a butyral resin may be included as a binder resin. The binder resin other than the above is not particularly limited, and a known resin can be used, and examples thereof include cellulose-based resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, and acrylic resins. Among these, from the viewpoints of solubility in a solvent, combustion decomposition property, etc., it is preferable to include a cellulose-based resin, and it is more preferable to include ethyl cellulose.

For example, when a cellulose-based resin is included as the binder resin, the weight average molecular weight (Mw) may be 10,000 or more and 300,000 or less, 30,000 or more and 250,000 or less, or 50,000 or more and 200,000 or less. In addition, the hydroxyl value of the cellulose-based resin is not particularly limited, but is preferably 0.1 mgKOH/g or more and 15 mgKOH/g or less, more preferably 0.5 mgKOH/g or more and 7 mgKOH/g or less, and even more preferably 1.5 mgKOH/g or more and 3 mgKOH/g or less. In addition, the cellulose-based resin may be included alone or in combination of two or more.

In addition, when the binder resin contains a cellulose-based resin and a butyral-based resin, from the viewpoint of improving adhesion, the butyral-based resin may be contained in an amount of 20 mass% or more, 40 mass% or more, more than 50 mass%, or 60 mass% or more with respect to the total content (100 mass%) of the cellulose-based resin and the butyral-based resin. When the content of both resins is in the above range, the adhesion is further improved, and there are cases where the adhesion strength of the dry film and the green sheet (substrate) is improved. In addition, the upper limit of the content of the butyral-based resin is not particularly limited, and may be less than 100 mass%, 90 mass% or less, or 80 mass% or less. When the content of both resins is in the above range, the conductive paste can have an appropriate hardness, so that problems such as the printing film not being peeled off from the support film or the electrode being crushed during heat compression are unlikely to occur.

The content of the binder resin is preferably 0.5 mass% or more and 10 mass% or less, and more preferably 1 mass% or more and 7 mass% or less, relative to the entire conductive paste. When the content of the binder resin is within the above range, the conductivity and dispersibility are excellent.

The content of the binder resin is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 1 part by mass or more and 14 parts by mass or less, per 100 parts by mass of the conductive powder.

(organic solvent)

As the organic solvent, there is no particular limitation, and any known organic solvent capable of dissolving the binder resin can be used. Examples of the organic solvent include terpene solvents, acetate solvents, ether solvents, ketone solvents, etc.

Terpene solvents include terpineol, dihydroterpineol, and dihydroterpineyl acetate.

Examples of acetate solvents include isobornyl acetate, isobornyl propionate, isobornyl butyrate, and isobornyl isobutyrate; glycol ether acetates such as ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, 3-methoxy-3-methylbutyl acetate, and 1-methoxypropyl-2-acetate; glycol diacetates such as propylene glycol diacetate, 1,4-butanediol diacetate, 1,3-butylene glycol diacetate, and 1,6-hexanediol diacetate; and cyclohexanol acetate.

Examples of ether solvents include propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether; ethylene glycol ethers such as diethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monohexyl ether, and ethylene glycol monohexyl ether; dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl-n-butyl ether, and dipropylene glycol dimethyl ether.

Ketone solvents include methyl isobutyl ketone, diisobutyl ketone, etc. When a ketone solvent is included, viscosity can be adjusted without hindering dispersibility, and drying properties can also be improved.

As the organic solvent, it is preferable to include at least one selected from the group consisting of terpineol, dihydroterpineol, dihydroterpineyl acetate, propylene glycol monobutyl ether, and diethylene glycol monobutyl ether acetate. By including these organic solvents, the compatibility with the binder resin is excellent, and further, the dispersibility of the filler is excellent.

The content of the organic solvent (total) is preferably 20 mass% or more and 60 mass% or less, and more preferably 25 mass% or more and 45 mass% or less, with respect to the total amount of the conductive paste. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

The content of the organic solvent is preferably 50 parts by mass or more and 130 parts by mass or less, and more preferably 60 parts by mass or more and 90 parts by mass or less, per 100 parts by mass of the conductive powder. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

In addition, the organic solvent may be used alone or in combination of two or more types. For example, when the organic solvent comprises two or more types, at least one type selected from the group consisting of terpineol, dihydroterpineol, dihydroterpineol acetate, propylene glycol monobutyl ether, and diethylene glycol monobutyl ether acetate may be included, and a hydrocarbon solvent may be included. In addition to these organic solvents, at least one type selected from methyl isobutyl ketone and diisobutyl ketone may be included.

Examples of the hydrocarbon solvent include solvents containing tridecane, nonane, cyclohexane, mineral spirits, naphthenic solvents, etc. Among them, those containing mineral spirits are preferable. The content of the hydrocarbon solvent may be 10 mass% or more and 50 mass% or less, or 20 mass% or more and 40 mass% or less, relative to the entire organic solvent.

(additive)

(a) Ester compound

The conductive paste according to the present embodiment contains, as an additive, a compound having a structural part represented by the following formula (A) or formula (B) (hereinafter also referred to as an “ester compound”).

[Chemical formula 2]

(However, R ¹ represents a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched, and one or more methylenes (-CH ₂ -) contained in the aliphatic hydrocarbon group may be replaced with oxygen (-O-).)

The ester compound has, specifically, a structure represented by the following structural formula (1) or the following structural formula (2).

[Chemical Formula 3]

In the above formulas (1) and (2), R ¹ , R ² , and R ³ each independently represent a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched, and one or more methylene (-CH ₂ -) contained in the aliphatic hydrocarbon group may be replaced with oxygen (-O-). In addition, the carbon number of R ¹ , R ² , and R ³ includes the number of carbons of methylene (-CH ₂ -) substituted with oxygen (-O-).

When the conductive paste contains the ester compound, the adhesion of the dry film can be improved. The details of the reason for this are unknown, but for example, it is thought that the adhesion between the dry film and the ceramic green sheet (dielectric layer) is improved because the ester compound inhibits the interaction between the resins, thereby causing the dry film to be moderately softened, and thus the dry film is easily deformed by the softening, or the resin that does not interact easily causes entanglement at the adhesive interface.

In the above formulas (1) and (2), the lower limits of the carbon number of R ¹ and R ³ may each independently be 3 or more, or 5 or more. In addition, the upper limits of the carbon number of R ¹ and R ³ may each independently be 10 or less, or 8 or less. In addition, the carbon numbers of R ¹ and R ³ may be the same.

In addition, R ¹ and R ³ may be unsubstituted aliphatic hydrocarbon groups, for example, one methylene (-CH ₂ -) may be replaced with oxygen (-O-). In addition, R ¹ and R ³ may have the same structure.

In the above (1) and (2), the lower limit of the carbon number of R ² may be 3 or more. In addition, the upper limit of the carbon number of R ² may be 10 or less, or 8 or less. In addition, R ² may be, for example, one or more methylene (-CH ₂ -) groups substituted with oxygen (-O-), but may also be an unsubstituted aliphatic hydrocarbon group.

The temperature at which the weight loss rate in the thermogravimetric analysis of the above ester compound is maximum (maximum thermal decomposition temperature) may be, for example, 200°C or higher, 220°C or higher, or preferably 250°C or higher. When the maximum thermal decomposition temperature is within the above range, delamination or cracking of the laminate can be suppressed. In addition, the upper limit of the boiling point or thermal decomposition temperature is not particularly limited, and may be, for example, 450°C or lower, 400°C or lower, or 350°C or lower.

In addition, the maximum pyrolysis temperature is a value obtained by the thermogravimetric (TG) method in the following manner. That is, when a pyrolysis weight measuring device (NETZSCH, STA25000REGULUS) is used to increase the temperature from 20°C to 550°C at a heating rate of 5°C/min in a nitrogen atmosphere and the weight loss at that time is measured, the temperature at which the differential heating loss is the greatest is taken as the maximum pyrolysis temperature.

The molecular weight of the above ester compound is preferably 250 or more and 3000 or less, more preferably 250 or more and 1000 or less, and even more preferably 250 or more and 500 or less. When the molecular weight of the above ester compound is within the above range, the adhesion to the ceramic green sheet (dielectric layer) is further improved.

In addition, the content of the ester compound is preferably 0.01 mass% or more and 1.0 mass% or less with respect to the entire conductive paste. When the content of the ester compound is within the above range, the adhesion between the dry film and the ceramic green sheet (dielectric layer) is improved. In addition, the lower limit of the content of the ester compound may be 0.05 mass% or more or 0.1 mass% or more with respect to the entire conductive paste from the viewpoint of further improving the adhesion. In addition, the upper limit of the content of the ester compound may be 0.7 mass% or less or 0.4 mass% or less.

The upper limit of the content of the ester compound is not particularly limited, but may be, for example, 2 mass% or less, 1.8 mass% or less, 1.5 mass% or less, or 1.0 mass% or less. When the content of the ester compound exceeds 1.0 mass%, the adhesion is improved, but when the press body of the laminate of the dry film and the ceramic green sheet is subjected to binder decomposition, there are cases where gas is generated due to thermal decomposition. The content of the ester compound can be appropriately adjusted within the above range depending on the usage environment, etc.

In addition, the content of the ester compound can be appropriately set depending on the type and content of the binder resin. For example, the content of the ester compound can be set depending on the content of the butyral resin. The content of the ester compound can be, for example, 10 parts by mass or more and 90 parts by mass or less, 10 parts by mass or more and 60 parts by mass or less, or 10 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the butyral resin.

(b) Dispersant

When the conductive paste contains a dispersant, the dispersibility of the conductive powder and the ceramic powder can be improved. The dispersant may include, for example, an acid-based dispersant, a base-based dispersant, a nonionic dispersant, an amphoteric dispersant, etc., and it is preferable to contain at least one of an acid-based dispersant and a base-based dispersant, and it is more preferable to contain an acid-based dispersant. In addition, these dispersants may be used alone or in combination of two or more.

The acid dispersant may include an acid group-containing dispersant such as a carboxylic acid-containing dispersant such as a higher fatty acid, a polycarboxylic acid-containing dispersant, a phosphoric acid-containing dispersant, or a polymeric surfactant, and it is preferable to include at least one of a polycarboxylic acid-containing dispersant and a phosphoric acid-containing dispersant. In addition, the polycarboxylic acid-containing dispersant may be a comb-shaped carboxylic acid having a comb-shaped structure.

As for the higher fatty acids, they may be unsaturated or saturated carboxylic acids, and include, but are not particularly limited to, those having 11 or more carbon atoms, such as stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, and linolenic acid. Among them, oleic acid or stearic acid is preferable.

In addition, the acid dispersant may be, for example, oleoylsarcosine, a compound of glycine and oleic acid, or an alkyl monoamine salt type, which is an amide compound using a higher fatty acid such as stearic acid or lauric acid instead of oleic acid.

In addition, from the viewpoint of further improving the effect of inhibiting the separation of the conductive powder and the ceramic powder, a dicarboxylic acid may be included. The dicarboxylic acid is a carboxylic acid having two carboxyl groups (COO- groups). In addition, the average molecular weight of the dicarboxylic acid is not particularly limited, but may be, for example, 200 or more and 1000 or less.

Examples of the base dispersant include aliphatic amines such as laurylamine, rosinamine, cetylamine, myristylamine, and stearylamine. When the conductive paste contains the acid dispersant and base dispersant, the conductive paste has better dispersibility and sometimes also has better viscosity stability over time.

The dispersant is contained in an amount of, for example, 0.01 mass% or more and 3 mass% or less relative to the entire conductive paste. The range including the upper limit of the content of the dispersant may be 2 mass% or less, 1 mass% or less, or 0.5 mass% or less. When the content of the dispersant is within the above range, the dispersibility of the conductive paste can be improved, or sheet attack or green sheet peeling defects can be suppressed.

(c) Other additives

The conductive paste of the present embodiment may contain additives other than the above components, if necessary. As other additives, for example, conventionally known additives such as antifoaming agents, plasticizers, surfactants, and thickeners can be used.

(challenging paste)

The method for producing the conductive paste related to the present embodiment is not particularly limited, and a conventionally known method can be used. The conductive paste can be produced, for example, by stirring and kneading each of the above components using a three-roll mill, a ball mill, a mixer, or the like.

The conductive paste related to the present embodiment can improve the adhesion between the dry film and the green sheet by including the ester compound, and as one factor of the improvement in adhesion, it is thought that the ester compound inhibits the interaction between resins, thereby appropriately softening the dry film (lowering the glass transition point Tg), thereby making it easy to deform.

For example, when a dried body (sample for evaluation) is prepared by drying the components other than the conductive powder and ceramic powder in the conductive paste at 120°C for 40 minutes to remove the organic solvent, the glass transition point Tg of this dried body is preferably lower than the glass transition point Tg' of a dried body formed under the same conditions except that it does not contain the ester compound. The ester compound may lower Tg by 10°C or more, 13°C or more, 15°C or more, or 20°C or more compared to Tg'. For example, the glass transition point Tg of the dried body (sample for evaluation) may be 60°C or less, 55°C or less, or 50°C or less. In addition, the lower limit of the glass transition point Tg is, for example, 30°C or more.

In addition, when the conductive paste contains two or more types of resins as the binder resin, there are cases where multiple glass transition points Tg are measured depending on the included resins. The glass transition point Tg of the evaluation sample in this specification represents the glass transition point Tg in the lowest temperature range. In addition, the glass transition point Tg of the dried body (evaluation sample) can be measured by the method described in the Examples.

In addition, when a conductive paste is applied to the surface of a substrate and dried at 75°C for 20 minutes to form a dry film, the Vickers hardness of the dry film surface at room temperature is preferably 10 or less, more preferably 9 or less, and even more preferably 8 or less. In addition, the lower limit of the Vickers hardness (room temperature) is, for example, 3.5 or more.

In addition, it is preferable that the Vickers hardness of the surface of the dried film at 60°C is 8 or less, more preferably 7 or less, and even more preferably 6 or less. In addition, the lower limit of the Vickers hardness (60°C) is, for example, 3 or more. In addition, it is preferable that the dried film, when measuring the Vickers hardness (60°C), is condition-controlled by leaving the dried film to be measured at 60°C for 3 minutes in advance.

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

[Laminated Ceramic Capacitor]

Hereinafter, embodiments of the multilayer ceramic capacitor of the present invention will be described with reference to the drawings. In the drawings, there are cases where they are appropriately represented schematically or where they are represented with a changed scale. In addition, positions and directions of members, etc. are appropriately described with reference to the XYZ rectangular coordinate system shown in Fig. 1, etc. In this XYZ rectangular coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction (up-down direction).

Figures 1A and B are drawings showing a multilayer ceramic capacitor (1). The multilayer ceramic capacitor (1) has a ceramic multilayer body (10) in which dielectric layers (12) and internal electrode layers (11) are alternately laminated, and an external electrode (20).

Hereinafter, a method for manufacturing a multilayer ceramic capacitor using the conductive paste will be described. First, a conductive paste is printed on a ceramic green sheet, dried, and a dry film is formed. A plurality of ceramic green sheets having the dry film on their upper surfaces are laminated by pressing to obtain a laminate, and then the laminate is fired to become an integral body, thereby manufacturing a ceramic laminate (10) in which internal electrode layers (11) and dielectric layers (12) are alternately laminated. Thereafter, a pair of external electrodes (20) are formed at both ends of the ceramic laminate (10), thereby manufacturing a multilayer ceramic capacitor (1). This will be described in more detail below.

First, a green sheet, which is a microporous ceramic sheet, is prepared. As the green sheet, for example, a dielectric layer paste obtained by adding a binder resin such as polyvinyl butyral and a solvent such as terpineol to a raw material powder of a given ceramic such as barium titanate is applied in a sheet shape on a support film such as PET film, and the solvent is removed by drying. In addition, the thickness of the dielectric layer formed of the green sheet is not particularly limited, but from the viewpoint of the demand for miniaturization of the multilayer ceramic capacitor, it is preferably 0.05 ㎛ or more and 3 ㎛ or less.

Next, the conductive paste described above is printed and applied on one side of a green sheet, dried, and a plurality of sheets are prepared by forming a dry film on one side of the green sheet. In addition, the thickness of the dry film formed with the conductive paste is preferably 1 ㎛ or less after drying from the viewpoint of the requirement for thinning of the inner electrode layer (11).

Next, the green sheet is peeled off from the support film, and the green sheet and the dry film formed on one side thereof are alternately laminated, and then a laminate is obtained by heating and pressurizing. In addition, a configuration may be adopted in which a protective ceramic green sheet to which no conductive paste is applied is additionally arranged on both sides of the laminate.

Next, the laminate is cut into a predetermined size to form a green chip, and then a binder removal treatment is performed on the green chip, and firing is performed in a reducing atmosphere to manufacture a laminated ceramic sintered body (ceramic laminate (10)). In addition, the atmosphere in the binder removal treatment is preferably the air or an N ₂ gas atmosphere. The temperature when performing the binder removal treatment is, for example, 200° C. or more and 400° C. or less. In addition, the temperature maintenance time when performing the binder removal treatment is, for example, 0.5 hour or more and 24 hours or less. In addition, the firing is performed in a reducing atmosphere in order to suppress oxidation of the metal used in the internal electrode layer, and further, the temperature when performing the firing of the laminate is, for example, 1000° C. or more and 1350° C. or less, and the temperature maintenance time when performing the firing is, for example, 0.5 hour or more and 8 hours or less.

By firing the green chip, the organic binder in the ceramic green sheet is completely removed, and the ceramic raw material powder is fired, thereby forming a dielectric layer (12) made of ceramic. In addition, the organic vehicle in the dry film is removed, and the nickel powder or the alloy powder containing nickel as a main component is sintered or melted and integrated, thereby forming an internal electrode layer (11), and a laminated ceramic sintered body in which the dielectric layers (12) and the internal electrode layers (11) are alternately laminated in multiple layers is formed. In addition, from the viewpoint of increasing reliability by introducing oxygen into the dielectric layer and suppressing re-oxidation of the internal electrode, an annealing treatment may be performed on the laminated ceramic sintered body after firing.

And, by forming a pair of external electrodes (20) for the manufactured multilayer ceramic sintered body, a multilayer ceramic capacitor (1) is manufactured. For example, the external electrode (20) has 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 for the external electrode (20), copper, nickel, or an alloy thereof can be preferably used, for example. In addition, as an electronic component, an electronic component other than a multilayer ceramic capacitor can also be used.

Example

Hereinafter, the present invention will be described in detail based on examples and comparative examples, but the present invention is not limited at all by the examples.

[Evaluation method]

(Adhesion evaluation)

A conductive paste (sample) was applied onto the surface of a green sheet containing barium titanate and polyvinyl butyral that had been manufactured in advance, to form a conductive paste film having a wet film thickness of 35 ㎛. A sheet comprising the obtained green sheet and the conductive paste film for internal electrodes formed on the surface thereof was dried at 75° C. for 20 minutes, to form a dry film on the green sheet. The dried sheet (dry film-green sheet) and another green sheet were overlapped in a manner in which the side to which the conductive paste was applied was sandwiched between the green sheets, and then a laminate (for evaluation) was manufactured by pressing at a temperature of 40° C. and a pressure of 20 MPa for 20 seconds.

After cutting the obtained laminate into 1 cm length and width pieces, both sides of the laminate were set on the jig of a tensile testing machine (AGS-50NX, manufactured by Shimadzu Corporation) using tape, and a tensile test was performed. The breaking force (the force to peel the dry film from the green sheet) was recorded at a test speed of 20 mm/min. The breaking force of Comparative Example 1 was considered 100%, and each breaking force was evaluated in %.

(hardness measurement)

The surface (dry film side) of the green sheet on which a conductive paste film (dry film) was formed under the same conditions as those for the adhesion evaluation was measured for the Vickers hardness of the surface at n = 5 points using a micro Vickers hardness tester (HMV-G21DT, manufactured by Shimadzu Corporation) under a test force of 98 mN, and their average value was obtained. The hardness measurement was performed by attaching the sample to a glass substrate, placing it on the heating stage, which is the sample stage of the hardness tester, and at room temperature (25°C) without heating and in a state where it was heated to 60°C. In addition, when measuring the Vickers hardness (60°C), the dry film to be measured was left at 60°C for 3 minutes in advance to adjust its condition, and then measured in a state where it was heated at 60°C.

(Measurement of glass transition point Tg)

Among the components included in the conductive paste, components other than the conductive powder and ceramic powder, i.e., ethyl cellulose resin, polyvinyl butyral resin, additives, and organic solvents, are weighed so as to be the same amount as that included in the conductive paste, and mixed at 2000 rpm for 4 minutes using a self-contained mixer (ARE-310 manufactured by Thinky), and then the obtained liquid (mixture) is applied onto a PET film using an applicator at a wet film thickness of 254 ㎛, and dried at 120°C for 40 minutes to obtain a sample for evaluation. In addition, the organic solvent in the mixture is removed during drying.

Using a differential scanning calorimeter (DSC3100, Netsch Japan Co., Ltd.), 10 mg of the dried evaluation sample was placed in an aluminum pan, and under a nitrogen flow of 100 mL/min, the temperature was increased from 0°C to 140°C at a heating rate of 10°C/min. From the peak of the endothermic curve obtained, the glass transition point Tg in the low-temperature region was determined.

(Measuring thermal decomposition temperature)

The thermal decomposition temperature of the additive used in the conductive paste was measured using a thermal decomposition weight measuring device (NETZSCH, STA25000REGULUS). The measurement temperature atmosphere was nitrogen, and the measurement temperature range was from 20°C to 550°C, with a heating rate of 5°C/min. The temperature at which the differential heating loss was the greatest, i.e., the temperature at which the weight reduction rate in thermogravimetric analysis was the greatest, was defined as the thermal decomposition temperature (maximum thermal decomposition temperature).

[Materials used]

(challenging powder)

As the challenging powder, Ni powder (SEM average particle size 0.2 ㎛) was used.

(ceramic powder)

As ceramic powder, barium titanate (BaTiO ₃ ; SEM average particle size 0.10 ㎛) was used.

(Binder resin)

Polyvinyl butyral resin (PVB) and ethyl cellulose resin (EC) were used as binder resin.

(dispersant)

In the examples and comparative examples, a polycarboxylic acid-based dispersant, which is an acid-based dispersant, was used as a commonly contained dispersant (additive).

(additive)

As ester compounds, compounds 1-A, 2-A to C in Table 1 having a structure represented by the following structural formula (1) or the following structural formula (2) were used.

[Chemical Formula 4]

Additionally, as a comparative example, the following additives were used.

·Additive a: Polycarboxylic acid having polyoxyalkylene as a graft chain (not having the structure of the above formula (1) or (2))

·Additive b: Oxyethylene laurylamine (polyetheramine)

·Additive c: Dicarboxylic acid (2-(octadecene-1-yl)succinic acid)

(organic solvent)

Dihydroterpineol (DHT) and mineral spirits (MSA) were used as organic solvents.

[Example 1]

A conductive paste was manufactured by adding 49 mass% of a conductive powder, 12 mass% of a ceramic powder, 0.15 mass% of an acid dispersant, 0.3 mass% of an additive of formula (2-A), 2.5 mass% of a binder resin (PVB: EC = 7:3 (mass ratio)), and the remainder as an organic solvent (DHT: MSA = 60:40 (mass ratio)), mixing the ingredients so that the total amount would be 100 mass%, and mixing these materials. The content of each material of the conductive paste and the evaluation results are shown in Table 2.

[Examples 2 to 9, Comparative Examples 1 to 4]

A conductive paste was manufactured and evaluated in the same manner as in Example 1, except that the type and content of the additive were changed as shown in Table 2. The content of each material of the conductive paste and the evaluation results are shown in Table 2.

(Evaluation Results)

The conductive pastes of Examples 1 to 9 had a lower glass transition point (Tg) in the low-temperature region, a lower Vickers hardness, and improved adhesion compared to the conductive pastes of Comparative Examples 1 to 4 that did not contain the ester compound represented by Formula (1) or (2).

Industrial applicability

When the conductive paste of the present invention is used to form the internal electrode of a multilayer ceramic capacitor, a highly reliable multilayer ceramic capacitor can be obtained with high productivity. Therefore, the conductive paste of the present invention can be preferably used as an internal electrode of a multilayer ceramic capacitor, which is a chip component of electronic devices such as mobile phones and digital devices, which are becoming increasingly miniaturized.

In addition, the technical scope of the present invention is not limited to the aspects described in the above-described embodiments, etc. One or more of the requirements described in the above-described embodiments, etc. may be omitted. In addition, the requirements described in the above-described embodiments, etc. may be appropriately combined. In addition, to the extent permitted by law, the disclosures of all documents cited in the above-described embodiments, etc. are incorporated into and made a part of the description of the text. In addition, to the extent permitted by law, the contents of Japanese Patent Application No. 2022-052665, a Japanese patent application, are incorporated into and made a part of the description of the text.

An embodiment of the present invention may include the following configuration.

〔1〕Containing a challenging powder, a binder resin, an additive, and an organic solvent,

A conductive paste comprising a compound having a structure represented by the following structural formula (1) or the following structural formula (2) as the additive.

[Chemical Formula 5]

(However, R ¹ , R ² , and R ³ each independently represent a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched, and one or more methylene (-CH ₂ -) contained in the aliphatic hydrocarbon group may be replaced with oxygen (-O-).)

〔2〕The conductive paste described in 〔1〕, wherein the compound is contained in an amount of 0.01 mass% or more and 2.0 mass% or less with respect to the entire conductive paste.

〔3〕The conductive paste according to 〔1〕or 〔2〕, wherein the temperature at which the weight loss rate in thermogravimetric analysis is maximum is 200°C or higher.

〔4〕A conductive paste according to any one of 〔1〕 to 〔3〕, wherein the molecular weight of the compound is 250 or more and 3000 or less.

〔5〕Additionally, a conductive paste according to any one of 〔1〕 to 〔4〕, comprising an acid-based dispersant and/or a base-based dispersant.

〔6〕The conductive paste according to any one of 〔1〕 to 〔5〕, wherein the conductive powder comprises at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof.

〔7〕The conductive powder is a conductive paste according to any one of 〔1〕 to 〔6〕, having an average particle size of 0.05 ㎛ or more and 1.0 ㎛ or less.

〔8〕A conductive paste according to any one of 〔1〕 to 〔7〕, wherein the binder resin contains a butyral resin.

〔9〕Additionally, a conductive paste according to any one of 〔1〕 to 〔8〕, comprising ceramic powder.

〔10〕The conductive paste described in 〔9〕, wherein the ceramic powder contains barium titanate.

〔11〕The conductive paste described in 〔9〕or 〔10〕, wherein the ceramic powder has an average particle size of 0.01 ㎛ or more and 0.5 ㎛ or less.

〔12〕A conductive paste according to any one of 〔9〕 to 〔11〕, wherein the ceramic powder is contained in an amount of 1 mass% or more and 20 mass% or less with respect to the entire conductive paste.

〔13〕A conductive paste as described in any one of 〔1〕 to 〔12〕 for use as an internal electrode of a laminated ceramic component.

〔14〕An electronic component formed using the conductive paste described in any one of 〔1〕∼〔13〕.

〔15〕At least a laminated body having a dielectric layer and an internal electrode layer,

The above inner electrode layer is a laminated ceramic capacitor formed using the conductive paste described in [13].

1: Multilayer ceramic capacitor
10: Ceramic laminate
11: Inner electrode layer
12: Dielectric layer
20 : External electrode
21: Outer electrode layer
22: Plating layer

Claims (15)

Containing a challenging powder, a binder resin, an additive, and an organic solvent,
A conductive paste comprising a compound having a structure represented by the following structural formula (1) or the following structural formula (2) as the additive.

(However, R ¹ , R ² , and R ³ each independently represent a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched, and one or more methylene (-CH ₂ -) contained in the aliphatic hydrocarbon group may be replaced with oxygen (-O-).) In paragraph 1,
A conductive paste, wherein the compound is contained in an amount of 0.01 mass% or more and 2.0 mass% or less relative to the entire conductive paste. In paragraph 1,
The above compound is a conductive paste having a temperature of 200°C or higher at which the weight loss rate in thermogravimetric analysis is maximum. In paragraph 1,
A conductive paste wherein the molecular weight of the compound is 250 or more and 3000 or less. In paragraph 1,
Additionally, a conductive paste comprising an acid dispersant and/or a base dispersant. In paragraph 1,
The conductive powder is a conductive paste containing at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu and alloys thereof. In paragraph 1,
The above-mentioned conductive powder is a conductive paste having an average particle size of 0.05 ㎛ or more and 1.0 ㎛ or less. In paragraph 1,
A conductive paste wherein the binder resin comprises a butyral resin. In paragraph 1,
Additionally, a conductive paste containing ceramic powder. In Article 9,
A conductive paste comprising the above ceramic powder and barium titanate. In Article 9,
The above ceramic powder is a conductive paste having an average particle size of 0.01 ㎛ or more and 0.5 ㎛ or less. In Article 9,
A conductive paste, wherein the above ceramic powder is contained in an amount of 1 mass% or more and 20 mass% or less with respect to the entire conductive paste. In paragraph 1,
Conductive paste for internal electrodes of laminated ceramic components. An electronic component formed using the conductive paste described in any one of claims 1 to 13. At least a laminated body having a dielectric layer and an internal electrode layer,
A multilayer ceramic capacitor, wherein the inner electrode layer is formed using the conductive paste described in claim 13.

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