WO2023190613A1

WO2023190613A1 - Conductive paste, electronic component, and multilayer ceramic capacitor

Info

Publication number: WO2023190613A1
Application number: PCT/JP2023/012692
Authority: WO
Inventors: 尚史吉田; 達男相川; 清高野; 卓哉河村; 周星成田; 健二福田
Original assignee: 住友金属鉱山株式会社
Priority date: 2022-03-28
Filing date: 2023-03-28
Publication date: 2023-10-05
Also published as: TW202403789A

Abstract

Provided is a conductive paste of which adhesion with a base material is further improved.　The conductive paste comprises a conductive powder, a binder resin, an additive, and an organic solvent, the additive comprising a compound having a structure indicated by structural formula (1) or structural formula (2). (wherein R1, R2, and R3 each independently represent a saturated or unsaturated aliphatic hydrocarbon group comprising 2 to 12 carbon atoms, the aliphatic hydrocarbon group may be straight or branched, and one or more methylenes (-CH2-) included in the aliphatic hydrocarbon group may be substituted with oxygen (-O-)).

Description

Conductive 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 have higher performance, electronic components including multilayer ceramic capacitors are also desired to be smaller and have higher capacity. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked, and by making these dielectric layers and internal electrode layers thinner, they can be made smaller and have 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) is formed. Next, the dry membranes and green sheets are laminated in an alternating manner to obtain a laminate. Next, this laminate is heat-pressed and integrated to form a crimped body. This pressed body is cut, subjected to an organic binder removal treatment in an oxidizing atmosphere or an inert atmosphere, and then fired to obtain fired chips. Next, an external electrode paste is applied to both ends of the fired chip, and after firing, nickel plating or the like is applied to the external electrode surface to obtain a multilayer ceramic capacitor.

In the process of heat-pressing and cutting a laminate formed by stacking 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 (base material) or the layer structure may shift, resulting in the resulting multilayer ceramic capacitor not having the desired electrical characteristics.

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

Furthermore, Patent Document 2 discloses a conductive paste for forming an electrode layer on a base material, with the aim of providing a conductive paste that can form a conductive film with excellent adhesion to a base material. The organic additive contains a conductive powder, a resin binder, an organic additive, and an organic solvent, and the organic additive has two or more (meth)acryloyl groups in one molecule, and has a number average A conductive paste containing a (meth)acrylate compound having a molecular weight of 1000 or less is disclosed.

Furthermore, Patent Document 3 discloses a conductive dry film for the purpose of providing a dry film for internal electrodes that has excellent adhesion to a dielectric layer and can form internal electrodes whose shape does not change significantly before and after heat treatment. A dry film for internal electrodes of a multilayer ceramic capacitor formed of a composition containing a powder and an organic binder resin, characterized in that the film has a Vickers hardness of 47 Hv or more and 51 Hv or less. A dry membrane is disclosed.

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

In recent years, from the perspective of improving productivity and reducing costs, in the manufacturing process of multilayer ceramic capacitors, the pressing time during pressure bonding has been reduced when heat-pressing the laminate obtained by alternately laminating dry membranes and ceramic green sheets. may shorten or lower pressure.

However, when the pressing time or pressure during crimping is shortened or the pressure is lowered, the conventional conductive paste does not provide sufficient adhesion between the dried film and the base material, resulting in misalignment of the dried film and This may lead to a decrease in the rate. Therefore, there is a need for a conductive paste that can further improve adhesion to a base material when a dry film is formed.

In view of this situation, the present invention aims to provide a conductive paste that can further improve adhesion to a base material.

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

(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 is linear or branched. It may be chain-like, and one or more methylene (-CH ₂ -) contained in the aliphatic hydrocarbon group may be substituted with oxygen (-O-).)

Furthermore, it is preferable that the above compound is contained in an amount of 0.01% by mass or more and 2.0% by mass or less based on the entire conductive paste. Further, it is preferable that the temperature of the above compound at which the weight loss rate in thermogravimetric analysis is maximum is 200° C. or higher. Further, it is preferable that the molecular weight of the above compound is 250 or more and 3000 or less. It is preferable that the conductive paste further contains an acidic dispersant and/or a basic dispersant. Moreover, it is preferable that the conductive powder contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. Moreover, it is preferable that the conductive powder has an average particle size of 0.05 μm or more and 1.0 μm or less. Moreover, it is preferable that the binder resin contains a butyral resin. Moreover, it is preferable that the conductive paste further contains ceramic powder. Moreover, it is preferable that the ceramic powder contains barium titanate. Moreover, it is preferable that the ceramic powder has an average particle size of 0.01 μm or more and 0.5 μm or less. Further, it is preferable that the ceramic powder is contained in an amount of 1% by mass or more and 20% by mass or less based on the entire conductive paste. Moreover, it is preferable that the conductive paste is used for internal electrodes of laminated ceramic components.

A second aspect of the present invention provides an electronic component formed using the above conductive paste.

A third aspect of the present invention provides a multilayer ceramic capacitor having at least a laminate in which a dielectric layer and an internal electrode layer are stacked, the internal electrode layer being formed using the above conductive paste.

The conductive paste of the present invention can further improve adhesion to the base material. Furthermore, in the manufacturing process of a multilayer ceramic capacitor, the dry film (internal electrode layer) formed using the conductive paste of the present invention has high adhesion to the green sheet (dielectric layer).

FIG. 1 is a perspective view and a sectional view showing a multilayer ceramic capacitor according to an embodiment.

[Conductive paste]
The conductive paste of this embodiment includes conductive powder, ceramic powder, dispersant, binder resin, and organic solvent. Each component will be explained in detail below.

(conductive powder)
The conductive powder is not particularly limited, and metal powder can be used, for example, one or more powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof can be used. . Among these, powder of Ni or an alloy thereof (hereinafter sometimes referred to as "Ni powder") is preferred from the viewpoints of conductivity, corrosion resistance, and cost. As the Ni alloy, for example, an alloy of Ni and 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. can. The Ni content in the Ni alloy is, for example, 50% by mass or more, preferably 80% by mass or more. Further, 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 binder removal treatment.

The average particle size of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.5 μm 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 internal electrodes of thin-film multilayer ceramic capacitors (multilayer ceramic components). The average particle size is a value obtained from observation with a scanning electron microscope (SEM), and is obtained by measuring the particle size of each particle from an image observed with a SEM at a magnification of 10,000 times. This is the average value (SEM average particle size).

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

(ceramic powder)
The ceramic powder is not particularly limited, and for example, in the case of a paste for internal electrodes of a multilayer ceramic capacitor, a known ceramic powder is appropriately selected depending on the type of multilayer ceramic capacitor to which it is applied. As the ceramic powder, for example, a perovskite oxide containing Ba and Ti can be used, and preferably barium titanate (BaTiO ₃ ) is used.

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

When used as a conductive paste for internal electrodes, the ceramic powder may have the same composition as the dielectric ceramic powder that constitutes the green sheet of a multilayer ceramic capacitor (electronic component). This suppresses the occurrence of cracks due to shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer during the sintering process. In addition to the above, such ceramic powders include, for example, ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , R (rare earth element) ₂ O ₃ , TiO ₂ , Nd ₂ O ₃ and the like. Examples include oxides. Note that one type of ceramic powder may be used, or two or more types of ceramic powder may be used.

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

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

Further, 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, based on 100 parts by mass of the conductive powder.

(binder resin)
The binder resin preferably contains a butyral resin. Furthermore, when used as a paste for internal electrodes, a butyral-based resin may be included, or a butyral-based resin may be used alone, from the viewpoint of improving the adhesive strength with the green sheet. Examples of the butyral resin include polyvinyl butyral (PVB). When the conductive paste contains 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% by mass or more, 40% by mass or more, or 60% by mass or more based on 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.

Further, the upper limit of the content of the butyral resin is not particularly limited, but may be, for example, 90% by mass or less, or 80% by mass or less, based on the entire binder resin. When the content of the butyral resin is within the above range, the conductive paste has appropriate hardness, so problems such as the printed film not peeling off from the support film and the electrode being crushed during thermocompression bonding are less likely to occur.

Further, 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. Further, 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 below-mentioned additives in addition to the butyral resin having the above characteristics, a conductive paste with improved adhesion can be obtained. In addition, one type of butyral resin may be used alone, or two or more types may be used in combination.

Additionally, resins other than butyral-based resins may be included as binder resins. Binder resins other than those mentioned above are not particularly limited, and known resins can be used, such as cellulose resins such as methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, and nitrocellulose, and acrylic resins. Among these, from the viewpoint of solubility in solvents and combustion decomposability, it is preferable to contain cellulose resin, and more preferably to contain ethyl cellulose.

For example, when a cellulose 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. It may be. The hydroxyl value of the cellulose 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, one type of cellulose resin may be contained alone, or two or more types of cellulose resins may be contained.

In addition, when the binder resin contains a cellulose resin and a butyral resin, from the viewpoint of improving adhesion, the butyral resin is added to the total content (100% by mass) of the cellulose resin and the butyral resin. The content may be 20% by mass or more, 40% by mass or more, more than 50% by mass, or 60% by mass or more. When the content of both resins is within the above range, the adhesiveness may be further improved, and the adhesive strength between the dry film and the green sheet (substrate) may be improved. Further, the upper limit of the content of the butyral resin is not particularly limited, and may be less than 100% by mass, may be less than 90% by mass, or may be less than 80% by mass. When the content of both resins is within the above range, the conductive paste can have appropriate hardness, and problems such as the printed film not peeling off from the support film and the electrode being crushed during thermocompression bonding are less likely to occur.

The content of the binder resin is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 7% by mass or less, based on 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, more preferably 1 part by mass or more and 14 parts by mass or less, based on 100 parts by mass of the conductive powder.

(Organic solvent)
The organic solvent is not particularly limited, and any known organic solvent that can dissolve the binder resin can be used. Examples of the organic solvent include terpene solvents, acetate solvents, ether solvents, and ketone solvents.

Examples of terpene solvents include terpineol, dihydroterpineol, dihydroterpineyl acetate, and the like.

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

Ether solvents include propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, diethylene glycol mono-2-ethylhexyl ether, and ethylene glycol mono-2- Examples include ethylene glycol ethers such as 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.

Examples of ketone solvents include methyl isobutyl ketone and diisobutyl ketone. When a ketone solvent is included, the viscosity can be adjusted without impairing the dispersibility, and the drying properties can be improved.

The organic solvent preferably contains at least one selected from the group consisting of terpineol, dihydroterpineol, dihydroterpineyl acetate, propylene glycol monobutyl ether, and diethylene glycol monobutyl ether acetate. By containing these organic solvents, the composition has excellent compatibility with the binder resin and excellent dispersibility of the filler.

The content of the organic solvent (total) is preferably 20% by mass or more and 60% by mass or less, more preferably 25% by mass or more and 45% by mass or less, based on 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, more preferably 60 parts by mass or more and 90 parts by mass or less, based on 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.

Moreover, one type of organic solvent may be used, or two or more types may be used. For example, when two or more organic solvents are included, at least one selected from the group consisting of terpineol, dihydroterpineol, dihydroterpineyl acetate, propylene glycol monobutyl ether, and diethylene glycol monobutyl ether acetate, and a hydrocarbon solvent. May include. In addition to these organic solvents, at least one 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, and the like. Among these, it is preferable to include mineral spirits. The content of the hydrocarbon solvent may be 10% by mass or more and 50% by mass or less, or 20% by mass or more and 40% by mass or less, based on the entire organic solvent.

(Additive)
(a) Ester compound The conductive paste according to the present embodiment contains a compound having a structural moiety represented by the following formula (A) or formula (B) (hereinafter also referred to as "ester compound") as an additive. .

(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; One or more methylenes (-CH ₂ -) contained in the group hydrocarbon group may be substituted with oxygen (-O-).)

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

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; may be linear or branched, and one or more methylene (-CH ₂ -) contained in the aliphatic hydrocarbon group may be substituted with oxygen (-O-). Note that the number of carbon atoms in R ¹ , R ² and R ³ includes the number of carbon atoms in methylene (-CH ₂ -) substituted with oxygen (-O-).

When the conductive paste contains the above-mentioned ester compound, the adhesion of the dried film can be improved. The details of the reason for this are unknown, but for example, the above ester compound inhibits the interaction between resins, causing the dried film to become moderately soft, resulting in a dry film that becomes easily deformed due to softening, and a dry film that does not interact. It is thought that the adhesion between the dried film and the ceramic green sheet (dielectric layer) is improved because the resin or the like tends to cause entanglement at the adhesive interface.

In the above formulas (1) and (2), the lower limit of the number of carbon atoms in R ¹ and R ³ may each independently be 3 or more, or 5 or more. Further, the upper limit of the number of carbon atoms in R ¹ and R ³ may be independently 10 or less, or 8 or less. Moreover, the number of carbon atoms in R ¹ and R ³ may be the same.

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

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

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

Note that the maximum thermal decomposition temperature is a value determined by the thermogravimetry (TG) method using the following method. That is, when the temperature was raised from 20°C to 550°C at a rate of 5°C/min in a nitrogen atmosphere using a pyrolysis weight measuring device (manufactured by Netch, STA25000REGULUS), and the weight loss at that time was measured, differential heating was detected. The temperature at which the weight loss was greatest was defined as the maximum thermal decomposition temperature.

The molecular weight of the 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 ester compound is within the above range, the adhesion to the ceramic green sheet (dielectric layer) is further improved.

Furthermore, the content of the ester compound is preferably 0.01% by mass or more and 1.0% by mass or less based on 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% by mass or more, and may be 0.1% by mass or more, based on the entire conductive paste, from the viewpoint of further improving adhesion. Good too. Moreover, the upper limit of the content of the ester compound may be 0.7% by mass or less, or may be 0.4% by mass or less.

The upper limit of the content of the ester compound is not particularly limited, but may be, for example, 2% by mass or less, 1.8% by mass or less, 1.5% by mass or less, It may be 1.0% by mass or less. When the content of the ester compound exceeds 1.0% by mass, although adhesion improves, gas is generated due to thermal decomposition during debinding of the pressed laminate of the dry membrane and ceramic green sheet. There are things to do. The content of the ester compound can be adjusted as appropriate within the above range depending on the usage environment and the like.

Furthermore, 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 may be set depending on the content of the butyral resin. The content of the ester compound may be, for example, 10 parts by mass or more and 90 parts by mass or less, 10 parts by mass and 60 parts by mass or less, 10 parts by mass or less, based on 100 parts by mass of the butyral resin. The amount may be 50 parts by mass or more and 50 parts by mass or less.

(b) Dispersant When the conductive paste contains a dispersant, the dispersibility of the conductive powder and ceramic powder can be improved. The dispersant may include, for example, an acidic dispersant, a basic dispersant, a nonionic dispersant, an amphoteric dispersant, etc., and preferably includes at least one of an acidic dispersant and a basic dispersant, It is more preferable that an acidic dispersant is included. Note that these dispersants may be used alone or in combination of two or more.

The acid-based dispersant may include acid-based dispersants having acidic groups such as carboxylic acid-based dispersants such as higher fatty acids, polycarboxylic acid-based dispersants, phosphoric acid-based dispersants, and polymeric surfactants. , a polycarboxylic acid dispersant, and a phosphoric acid dispersant. Further, the polycarboxylic acid dispersant may be a comb-shaped carboxylic acid having a comb-shaped structure.

Higher fatty acids may be unsaturated carboxylic acids or saturated carboxylic acids, and are not particularly limited, but include stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, linolenic acid, etc. having 11 or more carbon atoms. Examples include: Among these, oleic acid or stearic acid is preferred.

Examples of acid-based dispersants include oleoyl sarcosine, which is a compound of glycine and oleic acid, and alkyl monoamine salt type, which is an amide compound using higher fatty acids such as stearic acid or lauric acid instead of oleic acid. It may be.

Further, from the viewpoint of further improving the effect of suppressing separation between the conductive powder and the ceramic powder, dicarboxylic acid may be included. A dicarboxylic acid is a carboxylic acid having two carboxyl groups (COO- groups). Further, 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 basic dispersant include aliphatic amines such as laurylamine, rosinamine, cetylamine, myristylamine, and stearylamine. When the conductive paste contains the above-mentioned acid-based dispersant and base-based dispersion, it may have better dispersibility and better viscosity stability over time.

The dispersant is contained, for example, from 0.01% by mass to 3% by mass with respect to the entire conductive paste. The range including the upper limit of the dispersant content may be 2% by mass or less, 1% by mass or less, or 0.5% by mass or less. When the content of the dispersant is within the above range, it is possible to improve the dispersibility of the conductive paste and to suppress sheet attack and poor peeling of the green sheet.

(c) Other additives The conductive paste of this embodiment may contain other additives other than the above-mentioned components, as necessary. As other additives, conventionally known additives such as antifoaming agents, plasticizers, surfactants, and thickeners can be used.

(conductive paste)
The method for manufacturing the conductive paste according to this embodiment is not particularly limited, and conventionally known methods can be used. The conductive paste can be produced, for example, by stirring and kneading the above-mentioned components using a three-roll mill, a ball mill, a mixer, or the like.

By containing the above-mentioned ester compound, the conductive paste according to the present embodiment can improve the adhesion between the dry film and the green sheet. It is thought that by inhibiting the interaction between the resins, the dried film is moderately softened (lowering the glass transition point Tg) and becomes easily deformed.

For example, if a dried product (evaluation sample) is prepared by drying the components of the conductive paste excluding the conductive powder and ceramic powder at 120°C for 40 minutes and removing the organic solvent, the glass transition of this dried product is It is preferable that the point Tg is lower than the glass transition point Tg' of a dried body formed under the same conditions except that it does not contain the above-mentioned 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 lower, 55°C or lower, or 50°C or lower. Note that the lower limit of the glass transition point Tg is, for example, 30° C. or higher.

Note that when the conductive paste contains two or more types of resins as binder resins, multiple glass transition points Tg may be measured depending on the resins contained. The glass transition point Tg indicates the glass transition point Tg in the lowest temperature region. Further, the glass transition point Tg of the dried body (sample for evaluation) can be measured by the method described in Examples.

In addition, when a conductive paste is applied to the surface of a base material 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, and 9 or less. More preferably, it is 8 or less. Note that the lower limit of Vickers hardness (room temperature) is, for example, 3.5 or more.

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

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

[Multilayer ceramic capacitor]
Embodiments of the multilayer ceramic capacitor of the present invention will be described below with reference to the drawings. In the drawings, the drawings may be expressed schematically or with a changed scale, as appropriate. Further, the positions and directions of members will be explained with reference to the XYZ orthogonal coordinate system shown in FIG. 1 and the like as appropriate. In this XYZ orthogonal coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction (up and down direction).

FIGS. 1A and 1B are diagrams showing a multilayer ceramic capacitor 1. The multilayer ceramic capacitor 1 includes a ceramic laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately stacked, and an external electrode 20.

Hereinafter, a method for manufacturing a multilayer ceramic capacitor using the above conductive paste will be explained. First, a conductive paste is printed on a ceramic green sheet and dried to form a dry film. A plurality of ceramic green sheets having this dry film on the upper surface are laminated by pressure bonding to obtain a laminate, and then the laminate is baked and integrated, so that the internal electrode layer 11 and the dielectric layer 12 are alternately formed. A ceramic laminate 10 is produced in which the ceramic laminate 10 is laminated. Thereafter, a pair of external electrodes 20 are formed at both ends of the ceramic laminate 10, thereby manufacturing the multilayer ceramic capacitor 1. This will be explained in more detail below.

First, a green sheet, which is an unfired ceramic sheet, is prepared. This green sheet is made of a dielectric layer paste obtained by adding a binder resin such as polyvinyl butyral and a solvent such as terpineol to a predetermined ceramic raw material powder such as barium titanate. Examples include those that are applied in the form of a sheet onto a film and dried to remove the solvent. Note that the thickness of the dielectric layer made of green sheets is not particularly limited, but from the viewpoint of the demand for miniaturization of multilayer ceramic capacitors, it is preferably 0.05 μm or more and 3 μm or less.

Next, a plurality of green sheets are prepared in which the above-mentioned conductive paste is printed and applied on one side of the green sheet and dried to form a dry film on one side of the green sheet. Note that the thickness of the dried film formed from the conductive paste is preferably 1 μm or less after drying, from the viewpoint of reducing the thickness of the internal electrode layer 11.

Next, the green sheets are peeled off from the support film, and the green sheets and the dry film formed on one side of the green sheets are laminated so that they are alternately arranged, and then a laminate is obtained by heat and pressure treatment. Note that a configuration may be adopted in which protective ceramic green sheets to which no conductive paste is applied are further disposed on both sides of the laminate.

Next, after cutting the laminate into a predetermined size to form a green chip, the green chip is subjected to binder removal treatment and fired in a reducing atmosphere to produce a laminated ceramic fired body (ceramic laminate 10). do. Note that the atmosphere during the binder removal treatment is preferably air or N ₂ gas atmosphere. The temperature during the binder removal treatment is, for example, 200°C or more and 400°C or less. Further, it is preferable that the holding time at the above temperature during the binder removal treatment is 0.5 hours or more and 24 hours or less. Further, the firing is performed in a reducing atmosphere to suppress oxidation of the metal used for the internal electrode layer, and the temperature when firing the laminate is, for example, 1000°C or more and 1350°C or less, and the firing is The temperature is maintained for a period of, for example, 0.5 hours 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 to form the ceramic dielectric layer 12. Further, the organic vehicle in the dry film is removed, and the nickel powder or alloy powder mainly composed of nickel is sintered or melted and integrated to form the internal electrode layer 11, and the dielectric layer 12 and the internal electrode A laminated ceramic fired body is formed in which a plurality of layers 11 are alternately laminated. Note that from the viewpoint of increasing reliability by incorporating oxygen into the dielectric layer and suppressing re-oxidation of the internal electrodes, the fired multilayer ceramic fired body may be subjected to an annealing treatment.

Then, the multilayer ceramic capacitor 1 is manufactured by providing a pair of external electrodes 20 on the produced multilayer ceramic fired body. For example, the external electrode 20 includes an external electrode layer 21 and a plating layer 22. External electrode layer 21 is electrically connected to internal electrode layer 11 . Note that as the material for the external electrode 20, for example, copper, nickel, or an alloy thereof can be suitably used. Note that electronic components other than multilayer ceramic capacitors can also be used as the electronic components.

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

[Evaluation method]
(Adhesion evaluation)
A conductive paste (sample) was applied to the surface of a green sheet containing barium titanate and polyvinyl butyral prepared in advance to form a conductive paste film with a WET thickness of 35 μm. The obtained green sheet and a sheet consisting of a conductive paste film for internal electrodes formed on the surface thereof were dried at 75° C. for 20 minutes to form a dry film on the green sheet. The dried sheet (dried film - green sheet) and another green sheet were stacked with the conductive paste applied side sandwiched between the green sheets, and then pressed at a temperature of 40°C and a pressure of 20 MPa for 20 seconds. By doing so, a laminate (for evaluation) was created.

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

(hardness measurement)
The surface (dry film side) of a green sheet on which a conductive paste film (dry film) was formed under the same conditions as for adhesion evaluation was measured using a micro Vickers hardness meter (manufactured by Shimadzu Corporation, HMV-G21DT). The Vickers hardness of the surface was measured at n=5 points under the conditions of a test force of 98 mN, and the average value thereof was determined. Hardness measurements were carried out at room temperature (25° C.) without heating and at 60° C. by attaching the sample to a glass substrate and placing it on a heating stage, which is the sample stand of the hardness meter. In addition, when measuring the Vickers hardness (60°C), the dried film to be measured was left at 60°C for 3 minutes to condition it, and then the measurement was performed while it was heated at 60°C.

(Measurement of glass transition point Tg)
Among the components contained in the conductive paste, the components excluding the conductive powder and the ceramic powder, that is, the ethyl cellulose resin, polyvinyl butyral resin, additives, and organic solvents, are the same as the amounts contained in the conductive paste. After mixing at 2000 rpm for 4 minutes using a rotation-revolution mixer (ARE-310 manufactured by Shinky), the obtained liquid (mixture) was applied onto a PET film using an applicator to form a wet film thickness of 254 μm. It was coated and dried at 120° C. for 40 minutes to obtain a sample for evaluation. Note that the organic solvent in the mixture is removed during drying.

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

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

[Materials used]
(conductive powder)
As the conductive powder, Ni powder (SEM average particle size: 0.2 μm) was used.

(ceramic powder)
Barium titanate (BaTiO ₃ ; SEM average particle size 0.10 μm) was used as the ceramic powder.

(binder resin)
As the binder resin, polyvinyl butyral resin (PVB) and ethyl cellulose resin (EC) were used.

(dispersant)
In Examples and Comparative Examples, a polycarboxylic acid dispersant, which is an acid dispersant, was used as a commonly contained dispersant (additive).

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

Further, as a comparative example, the following additives were used.
・Additive a: Polycarboxylic acid having polyoxyalkylene as a graft chain (does not have the structure of formula (1) or (2) above)
・Additive b: Oxyethylene laurylamine (polyetheramine)
・Additive c: dicarboxylic acid (2-(octadecen-1-yl)succinic acid)

(Organic solvent)
Dihydroterpineol (DHT) and mineral spirit (MSA) were used as organic solvents.

[Example 1]
Conductive powder 49% by mass, ceramic powder 12% by mass, acid dispersant 0.15% by mass, additive of formula (2-A) 0.3% by mass, binder resin 2.5% by mass (PVB:EC= 7:3 (mass ratio)) and the remainder an organic solvent (DHT:MSA = 60:40 (mass ratio)) to make a total of 100% by mass, and mix these materials. A conductive paste was prepared. Table 1 shows the content of each material in the conductive paste and the evaluation results.

[Examples 1 to 9, Comparative Examples 1 to 4]
A conductive paste was prepared 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 1. Table 2 shows the content of each material in the conductive paste and the evaluation results.

(Evaluation results)
The conductive pastes of Examples 1 to 9 have lower glass transition points (Tg ) decreased, Vickers hardness decreased, and adhesion improved.

When the conductive paste of the present invention is used to form internal electrodes 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 particularly suitably used for internal electrodes of multilayer ceramic capacitors, which are chip components of electronic devices that are becoming increasingly smaller, such as mobile phones and digital devices.

Note that the technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments. One or more of the requirements described in the above embodiments and the like may be omitted. Furthermore, the requirements described in the above embodiments and the like can be combined as appropriate. In addition, to the extent permitted by law, the disclosures of all documents cited in the above-mentioned embodiments are incorporated into the description of the main text. In addition, to the extent permitted by law, the content of Japanese Patent Application No. 2022-052665, which is a Japanese patent application, is incorporated into the main text.

Embodiments of the present invention can include the following configurations.

[1] Contains conductive powder, binder resin, additives, and organic solvent,
A conductive paste containing, as the 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 is a linear or branched aliphatic hydrocarbon group. One or more methylenes (-CH ₂ -) contained in the aliphatic hydrocarbon group may be substituted with oxygen (-O-).)

[2] The conductive paste according to [1], wherein the compound is contained in an amount of 0.01% by mass or more and 2.0% by mass or less based on the entire conductive paste.

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

[4] The conductive paste according to any one of [1] to [3], wherein the compound has a molecular weight of 250 or more and 3000 or less.

[5] The conductive paste according to any one of [1] to [4], further comprising an acidic dispersant and/or a basic dispersant.

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

[7] The conductive paste according to any one of [1] to [6], wherein the conductive powder has an average particle size of 0.05 μm or more and 1.0 μm or less.

[8] The conductive paste according to any one of [1] to [7], wherein the binder resin contains a butyral resin.

[9] The conductive paste according to any one of [1] to [8], further comprising ceramic powder.

[10] The conductive paste according to [9], wherein the ceramic powder contains barium titanate.

[11] The conductive paste according to [9] or [10], wherein the ceramic powder has an average particle size of 0.01 μm or more and 0.5 μm or less.

[12] The conductive paste according to any one of [9] to [11], wherein the ceramic powder is contained in an amount of 1% by mass or more and 20% by mass or less based on the entire conductive paste.

[13] The conductive paste according to any one of [1] to [12], which is used for internal electrodes of laminated ceramic parts.

[14] An electronic component formed using the conductive paste according to any one of [1] to [13].

[15] At least a laminate including a dielectric layer and an internal electrode layer,
A multilayer ceramic capacitor in which the internal electrode layer is formed using the conductive paste described in [13].

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

Claims

Contains conductive powder, binder resin, additives, and organic solvent,
A conductive paste containing, as the 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 is a linear or branched aliphatic hydrocarbon group. One or more methylenes (-CH 2 -) contained in the aliphatic hydrocarbon group may be substituted with oxygen (-O-).)
The conductive paste according to claim 1, wherein the compound is contained in an amount of 0.01% by mass or more and 2.0% by mass or less based on the entire conductive paste.
The conductive paste according to claim 1, wherein the compound has a maximum weight loss rate in thermogravimetric analysis at a temperature of 200°C or higher.
The conductive paste according to claim 1, wherein the compound has a molecular weight of 250 or more and 3000 or less.
The conductive paste according to claim 1, further comprising an acidic dispersant and/or a basic dispersant.
The conductive paste according to claim 1, wherein the conductive powder contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof.
The conductive paste according to claim 1, wherein the conductive powder has an average particle size of 0.05 μm or more and 1.0 μm or less.
The conductive paste according to claim 1, wherein the binder resin includes a butyral resin.
The conductive paste according to claim 1, further comprising ceramic powder.
The conductive paste according to claim 9, wherein the ceramic powder contains barium titanate.
The conductive paste according to claim 9, wherein the ceramic powder has an average particle size of 0.01 μm or more and 0.5 μm or less.
The conductive paste according to claim 9, wherein the ceramic powder is contained in an amount of 1% by mass or more and 20% by mass or less based on the entire conductive paste.
The conductive paste according to claim 1, which is used for internal electrodes of laminated ceramic parts.
An electronic component formed using the conductive paste according to any one of claims 1 to 13.
It has at least a laminate including a dielectric layer and an internal electrode layer,
A multilayer ceramic capacitor in which the internal electrode layer is formed using the conductive paste according to claim 13.