JP7648002B2 - Conductive paste, electronic components, and multilayer ceramic capacitors - Google Patents

Description

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, there is a demand for electronic components, including multilayer ceramic capacitors, 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 thinning these dielectric layers and internal electrode layers, it is possible to achieve smaller size and higher capacity.

For example, a multilayer ceramic capacitor is manufactured 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 then dried to form a dry film (conductive film). Next, the dry film and the green sheet are alternately stacked to obtain a laminate. Next, this laminate is integrated by heat and pressure bonding to form a pressed body. This pressed body is cut, and an organic binder removal process is performed in an oxidizing atmosphere or an inert atmosphere, and then sintered 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 surface of the external electrodes to obtain a multilayer ceramic capacitor.

During the process of heating and pressing the laminate formed by stacking the dry film and the green sheet, and cutting it, 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 become misaligned, resulting in the resulting multilayer ceramic capacitor not having the desired electrical characteristics.

For example, Patent Document 1 discloses a conductive paste containing (meth)acrylic resin as a binder resin, an organic solvent, and a metal powder, with the aim of improving the adhesion of the conductive paste containing (meth)acrylic resin as a binder resin to a ceramic green sheet, in which the (meth)acrylic resin has a glass transition temperature Tg in the range of -60°C to 120°C, hydroxyl groups in the molecule in the range of 0.01% to 5% by mass, 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 substrate, with the aim of providing a conductive paste capable of forming a conductive film with excellent adhesion to the substrate, the conductive paste comprising a conductive powder, a resin binder, an organic additive, and an organic solvent, the organic additive comprising a (meth)acrylate compound having two or more (meth)acryloyl groups in one molecule and having a number average molecular weight of 1,000 or less.

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, with the aim of providing a dry film for an internal electrode that is capable of forming an internal electrode that has excellent adhesion to a dielectric layer and does not change shape significantly before and after heat treatment, and which is characterized by having a Vickers hardness of 47 Hv or more and 51 Hv or less.

International Publication No. 2013/187183 JP 2018-055933 A JP 2019-121744 A

In recent years, in order to improve productivity and reduce costs, the manufacturing process for multilayer ceramic capacitors has seen the pressing time and pressure being reduced when heat-pressing the laminate obtained by alternately stacking dry films and ceramic green sheets.

However, when the pressing time or pressure during bonding is reduced, conventional conductive pastes do not provide sufficient adhesion between the dried film and the substrate, which can lead to misalignment of the dried film and reduced yield. Therefore, there is a demand for a conductive paste that can further improve adhesion to the substrate when the dried film is formed.

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

In a first aspect of the present invention, there is provided a conductive paste comprising a conductive powder, an additive, a binder resin and an organic solvent, the conductive paste comprising, as an additive, a compound having a structural portion shown in the following formula (1):

In the above formula (1), R ¹ represents a saturated or unsaturated aliphatic hydrocarbon group having 8 to 25 carbon atoms, which may be linear or branched, and in which one or more methylenes (-CH ₂ -) in the aliphatic hydrocarbon group may be substituted with oxygen (-O-), and R ² represents hydrogen, or a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, which may be linear or branched, and in which one or more methylenes (-CH ₂ -) in the aliphatic hydrocarbon group may be substituted with oxygen (-O-).

It is also preferable that the compound has a structure represented by the following formula (2) or the following formula (3).

In the above formulas (2) and (3), R ¹ and R ⁵ each independently represent a saturated or unsaturated aliphatic hydrocarbon group having 8 to 25 carbon atoms, which may be linear or branched, and in the aliphatic hydrocarbon group, one or more methylenes (-CH ₂ -) may be substituted with oxygen (-O-), R ² , R ³ , and R ⁴ each independently represent hydrogen, a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, which may be linear or branched, and in the aliphatic hydrocarbon group, one or more methylenes (-CH ₂ -) may be substituted with oxygen (-O-), R ⁶ represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, which may be linear or branched, and in the aliphatic hydrocarbon group, one or more methylenes (-CH _{2 -)} may be substituted with oxygen (-O-), -) may be replaced with oxygen (-O-).

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

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

In a third aspect of the present invention, a multilayer ceramic capacitor is provided which has at least a laminate having a dielectric layer and an internal electrode layer stacked thereon, the internal electrode layer being formed using the above-mentioned conductive paste.

The conductive paste of the present invention can further improve adhesion to the substrate. Furthermore, in the manufacturing process of a multilayer ceramic capacitor, the dried 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 cross-sectional view showing a multilayer ceramic capacitor according to an embodiment.

[Conductive paste]
The conductive paste of the present embodiment contains a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent. Each component will be described in detail below.

(Conductive powder)
The conductive powder is not particularly limited, and metal powder can be used, for example, powder of one or more selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. Among these, from the viewpoints of conductivity, corrosion resistance, and cost, Ni or its alloy powder (hereinafter, sometimes referred to as "Ni powder") is preferable. 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. 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 binder removal process.

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 an internal electrode paste for thin-film multilayer ceramic capacitors (multilayer ceramic components). The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the average value (SEM average particle size) obtained by measuring the particle size of each of multiple particles from an image observed with an SEM at a magnification of 10,000 times.

The content of the conductive powder is preferably 30% by mass or more and less than 70% by mass, and 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 conductive paste has excellent conductivity and dispersibility.

(ceramic powder)
The ceramic powder is not particularly limited, and for example, in the case of a paste for an internal electrode of a multilayer ceramic capacitor, a known ceramic powder is appropriately selected depending on the type of 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 contains barium titanate ( _BaTiO3 ).

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

When used as a conductive paste for internal electrodes, the ceramic powder may be a powder of 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 the mismatch of shrinkage at the interface between the dielectric layer and the internal electrode layer in the sintering process. In addition to the above, such ceramic powders 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. It is to be noted that one type of ceramic powder may be used, or two or more types may be used.

The average particle size of the ceramic powder is, for example, 0.01 μm to 0.5 μm, preferably 0.01 μm to 0.3 μm. When the average particle size of the ceramic powder is in the above range, it is possible to form a sufficiently thin and uniform internal electrode when used as an internal electrode paste. The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the average value (SEM average particle size) obtained by measuring the particle size of each of multiple particles from an image observed with an SEM at a magnification of 50,000 times.

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 paste has excellent dispersibility and sinterability.

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

(Binder resin)
The binder resin preferably contains a butyral resin. When used as an internal electrode paste, the butyral resin may be contained or the butyral resin may be used alone in order to improve the adhesive strength with the green sheet. An example of the butyral resin is 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 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 total binder resin. When the content of butyral resin is within the above range, the adhesion is further improved, and the adhesive strength between the dried 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% by mass or less, or 80% by mass or less, based on the total binder resin. When the content of the butyral resin is within the above range, the conductive paste has an appropriate hardness, so that the printed film does not peel off from the support film, the electrodes are crushed during thermocompression bonding, and other defects are unlikely to occur.

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. 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 additive described below in addition to the butyral resin having the above characteristics, a conductive paste with improved adhesion can be obtained. The butyral resin may be used alone or in combination of two or more types.

In addition, a resin other than a butyral-based resin may be included as a binder resin. The binder resin other than the above is not particularly limited, and known resins can be used, for example, cellulose-based resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, and acrylic resins. Among them, from the viewpoints of solubility in a solvent and combustion decomposition, 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 a binder resin, the weight average molecular weight (Mw) may be 10,000 to 300,000, 30,000 to 250,000, or 50,000 to 200,000. The hydroxyl value of the cellulose-based resin is not particularly limited, but is preferably 0.1 mgKOH/g to 15 mgKOH/g, more preferably 0.5 mgKOH/g to 7 mgKOH/g, and even more preferably 1.5 mgKOH/g to 3 mgKOH/g. The cellulose-based resin may be included in one type alone or in two or more types.

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% by mass or more, 40% by mass or more, more than 50% by mass, or 60% by mass or more relative to the total content (100% by mass) of the cellulose-based resin and the butyral-based resin. When the contents of both resins are within the above ranges, the adhesion is further improved, and the adhesive strength between the dry film and the green sheet (substrate) may be improved. In addition, the upper limit of the content of the butyral-based resin is not particularly limited, and may be less than 100% by mass, 90% by mass or less, or 80% by mass or less. When the contents of both resins are within the above ranges, the conductive paste can have an appropriate hardness, and defects such as the printed film not peeling off from the support film and the electrodes 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, and 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 conductive paste has excellent conductivity and dispersibility.

The binder resin content 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 conductive powder.

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

Terpene solvents include terpineol, dihydroterpineol, dihydroterpinyl acetate, etc.

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-based solvents include methyl isobutyl ketone, diisobutyl ketone, etc. When a ketone-based solvent is included, it is possible to adjust the viscosity and improve the drying property without impairing the dispersibility.

The organic solvent preferably contains at least one selected from the group consisting of terpineol, dihydroterpineol, dihydroterpinyl 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, and 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 conductive paste has excellent conductivity and dispersibility.

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.

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

Examples of hydrocarbon solvents include solvents containing tridecane, nonane, cyclohexane, etc., mineral spirits, naphthenic solvents, etc. Among them, it is preferable to contain 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 total organic solvent.

(Additives)
(a) Amide Compound The conductive paste according to this embodiment contains, as an additive, a compound having a structural portion represented by the following formula (1) (hereinafter also referred to as an "amide compound").

In the above formula (1), R ¹ represents a saturated or unsaturated aliphatic hydrocarbon group having 8 to 25 carbon atoms, which may be linear or branched, and in which one or more methylenes (-CH ₂ -) in the aliphatic hydrocarbon group may be substituted with oxygen (-O-), and R ² represents hydrogen, a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, which may be linear or branched, and in which one or more methylenes (-CH ₂ -) in the aliphatic hydrocarbon group may be substituted with oxygen (-O-). The amide compound may not contain an acidic group (e.g., a carboxyl group). If an acidic group is contained, the softening effect of the dried film may be reduced.

It is also preferable that the amide compound has a structure represented by the following structural formula (2) or the following structural formula (3).

In the above formulas (2) and (3), R ¹ and R ⁵ each independently represent a saturated or unsaturated aliphatic hydrocarbon group having 8 to 25 carbon atoms, which may be linear or branched, and in the aliphatic hydrocarbon group, one or more methylenes (-CH ₂ -) may be substituted with oxygen (-O-), R ² , R ³ , and R ⁴ each independently represent hydrogen, a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, which may be linear or branched, and in the aliphatic hydrocarbon group, one or more methylenes (-CH ₂ -) may be substituted with oxygen (-O-), R ⁶ represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, which may be linear or branched, and in the aliphatic hydrocarbon group, one or more methylenes (-CH _{2 -)} may be substituted with oxygen (-O-), The carbon number of R ¹ to R ⁶ includes the number of carbon atoms of methylene (-CH ₂ -) substituted with oxygen (-O-).

When the conductive paste contains the above-mentioned amide compound, the adhesion of the dried film can be improved. The details of why this is the case are unclear, but it is thought that, for example, the above-mentioned amide compound inhibits the interaction between resins, softening the dried film to an appropriate degree, and the dried film that becomes easily deformed due to the softening, and the resins that did not interact with each other, etc., tend to become entangled at the adhesive interface, thereby improving the adhesion between the dried film and the ceramic green sheet (dielectric layer).

In the above formulas (1) to (3), the lower limit of the number of carbon atoms in ^R1 and ^R5 may be independently 8 or more, 12 or more, or 15 or more. In addition, the number of carbon atoms in ^R1 and ^R5 may be the same.

Furthermore, ^R1 and ^R5 may be an unsubstituted aliphatic hydrocarbon group in which one or more methylene ( _-CH2- ) groups are replaced with oxygen (-O-). Furthermore, ^R1 and ^R5 may have the same structure.

In the above formulas (1) to (3), the upper limit of the carbon number of R ² , R ³ , and R ⁴ may be 5 or less, or may be 3 or less. Furthermore, R ² , R ³ , and R ⁴ may be an unsubstituted aliphatic hydrocarbon group, for example, one or more methylene (-CH ₂ -) may be replaced with oxygen (-O-), or may be hydrogen.

In the above formula (3), the upper limit of the number of carbon atoms in R ⁶ may be 5 or less, 3 or less, or 2 or less. Furthermore, R ⁶ may be an unsubstituted saturated hydrocarbon group in which one or more methylene (-CH ₂ -) groups are replaced with oxygen (-O-).

The temperature at which the weight loss rate of the amide compound is maximized in the thermogravimetric analysis (maximum thermal decomposition temperature) may be, for example, 200°C or higher, 220°C or higher, and preferably 250°C or higher. When the boiling point or thermal decomposition temperature is within the above range, delamination and cracking of the laminate can be suppressed. In addition, 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.

The maximum thermal decomposition temperature is a value determined by thermogravimetry (TG) using the following method: A thermal decomposition weight measuring device (STA25000REGULUS, manufactured by Netsch) was 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 was measured. The temperature at which the differential loss on heating was the largest was determined as the maximum thermal decomposition temperature.

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

In addition, the content of the amide compound is preferably 0.01% by mass or more and 1.0% by mass or less with respect to the entire conductive paste. When the content of the amide 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 amide compound may be 0.05% by mass or more, or 0.1% by 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 amide compound may be 0.7% by mass or less, or 0.4% by mass or less.

The upper limit of the content of the amide compound may be 2% by mass or less, 1.8% by mass or less, 1.5% by mass or less, 1.0% by mass or less, or less than 1.0% by mass. If the content of the amide compound exceeds 1.0% by mass, the adhesion is improved, but when the laminate of the dried film and the ceramic green sheet is subjected to a binder removal treatment, the laminate may be thermally decomposed and gas may be generated. The content of the amide compound may be appropriately adjusted within the above range according to the usage environment, etc.

In addition, the content of the amide compound can be appropriately set according to the type and content of the binder resin.For example, the content of the amide compound can be set according to the content of the butyral resin.For example, the content of the amide compound can be 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, relative to 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 dispersant, a base dispersant, a nonionic dispersant, an amphoteric dispersant, etc., and it is preferable to include at least one of an acid dispersant and a base dispersant, and it is more preferable to include an acid dispersant. Note that these dispersants may be used alone or in combination of two or more.

The acid dispersant may include a carboxylic acid dispersant such as a higher fatty acid, a polycarboxylic acid dispersant, a phosphoric acid dispersant, an acid dispersant having an acidic group such as a polymer surfactant, and the like. It is preferable to include at least one of a polycarboxylic acid dispersant and a phosphoric acid dispersant. The polycarboxylic acid dispersant may be a comb-shaped carboxylic acid having a comb structure.

The higher fatty acid may be an unsaturated or saturated carboxylic acid, and is not particularly limited, but examples include stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, linolenic acid, and other acids having 11 or more carbon atoms. Of these, oleic acid or stearic acid is preferred.

Acid dispersants may also be, for example, oleoyl sarcosine, which is a compound of glycine and oleic acid, or alkyl monoamine salt type amide compounds using higher fatty acids such as stearic acid or lauric acid instead of oleic acid.

In addition, from the viewpoint of further improving the effect of suppressing separation between 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). 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 acid dispersant and the basic dispersant , the conductive paste may have better dispersibility and better viscosity stability over time.

The dispersant is contained in an amount of, for example, 0.01% by mass or more and 3% by mass or less relative 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 dispersant content is within the above range, it is possible to improve the dispersibility of the conductive paste and to suppress sheet attack and peeling failure of the green sheet.

(c) Other Additives The conductive paste of the present embodiment may contain other additives other than the above components as necessary. As the other additives, for example, conventionally known additives such as defoamers, plasticizers, surfactants, and thickeners can be used.

(Conductive paste)
The method for producing the conductive paste according to the present embodiment is not particularly limited, and a conventionally known method can be used. For example, the conductive paste can be produced by stirring and kneading the above-mentioned components with a triple roll mill, a ball mill, a mixer, or the like.

The conductive paste according to this embodiment contains the above-mentioned amide compound, which improves the adhesion between the dry film and the green sheet. One of the reasons for this improved adhesion is thought to be that, as described above, the amide compound inhibits the interaction between resins, thereby softening the dry film moderately (reducing the glass transition temperature Tg), making it easier to deform.

For example, when the components other than the conductive powder and ceramic powder in the conductive paste are dried at 120°C for 40 minutes to remove the organic solvent, the glass transition point Tg of this dried body (evaluation sample) is preferably lower than the glass transition point Tg' of a dried body formed under similar conditions except that it does not contain the amide compound. The amide compound may lower Tg by 10°C or more, 14°C or more, 20°C or more, 25°C or more, or 30°C or more compared to Tg'. For example, the glass transition point Tg of the dried body may be 60°C or less, 55°C or less, or 50°C or less. 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 resin as binder resin, multiple glass transition points Tg may be measured depending on the resins contained, but the glass transition point Tg of the evaluation sample in this specification indicates the glass transition point Tg in the lowest temperature range. In addition, the glass transition point Tg of the above-mentioned dried body (evaluation sample) can be measured by the method described in the examples.

In addition, when the conductive paste is applied to the surface of the 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. The lower limit of the Vickers hardness (room temperature) is, for example, 3.5 or more.

In addition, 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. The lower limit of the Vickers hardness (60°C) is, for example, 3 or more. When measuring the Vickers hardness (60°C), it is desirable to condition the dry film to be measured by leaving it at 60°C for 3 minutes in advance.

The conductive paste can be suitably used in electronic components such as multilayer ceramic capacitors, and in particular, can be suitably used as a paste for internal electrodes of multilayer ceramic capacitors. When the conductive paste is used as a paste for internal electrodes, the viscosity of the conductive paste can be, for example, about 0.2 Pa·S or more and 30 Pa·S or less at a shear rate of 100 (s ⁻¹ ).

[Multilayer ceramic capacitor]
Hereinafter, embodiments of the multilayer ceramic capacitor of the present invention will be described with reference to the drawings. In the drawings, the drawings may be represented diagrammatically or at a different scale as appropriate. The positions and directions of the members will be described with reference to an XYZ orthogonal coordinate system as shown in FIG. 1 as appropriate. In this XYZ orthogonal coordinate system, the X and Y directions are horizontal directions, and the Z direction is vertical (up-down direction).

1A and 1B are diagrams showing a multilayer ceramic capacitor 1. The multilayer ceramic capacitor 1 comprises a ceramic laminate 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 above-mentioned conductive paste as a paste for internal electrodes will be described. First, the 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 their upper surfaces are laminated by pressure bonding to obtain a laminate, and the laminate is then fired and integrated to produce a ceramic laminate 10 in which internal electrode layers 11 and dielectric layers 12 are alternately laminated. Then, a pair of external electrodes 20 are formed at both ends of the ceramic laminate 10 to manufacture a multilayer ceramic capacitor 1. This will be described in more detail below.

First, a green sheet, which is an unfired ceramic sheet, is prepared. For example, this green sheet may be prepared by adding a binder resin such as polyvinyl butyral and a solvent such as terpineol to a powder of a specific ceramic such as barium titanate, applying the resulting dielectric layer paste to a support film such as a PET film in the form of a sheet, and then drying to remove the solvent. The thickness of the dielectric layer made of the green sheet is not particularly limited, but is preferably 0.05 μm or more and 3 μm or less in view of the demand for miniaturization of multilayer ceramic capacitors.

Next, the above-mentioned conductive paste is printed and applied to one side of the green sheet, and then dried to form a dry film on one side of the green sheet to prepare multiple sheets. Note that, from the viewpoint of the requirement to make the internal electrode layer 11 thin, it is preferable that the thickness of the dry film formed from the conductive paste is 1 μm or less after drying.

Next, the green sheet is peeled off from the support film, and the green sheet and the dry film formed on one side of the green sheet are laminated so that they are arranged alternately, and then a laminate is obtained by a heat and pressure treatment. Note that it is also possible to further arrange protective ceramic green sheets that are not coated with conductive paste on both sides of the laminate.

Next, the laminate is cut to a predetermined size to form a green chip, and then the green chip is subjected to a binder removal treatment and fired under a reducing atmosphere to produce a laminated ceramic fired body (ceramic laminate 10). The atmosphere in the binder removal treatment is preferably air or _N2 gas atmosphere. The temperature during the binder removal treatment is, for example, 200°C or higher and 400°C or lower. The temperature is preferably held for 0.5 hours or longer and 24 hours or shorter during the binder removal treatment. The firing is performed in a reducing atmosphere to suppress oxidation of the metal used in the internal electrode layer, and the temperature during firing of the laminate is, for example, 1000°C or higher and 1350°C or lower, and the temperature is held for, for example, 0.5 hours or longer and 8 hours or shorter.

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. The organic vehicle in the dry film is also removed, and the nickel powder or the alloy powder mainly composed of nickel is sintered or melted and integrated to form the internal electrode layer 11, forming a multilayer ceramic sintered body in which multiple dielectric layers 12 and internal electrode layers 11 are alternately stacked. Note that the sintered multilayer ceramic sintered body may be annealed from the viewpoint of taking oxygen into the dielectric layer to increase reliability and suppressing reoxidation of the internal electrodes.

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

The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited in any way by the examples.

[Evaluation method]
(Adhesion Evaluation)
A conductive paste (sample) was applied to the surface of a green sheet containing barium titanate and polyvinyl butyral that had been prepared in advance, forming a conductive paste film with a wet film thickness of 35 μm. The obtained green sheet and a sheet consisting of the conductive paste film for the internal electrodes formed on the surface 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 in such a way that the surface coated with the conductive paste was sandwiched between the green sheets, and then pressed at a temperature of 40° C. and a pressure of 20 MPa for 20 seconds to create a laminate (for evaluation).

The resulting laminate was cut into 1 cm squares, and then both sides of the laminate were set on the fixture of a tensile tester (Shimadzu Corporation, AGS-50NX) using tape, after which a tensile test was performed. The breaking force (the force required to peel the dried film from the green sheet) was recorded at a test speed of 20 mm/min. The breaking force of Comparative Example 1 was set as 100%, and each breaking force was evaluated as a percentage.

(Hardness measurement)
The surface (dried film side) of the green sheet on which the conductive paste film (dry film) was formed under the same conditions as those for the adhesion evaluation was measured at n=5 points using a micro Vickers hardness tester (Shimadzu Corporation, HMV-G21DT) under a test force of 98 mN, and the average value was calculated. The hardness measurement was performed by attaching the sample to a glass substrate and placing it on a heating stage, which is the sample stand of the hardness tester, at room temperature (25°C) without heating and at a heated state of 60°C. 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 measured while it was heated at 60°C.

(Measurement of glass transition temperature Tg)
The components contained in the conductive paste, excluding the conductive powder and ceramic powder, i.e., the ethyl cellulose resin, polyvinyl butyral resin, additives, and organic solvent, were weighed out in the same amounts as those contained in the conductive paste, and mixed for 4 minutes at 2000 rpm using a planetary mixer (Thinky, ARE-310). The resulting liquid (mixture) was then applied to a PET film with a wet film thickness of 254 μm using an applicator, and dried at 120° C. for 40 minutes to obtain a sample for evaluation. The organic solvent in the mixture was removed during drying.

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

(Measurement of thermal decomposition temperature)
The thermal decomposition temperature of the additives used in the conductive paste was measured using a thermal decomposition weight measuring device (STA25000REGULUS, manufactured by Netsch). The measurement temperature was measured in a nitrogen atmosphere, and the temperature range was from 20°C to 550°C at a heating rate of 5°C/min. The temperature at which the differential heat loss was the largest, i.e., the temperature at which the weight loss rate in the thermogravimetric analysis was the largest, was taken 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 both the examples and the comparative examples, a polycarboxylic acid-based dispersant, which is an acid-based dispersant, was used as the dispersant (additive) contained in common.

(Additives)
As the amide compound, the following compounds (4) (compound of the above structural formula (2)) and (5) (compound of the above structural formula (3)) were used.

As comparative examples, the following additives were used.
Additive a: polycarboxylic acid having polyoxyalkylene as a graft chain Additive b: oxyethylene laurylamine (polyetheramine)
Additive c: Dicarboxylic acid

(Organic Solvent)
As the organic solvent, dihydroterpineol (DHT) and mineral spirits (MSA) were used.

[Example 1]
Conductive powder 49 mass%, ceramic powder 12 mass%, acid dispersant 0.15 mass%, additive of formula (4) 0.3 mass%, binder resin 2.5 mass% (PVB:EC = 7:3 (mass ratio)), and organic solvent (DHT:MSA = 60:40 (mass ratio)) as the remainder were added to make a total of 100 mass%, and these materials were mixed to prepare a conductive paste. The content of each material in the conductive paste and the evaluation results are shown in Table 1.

[Examples 2 to 5, Comparative Examples 1 to 4]
Conductive pastes were prepared and evaluated in the same manner as in Example 1, except that the types and contents of additives were changed as shown in Table 1. The contents of each material in the conductive paste and the evaluation results are shown in Table 1.

(Evaluation Results)
The conductive pastes of Examples 1 to 5 had a lower glass transition point (Tg) in the low temperature range, a lower Vickers hardness, and improved adhesion, as compared with the conductive pastes of Comparative Examples 1 to 4, which did not contain the amide compound represented by formula (1) or (2).

When the conductive paste of the present invention is used to form the 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 suitably used for the internal electrodes of multilayer ceramic capacitors, which are chip components of electronic devices that are becoming increasingly miniaturized, 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-mentioned embodiments may be omitted. Furthermore, the requirements described in the above-mentioned embodiments may be combined as appropriate. Furthermore, to the extent permitted by law, the disclosures of all documents cited in the above-mentioned embodiments are incorporated by reference into this text. Furthermore, to the extent permitted by law, the contents of Japanese patent application No. 2022-052666 are incorporated by reference into this text.

Embodiments of the present invention may include the following configurations:

（ただし、Ｒ^１は、飽和又は不飽和の炭素数８～２５の脂肪族炭化水素基を表し、前記脂肪族炭化水素基は、直鎖状、又は分岐鎖状であってもよく、前記脂肪族炭化水素基は、１以上のメチレン（－ＣＨ_２－）が酸素（－Ｏ－）で置換されてもよく、Ｒ^２は、水素、飽和又は不飽和の炭素数１～６の脂肪族炭化水素基を表し、前記脂肪族炭化水素基は、直鎖状、又は分岐鎖状であってもよく、前記脂肪族炭化水素基は、１以上のメチレン（－ＣＨ_２－）が酸素（－Ｏ－）で置換されてもよい。） [1] A conductive paste containing a conductive powder, an additive, a binder resin and an organic solvent,
The additive includes a compound having a structural portion represented by the following formula (1):
Conductive paste.

(wherein R ¹ represents a saturated or unsaturated aliphatic hydrocarbon group having 8 to 25 carbon atoms, which may be linear or branched, and in which one or more methylenes (-CH ₂ -) in the aliphatic hydrocarbon group may be substituted with oxygen (-O-), and R ² represents hydrogen, or a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, which may be linear or branched, and in which one or more methylenes (-CH ₂ -) in the aliphatic hydrocarbon group may be substituted with oxygen (-O-).)

（ただし、Ｒ^１、Ｒ^５は、それぞれ独立に、飽和又は不飽和の炭素数８～２５の脂肪族炭化水素基を表し、前記脂肪族炭化水素基は、直鎖状、又は分岐鎖状であってもよく、前記脂肪族炭化水素基は、１以上のメチレン（－ＣＨ_２－）が酸素（－Ｏ－）で置換されてもよく、
Ｒ^２、Ｒ^３、Ｒ^４は、それぞれ独立に、水素、飽和又は不飽和の炭素数１～６の脂肪族炭化水素基を表し、前記脂肪族炭化水素基は、直鎖状、又は分岐鎖状であってもよく、前記脂肪族炭化水素基は、１以上のメチレン（－ＣＨ_２－）が酸素（－Ｏ－）で置換されてもよく、
Ｒ^６は、飽和又は不飽和の炭素数１～６の脂肪族炭化水素基を表し、前記脂肪族炭化水素基は、直鎖状、又は分岐鎖状であってもよく、前記脂肪族炭化水素基は、１以上のメチレン（－ＣＨ_２－）が酸素（－Ｏ－）で置換されてもよい。） [2] The conductive paste according to [1], wherein the compound has a structure represented by the following formula (2) or the following formula (3):

(wherein R ¹ and R ⁵ each independently represent a saturated or unsaturated aliphatic hydrocarbon group having 8 to 25 carbon atoms, the aliphatic hydrocarbon group may be linear or branched, and the aliphatic hydrocarbon group may have one or more methylene (—CH ₂ —) substituted with oxygen (—O—),
R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, the aliphatic hydrocarbon group may be linear or branched, and one or more methylene groups (—CH ₂ —) in the aliphatic hydrocarbon group may be replaced by oxygen (—O—);
R ⁶ represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, the aliphatic hydrocarbon group may be linear or branched, and the aliphatic hydrocarbon group may have one or more methylenes (-CH ₂ -) substituted with oxygen (-O-).

[3] A conductive paste described in [1] or [2], in which 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.

[4] A conductive paste described in any one of [1] to [3], wherein the compound has a temperature at which the weight loss rate is maximum in thermogravimetric analysis of 200°C or higher.

[5] A conductive paste described in any one of [1] to [4], wherein the molecular weight of the compound is 250 or more and 3,000 or less.

[6] A conductive paste described in any one of [1] to [5], further containing an acid-based dispersant and/or a base-based dispersant.

[7] A conductive paste described in any one of [1] to [6], wherein the conductive powder contains at least one type of metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof.

[8] A conductive paste described in any one of [1] to [7], wherein the conductive powder has an average particle size of 0.05 μm or more and 1.0 μm or less.

[9] A conductive paste described in any one of [1] to [8], wherein the binder resin contains a butyral-based resin.

[10] A conductive paste described in any one of [1] to [9], further containing ceramic powder.

[11] A conductive paste described in [10], wherein the ceramic powder contains barium titanate.

[12] A conductive paste described in [10] or [11], wherein the ceramic powder has an average particle size of 0.01 μm or more and 0.5 μm or less.

[13] A conductive paste described in any one of [10] to [12], wherein the ceramic powder is contained in an amount of 1 mass% or more and 20 mass% or less relative to the entire conductive paste.

[14] A conductive paste described in any one of [1] to [13], for use as an internal electrode for a multilayer ceramic component.

[15] An electronic component formed using a conductive paste described in any one of [1] to [14].

[16] At least a laminate in which a dielectric layer and an internal electrode layer are laminated,
The internal electrode layers are formed using the conductive paste according to [14].

REFERENCE SIGNS LIST 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 (16)

A conductive paste comprising a conductive powder, an additive, a binder resin and an organic solvent,
The additive includes a compound having a structural portion represented by the following formula (1):
Conductive paste.

(wherein R ¹ represents a saturated or unsaturated aliphatic hydrocarbon group having 8 to 25 carbon atoms, which may be linear or branched, and in which one or more methylenes (-CH ₂ -) in the aliphatic hydrocarbon group may be substituted with oxygen (-O-), and R ² represents hydrogen, or a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, which may be linear or branched, and in which one or more methylenes (-CH ₂ -) in the aliphatic hydrocarbon group may be substituted with oxygen (-O-).) The conductive paste according to claim 1 , wherein the compound has a structure represented by the following formula (2) or the following formula (3):

(wherein R ¹ and R ⁵ each independently represent a saturated or unsaturated aliphatic hydrocarbon group having 8 to 25 carbon atoms, the aliphatic hydrocarbon group may be linear or branched, and the aliphatic hydrocarbon group may have one or more methylene (—CH ₂ —) substituted with oxygen (—O—),
R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, the aliphatic hydrocarbon group may be linear or branched, and one or more methylene groups (—CH ₂ —) in the aliphatic hydrocarbon group may be replaced by oxygen (—O—);
R ⁶ represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, the aliphatic hydrocarbon group may be linear or branched, and the aliphatic hydrocarbon group may have one or more methylenes (-CH ₂ -) 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 relative to the entire conductive paste. The conductive paste according to claim 1, wherein the compound has a temperature at which the weight loss rate is maximized in thermogravimetric analysis of 200°C or higher. The conductive paste described in claim 1, wherein the molecular weight of the compound is 250 or more and 3,000 or less. The conductive paste according to claim 1, further comprising an acid dispersant and/or a base 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 described in 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 comprises a butyral resin. The conductive paste of claim 1, further comprising a ceramic powder. The conductive paste of claim 10, wherein the ceramic powder comprises barium titanate. The conductive paste described in claim 10, 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 10, wherein the ceramic powder is contained in an amount of 1% by mass or more and 20% by mass or less with respect to the entire conductive paste. The conductive paste according to claim 1, which is for use in internal electrodes of multilayer ceramic components. An electronic component formed using the conductive paste according to any one of claims 1 to 14. The laminate has at least a dielectric layer and an internal electrode layer stacked thereon,
A multilayer ceramic capacitor, wherein the internal electrode layers are formed using the conductive paste according to claim 14.

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