JP7405098B2 - 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.

BACKGROUND ART 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 (coated) in a predetermined electrode pattern on the surface of a dielectric green sheet containing a dielectric powder such as barium titanate (BaTiO ₃ ) and a binder resin, and then dried. to form a dry film. Next, the dry films and dielectric green sheets are laminated so as to overlap alternately, and are heat-pressed and integrated to form a pressed body. This pressed body is cut, subjected to organic binder removal treatment in an oxidizing atmosphere or inert atmosphere, and then fired to obtain fired chips (laminates). Next, an external electrode paste is applied to both ends of the fired chip (laminated body), and after firing, nickel plating or the like is applied to the external electrode surface to obtain a multilayer ceramic capacitor.

Conventionally, screen printing has been commonly used as the printing method for printing conductive paste onto dielectric green sheets, but due to demands for smaller electronic devices, thinner films, and improved productivity. There is a need to print finer electrode patterns with high productivity.

Gravure is one of the printing methods for conductive paste, which is a continuous printing method in which the conductive paste is filled in the recesses provided in the plate and the conductive paste is transferred from the plate by pressing it against the surface to be printed. A printing method has been proposed. Gravure printing has fast printing speed and excellent productivity. When using the gravure printing method, it is necessary to appropriately select the binder resin, dispersant, solvent, etc. in the conductive paste, and adjust the properties such as viscosity to a range suitable for gravure printing.

For example, in Patent Document 1, a conductive paste is used to form an inner conductor film by gravure printing in a laminated ceramic electronic component including a plurality of ceramic layers and an inner conductor film extending along a specific interface between the ceramic layers. 30 to 70% by weight solid component containing metal powder, 1 to 10% by weight ethyl cellulose resin component having an ethoxy group content of 49.6% or more, and 0.05 to 5% by weight dispersant. and a solvent component as the remainder, the viscosity η _0.1 at a shear rate of 0.1 (s ^-1 ) is 1 Pa·s or more, and the viscosity at a shear rate of 0.02 (s ^-1 ) A conductive paste is described that is a thixotropic fluid, satisfying the condition that η _0.02 is expressed by a specific formula.

Furthermore, Patent Document 2 discloses a conductive paste used for forming by gravure printing as in Patent Document 1, which contains 30 to 70% by weight of a solid component including metal powder and 1 to 10% by weight of a conductive paste. A thixotropic fluid containing a resin component, 0.05 to 5% by weight of a dispersant, and the remainder a solvent component, and having a viscosity of 1 Pa·s or more at a shear rate of 0.1 (s ^-1 ), A conductive paste is described that has a viscosity change rate of 50% or more at a shear rate of 10 (s ^-1 ), based on the viscosity at a shear rate of 0.1 (s ^-1 ).

According to Patent Documents 1 and 2, these conductive pastes are thixotropic fluids with a viscosity of 1 Pa·s or more at a shear rate of 0.1 (s ⁻¹ ), and are stable at high speeds in gravure printing. It is said that continuous printing can be achieved and multilayer ceramic electronic components such as multilayer ceramic capacitors can be manufactured with good production efficiency.

Furthermore, Patent Document 3 discloses a conductive material for multilayer ceramic capacitor internal electrodes containing a conductive powder (A), an organic resin (B), an organic solvent (C), an additive (D), and a dielectric powder (E). The organic resin (B) is composed of polyvinyl butyral having a degree of polymerization of 10,000 or more and 50,000 or less, and ethyl cellulose having a weight average molecular weight of 10,000 or more and 100,000 or less, and the organic solvent (C) is propylene glycol monobutyl ether, or a mixed solvent of propylene glycol monobutyl ether and propylene glycol methyl ether acetate, or a mixed solvent of propylene glycol monobutyl ether and mineral spirit; the additive (D) consists of a separation inhibitor and a dispersant; A conductive paste for gravure printing is described, which comprises a composition containing a polycarboxylic acid polymer or a salt of a polycarboxylic acid as an inhibitor. According to Patent Document 3, this conductive paste has a viscosity suitable for gravure printing, has improved paste uniformity and stability, and has good drying properties.

Japanese Patent Application Publication No. 2003-187638 Japanese Patent Application Publication No. 2003-242835 Japanese Patent Application Publication No. 2012-174797

As internal electrode layers have become thinner in recent years, the particle size of conductive powder has also tended to become smaller. When the particle size of the conductive powder is small, the specific surface area of the particle surface becomes large, which increases the surface activity of the conductive powder (metal powder), which may reduce the dispersibility of the conductive paste, resulting in higher There is a need for a conductive paste with dispersibility.

In addition, when printing conductive paste using gravure printing, a lower paste viscosity is required than with screen printing, so conductive powder with a relatively high specific gravity settles, reducing the dispersibility of the paste. It is possible that Note that in the conductive pastes described in Patent Documents 1 and 2, the dispersibility of the paste is improved by removing lumps in the conductive paste using a filter. The manufacturing process tends to be complicated.

In view of these circumstances, an object of the present invention is to provide a conductive paste that has excellent paste dispersibility and productivity, and has a paste viscosity suitable for gravure printing.

In a first aspect of the present invention, there is provided a conductive paste containing a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent, the dispersant comprising a first acid-based dispersant and a second acid-based dispersant. The first acid-based dispersant has an average molecular weight of more than 500 and 2000 or less, and has one or more branched chains consisting of a hydrocarbon group with respect to the main chain, and the first acid-based dispersant A conductive paste is provided in which the system dispersant other than the first acid-based dispersant has a carboxyl group, the binder resin includes an acetal resin, and the organic solvent includes a glycol ether solvent.

Further, the first acid-based dispersant is preferably an acid-based dispersant having a carboxyl group, and more preferably a hydrocarbon-based graft copolymer having a polycarboxylic acid as its main chain. Further, the second acidic dispersant preferably has a molecular weight of 5000 or less and contains an alkyl group having 10 to 20 carbon atoms or an alkenyl group having 10 to 20 carbon atoms. Further, the first acid-based dispersant is contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder, and the second acid-based dispersant is contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder. The content is preferably 0.01 parts by mass or more and 2 parts by mass or less. 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 ceramic powder contains a perovskite type oxide. 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. Moreover, it is preferable that the binder resin contains a butyral resin. Further, it is preferable that the conductive paste is used for internal electrodes of laminated ceramic components. Further, the conductive paste preferably has a viscosity of 0.8 Pa·S or less at a shear rate of 100 sec ⁻¹ , and a viscosity of 0.18 Pa·S or less at a shear rate of 10,000 sec ⁻¹ .

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 including a dielectric layer and an internal electrode layer, the internal electrode layer being formed using the conductive paste described above.

The conductive paste of the present invention has excellent paste dispersibility and productivity. Further, the conductive paste of the present invention has a viscosity suitable for gravure printing. Further, the electrode pattern of an electronic component such as a multilayer ceramic capacitor formed using the conductive paste of the present invention has excellent printability and uniform thickness even when forming a thin electrode.

FIG. 1A is a perspective view showing a multilayer ceramic capacitor according to an embodiment, and FIG. 1B is a cross-sectional view thereof.

[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. Among these, from the viewpoints of conductivity, corrosion resistance, and cost, it is preferable to use powder of Ni or an alloy thereof (hereinafter sometimes referred to as "Ni powder"). 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 parts). improves. 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 of the number of pieces.

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 total amount of the 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 conductive paste for internal electrodes of a multilayer ceramic capacitor, a known ceramic powder is selected as appropriate depending on the type of multilayer ceramic capacitor to which it is applied. Examples of the ceramic powder include perovskite oxides containing Ba and Ti, preferably barium titanate (BaTiO ₃ ).

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 the oxide include one or more oxides selected from Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and 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 constituting the dielectric 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. Examples of such ceramic powders include, in addition to the above-mentioned perovskite oxides containing Ba and Ti, 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. 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 of the number of pieces.

The content of the ceramic powder is preferably 1 part by mass or more and 30 parts by mass or less, 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.

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 20% by mass or less, based on the total amount of the conductive paste.

(binder resin)
The binder resin includes an acetal resin. As the acetal resin, butyral resins such as polyvinyl butyral are preferred. When the binder resin contains an acetal resin, the viscosity can be adjusted to be suitable for gravure printing, and the adhesive strength with the green sheet can be further improved. The binder resin may contain, for example, 20% by mass or more of acetal-based resin, 30% by mass or more of acetal-based resin, or may consist only of acetal-based resin. Furthermore, even if the content of the acetal resin is less than 40% by mass based on the entire binder resin, it is possible to have low paste viscosity and sufficient adhesive strength.

The content of the acetal resin is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 8 parts by mass or less, based on 100 parts by mass of the conductive powder.

Moreover, the binder resin may contain other resins below the acetal resin. Other resins are not particularly limited, and known resins can be used. Examples of other resins include cellulose resins such as methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, and nitrocellulose, and acrylic resins. Among them, ethylcellulose is preferred from the viewpoint of solubility in solvents and combustion decomposition properties. preferable. Further, the molecular weight of the binder resin is, for example, about 20,000 to 200,000.

The content of the binder resin is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 8 parts by mass or less, based on 100 parts by mass of the conductive powder.

The content of the binder resin is preferably 0.5% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 6% by mass or less, based on the total amount of the conductive paste. When the content of the binder resin is within the above range, the conductivity and dispersibility are excellent.

(Organic solvent)
Organic solvents include glycol ether solvents.

Examples of glycol ether solvents include (di)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, and propylene glycol. Examples include propylene glycol monoalkyl ethers such as monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether (PNB). Among them, propylene glycol monoalkyl ethers are preferred, and propylene glycol monobutyl ether (PNB) is more preferred. When the organic solvent contains a glycol ether solvent, it has excellent compatibility with the above-mentioned binder resin and has excellent drying properties.

The organic solvent may contain, for example, 25% by mass or more of a glycol ether solvent, 50% by mass or more of a glycol ether solvent, or may consist only of a glycol ether solvent. Moreover, one type of glycol ether solvent may be used alone, or two or more types may be used in combination.

The organic solvent may further include an acetate solvent. Examples of acetate solvents include dihydroterpinyl acetate, isobornyl acetate, isobornyl propinate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, and dipropylene glycol methyl ether. Examples include glycol ether acetates such as acetate, 3-methoxy-3-methylbutyl acetate, and 1-methoxypropyl-2-acetate.

When the organic solvent contains an acetate-based solvent, for example, at least one acetate-based solvent selected from dihydroterpinyl acetate, isobornyl acetate, isobornylpropinate, isobornyl butyrate, and isobornyl isobutyrate. It may also contain a solvent (A). Among these, isobornyl acetate is more preferred. The acetate solvent is contained in an amount of 0% by mass or more and 80% by mass or less, preferably 10% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 40% by mass or less, based on the entire organic solvent. .

In addition, when the organic solvent contains an acetate-based solvent, for example, the above-mentioned acetate-based solvent (A) and at least one acetate-based solvent (B) selected from ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate. May include. When such a mixed solvent is used, the viscosity of the conductive paste can be easily adjusted and the drying speed of the conductive paste can be increased.

In the case of a mixed solution containing an acetate-based solvent (A) and an acetate-based solvent (B), the organic solvent preferably contains the acetate-based solvent (A) in an amount of 50% by mass or more and 90% by mass or less based on the total acetate-based solvent. The content is more preferably 60% by mass or more and 80% by mass or less. In the case of the above mixed solution, the acetate solvent (B) preferably contains 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less, based on 100% by mass of the total acetate solvent. .

Further, the organic solvent may include other organic solvents than glycol ether solvents and acetate solvents. The other organic solvent is not particularly limited, and any known organic solvent that can dissolve the binder resin can be used. Examples of other organic solvents include acetate ester solvents such as ethyl acetate, propyl acetate, isobutyl acetate, and butyl acetate, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, terpene solvents such as terpineol and dihydroterpineol, tridecane, Examples include aliphatic hydrocarbon solvents such as nonane and cyclohexane. Among these, aliphatic hydrocarbon solvents are preferred, and among the aliphatic hydrocarbon solvents, mineral spirits are more preferred. Note that one type or two or more types of other organic solvents may be used.

The organic solvent may include, for example, a glycol ether solvent as a main solvent and an aliphatic hydrocarbon solvent as a subsolvent. In this case, the glycol ether solvent is preferably contained in an amount of 30 parts by mass or more and 50 parts by mass or less, more preferably 40 parts by mass or more and 50 parts by mass or less, based on 100 parts by mass of the conductive powder, and the aliphatic hydrocarbon solvent is preferably contained in an amount of 20 parts by mass or more and 80 parts by mass or less, more preferably 20 parts by mass or more and 40 parts by mass or less, per 100 parts by mass of the conductive powder. Further, even when the aliphatic hydrocarbon solvent is contained in an amount of 25 parts by mass or more based on 100 mass parts of the conductive powder, the conductive paste can have excellent dispersibility.

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.

The content of the organic solvent is preferably 20% by mass or more and 50% 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.

(dispersant)
As a result of examining various dispersants for use in conductive paste, the present inventors found that the average molecular weight is more than 500 and less than 2000, and the main chain has a branched chain consisting of a hydrocarbon group. By using a dispersant containing one or more first acid-based dispersants and a second acid-based dispersant other than the first acid-based dispersant that has a carboxyl group, the conductive paste contains It has been found that the powder material (conductive powder and ceramic powder) has excellent dispersibility, and the dry film surface has excellent smoothness.

Although the details of the reason for this effect are not clear, the first acid-based dispersant has branches consisting of hydrocarbon groups, which effectively forms steric hindrance and suppresses agglomeration of the powder material. In addition, it is considered that when the second acid-based dispersant has a carboxyl group, this carboxyl group can disperse the first acid-based dispersant more effectively. Further, it is considered that by setting the molecular weight of the first acidic dispersant to a specific value, it is possible to maintain a suitable viscosity depending on the use of the conductive paste. Note that the present invention is not restricted by the above theory (reason). Hereinafter, the dispersant according to this embodiment will be explained in more detail.

The first acid-based dispersant has one or more branched chains consisting of hydrocarbon groups in its main chain, preferably a plurality of branched chains. Further, the first acid-based dispersant preferably has a carboxyl group, and is more preferably a hydrocarbon-based graft copolymer having a polycarboxylic acid as its main chain. Moreover, it is preferable that the polycarboxylic acid has an ester structure. Moreover, it is preferable that the hydrocarbon group has a chain structure. Further, the hydrocarbon group may be an alkyl group. Furthermore, the alkyl group may be composed only of carbon and hydrogen, or a portion of the hydrogen constituting the alkyl group may be substituted with a substituent.

The molecular weight of the first acidic dispersant is greater than 500 and less than or equal to 2000, and may be greater than or equal to 1000 and less than or equal to 2000. When the molecular weight is within the above range, the conductive powder and ceramic powder will have excellent dispersibility, and the dry film surface will have excellent density and smoothness. In this specification, when the molecular weight of the dispersant has a certain degree of distribution, the molecular weight of the dispersant indicates the weight average molecular weight.

As the first acid-based dispersant, one that satisfies the above characteristics can be selected from commercially available products. Further, the acidic dispersant may be manufactured using a conventionally known manufacturing method so as to satisfy the above characteristics.

The first acidic dispersant is preferably contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder. When the content of the acid dispersant is within the above range, the dispersibility of the conductive powder and ceramic powder and the smoothness of the dried electrode surface after application are excellent, and the viscosity of the conductive paste is adjusted to an appropriate range. In addition, it is possible to suppress sheet attacks and poor peeling of green sheets. Further, the conductive paste according to the present embodiment can have high dispersibility even if the content of the acid-based dispersant is 1 part by mass or less.

The second acidic dispersant is an acidic dispersant having a carboxyl group. The second acidic dispersant preferably has a molecular weight of 5000 or less, more preferably 1000 or less, and even more preferably 500 or less. The second acidic dispersant is, for example, an acidic dispersant having a hydrocarbon group. The hydrocarbon group preferably includes an alkyl group having 10 to 20 carbon atoms or an alkenyl group having 10 to 20 carbon atoms. When the second acid-based dispersant has the above structure, the effect of adding the first acid-based dispersant is further improved, and the dispersibility when forming a conductive paste is further improved. be able to.

Examples of the second acidic dispersant include acidic dispersants such as higher fatty acids and amino acids. Note that the second dispersant may be used alone or in combination of two or more.

Higher fatty acids may be unsaturated carboxylic acids or saturated carboxylic acids, and are not particularly limited to carbonaceous acids such as stearic acid, oleic acid, behenic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, and linolenic acid. Examples include those of number 11 or more. Among these, oleic acid or stearic acid is preferred.

The second acid-based dispersant other than higher fatty acids is not particularly limited, and may be an alkyl monoamine salt type represented by a monoalkylamine salt, or an alkyl monoamine salt type represented by a N-alkyl (C14 to C18) propylene diamine dioleate. Alkyl diamine salt type, alkyl trimethyl ammonium salt type represented by alkyl trimethyl ammonium chloride, alkyl dimethyl benzyl ammonium salt type represented by coconut alkyl dimethyl benzyl ammonium chloride, and 4 represented by alkyl dipolyoxyethylene methyl ammonium chloride. grade ammonium salt type, alkylpyridinium salt type, tertiary amine type represented by dimethylstearylamine, polyoxyethylene alkylamine type represented by polyoxypropylene/polyoxyethylene alkylamine, N, N', N'- Examples include surfactants selected from oxyethylene-adducted diamines represented by tris(2-hydroxyethyl)-N-alkyl(C14-18)1,3-diaminopropane, and among these, alkyl monoamine salts Type is preferred.

As the alkyl monoamine salt type, oleoyl sarcosine, lauriloyl sarcosine, stearic acid amide, etc. are preferable.

The second acidic dispersant is preferably contained in an amount of 0.01 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder. When the second acid-based dispersant is included in the above range in addition to the first acid-based dispersant, the conductive powder and ceramic powder in the conductive paste have better dispersibility, and the dry electrode surface becomes smoother after coating. In addition, the viscosity of the conductive paste can be adjusted to an appropriate range, and sheet attack and poor peeling of the green sheet can be suppressed. Further, in the conductive paste according to the present embodiment, the content of the second acidic dispersant may be 1 part by mass or less, 0.1 part by mass or less, or 0.05 part by mass. The following may be sufficient.

Further, the second acid-based dispersant is, for example, about 1 part by mass or more and 500 parts by mass or less, preferably 50 parts by mass or more and 300 parts by mass or less, more preferably, based on 100 parts by mass of the first acid-based dispersant. may be contained in an amount of 50 parts by mass or more and 200 parts by mass, more preferably 50 parts by mass or more and 150 parts by mass. When the second acidic dispersant is contained within the above range, the dry film density and surface roughness tend to be good.

The conductive paste may contain only the first acid-based dispersant and the second acid-based dispersant as dispersants, or may contain dispersants other than the above-mentioned acid-based dispersants to achieve the effects of the present invention. It may be included as long as it does not inhibit it. Dispersants other than those mentioned above may include, for example, acidic dispersants including higher fatty acids, polymeric surfactants, basic dispersants, amphoteric surfactants, polymeric dispersants, etc. It is more preferable to include a system dispersant. Further, these dispersants may be used alone or in combination of two or more.

Further, the content of the entire dispersant (total content) including the first and second acid-based dispersants is 0.01 parts by mass or more and 3 parts by mass or less based on 100 parts by mass of the conductive powder. The content is preferably 0.23 parts by mass or more and 3 parts by mass or less. Further, in the conductive paste according to the present embodiment, the content of the entire dispersant (total content) may be 2 parts by mass or less, or 1 part by mass or less. Even if the total content of the dispersant is within the above range, high dispersibility can be achieved.

Further, the total content of the acid-based dispersant is preferably 3% by mass or less based on the total amount of the conductive paste. The upper limit of the total content of dispersants is preferably 2% by mass or less, more preferably 1% by mass or less. The lower limit of the total content of dispersants is not particularly limited, but is, for example, 0.01% by mass or more, preferably 0.05% by mass or more. When the total content of the dispersant is within the above range, the viscosity of the conductive paste can be adjusted to an appropriate range, and sheet attack and poor peeling of the green sheet can be suppressed.

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

(conductive paste)
The method for manufacturing the conductive paste of 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. At that time, if a dispersant is applied to the surface of the conductive powder in advance, the conductive powder will be sufficiently loosened without agglomerating, and the dispersant will be spread over the surface, making it easier to obtain a uniform conductive paste. In addition, after preparing an organic vehicle by dissolving the binder resin in a part of an organic solvent in advance, the conductive powder, ceramic powder, dispersant, and organic vehicle are added to the organic solvent for paste preparation. , may be stirred and kneaded to prepare a conductive paste.

The viscosity of the conductive paste at a shear rate of 100 sec ^-1 is preferably 0.8 Pa·S or less, may be 0.5 Pa·S or less, may be 0.4 Pa·S or less, It may be .3 Pa·S or less, or it may be 0.25 Pa·S or less. When the viscosity at a shear rate of 100 sec ^-1 is within the above range, it can be suitably used as a conductive paste for gravure printing. If it exceeds the above range, the viscosity may be too high and may not be suitable for gravure printing. The lower limit of the viscosity of the conductive paste of this embodiment at a shear rate of 100 sec ^-1 is not particularly limited, but is, for example, 0.1 Pa·S or more.

Further, the viscosity of the conductive paste at a shear rate of 10,000 sec ^-1 is preferably 0.18 Pa·S or less, and 0.14 Pa. It may be less than a. When the viscosity at a shear rate of 10,000 sec ^-1 is within the above range, it can be suitably used as a conductive paste for gravure printing. If it exceeds the above range, the viscosity may be too high and may not be suitable for gravure printing. The lower limit of the viscosity at a shear rate of 10,000 sec ^-1 is not particularly limited, but is, for example, 0.05 Pa·S or more.

Further, the dry film density (DFD) of the dried film obtained by printing and drying the conductive paste is preferably more than 5.0 g/cm ³ , and may be 5.2 g/cm ³ or more. , may exceed 5.2 g/cm ³ , and may exceed 5.3 g/cm ³ . The upper limit of the dry film density is not particularly limited, and may not exceed the true density of metal nickel, 9.8 g/cm ³ , and may be, for example, 6.5 g/cm ³ or less.

Furthermore, by printing the conductive paste and drying it in the atmosphere at 120°C for 1 hour, a dry film of 20 mm square and 1 to 3 μm in thickness was produced, and the arithmetic mean roughness Sa was 0.2 μm or less. is preferable, and may be 0.16 μm or less. On the other hand, the lower limit of the arithmetic mean roughness Sa is not particularly limited, and it is preferable that the surface is flat, and the smaller the value that exceeds 0, the more preferable it is. Note that the arithmetic mean roughness Sa is measured based on the ISO 25178 standard.

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

In the multilayer ceramic capacitor, it is preferable that the dielectric ceramic powder contained in the dielectric green sheet and the ceramic powder contained in the conductive paste have the same composition. In the multilayer ceramic device manufactured using the conductive paste of the present embodiment, sheet attack and poor peeling of the green sheet are suppressed even when the thickness of the dielectric green sheet is, for example, 3 μm or less.

[Electronic parts]
Embodiments of electronic components and the like 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).

1A and 1B are diagrams showing a multilayer ceramic capacitor 1, which is an example of an electronic component according to an embodiment. The multilayer ceramic capacitor 1 includes a 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 described. First, a conductive paste is printed on a dielectric green sheet and dried to form a dry film. A plurality of dielectric green sheets having this dry film on the upper surface are laminated by pressure bonding, and then fired. By integrating, a laminated ceramic fired body (laminated body 10) which becomes a ceramic capacitor body is produced. Thereafter, the multilayer ceramic capacitor 1 is manufactured by forming a pair of external electrodes 20 at both ends of the multilayer body 10. This will be explained in more detail below.

First, a dielectric green sheet (ceramic green sheet), which is an unfired ceramic sheet, is prepared. This dielectric green sheet is made of a dielectric layer paste obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a predetermined ceramic raw material powder such as barium titanate, and a PET film or the like. Examples include those obtained by coating a sheet on a support film and drying it to remove the solvent. Note that the thickness of the dielectric layer made of the dielectric green sheet is not particularly limited, but from the viewpoint of the demand for miniaturization of the multilayer ceramic capacitor 1, it is preferably 0.05 μm or more and 3 μm or less.

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

Next, the dielectric green sheet is peeled off from the support film, and the dielectric green sheet and the conductive paste (dry film) formed on one side are laminated in an alternating manner, and then heated and pressed. A laminate (crimped body) is obtained by the treatment. Note that a configuration may be adopted in which protective dielectric green sheets to which no conductive paste is applied are further disposed on both surfaces of the laminate.

Next, after cutting the laminate into a predetermined size to form a green chip, the green chip is subjected to a binder removal treatment and fired in a reducing atmosphere to produce a laminated ceramic fired body (laminated body 10). do. Note that the atmosphere in 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 11, and the temperature at which the laminate 10 is fired is, for example, 1000°C or more and 1350°C or less, The temperature retention time during firing is, for example, 0.5 hours or more and 8 hours or less.

By firing the green chip, the organic binder in the dielectric 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 dried film is 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, and the dielectric layer 12 and the internal electrode A laminated ceramic fired body (laminated body 10) in which a plurality of layers 11 are alternately laminated is formed. Note that from the viewpoint of increasing reliability by incorporating oxygen into the dielectric layer 12 and suppressing re-oxidation of the internal electrode layer 11, the fired multilayer ceramic fired body (laminated body 10) is annealed. Processing may be performed.

Then, by providing a pair of external electrodes 20 on the produced multilayer ceramic fired body (laminate 10), the multilayer ceramic capacitor 1 is manufactured. 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]
(Viscosity of conductive paste)
The viscosity of the conductive paste after production was measured using a rheometer at a shear rate of 100 sec ^-1 and 10,000 sec ^-1 .

(Dry film density)
The prepared conductive paste was placed on a PET film and stretched to a length of about 100 mm using an applicator with a width of 50 mm and a gap of 125 μm. The obtained PET film was dried at 120°C for 40 minutes to form a dry film, and then the dried film was cut into four pieces of 2.54 cm (1 inch) square, and the PET film was peeled off. The thickness and weight of each dry film were measured, and the dry film density (average value) was calculated.

(Surface roughness)
The prepared conductive paste was printed on a 2.54 cm (1 inch) square heat-resistant tempered glass and dried in the air at 120°C for 1 hour to produce a 20 mm square dry film with a film thickness of 1 to 3 μm. . The surface roughness Sa (arithmetic mean roughness) of the produced dry film was measured using a measuring device based on the ISO 25178 standard. Note that the arithmetic mean roughness Sa is a parameter obtained by extending the arithmetic mean roughness Ra (arithmetic mean height of a line) to a surface.

[Materials used]
(conductive powder)
As the conductive powder, Ni powder (SEM average particle size: 0.3 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 (EC) were used.

(dispersant)
(1) The first acid-based dispersant (A) is an acid-based dispersion made of a hydrocarbon-based graft copolymer (having a branched chain made of hydrocarbons) having a polycarboxylic acid as its main chain and having an average molecular weight of 1500. A drug was used.
(2) As the second acidic dispersant (B), oleoylsarcosine (C ₂₁ H ₃₉ NO ₃ ) was used.
(3) For comparison, a phosphoric acid dispersant (C) (molecular weight: 1400, no branched chain consisting of hydrocarbons) used in conventional conductive pastes was used.

(Organic solvent)
Propylene glycol monobutyl ether (PNB), mineral spirit (MA), and terpineol (TPO) were used as organic solvents.

[Example 1]
For 100 parts by mass of Ni powder, which is a conductive powder, 25 parts by mass of ceramic powder, 0.2 parts by mass of a first acid-based dispersant (A), and a second acid-based dispersant (B) as a dispersant. A conductive paste was prepared by mixing 1.0 parts by mass, 2 parts by mass of PVB and 4 parts by mass of EC as binder resins, and 41 parts by mass of PNB and 27 parts by mass of MA as organic solvents. The viscosity of the produced conductive paste, the dry film density of the paste, and the surface roughness were evaluated using the above methods. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.
[Example 2]
A conductive paste was prepared and evaluated in the same manner as in Example 1, except that the content of the first acidic dispersant (A) was 0.74 parts by mass. The content of dispersants, etc. in the conductive paste is shown in Table 1.
A conductive paste was prepared and evaluated in the same manner as in Example 1, except that the content of the first acidic dispersant (A) was 2.0 parts by mass. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.
[Example 4]
A conductive paste was prepared and evaluated in the same manner as in Example 2, except that the content of the second acidic dispersant (B) was 0.01 part by mass. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.
[Example 5]
A conductive paste was prepared and evaluated in the same manner as in Example 2, except that the content of the second acidic dispersant (B) was 2.0 parts by mass. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.
[Example 6]
Same as Example 1 except that the content of the first acidic dispersant (A) was 0.6 parts by mass, and the content of the second acidic dispersant (B) was 1.2 parts by mass. A conductive paste was prepared and evaluated. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Comparative example 1]
A conductive paste was prepared and evaluated in the same manner as in Example 1, except that 0.8 parts by mass of a phosphoric acid-based dispersant was used as the dispersant. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.
[Comparative example 2]
A conductive paste was prepared and evaluated in the same manner as in Example 2, except that 68 parts by mass of TPO was used as the main solvent and no subsolvent was used. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.
[Comparative example 3]
A conductive paste was prepared and evaluated in the same manner as in Example 2, except that 6 parts by mass of EC was used as the binder resin and PVB was not used. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Reference example 1]
A conductive paste was prepared and evaluated in the same manner as in Example 2, except that the second acid-based dispersant (B) was not used as the dispersant. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.
[Reference example 2]
Conductivity was obtained in the same manner as in Example 2, except that the first acidic dispersant (A) was not used as the dispersant, and the content of the second acidic dispersant (B) was 0.8 parts by mass. A paste was prepared and evaluated. Table 1 shows the content of the dispersant, etc. in the conductive paste, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

(Evaluation results)
The conductive paste of the example has a viscosity of 0.20 to 0.23 Pa·s at a shear rate of 100 sec ⁻¹ and a viscosity of 0.11 to 0.14 Pa·s at a shear rate of 10000 sec ⁻¹ , It showed a stable low value at any shear rate, indicating that it had a viscosity suitable for gravure printing. In addition, the conductive paste of the example exhibited a high dry film density of 5.1 to 5.4 g/cm ³ , and the surface roughness of the dry film was 0.13 to 0.16 μm. It was confirmed that it has excellent properties.

Furthermore, when comparing the conductive pastes of Examples 1 to 3, it was found that as the content of the first acid dispersant (A) increased, the dry film density improved and the surface roughness became smoother. I understand. However, the values of the dry film density and surface roughness of Example 3 are approximately saturated values. From Examples 2, 4, and 5, it can be seen that the dry film density and surface roughness can also be improved by increasing the content of the second acidic dispersant. Furthermore, from a comparison of the conductive pastes of Examples 1 and 4 and Example 6, there is a large difference in the blending ratio of the first acid-based dispersant (A) and the second acid-based dispersant (B). The closer the blending ratio is, the better the dry film density and surface roughness tend to be.

On the other hand, the conductive paste of Comparative Example 1, which did not contain the acid-based dispersant in the first film but used a phosphoric acid-based dispersant, had a higher viscosity than that of the example when manufactured under the same conditions. However, the dry film density could not be made sufficiently high, and the surface roughness was also higher than in Examples.

Further, the conductive paste of Comparative Example 2 using TPO as the main solvent, which is commonly used, had a very high viscosity and was not suitable for gravure paste, and the surface roughness was also high compared to the example. Further, the conductive paste of Comparative Example 3 in which the binder resin did not contain an acetal resin had a high viscosity, and the dry film density could not be made sufficiently high.

Further, in the conductive paste of Reference Example 1 containing the first acidic dispersant (A) alone as a dispersant, or the conductive paste of Reference Example 2 containing the second dispersant (B) alone, It was shown that the dry film density was higher and the surface roughness was lower than in Comparative Example 1 using a phosphoric acid dispersant, and the dispersibility was improved.

From the above, the conductive paste of the example of the present invention containing both the first acidic dispersant (A) and the second acidic dispersant (B) is different from that of the comparative example and the reference example. When compared with the conductive paste, it is clear that the dry film density is higher, the surface roughness is further reduced, and the dispersibility of the conductive paste is further improved. Furthermore, the viscosity of the conductive paste is lower in the conductive paste of the example of the present invention, which contains both dispersants, than the conductive paste of the comparative example and the reference example, making it more suitable for gravure printing. I understand that.

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.

The conductive paste of the present invention has a viscosity suitable for gravure printing, has a high dry film density after application, has excellent dry film surface smoothness, and has excellent dispersibility. Therefore, the conductive paste of the present invention can be suitably used as a raw material 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, and particularly suitable for gravure printing. It can be suitably used as a conductive paste.

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. Furthermore, to the extent permitted by law, the contents of Japanese Patent Application No. 2018-241705, which is a Japanese patent application, and all documents cited in this specification are incorporated into the main text.

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 (14)

A conductive paste containing a conductive powder, a ceramic powder, a dispersant, a binder resin and an organic solvent,
The dispersant includes a first acid-based dispersant and a second acid-based dispersant,
The first acid-based dispersant has an average molecular weight of more than 500 and less than 2000, and has one or more branched chains consisting of a hydrocarbon group with respect to the main chain,
The second acid-based dispersant is other than the first acid-based dispersant and has a carboxyl group,
The binder resin includes an acetal resin,
The organic solvent includes a glycol ether solvent.
conductive paste. The conductive paste according to claim 1, wherein the first acid-based dispersant has a carboxyl group. The conductive paste according to claim 1 or 2, wherein the first acid-based dispersant is a hydrocarbon-based graft copolymer having a polycarboxylic acid as its main chain. The second acid-based dispersant has a molecular weight of 5000 or less and contains an alkyl group having 10 to 20 carbon atoms or an alkenyl group having 10 to 20 carbon atoms. The conductive paste described in Section. The first acid-based dispersant is contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder, and the second acid-based dispersant is contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder. The conductive paste according to any one of claims 1 to 4, wherein the conductive paste is contained in an amount of 0.01 parts by mass or more and 2 parts by mass or less. The conductive paste according to any one of claims 1 to 5, 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 any one of claims 1 to 6, 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 any one of claims 1 to 7, wherein the ceramic powder contains a perovskite oxide. The conductive paste according to any one of claims 1 to 8, 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 any one of claims 1 to 9, wherein the binder resin contains a butyral resin. The conductive material according to any one of claims 1 to 10, having a viscosity of 0.8 Pa·S or less at a shear rate of 100 sec ^-1 and a viscosity of 0.18 Pa·S or less at a shear rate of 10000 sec ^-1 . sex paste. The conductive paste according to any one of claims 1 to 11, 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 11. It has at least a laminate including a dielectric layer and an internal electrode,
A multilayer ceramic capacitor, wherein the internal electrode is formed using the conductive paste according to claim 12.

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