JPWO2020067363A1 - Conductive pastes, electronic components, and multilayer ceramic capacitors - Google Patents

Abstract

Provided is a conductive paste having excellent dispersibility.
A conductive paste containing a conductive powder, a ceramic powder, a dispersant, a binder resin and an organic solvent. The dispersant contains an acid-based dispersant having a molecular weight of more than 500 and 2000 or less, and the acid-based dispersant is mainly used. A conductive paste having one or more branched chains composed of hydrocarbon groups with respect to the chain, the binder resin containing an acetal resin, and the organic solvent containing a glycol ether solvent.

Description

The present invention relates to conductive pastes, electronic components, and multilayer ceramic capacitors.

With the miniaturization and high performance of electronic devices such as mobile phones and digital devices, it is desired to reduce the size and capacity of electronic components including multilayer ceramic capacitors. Multilayer ceramic capacitors have a structure in which a plurality of dielectric layers and a plurality of internal electrode layers are alternately laminated, and by thinning these dielectric layers and internal electrode layers, miniaturization and high capacity can be achieved. Can be planned.

Multilayer ceramic capacitors are manufactured, for example, as follows. First, a paste for an internal electrode (conductive) containing a conductive powder, a binder resin, an organic solvent, etc. on the surface of a dielectric green sheet containing a dielectric powder such as barium titanate (BaTIO _{3) and a binder resin.} By stacking the paste) printed with a predetermined electrode pattern in multiple layers, a laminated body in which the internal electrodes and the dielectric green sheet are stacked in multiple layers is obtained. Next, the laminated body is heat-bonded and integrated to form a pressure-bonded body. The pressure-bonded body is cut, subjected to a deorganizing binder treatment in an oxidizing atmosphere or an inert atmosphere, and then fired to obtain a fired chip. Next, pastes for external electrodes are applied to both ends of the fired chip, and after firing, the surface of the external electrodes is nickel-plated or the like to obtain a multilayer ceramic capacitor.

Conventionally, a screen printing method has been generally used as a printing method used when printing a conductive paste on a dielectric green sheet, but due to the demand for miniaturization, thinning, and productivity improvement of electronic devices. , It is required to print finer electrode patterns with high productivity.

As one of the printing methods of the conductive paste, gravure is a continuous printing method in which the concave portion provided in the plate making is filled with the conductive paste and pressed against the surface to be printed to transfer the conductive paste from the plate making. A printing method has been proposed. The gravure printing method has a high printing speed and is excellent in productivity. When the gravure printing method is used, it is necessary to appropriately select the binder resin, dispersant, solvent, etc. in the conductive paste and adjust the characteristics such as viscosity within a range suitable for gravure printing.

For example, in Patent Document 1, a conductive paste used for forming the internal conductor film in a laminated ceramic electronic component including a plurality of ceramic layers and an internal conductor film extending along a specific interface between the ceramic layers by gravure printing. A solid component of 30 to 70% by weight containing a metal powder, an ethyl cellulose resin component having a ethoxy group content of 1 to 10% by weight of 49.6% or more, and a dispersant of 0.05 to 5% by weight. And the solvent component as the balance, 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).} Described is a conductive paste that is a thixotropy fluid that satisfies the condition that η _{0.02 is expressed by a specific formula.}

Further, in Patent Document 2, a conductive paste used for forming by gravure printing as in Patent Document 1, wherein 30 to 70% by weight of a solid component containing a metal powder and 1 to 10% by weight of a solid component are used. A thixotropy fluid containing a resin component, a dispersant of 0.05 to 5% by weight, and a solvent component as a balance, and having a viscosity of 1 Pa · s or more at a ^{shear rate of 0.1 (s -1).} Described are conductive pastes having 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 thixotropy fluids having a viscosity of 1 Pa · s or more at a ^{shear rate of 0.1 (s -1), and are stable at high speed in gravure printing.} It is said that continuous printability can be obtained and laminated ceramic electronic components such as multilayer ceramic capacitors can be manufactured with good production efficiency.

Further, Patent Document 3 describes conductivity for an internal electrode of a multilayer ceramic capacitor containing a conductive powder (A), an organic resin (B), an organic solvent (C), an additive (D), and a dielectric powder (E). In the sex paste, 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. Alternatively, it is composed of either 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, and the additive (D) is composed of a separation inhibitor and a dispersant, and the separation thereof. A conductive paste for gravure printing, which comprises a composition containing a polycarboxylic acid polymer or a salt of a polycarboxylic acid as an inhibitor, is described. According to Patent Document 3, this conductive paste has a viscosity suitable for gravure printing, the uniformity and stability of the paste are improved, and the drying property is good.

Japanese Unexamined Patent Publication No. 2003-187638 Japanese Unexamined Patent Publication No. 2003-242835 Japanese Unexamined Patent Publication No. 2012-174977

With the recent thinning of the internal electrode layer, the conductive powder also tends to have a smaller particle size. When the particle size of the conductive powder is small, the specific surface area of the particle surface is large, so that the surface activity of the conductive powder (metal powder) is high, and the dispersibility of the conductive paste may be lowered, which is higher. There is a demand for a conductive paste having dispersibility.

Further, when the conductive paste is printed by using the gravure printing method, a paste viscosity lower than that of the screen printing method is required, so that the conductive powder having a relatively large specific gravity precipitates and the dispersibility of the paste is lowered. Can be considered. In the conductive pastes described in Patent Documents 1 and 2, the dispersibility of the paste is improved by removing the lumps in the conductive paste using a filter, but the lumps are removed. Since the process of performing is required, the manufacturing process tends to be complicated.

In view of such a situation, an object of the present invention is to provide a conductive paste having a paste viscosity suitable for gravure printing and having excellent paste dispersibility and productivity.

In the first aspect of the present invention, the dispersant is a conductive paste containing a conductive powder, a ceramic powder, a dispersant, a binder resin and an organic solvent, and the dispersant is an acid-based dispersant having an average molecular weight of more than 500 and 2000 or less. The acid-based dispersant has one or more branched chains composed of hydrocarbon groups with respect to the main chain, the binder resin contains an acetal-based resin, and the organic solvent contains a glycol ether-based solvent. , A conductive paste characterized by the above is provided.

Further, the 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 a main chain. The acid-based dispersant is preferably contained in an amount of 0.4 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the conductive powder. Further, the conductive powder preferably contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu and alloys thereof. Further, the conductive powder preferably has an average particle size of 0.05 μm or more and 1.0 μm or less. Further, the ceramic powder preferably contains a perovskite type oxide. Further, the ceramic powder preferably has an average particle size of 0.01 μm or more and 0.5 μm or less. Further, the binder resin preferably contains a butyral resin. Further, the conductive paste is preferably used for internal electrodes of laminated ceramic parts. Further, it is preferable that the conductive paste 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 10000 ^{sec -1.}

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

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

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

1A and 1B are perspective views and cross-sectional views showing the multilayer ceramic capacitor according to the embodiment.

[Conductive paste]
The conductive paste of this embodiment contains a conductive powder, a dispersant, a binder resin and an organic solvent. Hereinafter, each component will be described in detail.

(Conductive powder)
The conductive powder is not particularly limited, and a metal powder can be used, and for example, one or more powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof can be used. Among these, from the viewpoint of conductivity, corrosion resistance and cost, it is preferable to use Ni or an alloy powder thereof (hereinafter, may be referred to as "Ni powder"). As the Ni alloy, for example, an alloy of Ni with at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt and Pd can be used. can. The content of Ni in the Ni alloy is, for example, 50% by mass or more, preferably 80% by mass or more. Further, the Ni powder may contain an element S of about several hundred ppm in order to suppress rapid gas generation due to partial thermal decomposition of the binder resin during the debinder treatment.

The average particle size of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. When the average particle size of the conductive powder is within the above range, it can be suitably used as a paste for an internal electrode of a thinned laminated ceramic capacitor (laminated ceramic component). 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 of a plurality of particles from an image observed with an SEM at a magnification of 10,000 times. It is an average value (SEM average particle diameter) to be obtained.

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 with respect to 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 conductive paste may include 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 the laminated ceramic capacitor to be applied. Examples of the ceramic powder include perovskite-type oxides containing Ba and Ti, and barium titanate (BaTIO ₃ ) is preferable.

As the ceramic powder, a ceramic powder containing barium titanate as a main component and an oxide as a sub component may be used. Examples of the oxide include oxides of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb and one or more rare earth elements. Examples of such a ceramic powder include _{a perovskite-type oxide ferroelectric ceramic powder in which the Ba atom or Ti atom of barium titanate (BaTIO 3} ) is replaced with another atom, for example, Sn, Pb, Zr or the like. Can be mentioned.

When used as the paste for the internal electrode, the ceramic powder may be a powder having the same composition as the dielectric ceramic powder constituting the green sheet of the multilayer ceramic capacitor (electronic component). As a result, crack generation due to a shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer in the sintering process is suppressed. In addition to the above, such ceramic powders include, for example, ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , R (rare earth element) ₂ O ₃ , TIO ₂ , Nd ₂ O _{3 and the} like. Oxides can be mentioned. As the ceramic powder, one type 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 or more and 0.5 μm or less, preferably 0.01 μm or more and 0.3 μm or less. When the average particle size of the ceramic powder is in the above range, it is possible to form a sufficiently thin and thin uniform internal electrode when used as a paste for an internal electrode. 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 of a plurality of particles from an image observed with an SEM at a magnification of 50,000 times. It is an average value (SEM average particle diameter) to be obtained.

The content of the ceramic powder is preferably 1 part by mass or more and 30 parts by mass or less, and more preferably 3 parts by mass or more and 30 parts by mass or less with respect to 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, and more preferably 3% by mass or more and 20% 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.

(Binder resin)
The binder resin includes an acetal resin. As the acetal resin, a butyral resin such as polyvinyl butyral is preferable. 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 the acetal resin, 30% by mass or more, or only the acetal resin with respect to the entire binder resin. Further, even if the content of the acetal-based resin is less than 40% by mass with respect to the entire binder resin, it is possible to have a low paste viscosity and sufficient adhesive strength.

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

Further, the binder resin may contain other resins below the acetal resin. The other resin is not particularly limited, and a known resin can be used. Examples of other resins include cellulose-based resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, and acrylic resins. Among them, cellulose-based resins are considered from the viewpoint of solubility in a solvent and combustion decomposability. Resins are preferred, ethyl celluloses are more preferred. The molecular weight of the binder resin is, for example, about 20000 to 20000.

The content of the binder resin is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 8 parts by mass or less with respect to 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, and 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)
The organic solvent contains a glycol ether solvent and may further contain an acetate solvent.

Examples of the glycol ether-based solvent 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 thereof include propylene glycol monoalkyl ethers such as monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether (PNB). Of these, propylene glycol monoalkyl ethers are preferable, and propylene glycol monobutyl ether (PNB) is more preferable. When the organic solvent contains a glycol ether solvent, it has excellent compatibility with the above-mentioned binder resin and excellent drying property.

The organic solvent may contain, for example, 25% by mass or more of the glycol ether solvent, 50% by mass or more, or only the glycol ether solvent with respect to the entire organic solvent. Further, the glycol ether solvent may be used alone or in combination of two or more.

Examples of the acetate solvent include dihydroterpinyl acetate, isobornyl acetate, isobornyl propinate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, and dipropylene glycol methyl ether. Examples thereof include glycol ether acetates such as acetate, 3-methoxy-3-methylbutyl acetate and 1-methoxypropyl-2-acetate.

When the organic solvent contains an acetate solvent, for example, at least one acetate type selected from dihydroterpinyl acetate, isobornyl acetate, isobornyl propinate, isobornyl butyrate and isobornyl isobutyrate. The solvent (A) may be contained. Of 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, and more preferably 20% by mass or more and 40% by mass or less with respect to the entire organic solvent. ..

When the organic solvent contains an acetate solvent, for example, the above acetate solvent (A) and at least one acetate solvent (B) selected from ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate are used. 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 the acetate solvent (A) and the acetate solvent (B), the organic solvent is preferably 50% by mass or more and 90% by mass or less of the acetate solvent (A) with respect to the entire acetate solvent. It is contained, more preferably 60% by mass or more and 80% by mass or less. In the case of the above mixed solution, the organic solvent contains the acetate solvent (B) in an amount of preferably 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass, based on 100% by mass of the total acetate solvent. % Or less.

Further, the organic solvent may contain an organic solvent other than the glycol ether solvent and the acetate solvent. The other organic solvent is not particularly limited, and a known organic solvent capable of dissolving the binder resin can be used. Examples of other organic solvents include acetate-based 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 tarpineol and dihydroterpineol, and tridecane. Examples thereof include aliphatic hydrocarbon solvents such as nonane and cyclohexane. Among them, an aliphatic hydrocarbon solvent is preferable, and among the aliphatic hydrocarbon solvents, the mineral spirit is more preferable. As the other organic solvent, one type may be used, or two or more types may be used.

The organic solvent can contain, for example, a glycol ether solvent as a main solvent and an aliphatic hydrocarbon solvent as a secondary solvent. In this case, the glycol ether-based 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 with respect to 100 parts by mass of the conductive powder, and is an aliphatic hydrocarbon solvent. Is preferably contained in an amount of 20 parts by mass or more and 80 parts by mass or less, and more preferably 20 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the conductive powder.

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 with respect to 100 parts by mass of the conductive powder. When the content of the organic solvent is in 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, and more preferably 25% by mass or more and 45% by mass or less with respect to the total amount of the conductive paste. When the content of the organic solvent is in the above range, the conductivity and dispersibility are excellent.

(Dispersant)
As a result of examining various dispersants for the dispersant used for the conductive paste, the present inventors have one or more, preferably a plurality of branched chains composed of hydrocarbon groups with respect to the main chain, and the average. By using a dispersant containing an acid-based dispersant having a molecular weight of more than 500 and 2000 or less, the conductive powder or ceramic powder, which is a powder material contained in the conductive paste, has excellent dispersibility and is dried after application. We have found that the surface of the electrode is excellent in smoothness. The details of the reason for this are unknown, but the dispersant has a branch consisting of hydrocarbon groups, which effectively forms steric hindrance, prevents agglomeration of the powder material, and has a molecular weight of an appropriate size. By having it, it is considered that the viscosity and dispersibility suitable for the conductive paste can be maintained. Hereinafter, the dispersant of the present invention will be described in more detail.

The acid-based dispersant used in the present embodiment preferably has a carboxyl group, and more preferably a hydrocarbon-based graft copolymer having a polycarboxylic acid as a main chain. Further, the polycarboxylic acid preferably has an ester structure. Further, the hydrocarbon group preferably has a chain structure.

The molecular weight of the acid-based dispersant is more than 500 and less than 2000. When the molecular weight is in the above range, the dispersibility of the conductive powder or the ceramic powder is excellent, and the density and smoothness of the surface of the dry electrode after coating are excellent.

As the acid-based dispersant, for example, a commercially available product that satisfies the above characteristics can be selected and used. Further, the acid-based dispersant may be produced so as to satisfy the above characteristics by using a conventionally known production method. The hydrocarbon group may be an alkyl group. Further, the alkyl group may be composed of only carbon and hydrogen, or a part of hydrogen constituting the alkyl group may be substituted with a substituent. Further, it is preferable that the main chain and the hydrocarbon group do not have a ring structure.

The acid-based dispersant is preferably contained in an amount of 0.01 part by mass or more and 5 parts by mass or less, more preferably 0.05 part by mass or more and 3 parts by mass or less, based on 100 parts by mass of the conductive powder. Is contained in an amount of 0.4 parts by mass or more and 3 parts by mass or less. When the content of the acid-based dispersant is within the above range, the dispersibility of the conductive powder or ceramic powder and the smoothness of the surface of the dry electrode 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 attack and poor peeling of the green sheet. Further, the conductive paste according to the present embodiment can have high dispersibility even if the total content of the acid-based dispersant is 2 parts by mass or less.

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

The conductive paste may contain a dispersant other than the above-mentioned acid-based dispersant as long as the effect of the present invention is not impaired. Dispersants other than the above may include, for example, acid-based dispersants containing higher fatty acids, polymer surfactants and the like, base-based dispersants, amphoteric surfactants, polymer-based dispersants and the like, and bases. It is more preferable to contain a system dispersant. Further, these dispersants may be used alone or in combination of two or more.

When a dispersant other than the above acid-based dispersant is contained, the total content (total content) of the dispersant, including the acid-based dispersant to be mainly added, is based on 100 parts by mass of the conductive powder. It may be 0.01 part by mass or more and 5 parts by mass or less, and preferably 0.01 part by mass or more and 3 parts by mass or less. Further, the conductive paste according to the present embodiment can have high dispersibility even when the total content (total content) of the dispersant is 2 parts by mass or less.

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

(Conductive paste)
The method for producing the conductive paste of the present embodiment is not particularly limited, and conventionally known methods can be used. The conductive paste can be produced, for example, by stirring and kneading each of the above components with a three-roll mill, a ball mill, a mixer or the like. At that time, if the dispersant is applied to the surface of the conductive powder in advance, the conductive powder is sufficiently loosened without agglomeration, and the dispersant spreads on the surface, so that a uniform conductive paste can be easily obtained. Further, after the binder resin is dissolved in a part of the organic solvent in advance to prepare an organic vehicle, the conductive powder, the ceramic powder, the dispersant, and the organic vehicle are added to the organic solvent for paste adjustment. , Stirring and kneading may be carried out to prepare a conductive paste.

The conductive paste has a viscosity of a shear rate of 100 sec ^-1 and is preferably 0.8 Pa · S or less. When the viscosity at a shear rate of 100 sec ^-1 is in 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 to be suitable for gravure printing. The lower limit of the viscosity at a shear rate of 100 sec ^-1 is not particularly limited, but is, for example, 0.2 Pa · S or more.

Further, the conductive paste has a viscosity of a shear rate of 10000 sec ^-1 and is preferably 0.18 Pa · S or less. When the viscosity at a shear rate of 10000 sec ^-1 is in the above range, it can be suitably used as a conductive paste for gravure printing. Even if it exceeds the above range, the viscosity may be too high to be suitable for gravure printing. The lower limit of the viscosity at a shear rate of 10000 sec ^-1 is not particularly limited, but is, for example, 0.05 Pa · S or more.

Further, the dry film density (DFD) of the dry film obtained by printing the conductive paste and then drying is preferably more than ^{5.0 g / cm 3,} and may exceed ^{5.2 g / cm 3.}

Further, the surface roughness Ra (arithmetic mean roughness) when a dry film having a size of 20 mm square and a thickness of 1 to 3 μm was produced by printing a conductive paste and drying it in the air at 120 ° C. for 1 hour was 0. It is preferably .2 μm or less, and may be 0.16 μm or less. The lower limit of the surface roughness Ra (arithmetic mean roughness) is preferably a flat surface and is not particularly limited, but a value exceeding 0 and a smaller value is preferable.

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

The multilayer ceramic capacitor preferably has the same composition as the dielectric ceramic powder contained in the dielectric green sheet and the ceramic powder contained in the conductive paste. In the laminated ceramic device manufactured by using the conductive paste of the present embodiment, sheet attack and peeling failure of the green sheet are suppressed even when the thickness of the dielectric green sheet is, for example, 3 μm or less.

[Electronic components]
Hereinafter, embodiments of the electronic components and the like of the present invention will be described with reference to the drawings. In the drawings, it may be represented schematically or the scale may be changed as appropriate. Further, the positions and directions of the members will be described as appropriate with reference to the XYZ Cartesian coordinate system shown in FIGS. 1A and 1B. In this XYZ Cartesian coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction (vertical 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 laminated ceramic capacitor 1 includes a laminated body 10 in which a dielectric layer 12 and an internal electrode layer 11 are alternately laminated, and an external electrode 20.

Hereinafter, a method for manufacturing a multilayer ceramic capacitor using the above conductive paste will be described. First, an internal electrode layer 11 made of a conductive paste is formed on a dielectric layer 12 made of a ceramic green sheet by a printing method, and a plurality of dielectric layers having the internal electrode layer on the upper surface are laminated by pressure bonding. After obtaining the laminated body 10, the laminated body 10 is fired and integrated to produce a laminated ceramic fired body (not shown) which is a ceramic capacitor main body. After that, the monolithic ceramic capacitor 1 is manufactured by forming a pair of external electrodes at both ends of the ceramic capacitor body. It will be described in more detail below.

First, a ceramic green sheet, which is an unfired ceramic sheet, is prepared. As this ceramic green sheet, for example, a paste for a dielectric layer obtained by adding an organic binder such as polyvinyl butyral and a solvent such as tarpineol to a predetermined ceramic raw material powder such as barium titanate is used as a PET film or the like. Examples thereof include those coated on a support film in the form of a sheet and dried to remove the solvent. The thickness of the dielectric layer made of the ceramic green sheet is not particularly limited, but is preferably 0.05 μm or more and 3 μm or less from the viewpoint of requesting miniaturization of the multilayer ceramic capacitor.

Next, on one side of this ceramic green sheet, the above-mentioned conductive paste is printed and applied by using a gravure printing method, and a plurality of sheets having an internal electrode layer 11 made of the conductive paste formed are prepared. The thickness of the internal electrode layer 11 made of the conductive paste is preferably 1 μm or less after drying from the viewpoint of requesting thinning of the internal electrode layer 11.

Next, the ceramic green sheet was peeled off from the support film, and the dielectric layer 12 made of the ceramic green sheet and the internal electrode layer 11 made of the conductive paste formed on one side thereof were laminated so as to be alternately arranged. After that, the laminate 10 is obtained by heating and pressurizing treatment. In addition, a protective ceramic green sheet to which the conductive paste is not applied may be further arranged on both sides of the laminate 10.

Next, after cutting the laminated body to a predetermined size to form a green chip, the green chip is subjected to a debinder treatment and fired in a reducing atmosphere to produce a laminated ceramic fired body. Incidentally, the atmosphere in the binder removal process is preferably in the air or N ₂ gas atmosphere. The temperature at which the debinder treatment is performed is, for example, 200 ° C. or higher and 400 ° C. or lower. Further, it is preferable that the holding time of the above temperature is 0.5 hours or more and 24 hours or less when the debinder treatment is performed. Further, the firing is performed in a reducing atmosphere in order to suppress the oxidation of the metal used for the internal electrode layer, and the temperature at which the laminated body is fired is, for example, 1000 ° C. or higher and 1350 ° C. or lower. The temperature holding time is, for example, 0.5 hours or more and 8 hours or less.

By firing the green chips, the organic binder in the 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 internal electrode layer 11 is removed, and nickel powder or an alloy powder containing nickel as a main component is sintered, melted, and integrated to form an internal electrode, and the dielectric layer 12 and the internal electrode are formed. A laminated ceramic fired body in which a plurality of layers 11 are alternately laminated is formed. From the viewpoint of incorporating oxygen into the dielectric layer to improve reliability and suppressing reoxidation of the internal electrodes, the laminated ceramic fired body after firing may be annealed.

Then, the laminated ceramic capacitor 1 is manufactured by providing a pair of external electrodes 20 with respect to the produced laminated ceramic fired body. 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. As the material of the external electrode 20, for example, copper, nickel, or an alloy thereof can be preferably used. As the electronic component, an electronic component other than the monolithic ceramic capacitor can also be used.

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

[Evaluation method]
(Viscosity of conductive paste)
The viscosity of the conductive paste after production was measured using a rheometer (manufactured by Anton Pearl Japan Co., Ltd .: rheometer MCR302). Viscosity, a cone angle of 1 °, by using a cone plate with a diameter of 25 mm, a shear rate (shear rate) 100 sec ^-1, and, using the value when measured under the conditions of 10000 sec ^-1.

(Dry film density)
The prepared conductive paste was placed on a PET film and stretched to a length of about 100 mm with an applicator having a width of 50 mm and a gap of 125 μm. The obtained PET film was dried at 120 ° C. for 40 minutes to form a dried body, and then four pieces of the dried body were cut into 2.54 cm (1 inch) squares, the PET film was peeled off, and each of the four pieces was peeled off. The thickness and weight of the 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 prepare a 20 mm square dry film having a thickness of 1 to 3 μm. The surface roughness Ra (arithmetic mean roughness) of the prepared dry film was measured based on the JIS B0601-2001 standard.

[Material used]
(Conductive powder)
As the conductive powder, Ni powder (SEM average particle size 0.3 μm) was used.

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

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

(Dispersant)
As the acid-based dispersant, an acid-based dispersant A having an average molecular weight of 1500, which is a hydrocarbon-based graft copolymer having a polycarboxylic acid as a main chain, was used. For comparison, a phosphoric acid-based dispersant used in a conventional conductive paste was used.

(Organic solvent)
As the organic solvent, propylene glycol monobutyl ether (PNB), mineral spirit (MA), and tarpineol (TPO) were used.

(Test 1)
[Example 1]
With respect to 100 parts by mass of Ni powder which is a conductive powder, 25 parts by mass of ceramic powder, 3.00 parts by mass of acid-based dispersant A as a dispersant, 2 parts by mass of PVB and 4 parts by mass of EC as a binder resin, and an organic solvent. A conductive paste was prepared by mixing 48 parts by mass of PNB (acetal solvent) and 21 parts by mass of MA. The viscosity of the prepared conductive paste, the density of the dry film of the paste, and the surface roughness were evaluated by the above method. Table 1 shows the content of the dispersant and the like of the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the density of the dried film, and the surface roughness.

[Example 2]
As the dispersant, a conductive paste was prepared and evaluated in the same manner as in Example 1 except that the content of the acid-based dispersant A was 1.74 parts by mass. Table 1 shows the content of the dispersant and the like of the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the density of the dried film, and the surface roughness.

[Example 3]
As the dispersant, a conductive paste was prepared and evaluated in the same manner as in Example 1 except that the content of the acid-based dispersant A was 1.24 parts by mass. Table 1 shows the content of the dispersant and the like of the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the density of the dried film, and the surface roughness.

[Example 4]
As the dispersant, a conductive paste was prepared and evaluated in the same manner as in Example 1 except that the content of the acid-based dispersant A was 0.74 parts by mass. Table 1 shows the content of the dispersant and the like of the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the density of the dried film, and the surface roughness.

[Example 5]
As the dispersant, a conductive paste was prepared and evaluated in the same manner as in Example 1 except that the content of the acid-based dispersant A was 0.42 parts by mass. Table 1 shows the content of the dispersant and the like of the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the density of the dried film, and the surface roughness.

[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 and the like of the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the density of the dried film, and the surface roughness.

[Comparative Example 2]
A conductive paste was prepared and evaluated in the same manner as in Example 4 except that only tarpineol (TPO) was used as the organic solvent. Table 1 shows the content of the dispersant and the like of the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the density of the dried film, and the surface roughness.
[Comparative Example 3]
A conductive paste was prepared and evaluated in the same manner as in Example 4 except that only EC was used as the binder resin. Table 1 shows the content of the dispersant and the like of the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the density of the dried film, and the surface roughness.
[Comparative Example 4]
A conductive paste was prepared and evaluated in the same manner as in Example 4 except that only EC was used as the binder resin and only tarpineol (TPO) was used as the organic solvent. Table 1 shows the content of the dispersant and the like of the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the density of the dried film, and the surface roughness.

(Evaluation results)
The conductive paste of the example has a lower viscosity than the conductive paste of Comparative Example 1 using a phosphoric acid-based dispersant and Comparative Examples 2 to 4 having different binder resins and organic solvents, and is suitable for gravure printing. It was confirmed that it had a high viscosity, a high dry film density, and a smooth dry film surface, and was excellent in dispersibility.

The technical scope of the present invention is not limited to the embodiments described in the above-described embodiments. One or more of the requirements described in the above embodiments and the like may be omitted. In addition, the requirements described in the above-described embodiments and the like can be combined as appropriate. In addition, to the extent permitted by law, the disclosure of all documents cited in the above-mentioned embodiments and the like shall be incorporated as part of the description in the main text.

The conductive paste of the present invention has a viscosity suitable for gravure printing, has a high dry film density after coating, is extremely excellent in dry film surface smoothness, and is excellent in dispersibility. Therefore, the conductive paste of the present invention can be suitably used as a raw material for an internal electrode of a multilayer ceramic capacitor, which is a chip component (electronic component) used in an electronic device such as a mobile phone or a digital device, which is becoming smaller and smaller. It can be preferably used as a conductive paste for gravure printing.

The technical scope of the present invention is not limited to the embodiments described in the above-described embodiments. One or more of the requirements described in the above embodiments and the like may be omitted. In addition, the requirements described in the above-described embodiments and the like can be combined as appropriate. In addition, to the extent permitted by law, the contents of Japanese Patent Application No. 2018-182502 and all documents cited in this specification shall be incorporated as part of the description of 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 (13)

A conductive paste containing a conductive powder, a ceramic powder, a dispersant, a binder resin and an organic solvent.
The dispersant contains an acid-based dispersant having an average molecular weight of more than 500 and 2000 or less.
The acid-based dispersant has one or more branched chains composed of hydrocarbon groups with respect to the main chain.
The binder resin contains an acetal resin and contains an acetal resin.
The organic solvent contains a glycol ether solvent.
A conductive paste characterized by that. The conductive paste according to claim 1, wherein the acid-based dispersant has a carboxyl group. The conductive paste according to claim 1 or 2, wherein the acid-based dispersant is a hydrocarbon-based graft copolymer having a polycarboxylic acid as a main chain. The conductivity according to any one of claims 1 to 3, wherein the acid-based dispersant is contained in an amount of 0.4 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the conductive powder. Sex paste. The invention according to any one of claims 1 to 4, wherein the conductive powder contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu and an alloy thereof. Conductive paste. The conductive paste according to any one of claims 1 to 5, 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 6, wherein the ceramic powder contains a perovskite-type oxide. The conductive paste according to any one of claims 1 to 7, 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 8, wherein the binder resin contains a butyral resin. Viscosity at shear rate 100 sec ^-1 is not higher than 0.8 Pa · S, any one of the preceding claims viscosity at a shear rate of 10000 sec ^-1 is equal to or less than 0.18Pa · S The conductive paste according to. The conductive paste according to any one of claims 1 to 10, wherein the conductive paste is used for an internal electrode of a laminated ceramic component. An electronic component formed by using the conductive paste according to any one of claims 1 to 10. It has at least a laminate in which a dielectric layer and internal electrodes are laminated,
The multilayer ceramic capacitor, wherein the internal electrode is formed by using the conductive paste according to claim 11.

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