WO2020137290A1

WO2020137290A1 - Conductive paste, electronic component, and laminated ceramic capacitor

Info

Publication number: WO2020137290A1
Application number: PCT/JP2019/045825
Authority: WO
Inventors: 剛川島; 祐伺舘; 勝彦高木; 純平山田; 武範久下
Original assignee: 住友金属鉱山株式会社
Priority date: 2018-12-25
Filing date: 2019-11-22
Publication date: 2020-07-02
Also published as: JP7498896B2; TW202034352A; CN113227246A; CN113227246B; KR20210110286A; JPWO2020137290A1

Abstract

Provided is a conductive paste or the like which has excellent dispersibility. This conductive paste comprises conductive powder, ceramic powder, a dispersant, a binder resin, and an organic solvent, wherein: the dispersant includes an acidic dispersant and a basic dispersant; the acidic dispersant has an average molecular weight of 500-2000 (exclusive of 500) and has at least one hydrocarbon group-containing branched chain with respect to a main chain; the binder resin includes an acetal-based resin; and the organic solvent includes a glycol ether-based solvent.

Description

Conductive paste, electronic parts, and multilayer ceramic capacitors

The present invention relates to a conductive paste, an electronic component, and a monolithic ceramic capacitor.

With the miniaturization and higher performance of electronic devices such as mobile phones and digital devices, there is a demand for miniaturization and higher capacity of electronic components including multilayer ceramic capacitors. A monolithic ceramic capacitor has a structure in which a plurality of dielectric layers and a plurality of internal electrode layers are alternately laminated. By thinning these dielectric layers and internal electrode layers, downsizing and high capacity can be achieved. Can be planned.

The monolithic ceramic capacitor is manufactured, for example, as follows. First, a conductive paste for internal electrodes is printed (applied) 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 dried. To form a dry film. The dry film and the dielectric green sheets are laminated so as to be alternately superposed, and heat-pressed to be integrated to form a pressure-bonded body. This pressure-bonded body is cut, and after the organic binder treatment is performed in an oxidizing atmosphere or an inert atmosphere, firing is performed to obtain a fired chip (laminated body). Next, the external electrode paste is applied to both ends of the fired chip (multilayer body), and after firing, nickel plating or the like is applied to the surfaces of the external electrodes to obtain a multilayer ceramic capacitor.

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

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

For example, in Patent Document 1, a conductive paste used for forming the internal conductor film in a multilayer 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 metal powder, an ethylcellulose resin component of 1 to 10% by weight having an ethoxy group content of 49.6% or more, and a dispersant of 0.05 to 5% by weight. And the balance of the solvent component, 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, which is a thixotropic fluid, in which η _0.02 satisfies the condition represented by a specific formula is described.

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

According to Patent Documents 1 and 2 described above, these conductive pastes are thixotropic 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 a monolithic ceramic electronic component such as a monolithic ceramic capacitor can be manufactured with good production efficiency.

Further, in Patent Document 3, a conductive powder (A), an organic resin (B), an organic solvent (C), an additive (D), and a conductive material for an internal electrode of a multilayer ceramic capacitor containing an additive (D) and a dielectric powder (E). Which is an organic paste (B), the degree of polymerization is 10,000 to 50,000 or less polyvinyl butyral and the weight average molecular weight is 10,000 to 100,000 ethyl cellulose, and the organic solvent (C) is propylene glycol monobutyl ether. Alternatively, it comprises 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) comprises a separation inhibitor and a dispersant, and the separation A conductive paste for gravure printing, which comprises a composition containing a polycarboxylic acid polymer or a salt of polycarboxylic acid as an inhibitor, is described. According to Patent Document 3, this conductive paste has a viscosity suitable for gravure printing, improves uniformity and stability of the paste, and has good dryness.

JP-A-2003-187638 JP, 2003-242835, A JP 2012-174797 A

With the thinning of internal electrode layers in recent years, conductive powder 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 becomes large, so the surface activity of the conductive powder (metal powder) becomes high, and the dispersibility of the conductive paste may decrease, 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 settles and the dispersibility of the paste is reduced. It is possible. In the conductive pastes described in Patent Documents 1 and 2 above, 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 manufacturing process is required, the manufacturing process tends to be complicated.

In view of such circumstances, 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.

A first aspect of the present invention is a conductive paste containing conductive powder, ceramic powder, a dispersant, a binder resin and an organic solvent, wherein the dispersant contains an acid-based dispersant and a base-based dispersant. The 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, the binder resin contains an acetal resin, and the organic solvent is A conductive paste containing a glycol ether solvent 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 contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less based on 100 parts by mass of the conductive powder, and the base-based dispersant is 0. It is preferably contained in an amount of 02 parts by mass or more and 2 parts by mass or less. 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 diameter of 0.01 μm or more and 0.5 μm or less. Further, the binder resin preferably contains a butyral resin. Further, it is preferable that the conductive paste is for an internal electrode of a laminated ceramic component. 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 10,000 sec ⁻¹ .

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

According to a 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 has excellent paste dispersibility and productivity. In addition, the electrode pattern of an electronic component such as a laminated ceramic capacitor formed by using the conductive paste of the present invention has excellent printability of the conductive paste even when forming a thinned electrode, and has a uniform thickness.

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

[Conductive paste]
The conductive paste of this embodiment contains conductive powder, ceramic 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 metal powder can be used, and for example, one or more kinds of powder 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 its alloy powder (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 may be used. it can. The Ni content in the Ni alloy is, for example, 50 mass% or more, preferably 80 mass% or more. In addition, the Ni powder may contain about several hundred ppm of the element S in order to suppress rapid gas generation due to partial thermal decomposition of the binder resin during the debinding process.

The average particle size of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.5 μm or less. When the average particle size of the conductive powder is within the above range, it can be suitably used as a paste for internal electrodes of a thinned multilayer ceramic capacitor (multilayer ceramic component). For example, the smoothness of the dry film and the dry film density are improves. The average particle size is a value obtained by 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 a SEM at a magnification of 10,000 times. It is the average value of the number.

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 in 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 laminated ceramic capacitor, a known ceramic powder is appropriately selected according to the type of the laminated ceramic capacitor to be applied. Examples of the ceramic powder include a perovskite type oxide containing Ba and Ti, and preferably barium titanate (BaTiO ₃ ).

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

When used as a conductive paste for internal electrodes, the ceramic powder may have the same composition as the dielectric ceramic powder forming the green sheet of the laminated ceramic capacitor (electronic component). This suppresses cracking due to shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer in the sintering process. Examples of such a ceramic powder include ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , and R (rare earth element) ₂ O _{3 in} addition to the above-described perovskite-type oxide containing Ba and Ti. , TiO ₂ , Nd ₂ O ₃ and other oxides. The ceramic powder may be used alone or in combination of two or more.

The average particle size of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, and preferably 0.01 μm or more and 0.3 μm or less. When the average particle diameter of the ceramic powder is within the above range, a sufficiently thin and thin uniform internal electrode can be formed when used as the internal electrode paste. The average particle size is a value obtained by 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. It is the average value of the number.

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, 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 in the above range, the conductivity and dispersibility are excellent.

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

The content of the acetal 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.

Also, the binder resin may include other resins below the acetal resin. The other resin is not particularly limited, and a known resin can be used. Examples of the other resin include, for example, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, cellulose resins such as nitrocellulose, acrylic resins, and the like. Among them, from the viewpoint of solubility in solvents, combustion decomposability, etc., ethyl cellulose is used. preferable. 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 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, 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 includes a glycol ether solvent. ..

Examples of the glycol ether solvent include (di)ethylene glycol ethers such as diethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monohexyl ether, 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). Among them, propylene glycol monoalkyl ethers are preferable, and propylene glycol monobutyl ether (PNB) is more preferable. When the organic solvent contains a glycol ether-based solvent, it has excellent compatibility with the above-mentioned binder resin and excellent drying property.

The organic solvent may include, for example, a glycol ether solvent in an amount of 25% by mass or more, or 50% by mass or more, or may be composed of only the glycol ether solvent, based on the entire organic solvent. The glycol ether solvent may be used alone or in combination of two or more.

The organic solvent may further include an acetate solvent. Examples of the acetate solvent include dihydroterpinyl acetate, isobornyl acetate, isobornyl propionate, 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 includes an acetate solvent, for example, at least one acetate solvent selected from dihydroterpinyl acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate and isobornyl isobutyrate. The solvent (A) may be included. Among these, isobornyl acetate is more preferable. The acetate solvent is contained in the organic solvent 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. ..

When the organic solvent contains an acetate solvent, for example, the above-mentioned acetate solvent (A) and at least one acetate solvent (B) selected from ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate. May be included. 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 liquid containing the acetate solvent (A) and the acetate solvent (B), the organic solvent preferably contains the acetate solvent (A) in an amount of 50% by mass or more and 90% by mass or less based on the whole organic solvent. However, 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) is contained in an amount of 10% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 40% by mass or less, based on 100% by mass of the whole acetate solvent.

Further, the organic solvent may include other 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. As other organic solvents, for example, ethyl acetate, propyl acetate, isobutyl acetate, acetic ester solvents such as butyl acetate, methyl ethyl ketone, ketone solvents such as methyl isobutyl ketone, terpineol, terpene solvents such as dihydroterpineol, tridecane, Examples include aliphatic hydrocarbon solvents such as nonane and cyclohexane. Among them, the aliphatic hydrocarbon solvent is preferable, and mineral spirit is more preferable among the aliphatic hydrocarbon solvents. In addition, 1 type may be used for another organic solvent and 2 or more types may be used for it.

The organic solvent may include, for example, a glycol ether solvent as the main solvent and an aliphatic hydrocarbon solvent as the auxiliary solvent. 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, and 100 parts by mass of the conductive powder. Is preferably 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 with respect to 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 parts by mass 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 with respect to 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, and more preferably 25% by mass or more and 45% by mass or less, based on the total amount of the conductive paste. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

(Dispersant)
As a result of examining various dispersants for the dispersant used in the conductive paste, the present inventors have one or more, preferably a plurality of branched chains composed of a hydrocarbon group with respect to the main chain, and have an average molecular weight. Is more than 500 and 2000 or less, and by using a dispersant containing a base dispersant, excellent dispersibility of conductive powder or ceramic powder, which is a powder material contained in the conductive paste, Moreover, they have found that the surface of the dried film is excellent in smoothness after the conductive paste is applied and dried.

Although the details of the reason why this effect is exhibited are not clear, since the acid-based dispersant has a branch consisting of a hydrocarbon group, it effectively forms a steric hindrance and prevents aggregation of the powder material. It is considered that the dispersant can be more effectively and uniformly dispersed by containing the base dispersant having good compatibility with the acid dispersant. Further, it is considered that by setting the molecular weight of the acid-based dispersant to a specific value, the conductive paste can be maintained at a suitable viscosity depending on the application. The present invention is not bound by the above theory (reason). Hereinafter, the dispersant according to this embodiment will be described in more detail.

The acid-based dispersant has at least one branched chain composed of a hydrocarbon group with respect to the main chain, and preferably has a plurality of branched chains. The acid dispersant preferably has a carboxyl group, and more preferably a hydrocarbon 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. Further, 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 replaced with a substituent.

The molecular weight of the acid dispersant is more than 500 and 2000 or less, and may be 1000 or more and 2000 or less. When the molecular weight is within the above range, the dispersibility of the conductive powder and the ceramic powder is excellent, and the density and smoothness of the dried electrode surface after coating are excellent. In the present 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 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 manufactured so as to satisfy the above properties by using a conventionally known manufacturing method.

The acid dispersant is preferably contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less based on 100 parts by mass of the conductive powder. When the content of the acid-based dispersant is in the above range, the dispersibility of the conductive powder or the ceramic powder and the smoothness of the dried electrode surface after coating are excellent, and the viscosity of the conductive paste is adjusted to an appropriate range. It is also possible to suppress sheet attack and defective peeling of the green sheet. Further, the conductive paste according to the present embodiment can have high dispersibility even when the content of the acid-based dispersant is 1 part by mass or less.

Also, 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 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 dispersant is not particularly limited, but is, for example, 0.01% by mass or more, preferably 0.05% by mass or more, and may be 0.5% 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 to an appropriate range, and the sheet attack and the peeling defect of the green sheet can be suppressed.

The base dispersant is not particularly limited in its structure. Can be mentioned. The base dispersant can further improve the effect of the above acid dispersant and further improve the dispersibility when the conductive paste is formed.

The base dispersant is preferably contained in an amount of 0.02 parts by mass or more and 2 parts by mass or less based on 100 parts by mass of the conductive powder. When the base dispersant is contained in the above range in combination with the acid dispersant of the present invention, the dispersibility of the conductive powder or the ceramic powder in the conductive paste is excellent, and the smoothness of the dried electrode surface after coating is excellent. Moreover, the viscosity of the conductive paste can be adjusted to an appropriate range, and the sheet attack and the peeling defect of the green sheet can be suppressed. The conductive paste according to the present embodiment may have a content of the base dispersant of 1 part by mass or less, 0.1 part by mass or less, and 0.05 part by mass or less. May be.

The base dispersant is, for example, about 1 part by mass or more and 500 parts by mass or less, preferably 10 parts by mass or more and 300 parts by mass or less, more preferably 50 parts by mass or more and 200 parts by mass with respect to 100 parts by mass of the acid dispersant. Parts or less, more preferably 50 parts by weight or more and 150 parts by weight or less. When the basic dispersion is contained in the above range, the conductive paste is more excellent in viscosity stability and the dry film density tends to be higher.

The base dispersant is contained, for example, in an amount of 0% by mass or more and 2.5% by mass or less, preferably 0% by mass or more and 1.0% by mass or less, and more preferably 0.1% by mass with respect to the entire conductive paste. The above content is 1.0 mass% or less, more preferably 0.1 mass% or more and 0.8 mass% or less. When the basic dispersion is contained in the above range, the paste is more excellent in viscosity stability over time. The amount of the base dispersant may be 0.5% by mass or less, may be less than 0.1% by mass, or may be 0.05% by mass or less with respect to the entire conductive paste. Good.

The conductive paste may contain, as a dispersant, only the acid-based dispersant and the base-based dispersant, or may contain a dispersant other than the above-mentioned dispersant within a range that does not impair the effects of the present invention. Good. As the dispersant other than the above, for example, an acid-based dispersant containing a higher fatty acid, a polymer surfactant or the like, an amphoteric surfactant, and a polymer-based dispersant may be included. These dispersants may be used alone or in combination of two or more.

In addition, the total content (total content) of the dispersants combined with the above acid-based dispersant is 0.01 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the conductive powder. It is preferably 0.23 parts by mass or more and 3 parts by mass or less. Further, the conductive paste according to the present embodiment may have a total dispersant content (total content) of 2 parts by mass or less, or 1 part by mass or less. Even if the content of the entire dispersant is in the above range, high dispersibility can be obtained.

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

(Conductive paste)
The method for producing the conductive paste of this embodiment is not particularly limited, and a conventionally known method can be used. The conductive paste can be produced, for example, by stirring and kneading 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 is spread over the surface, so that a uniform conductive paste is easily obtained. Further, in advance, after dissolving the binder resin in a part of the organic solvent to prepare an organic vehicle, after adding the conductive powder, the ceramic powder, the dispersant, and the organic vehicle to the organic solvent for paste preparation, Alternatively, the conductive paste may be prepared by stirring and kneading.

The viscosity of the conductive paste at a shear rate of 100 sec ⁻¹ is preferably 0.8 Pa·S or less, 0.5 Pa·S or less, or 0.4 Pa·S or less, 0 It may be less than or equal to 3 Pa·S. 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 of the conductive paste of the present embodiment at a shear rate of 100 sec ⁻¹ is not particularly limited, but is, for example, 0.1 Pa·S or more.

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.s or less. It may be less than a. When the viscosity at a shear rate of 10,000 sec ⁻¹ is in the above range, it can be suitably used as a conductive paste for gravure printing. If the amount 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 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 dry film obtained by printing the conductive paste and then drying is preferably more than 5.0 g/cm ^{3, and} may be more than 5.2 g/cm ³ . It may be 5.3 g/cm ³ or more. The upper limit of the dry film density is not particularly limited, and does not exceed the true density of metallic nickel of 9.8 g/cm ^3, and may be 6.5 g/cm ³ or less, for example.

The arithmetic mean roughness Sa when a dry film having a 20 mm square and a film thickness of 1 to 3 μm is produced by printing a conductive paste and drying it at 120° C. for 1 hour in the air is 0.25 μm or less. The thickness is preferably 0.2 μm or less, more preferably 0.16 μm or less. On the other hand, the lower limit of the arithmetic average roughness Sa is not particularly limited, and it is preferable that the surface is flat, and a value exceeding 0 and a smaller value are more preferable. The arithmetic mean roughness Sa is measured based on the standard of ISO 25178.

The conductive paste can be suitably used for electronic parts such as laminated ceramic capacitors. The monolithic 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 laminated ceramic device manufactured using the conductive paste of the present embodiment, even if the thickness of the dielectric green sheet is, for example, 3 μm or less, sheet attack and defective peeling of the green sheet are suppressed.

[Electronic parts]
Hereinafter, embodiments of an electronic component or the like of the present invention will be described with reference to the drawings. In the drawings, they may be represented schematically or with a reduced scale as appropriate. Further, the positions and directions of the members will be described with reference to the XYZ orthogonal coordinate system shown in FIG. In this XYZ orthogonal coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is the vertical direction (vertical direction).

1A and 1B are diagrams showing a monolithic ceramic capacitor 1 which is an example of an electronic component according to an embodiment. The monolithic ceramic capacitor 1 includes a laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately laminated, and external electrodes 20.

Hereinafter, a method for manufacturing a laminated ceramic capacitor using the conductive paste will be described. First, a conductive paste is printed on a dielectric green sheet, dried to form a dry film, and a plurality of dielectric green sheets having the dry film on the upper surface are laminated by pressure bonding and then fired. By being integrated, a laminated ceramic fired body (ceramic laminated body 10) which becomes a ceramic capacitor body is produced. Then, the multilayer ceramic capacitor 1 is manufactured by forming a pair of external electrodes 20 on both ends of the multilayer body 10. The details will be described below.

First, prepare a dielectric green sheet (ceramic green sheet) that is an unfired ceramic sheet. As the dielectric green sheet, for example, a dielectric layer paste obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a raw material powder of a predetermined ceramic such as barium titanate, a PET film or the like. And the like, in which the solvent is removed by coating the support film in a sheet form and drying. The thickness of the dielectric layer formed of the dielectric green sheet is not particularly limited, but is preferably 0.05 μm or more and 3 μm or less from the viewpoint of demand for miniaturization of the monolithic ceramic capacitor 1.

Next, prepare a plurality of sheets on which one side of this dielectric green sheet is printed and coated with the above-mentioned conductive paste using a gravure printing method and dried to form a dry film. In addition, the thickness of the conductive paste (dry film) after printing is preferably 1 μm or less after drying from the viewpoint of a request for thinning the internal electrode layers 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 surface of the dielectric green sheet are laminated so as to be alternately arranged, and then heated and pressed. A laminated body (pressure bonded body) is obtained by the treatment. It should be noted that a configuration may be adopted in which protective dielectric green sheets not coated with a conductive paste are further arranged on both surfaces of the laminated body.

Next, the laminated body is cut into a predetermined size to form a green chip, the green chip is subjected to a binder removal treatment, and is fired in a reducing atmosphere to manufacture a laminated ceramic fired body (laminated body 10). To do. The atmosphere for the binder removal processing is preferably the atmosphere or N ₂ gas atmosphere. The temperature at which the binder removal treatment is performed is, for example, 200° C. or higher and 400° C. or lower. Further, it is preferable that the holding time at the above-mentioned temperature at the time of performing the binder removal treatment is 0.5 hours or more and 24 hours or less. Further, the firing is performed in a reducing atmosphere in order to suppress the oxidation of the metal used for the internal electrode layer 11, and the temperature for firing the laminate 10 is, for example, 1000° C. or higher and 1350° C. or lower, The holding time of the temperature when 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 nickel powder or an alloy powder containing nickel as a main component 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. From the viewpoint of taking oxygen into the dielectric layer 12 to improve reliability and suppressing reoxidation of the internal electrode layers 11, the laminated ceramic fired body (laminated body 10) after firing is annealed. You may give a process.

Then, the monolithic ceramic capacitor 1 is manufactured by providing a pair of external electrodes 20 on the produced monolithic ceramic fired body (multilayer body 10 ). For example, the external electrode 20 includes an external electrode layer 21 and a plated layer 22. The outer electrode layer 21 is electrically connected to the inner electrode layer 11. In addition, as a material of the external electrode 20, for example, copper, nickel, or an alloy thereof can be preferably used. Electronic components other than the monolithic ceramic capacitor can be used as the electronic component.

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

[Evaluation method]
(Viscosity of conductive paste)
The viscosity after preparation of the conductive paste, by using a rheometer, shear rate ^{100 sec} -1, measured under the conditions of 10000 sec ^-1.

(Dry film density)
The produced conductive paste was placed on a PET film and extended 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 dry film, and then the dry film was cut into four 2.54 cm (1 inch) squares, and the PET film was peeled off to obtain 4 films each. The thickness and weight of each dry film were measured to calculate the dry film density (average value).

(Surface roughness)
The prepared conductive paste was printed on a 2.54 cm (1 inch) square heat-resistant tempered glass and dried in the atmosphere 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 Sa (arithmetic mean roughness) of the produced dry film was measured using a device that measures based on the standard of ISO 25178.

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

(Dispersant)
(1) As the acid-based dispersant (A), a hydrocarbon-based graft copolymer having a polycarboxylic acid as a main chain (having a branched chain composed of hydrocarbon) and an average molecular weight of 1500 is used. I was there.
(2) Rosin amine (B), polyoxyethylene lauryl amine (C) and oleyl amine (D) were used as the base dispersant.
(3) For comparison, a phosphoric acid-based dispersant (E) used in a conventional conductive paste (molecular weight: 1400, without hydrocarbon branched chain) was used.

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

[Example 1]
25 parts by mass of ceramic powder, 0.2 parts by mass of acid-based dispersant (A) as an acid-based dispersant, and a base-based dispersant as a base-based dispersant (100 parts by mass of Ni powder as a conductive powder). B) 1.0 part by mass, PVB 2 parts by mass and EC 4 parts by mass as the binder resin, and PNB 41 parts by mass and MA 27 parts by mass as the organic solvent were mixed to prepare a conductive paste. The viscosity of the produced conductive paste, the dry film density of the paste, and the surface roughness were evaluated by the above methods. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness Sa.
[Example 2]
A conductive paste was prepared and evaluated in the same manner as in Example 1 except that the content of the acid dispersant (A) was 0.74 parts by mass. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.
[Example 3]
A conductive paste was prepared and evaluated in the same manner as in Example 1 except that the content of the acid dispersant (A) was 2.0 parts by mass. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.
[Example 4]
A conductive paste was prepared and evaluated in the same manner as in Example 2 except that the content of the base dispersant (B) was 0.02 part by mass. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.
[Example 5]
A conductive paste was prepared and evaluated in the same manner as in Example 2 except that the content of the base dispersant (B) was 2.0 parts by mass. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.
[Example 6]
A conductive paste was prepared in the same manner as in Example 1 except that the content of the acid dispersant (A) was 0.6 parts by mass and the content of the base dispersant (B) was 1.2 parts by mass. And evaluated. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.

[Example 7]
A conductive paste was prepared and evaluated in the same manner as in Example 2 except that the base dispersant (C) was used as the base dispersant. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.

[Example 8]
A conductive paste was prepared and evaluated in the same manner as in Example 2 except that the base dispersant (D) was used as the base dispersant. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.

[Comparative Example 1]
A conductive paste was prepared and evaluated in the same manner as in Example 1 except that only 0.8 part by mass of the phosphoric acid-based dispersant (E) was used as the dispersant. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.

[Comparative example 2]
A conductive paste was prepared and evaluated in the same manner as in Example 1 except that 0.8 part by mass of the phosphoric acid dispersant (E) was used as the acid dispersant. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.
[Comparative Example 3]
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 auxiliary solvent was used. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.
[Comparative Example 4]
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 and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.

[Reference Example 1]
A conductive paste was prepared and evaluated in the same manner as in Example 2 except that the base dispersant (B) was not used as the dispersant. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.
[Reference Example 2]
As the dispersant, the conductive paste was prepared in the same manner as in Example 2 except that the acid dispersant (A) was not used and the content of the base dispersant (B) was 0.8 parts by mass. evaluated. Table 1 shows the content of the dispersant and the like in the conductive paste, and Table 2 shows the evaluation results of the viscosity of the conductive paste, the dry film density, and the surface roughness.

(Evaluation results)
The conductive paste of the example has a viscosity of 0.21 to 0.31 Pa·s at a shear rate of 100 sec ⁻¹ and a viscosity of 0.10 to 0.14 Pa·s at a shear rate of 10,000 sec ⁻¹ , It showed a stable low value at any shear rate, and was shown to have a viscosity suitable for gravure printing. In addition, the conductive pastes of Examples showed high dry film densities of 5.26 to 5.36 g/cm ³ , and surface roughness Sa of the dry films was 0.12 to 0.23 μm. It was confirmed that the dispersibility was excellent.

When the conductive pastes of Examples 1 to 3 were compared, the content of the acid-based dispersant (A) was 0.2 parts by mass (Example 1) or 0.74 parts by mass (Example 2). Even with a conductive paste, a high dry film density comparable to that of the conductive paste having an acid-based dispersant (A) content of 2.0 parts by mass (Example 3), and a relatively smooth dry film surface. It turns out that is obtained. In addition, from Examples 2, 4, and 5, it can be seen that when the content of the base dispersant is increased, the dry film density and the surface roughness of the obtained conductive paste tend to be improved. Further, comparing the conductive pastes of Examples 1 and 4 and Example 6 and the like, there is a large difference in the compounding ratio of the acid dispersant (A) and the base dispersant (B), and the compounding ratio is closer. The dry film density tends to improve. Further, it is clear from the comparison of the conductive pastes of Examples 2, 7, and 8 that good dry film density and surface roughness can be obtained even if the type of the base dispersant is changed.

On the other hand, the conductive paste of Comparative Example 1, which does not contain the acid dispersant according to the present embodiment and uses only the phosphoric acid dispersant, is the conductive paste of the example when manufactured under the same conditions. The viscosity was higher than the above, and the dry film density could not be increased sufficiently.

In addition, the conductive paste of Comparative Example 2 in which the basic dispersant (B) was further added to the same phosphoric acid-based dispersant as in Comparative Example 1 also improved the respective properties to some extent, but was a dry film similar to that of Example. No density was obtained. In addition, the conductive paste of Comparative Example 3 containing TPO as a main solvent, which is generally used in many cases, had an extremely high viscosity, and did not have a viscosity suitable for a gravure paste. In addition, the conductive paste of Comparative Example 2 also had a higher surface roughness than the conductive paste of Example. In addition, the conductive paste of Comparative Example 4 in which the resin did not contain an acetal resin had a high viscosity and could not sufficiently increase the dry film density.

Further, the conductive paste of Reference Example 1 containing the acid dispersant (A) alone as the dispersant had a higher dry film density than Comparative Example 1 using the phosphoric acid dispersant (E), and It was also shown that the viscosity of the conductive paste also decreased. The conductive paste of Reference Example 2 containing the base dispersant alone (B) had a slightly higher dry film density than Comparative Example 1 using the phosphoric acid dispersant (E), but the conductive paste Had a high viscosity.

From the above, the conductive pastes of Examples of the present invention containing both the acid-based dispersant (A) and the base-based dispersant (B) were compared with the conductive pastes of Comparative Examples and Reference Examples. In this case, it is apparent that the dry film density is higher and the dispersibility of the conductive paste is further improved. Further, the viscosity of the conductive paste at a shear rate of 10000 sec ⁻¹ is lower than that of the conductive paste of the comparative example and the conductive paste of the reference example, which contains both dispersants. It turns out that it is more suitable for gravure printing.

Note that the technical scope of the present invention is not limited to the modes described in the above embodiments and the like. 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 appropriately combined. In addition, as long as it is permitted by law, the disclosures of all the documents cited in the above-mentioned embodiments are incorporated into the description of the text.

The conductive paste of the present invention has a viscosity suitable for gravure printing, a high dry film density after coating, a very smooth dry film surface, and excellent dispersibility. Therefore, the conductive paste of the present invention can be suitably used as a raw material for the internal electrodes of a monolithic ceramic capacitor, which is a chip component of electronic devices such as mobile phones and digital devices, which are becoming smaller, and particularly for gravure printing. Can be suitably used as the conductive paste.

Note that the technical scope of the present invention is not limited to the modes described in the above embodiments and the like. 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 appropriately combined. In addition, the contents of Japanese Patent Application No. 2018-241706, which is a Japanese patent application, and all the documents cited in this specification are incorporated by reference as a part of the description of the text, as long as it is permitted by law.

1 Multilayer Ceramic Capacitor 10 Ceramic Multilayer 11 Internal Electrode Layer 12 Dielectric Layer 20 External Electrode 21 External Electrode Layer 22 Plating Layer

Claims

A conductive paste containing a conductive powder, a ceramic powder, a dispersant, a binder resin and an organic solvent,
The dispersant includes an acid-based dispersant and a base-based dispersant,
The acid-based dispersant has an average molecular weight of more than 500 and 2,000 or less, and has at least one branched chain composed of a hydrocarbon group with respect to the main chain,
The binder resin contains an acetal resin,
The organic solvent includes a glycol ether solvent,
Conductive paste.
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 dispersant is a hydrocarbon graft copolymer having a polycarboxylic acid as a main chain.
The 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 base-based dispersant is 0 with respect to 100 parts by mass of the conductive powder. The conductive paste according to any one of claims 1 to 3, which is contained in an amount of 0.02 parts by mass or more and 2 parts by mass or less.
The conductive paste 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 alloys thereof.
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, the viscosity at shear rate 10000 sec -1 is less than 0.18Pa · S, conducting according to any one of claims 1-9 Sex paste.
The conductive paste according to any one of claims 1 to 10, which is 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.
At least a laminated body in which a dielectric layer and an internal electrode are laminated,
The multilayer ceramic capacitor, wherein the internal electrodes are formed by using the conductive paste according to claim 11.