TW202034352A - Conductive paste, electronic component, and laminated ceramic capacitor - Google Patents

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, electronic parts, and multilayer ceramic capacitors.

With the miniaturization and higher performance of electronic devices such as mobile phones and digital devices, miniaturization and higher capacity are also desired for electronic components including multilayer ceramic capacitors. The multilayer ceramic capacitor has a structure in which a plurality of dielectric layers and a plurality of internal electrode layers are alternately laminated. By thinning the above-mentioned dielectric layers and internal electrode layers, miniaturization and high capacity can be achieved.

For example, a multilayer ceramic capacitor can be manufactured as follows. First, on the surface of a dielectric green sheet containing dielectric powder such as barium titanate (BaTiO ₃ ) and a binder resin, a conductive paste for internal electrodes is printed (coated) with a predetermined electrode pattern, and dried to form a dry membrane. The dry film and the dielectric green sheet are laminated alternately, and they are heated and pressure-bonded to integrate them to form a pressure-bonded body. The pressure-bonded body is cut, the organic binder is removed in an oxidizing gas atmosphere or an inert gas atmosphere, and then fired to obtain a fired wafer (laminated body). Next, the external electrode slurry is applied to both ends of the fired wafer (layered body), and after firing, nickel plating or the like is applied to the surface of the external electrode to obtain a multilayer ceramic capacitor.

As a printing method used when printing a conductive paste on a dielectric green sheet, screen printing is generally used in the past. However, from the requirements of miniaturization, thinning of electronic equipment, and improvement of productivity, higher production is required. It can print finer electrode patterns.

As one of the printing methods of conductive paste, a gravure printing method is proposed as a continuous printing method in which a conductive paste is filled in a concave portion provided on a plate making and the plate is pressed against the printed surface to transfer the conductive paste from the plate. Printing method. The gravure printing method has fast printing speed and excellent productivity. In the case of using the gravure printing method, it is necessary to appropriately select the binder resin, dispersant, solvent, etc. in the conductive paste, and adjust the characteristics such as viscosity to a range suitable for gravure printing.

For example, Patent Document 1 describes a conductive paste, which is a conductive paste for forming an internal conductive film by gravure printing. The internal conductive film is provided with a plurality of ceramic layers and a gap between the ceramic layers. The internal conductor film in the multilayer ceramic electronic component of the internal conductor film extended by the specific interface, the conductive paste contains 30 to 70% by weight of solid content containing metal powder, and 1 to 10% by weight of ethoxy group content Ethyl cellulose resin component of 49.6% or more, dispersant of 0.05 to 5% by weight, and solvent component as the balance. The viscosity η _0.1 at a shear rate of 0.1 (s ^-1 ) is 1 Pa. A thixotropic fluid whose viscosity η _0.02 at a shear rate of 0.02 (s ^-1 ) or more and a shear rate satisfying the conditions expressed by a specific formula.

In addition, Patent Document 2 describes a conductive paste, which is also a conductive paste for forming an internal conductor film by gravure printing similarly to the above-mentioned Patent Document 1. It contains 30 to 70% by weight of metal-containing The solid content of the powder, the resin content of 1-10% by weight, the dispersant of 0.05-5% by weight, and the remaining solvent component, and the viscosity when the shear rate is 0.1 (s ^-1 ) is 1 Pa. For thixotropic fluids above s, when the viscosity at a shear rate of 0.1 (s ^-1 ) is used as a reference, the viscosity change rate at a shear rate of 10 (s ^-1 ) is 50% or more.

According to Patent Documents 1 and 2, the conductive paste has a viscosity of 1 Pa at a shear rate of 0.1 (s ^-1 ). With thixotropic fluids above s, stable continuous printability at high speed can be obtained in gravure printing, and multilayer ceramic electronic parts such as multilayer ceramic capacitors can be manufactured with good production efficiency.

In addition, Patent Document 3 describes a conductive paste for gravure printing, which is a laminate containing conductive powder (A), organic resin (B), organic solvent (C), additive (D), and dielectric powder (E) Conductive paste for internal electrodes of ceramic capacitors. Organic resin (B) is composed of polyvinyl butyral with a degree of polymerization of 10,000 to 50,000 and ethyl cellulose with a weight average molecular weight of 10,000 to 100,000. Organic solvent (C ) Is composed of propylene glycol monobutyl ether, or a mixed solvent of propylene glycol monobutyl ether and propylene glycol methyl ether acetate, or a mixed solvent of propylene glycol monobutyl ether and mineral spirits, and the additive (D) is composed of separation inhibitor and dispersion Agent composition, as the separation inhibitor, is composed of a composition containing a polycarboxylic acid polymer or a polycarboxylic acid salt. According to Patent Document 3, the conductive paste has a viscosity suitable for gravure printing, can improve the uniformity and stability of the paste, and has good drying properties.

【Prior Technical Literature】

【Patent Literature】

[Patent Document 1] JP 2003-187638 A

[Patent Document 2] JP 2003-242835 A

[Patent Document 3] JP 2012-174797 A

With the thinning of the internal electrode layer in recent years, conductive powders also tend to have smaller particle sizes. When the particle size of the conductive powder is small, the specific surface area of the particle surface becomes larger. Therefore, the surface activity of the conductive powder (metal powder) becomes high, and the dispersibility of the conductive paste may be reduced. Conductive paste with higher dispersibility.

In addition, when the conductive paste is printed by the gravure printing method, a lower paste viscosity is required than the screen printing method. Therefore, it can be considered that the conductive powder with a larger specific gravity will settle and disperse the paste. Sexual decrease. In addition, in the conductive slurry described in Patent Documents 1 and 2, although the dispersibility of the slurry is improved by removing lumps in the conductive slurry using a filter, a step of removing the lumps is required , So the manufacturing process easily becomes complicated.

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

In a first aspect of the present invention, there is provided a conductive paste containing conductive powder, ceramic powder, dispersant, binder resin, and organic solvent, wherein the dispersant includes an acid-based dispersant and an alkali-based dispersant, The acid-based dispersant has an average molecular weight of more than 500 and 2,000 or less, and has one or more branched chains composed of a hydrocarbon group with respect to the main chain, the binder resin includes an acetal resin, and the organic solvent includes a glycol ether solvent.

In addition, 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. In addition, it is desirable to contain 0.2 parts by mass or more and 2 parts by mass of the acid-based dispersant relative to 100 parts by mass of the conductive powder, and contain 0.02 parts by mass or more and 2 parts by mass relative to 100 parts by mass of the aforementioned conductive powder. Alkaline-based dispersant less than 1 part. In addition, the conductive powder desirably contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys of the aforementioned elements. In addition, the average particle diameter of the conductive powder is desirably 0.05 μm or more and 1.0 μm or less. In addition, the ceramic powder preferably contains a perovskite-type oxide. In addition, the average particle diameter of the ceramic powder is desirably 0.01 μm or more and 0.5 μm or less. In addition, the binder resin desirably contains a butyral resin. In addition, the above-mentioned conductive paste is preferably used for internal electrodes of laminated ceramic parts. In addition, ideally, the viscosity of the conductive paste at a shear rate of 100sec ^-1 is 0.8Pa. Below S, the viscosity at a shear rate of 10000sec ^-1 is 0.18Pa. Below S.

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

In a third aspect of the present invention, 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 using the above-mentioned conductive paste.

The conductive paste of the present invention has a viscosity suitable for gravure printing, and is excellent in the dispersibility and productivity of the paste. In addition, the printing of the conductive paste when forming thin-film electrodes on the electrode pattern of electronic parts such as multilayer ceramic capacitors formed using the conductive paste of the present invention It also has excellent performance and uniform thickness.

1: Multilayer ceramic capacitor

10: Ceramic laminated body

11: Internal electrode layer

12: Dielectric layer

20: External electrode

21: External electrode layer

22: Plating layer

[Fig. 1] A in Fig. 1 is a perspective view showing a multilayer ceramic capacitor related to the embodiment, and B in Fig. 1 is a cross-sectional view thereof.

[Conductive Paste]

The conductive paste of this embodiment contains conductive powder, ceramic powder, dispersant, binder resin, and organic solvent. Hereinafter, each component is explained in detail.

(Conductive powder)

The conductive powder is not particularly limited, and metal powder can be used. For example, one or more powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys of the above elements can be used. Among them, from the viewpoint of conductivity, corrosion resistance, and cost, it is desirable to use powder of Ni or its alloy (hereinafter, sometimes referred to as "Ni powder"). As the Ni alloy, for example, an alloy of at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd and Ni can be used. The content of Ni in the Ni alloy is, for example, 50% by mass or more, and desirably 80% by mass or more. In addition, in order to suppress violent gas generation due to thermal decomposition of the binder resin portion during the debinding process, the Ni powder may contain the element S in the order of several hundred ppm.

The average particle size of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less, More preferably, it is 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 slurry for internal electrodes of multilayer ceramic capacitors (multilayer ceramic parts) that are thinned. For example, it can improve the smoothness of the dry film and the dry film. density. The average particle size is a value obtained from observations with a scanning electron microscope (SEM), and is obtained by measuring the particle sizes of multiple particles one by one from an image obtained by SEM observation at a magnification of 10,000 times Number average.

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

(Ceramic powder)

The ceramic powder is not particularly limited. For example, in the case of a conductive paste for the internal electrode of a multilayer ceramic capacitor, a conventional ceramic powder can be appropriately selected according to the type of the multilayer ceramic capacitor to be applied. Examples of ceramic powders include perovskite-type oxides containing Ba and Ti, and barium titanate (BaTiO ₃ ) is desirable.

As the ceramic powder, a ceramic powder containing barium titanate as a main component and oxides as a secondary component can be used. Examples of the oxide include one or more oxides selected from Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and rare earth elements. In addition, as the ceramic powder, for example, a ceramic powder of a perovskite-type oxide ferroelectric obtained by substituting Ba atoms and Ti atoms of barium titanate (BaTiO ₃ ) with other atoms such as Sn, Pb, and Zr can be used.

When used as a conductive paste for internal electrodes, the ceramic powder may have the same composition as the dielectric ceramic powder constituting the green sheet of the multilayer ceramic capacitor (electronic component). Thereby, it is possible to suppress the occurrence of cracks due to shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer in the sintering process. Such ceramic powders, in addition to the above-mentioned perovskite-type oxides containing Ba and Ti, for example, ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , R (rare earths) Element) ₂ O ₃ , TiO ₂ , Nd ₂ O ₃ and other oxides. In addition, one type of ceramic powder may be used, or two or more types may be used.

The average particle diameter of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, and desirably is in the range of 0.01 μm or more and 0.3 μm or less. By setting the average particle diameter of the ceramic powder within the above-mentioned range, when used as a slurry for internal electrodes, a sufficiently thin and uniform internal electrode can be formed. The average particle size is a value obtained from observations with a scanning electron microscope (SEM). It is a value obtained by measuring the particle sizes of multiple particles one by one from an image obtained by SEM observation at a magnification of 50,000 times. Number average.

Based on 100 parts by mass of the conductive powder, the content of the ceramic powder is desirably 1 part by mass or more and 30 parts by mass or less, more desirably 3 parts by mass or more and 30 parts by mass or less.

The content of the ceramic powder is desirably 1% by mass or more and 20% by mass or less, and more desirably 3% by mass or more and 20% by mass or less with respect to the total amount of the conductive paste. When the content of the conductive powder is in the above range, conductivity and dispersibility are excellent.

(Adhesive resin)

The binder resin contains an acetal resin. The acetal resin is preferably a butyral resin such as polyvinyl butyral. When the binder resin contains an acetal resin, the viscosity can be adjusted to a viscosity 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 with respect to the entire binder resin, or 30% by mass or more, or may be composed of only the acetal resin. In addition, even acetal The resin content is less than 40% by mass relative to the entire binder resin, and it can also have a low slurry viscosity and sufficient bonding strength.

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

In addition, the binder resin may contain other resins other than the acetal resin. The other resin is not particularly limited, and conventional resins can be used. As other resins, for example, cellulose resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, acrylic resins, etc., are listed in terms of solubility in solvents. From the viewpoint of combustion decomposability, etc., ethyl cellulose is ideal. In addition, the molecular weight of the binder resin is, for example, about 20,000 to 200,000.

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

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

(Organic solvents)

The organic solvent contains a glycol ether solvent.

Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monohexyl ether, and ethylene glycol monohexyl ether. (2) Glycol ethers, and propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether (PNB). Among them, propylene glycol monoalkyl ethers are desirable, and propylene glycol monobutyl ether (PNB) is more desirable. Contains glycol ethers in organic solvents In the case of a solvent, it has excellent compatibility with the above-mentioned binder resin and excellent drying properties.

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

The organic solvent may further contain an acetate-based solvent. Examples of the acetate-based solvents include dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, and ethylene glycol monobutyl. Glycol ether acetate, dipropylene glycol methyl ether acetate, 3-methoxy 3-methylbutyl acetate, 1-methoxypropyl-2-acetate, etc. .

When the organic solvent contains an acetate-based solvent, for example, it may contain selected from dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, and isobornyl isobutyrate. At least one kind of acetate solvent (A) among esters. Among them, isobornyl acetate is more desirable. With respect to the entire organic solvent, the acetate-based solvent is contained in an amount of 0% by mass to 80% by mass, desirably 10% by mass to 60% by mass, and more desirably 20% by mass to 40% by mass.

In addition, when the organic solvent contains an acetate-based solvent, for example, the above-mentioned acetate-based solvent (A) and selected from ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate may be included. At least one of the acetate-based solvents (B). In the case of using such a mixed solvent, the viscosity of the conductive paste can be easily adjusted, and the drying speed of the conductive paste can be increased.

It is a mixture containing acetate solvent (A) and acetate solvent (B) In the case of a liquid, the organic solvent preferably contains 50% by mass or more and 90% by mass or less of the acetate-based solvent (A) relative to the entire organic solvent, and more preferably 60% by mass or more and 80% by mass or less. In the case of the above-mentioned mixed liquid, the acetate solvent (B) is contained in an amount of 10% by mass or more and 50% by mass or less based on 100% by mass of the entire acetate solvent, and more preferably 20% by mass or more. Less than mass%.

In addition, the organic solvent may contain other organic solvents other than the glycol ether-based solvent and the acetate-based solvent. The other organic solvent is not particularly limited, and a conventional organic solvent capable of dissolving the above-mentioned binder resin can be used. As other organic solvents, for example, acetate solvents such as ethyl acetate, propyl acetate, isobutyl acetate, and butyl acetate, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, Terpine-based solvents such as terpineol and dihydroterpineol, aliphatic hydrocarbon solvents such as tridecane, nonane, and cyclohexane. Among them, aliphatic hydrocarbon solvents are preferable, and mineral spirits are more preferable among aliphatic hydrocarbon solvents. In addition, one type of other organic solvent may be used, or two or more types may be used.

The organic solvent may contain a glycol ether solvent as a main solvent and an aliphatic hydrocarbon solvent as a sub-solvent, for example. In this case, based on 100 parts by mass of the conductive powder, it is desirable to contain 30 parts by mass or more and 50 parts by mass or less of the glycol ether solvent, and more preferably 40 parts by mass or more and 50 parts by mass or less. The powder is based on 100 parts by mass, preferably 20 parts by mass or more and 80 parts by mass or less of aliphatic hydrocarbon solvent, and more preferably 20 parts by mass or more and 40 parts by mass or less. In addition, based on 100 parts by mass of the conductive powder, even when 25 parts by mass or more of the aliphatic hydrocarbon solvent is contained, the dispersibility of the conductive paste is excellent.

Based on 100 parts by mass of the conductive powder, the content of the organic solvent is ideally 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. When the content of the organic solvent is within the above range, conductivity and dispersibility are excellent.

The content of the organic solvent relative to the total amount of the conductive paste is desirably 20% by mass or more and 50% by mass or less, and more desirably 25% by mass or more and 45% by mass or less. When the content of the organic solvent is within the above range, conductivity and dispersibility are excellent.

(Dispersant)

The inventors of the present invention have studied various dispersants for the dispersants used in conductive pastes. As a result, they have found that by using one or more branches with respect to the main chain, ideally having multiple branches composed of hydrocarbon groups , And the average molecular weight is more than 500 and the dispersant of the acid-based dispersant and alkali-based dispersant of 2000 or less, so that the powder material contained in the conductive paste, that is, the conductive powder, ceramic powder has excellent dispersibility, and makes the coating The conductive paste is excellent in smoothness of the dried film surface after drying.

Although the details of the reason for this effect are not clear, it is considered that by making the acid-based dispersant have a branched chain composed of a hydrocarbon group, a steric obstacle is effectively formed to prevent agglomeration of the powder material, and by containing the acid The alkali-based dispersant with good compatibility with the dispersant can more effectively disperse the dispersant uniformly. In addition, by setting the molecular weight of the acid-based dispersant to a specific size, the conductive paste can be maintained at an appropriate viscosity according to the application. In addition, the present invention is not limited by the above-mentioned theory (reason). Hereinafter, the dispersant related to this embodiment will be described in further detail.

The acid-based dispersant has one or more branches composed of a hydrocarbon group with respect to the main chain, and desirably has a plurality of branches composed of a hydrocarbon group. The acid-based dispersant desirably has a carboxyl group, and more desirably is a hydrocarbon-based graft copolymer having a polycarboxylic acid as the main chain. In addition, the polycarboxylic acid ideally has an ester structure. In addition, the hydrocarbon group desirably has a chain structure. In addition, the hydrocarbon group may be an alkyl group. In addition, the alkyl group may be composed of only carbon and hydrogen, and part of the hydrogen constituting the alkyl group may be substituted with a substituent.

The molecular weight of the acid-based dispersant is greater than 500 and 2,000 or less, and may be 1,000 or more and 2,000 or less. When the molecular weight is in 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 addition, in this specification, when the molecular weight of the dispersant has a certain degree of distribution, the molecular weight of the dispersant represents the weight average molecular weight.

The acid-based dispersant can be used, for example, by selecting an acid-based dispersing agent that satisfies the aforementioned characteristics from commercially available products. In addition, the acid-based dispersant can also be manufactured using a conventionally known manufacturing method to satisfy the above-mentioned characteristics.

Based on 100 parts by mass of the above-mentioned conductive powder, it is desirable to contain 0.2 parts by mass or more and 2 parts by mass or less of an acid-based dispersant. When the content of the acid-based dispersant is in the above range, the dispersibility of the conductive powder and ceramic powder and the smoothness of the dried electrode surface after coating are excellent, and the viscosity of the conductive paste can be adjusted to an appropriate range. In addition, sheet erosion and green sheet peeling failure can be suppressed. In addition, in the conductive paste related to the present embodiment, even if the content of the acid-based dispersant is 1 part by mass or less, it can have high dispersibility.

In addition, it is desirable to contain an acid-based dispersant in an amount of 3% by mass or less with respect to the total amount of the conductive paste. The upper limit of the content of the acid-based dispersant is desirably 2% by mass or less, and more desirably 1% by mass or less. The lower limit of the content of the acid-based dispersant is not particularly limited. For example, it is 0.01% by mass or more, desirably 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 In addition, sheet erosion and green sheet peeling failure can be suppressed.

Alkaline dispersants are not particularly limited in their structure. Examples include lauryl amine, polyethylene glycol lauryl amine, rosin amine, cetyl amine, myristamine, stearyl amine, oleyl amine, polyoxyethylene lauryl amine, etc. Aliphatic amine. The alkali-based dispersant can further improve the effect of the above-mentioned acid-based dispersant, and can further improve the dispersibility when forming the conductive slurry.

Based on 100 parts by mass of the conductive powder, it is desirable to contain 0.02 parts by mass or more and 2 parts by mass or less of the alkaline dispersant. When an alkali-based dispersant is contained within the above-mentioned range together with the acid-based dispersant of the present invention, the dispersibility of the conductive powder and ceramic powder in the conductive paste is more excellent, and the surface of the dried electrode after coating is smooth It is more excellent, and the viscosity of the conductive paste can be adjusted to an appropriate range. In addition, sheet erosion and green sheet peeling failure can be suppressed. In addition, in the conductive paste related to this embodiment, the content of the alkaline dispersant may be 1 part by mass or less, may be 0.1 part by mass or less, or may be 0.05 parts by mass or less.

In addition, based on 100 parts by mass of the acid-based dispersant, for example, about 1 part by mass or more and 500 parts by mass or less of alkaline dispersant may be contained, preferably 10 parts by mass or more and 300 parts by mass or less, and more preferably 50 parts by mass Above 200 parts by mass or less, more preferably 50 parts by mass or more and 150 parts by mass or less. When the alkali-based dispersant is contained in the above range, the viscosity stability of the conductive paste is more excellent, and the dry film density tends to increase.

Relative to the entire conductive paste, for example, the alkali dispersant is contained in an amount of 0% by mass to 2.5% by mass, preferably 0% by mass to 1.0% by mass, more preferably 0.1% by mass to 1.0% by mass, and more It is desirable to contain 0.1% by mass or more and 0.8% by mass or less. When the alkali dispersant is contained in the above range, the viscosity of the slurry over time Stability is more excellent. In addition, with respect to the entire conductive paste, the alkali-based 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.

In addition, the conductive paste may contain only the acid-based dispersant and the alkali-based dispersant as a dispersant, or may contain a dispersant other than the above-mentioned dispersant within a range that does not inhibit the effects of the present invention. As a dispersant other than the above, for example, an acid-based dispersant containing a higher fatty acid, a polymer surfactant, etc., an amphoteric surfactant, a polymer-based dispersant, etc. may be included. In addition, these dispersants may be used in one kind or in combination of two or more kinds.

Based on 100 parts by mass of the conductive powder, the total content (total content) of the dispersant combined with the acid-based dispersant is preferably 0.01 part by mass or more and 3 parts by mass or less, more preferably 0.23 part by mass or more. 3 Parts by mass or less. In addition, in the conductive paste related to this embodiment, the content (total content) of the entire dispersant may be 2 parts by mass or less, or may be 1 part by mass or less. Even if the content of the entire dispersant is within the above range, it can have high dispersibility.

(Other ingredients)

The conductive paste of this embodiment may contain components other than the above-mentioned components as necessary. As other components, for example, conventionally known additives such as defoamers, plasticizers, and thickeners can be used.

(Conductive paste)

The manufacturing method of the conductive paste of this embodiment is not particularly limited, and conventionally known methods can be used. For example, the conductive slurry can be manufactured by stirring and kneading the above-mentioned components by a three-roll mill, a ball mill, a mixer, or the like. At this time, if a dispersing agent is applied to the surface of the conductive powder in advance, the conductive powder will not agglomerate and can be fully dispersed, and the dispersing agent will spread all over the surface. It is easy to obtain a uniform conductive paste. In addition, it is also possible to pre-dissolve the binder resin in a part of the organic solvent, and after preparing the organic vehicle, add conductive powder, ceramic powder, dispersant, and organic vehicle to the organic solvent for slurry adjustment, and then stir, Kneaded to prepare a conductive paste.

The viscosity of the conductive paste at a shear rate of 100sec ^-1 is ideally 0.8Pa. Below S, it can be 0.5Pa. Below S, it can also be 0.4Pa. Below S, it can also be 0.3Pa. Below S. When the viscosity at a shear rate of 100 sec ^-1 is within the above range, it can be suitably used as a conductive paste for gravure printing. If it exceeds the above range, the viscosity will be too high and it may be unsuitable for gravure printing. The lower limit of the viscosity of the conductive paste of this embodiment at a shear rate of 100sec ^-1 is not particularly limited, for example, 0.1Pa. Above S.

In addition, the viscosity of the conductive paste at a shear rate of 10000sec ^-1 is ideally 0.18Pa. Below S, it can be less than 0.14Pa. S. When the viscosity at a shear rate of 10000 sec ^-1 is within the above range, it can be suitably used as a conductive paste for gravure printing. In the case of exceeding the above range, the viscosity may be too high to be suitable for gravure printing. The lower limit of the viscosity when the shear rate is 10000sec ^-1 is not particularly limited, and is, for example, 0.05Pa. Above S.

In addition, after the conductive paste is printed, the dry film density (DFD) of the dried film obtained by drying desirably exceeds 5.0 g/cm ³ , may exceed 5.2 g/cm ³ , or 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 9.8 g/cm ³ of the true density of metallic nickel, and may be 6.5 g/cm ³ or less, for example.

In addition, the arithmetic mean roughness Sa of a dry film with a thickness of 1 to 3 μm and a 20 mm square by printing a conductive paste and drying in the air at 120°C for 1 hour It is desired to be 0.25 μm or less, more preferably 0.2 μm or less, and may be 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 desirable that the surface is flat, and it is a value exceeding 0 and a smaller value is more desirable. In addition, the arithmetic average roughness Sa is measured based on the ISO 25178 standard.

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

For multilayer ceramic capacitors, the dielectric ceramic powder contained in the dielectric green sheet and the ceramic powder contained in the conductive paste are preferably powders of the same composition. The laminated ceramic device manufactured using the conductive paste of this embodiment can suppress sheet erosion and peeling failure of the green sheet even when the thickness of the dielectric green sheet is 3 μm or less, for example.

[Electronic Parts]

Hereinafter, embodiments of electronic components and the like of the present invention will be described with reference to the drawings. In the drawings, it may be indicated in a schematic manner as appropriate and the scale may be changed. In addition, the position, direction, etc. of the part are demonstrated with reference to the XYZ orthogonal coordinate system shown in FIG. 1 etc. as appropriate. In this XYZ orthogonal coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is the vertical direction (up and down direction).

A in FIG. 1 and B in FIG. 1 are diagrams showing a multilayer ceramic capacitor 1 as an example of an electronic component related to the embodiment. The multilayer ceramic capacitor 1 has a multilayer body 10 and external electrodes 20 in which dielectric layers 12 and internal electrode layers 11 are alternately laminated.

Hereinafter, regarding the manufacturing method of multilayer ceramic capacitors using the above conductive paste Method to explain. First, a conductive paste is printed on a dielectric green sheet and dried to form a dry film, a plurality of dielectric green sheets having the dry film on the upper surface are laminated by pressure bonding, and then fired to integrate them. In this way, the laminated ceramic fired body (ceramic laminated body 10) which becomes the main body of the ceramic capacitor was prepared. After that, the multilayer ceramic capacitor 1 is manufactured by forming a pair of external electrodes 20 at both ends of the multilayer body 10. Hereinafter, a more detailed description will be given.

First, a dielectric green sheet (ceramic green sheet) as an unfired ceramic sheet is prepared. As the dielectric green sheet, for example, a dielectric layer slurry obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a predetermined ceramic raw material powder such as barium titanate is used in PET A support film such as a thin film is coated in a sheet shape and dried to remove a solvent to form a dielectric green sheet. In addition, the thickness of the dielectric layer composed of the dielectric green sheet is not particularly limited, but from the viewpoint of miniaturization of the multilayer ceramic capacitor 1, it is desirably 0.05 μm or more and 3 μm or less.

Next, a plurality of sheets in which a dry film is formed by printing and coating the above-mentioned conductive paste on one surface of the dielectric green sheet using a gravure printing method and drying it. In addition, from the viewpoint of the requirement for thinning of the internal electrode layer 11, the thickness of the conductive paste (dry film) after printing is desirably 1 μm or less after drying.

Next, the dielectric green sheet is peeled from the supporting film, and the dielectric green sheet is laminated with the conductive paste (dry film) formed on one surface of the dielectric green sheet alternately, and then heated , Pressure treatment to obtain a laminate (crimped body). Moreover, it can also be set as the structure which arrange|positions the dielectric green sheet for protection which does not apply a conductive paste further on both surfaces of a laminated body.

Next, after cutting the laminated body into a predetermined size to form a green wafer, the green wafer is subjected to a debonding agent treatment and fired in a reducing gas atmosphere, thereby manufacturing a laminated ceramic fired body (laminated body 10) . In addition, the gas environment in the debinding agent treatment is ideally the atmosphere or N ₂ gas environment. The temperature at the time of the debinding agent treatment is, for example, 200°C or more and 400°C or less. In addition, the holding time of the above-mentioned temperature when performing the debinding agent treatment is desirably 0.5 hour or more and 24 hours or less. In addition, in order to suppress oxidation of the metal used in the internal electrode layer 11, firing is performed in a reducing gas atmosphere. In addition, the temperature at which the laminate 10 is fired is, for example, 1000°C or more and 1350°C or less. The holding time of the temperature is, for example, 0.5 hour or more and 8 hours or less.

By firing the green wafer, the organic binder in the dielectric green sheet is completely removed, and the ceramic raw material powder is fired to form the dielectric layer 12 made of ceramic. In addition, the organic carrier in the dry film is removed, and the alloy powder with nickel powder or nickel as the main component is sintered or melted to be integrated to form the internal electrode layer 11, and then the dielectric layer 12 and the internal electrode layer 11 are alternately formed. Laminated ceramic fired body (laminated body 10) formed by layering. In addition, from the viewpoint of bringing oxygen into the dielectric layer 12 to improve reliability and suppress re-oxidation of the internal electrode layer 11, the fired laminated ceramic fired body (laminated body 10) may be annealed.

Then, by providing a pair of external electrodes 20 to the produced laminated ceramic fired body (laminated body 10), the laminated ceramic capacitor 1 is produced. 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. In addition, as the material of the external electrode 20, for example, copper, nickel, or an alloy of the aforementioned elements can be preferably used. In addition, electronic components other than multilayer ceramic capacitors can also be used.

[Example]

Hereinafter, the present invention will be described in detail based on examples and comparative examples, but the present invention is not limited by the examples at all.

[Evaluation method]

(Viscosity of conductive paste)

Using a rheometer at a shear rate of 100sec ^-1, the viscosity of the conductive paste after manufacture were measured under the conditions of 10000sec ^-1.

(Dry film density)

The prepared conductive paste was placed on a PET film and extended to a length of approximately 100 mm with an applicator with a width of 50 mm and a gap of 125 μm. After the obtained PET film was dried at 120°C for 40 minutes to form a dry film, the dry film was cut into four 2.54 cm (1 inch) squares, and after the PET film was peeled off, four dry films were dried. The thickness and weight of the 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 strengthened glass, and dried in the air at 120° C. for 1 hour to produce a 20 mm square dry film with a film thickness of 1 to 3 μm. The surface roughness Sa (arithmetic mean roughness) of the produced dry film was measured using an apparatus for measuring based on the ISO 25178 standard.

[Use materials]

(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 of 0.10 μm) was used.

(Adhesive resin)

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

(Dispersant)

(1) As the acid-based dispersant (A), an acid-based dispersant having an average molecular weight of 1500 and a hydrocarbon-based graft copolymer (having a branched chain composed of a hydrocarbon) having a polycarboxylic acid as the main chain is used.

(2) Rosin amine (B), polyoxyethylene lauryl amine (C), and oleyl amine (D) are used as alkali-based dispersants.

(3) For comparison, the phosphoric acid-based dispersant (E) (molecular weight: 1400, no branch made of hydrocarbon) used in the conventional conductive paste was used.

(Organic solvents)

As the organic solvent, propylene glycol monobutyl ether (PNB), mineral spirits (MA), and terpineol (TPO) are used.

[Example 1]

With respect to 100 parts by mass of Ni powder as conductive powder, 25 parts by mass of ceramic powder, 0.2 parts by mass of acid-based dispersant (A) as acid-based dispersant, and 1.0 parts by mass of alkali-based dispersant Alkaline dispersant (B), 2 parts by mass of PVB and 4 parts by mass of EC as a binder resin, 41 parts by mass of PNB and 27 parts by mass of MA as an organic solvent were mixed to prepare a conductive paste. The viscosity of the prepared conductive paste and the dry film density and surface roughness of the paste were evaluated by the above method. The dispersant of the conductive paste The amount is shown in Table 1, and the evaluation results of the viscosity, dry film density, and surface roughness Sa of the conductive paste are shown in Table 2.

[Example 2]

Except that the content of the acid-based dispersant (A) was 0.74 parts by mass, a conductive paste was prepared and evaluated in the same manner as in Example 1. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Example 3]

Except that the content of the acid-based dispersant (A) was 2.0 parts by mass, a conductive paste was prepared and evaluated in the same manner as in Example 1. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Example 4]

Except that the content of the alkaline dispersant (B) was 0.02 parts by mass, a conductive slurry was prepared and evaluated in the same manner as in Example 2. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Example 5]

Except that the content of the alkaline dispersant (B) was 2.0 parts by mass, a conductive slurry was prepared and evaluated in the same manner as in Example 2. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Example 6]

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 0.6 parts by mass and the content of the alkaline-based dispersants (B) was 1.2 parts by mass. . Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Example 7]

Except for using the alkaline dispersant (C) as the alkaline dispersant, a conductive paste was prepared and evaluated in the same manner as in Example 2. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Example 8]

Except for using the alkaline dispersant (D) as the alkaline dispersant, a conductive paste was prepared and evaluated in the same manner as in Example 2. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Comparative Example 1]

Except for using only 0.8 parts by mass of the phosphoric acid-based dispersant (E) as the dispersant, a conductive paste was prepared and evaluated in the same manner as in Example 1. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Comparative Example 2]

In addition to using 0.8 parts by mass of phosphoric acid dispersant (E) as an acid dispersant, according to In the same manner as in Example 1, a conductive paste was prepared and evaluated. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Comparative Example 3]

A conductive paste was prepared and evaluated in the same manner as in Example 2 except that 68 parts by mass of TPO was used as the main solvent and no auxiliary solvent was used. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Comparative Example 4]

Except for using 6 parts by mass of EC as the binder resin and not using PVB, a conductive paste was prepared and evaluated in the same manner as in Example 2. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Reference example 1]

A conductive paste was prepared and evaluated in the same manner as in Example 2 except that the alkali-based dispersant (B) was not used as the dispersant. Table 1 shows the contents of the dispersant of the conductive paste and the like, and Table 2 shows the evaluation results of the viscosity, dry film density, and surface roughness of the conductive paste.

[Reference example 2]

A conductive paste was prepared and evaluated in the same manner as in Example 2 except that the acid-based dispersant (A) was not used and 0.8 parts by mass of the alkali-based dispersant (B) was used as the dispersant. The content of the dispersant of the conductive paste is shown in Table 1, and the viscosity of the conductive paste and Table 2 shows the evaluation results of dry film density and surface roughness.

(Evaluation results)

The conductive paste of the embodiment has a viscosity of 0.21~0.31Pa when the shear rate is 100sec ^-1 . s, the viscosity at a shear rate of 10000sec ^-1 is 0.10~0.14Pa. s, which is stably displayed as a low value at any shear rate, indicating that it has a viscosity suitable for gravure printing. In addition, it was confirmed that the dry film density of the conductive paste of the example showed a high value of 5.26 to 5.36 g/cm ³ , and the surface roughness Sa of the dry film was 0.12 to 0.23 μm, which was excellent in dispersibility.

In addition, when comparing the conductive pastes of Examples 1 to 3, it can be seen that even the content of the acid-based dispersant (A) is 0.2 parts by mass (Example 1) and 0.74 parts by mass (Example 2) The conductive paste can also obtain a relatively high dry film density and a relatively smooth dry film surface similar to the conductive paste in which the content of the acid-based dispersant (A) is 2.0 parts by mass (Example 3). In addition, it can be seen from Examples 2, 4, and 5 that there is the following trend: When the content of the alkali-based dispersant is added, the dry film density and surface roughness of the conductive paste obtained increase. In addition, from the comparison of the conductive pastes of Examples 1 and 4 and Example 6, it can be seen that there is a tendency that the blending ratios of the acid-based dispersant (A) and the alkaline-based dispersant (B) are significantly different Compared with the case, the dry film density increases when the compounding ratio is close. In addition, from the comparison of the conductive pastes of Examples 2, 7, and 8, it can be seen that even if the type of alkali-based dispersant is changed, good dry film density and surface roughness can be obtained.

In contrast, when the conductive paste of Comparative Example 1 that did not contain the acid-based dispersant and only the phosphoric acid-based dispersant was produced under the same conditions, the conductive paste was comparable to that of the examples. Compared with the slurry, the viscosity became higher and the dry film density was not sufficiently increased.

In addition, the conductive paste of Comparative Example 2 in which the same phosphoric acid-based dispersant as Comparative Example 1 was further added with an alkali-based dispersant (B), although the characteristics were somewhat improved, the same as those in the Examples were not obtained. The same dry film density. In addition, the viscosity of the conductive paste of Comparative Example 3, which uses TPO as the main solvent, which is generally used in many cases, became very high, and could not become a viscosity suitable for gravure paste. In addition, the surface roughness of the conductive paste of Comparative Example 2 is also higher than that of the conductive paste of the examples. In addition, the conductive paste of Comparative Example 4, which did not contain an acetal resin in the resin, had a high viscosity and failed to sufficiently increase the dry film density.

In addition, it is shown that in the conductive paste of Reference Example 1 containing the acid-based dispersant (A) alone as the dispersant, the dry film density is higher than that of Comparative Example 1 using the phosphoric acid-based dispersant (E), and The viscosity of the conductive paste also decreases. In addition, in the conductive paste of Reference Example 2 containing the alkali-based dispersant (B) alone, the dry film density was slightly increased compared to Comparative Example 1 using the phosphoric acid-based dispersant (E), but the conductive paste The viscosity of the material is higher.

From the above, it can be seen that the conductive paste of the example of the present invention containing both the acid-based dispersant (A) and the alkali-based dispersant (B) is compared with the conductive pastes of the comparative example and the reference example Bottom, the dry film density is higher, and the dispersibility of the conductive paste is further improved. In addition, it can be seen that, regarding the viscosity of the conductive paste at a shear rate of 10000sec ^-1 , the conductive paste of the example of the present invention containing both dispersants is also compared with the conductive paste of the comparative example and the reference example. Lower, more suitable for gravure printing.

In addition, the technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments and the like. In some cases, one or more of the requirements described in the above-mentioned embodiments and the like are omitted. In addition, the requirements described in the above-mentioned 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 implementation patterns and the like are cited as part of the description of this article.

【Industrial Utilization】

The conductive paste of the present invention has a viscosity suitable for gravure printing, and the dry film density after coating is relatively high, the dry film surface is very smooth, and the dispersibility is excellent. Therefore, the conductive paste of the present invention is particularly suitable for use as a raw material for internal electrodes of multilayer ceramic capacitors as chip parts of electronic devices that are increasingly miniaturized such as mobile phones and digital devices, and is particularly suitable for use as a conductive paste for gravure printing. Sexual slurry.

In addition, the technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments and the like. In some cases, one or more of the requirements described in the above-mentioned embodiments and the like are omitted. In addition, the requirements described in the above-mentioned embodiments and the like can be appropriately combined. In addition, as long as permitted by law, the Japanese Patent Application No. 2018-241706 filed in Japan is cited And the contents of all the documents cited in this specification are part of the description of this article.

Claims (13)

A conductive paste containing conductive powder, ceramic powder, dispersant, binder resin and organic solvent, and its characteristics are: The aforementioned dispersants include acid-based dispersants and alkali-based dispersants, The average molecular weight of the aforementioned acid-based dispersant exceeds 500 and is 2000 or less, and has one or more branched chains composed of hydrocarbon groups with respect to the main chain, The aforementioned binder resin includes an acetal resin, The aforementioned organic solvent includes a glycol ether-based solvent. The conductive paste described in the first item of the patent application, wherein the acid-based dispersant has a carboxyl group. The conductive paste described in item 1 or 2 of the scope of patent application, wherein the acid-based dispersant is a hydrocarbon-based graft copolymer having a polycarboxylic acid as a main chain. The conductive paste described in any one of items 1 to 3 in the scope of the patent application, wherein, relative to 100 parts by mass of the conductive powder, 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, the alkali-based dispersant is contained in an amount of 0.02 parts by mass or more and 2 parts by mass or less. The conductive paste described in any one of items 1 to 4 in the scope of the patent application, wherein the conductive powder contains at least one selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys of the above elements mineral powder. The conductive paste described in any one of items 1 to 5 in the scope of patent application, wherein the average particle size of the conductive powder is 0.05 μm or more and 1.0 μm or less. The conductive paste described in any one of items 1 to 6 in the scope of patent application, wherein the ceramic powder contains a perovskite-type oxide. The conductive paste described in any one of items 1 to 7 of the scope of patent application, wherein the average particle size of the ceramic powder is 0.01 μm or more and 0.5 μm or less. The conductive paste described in any one of the claims 1 to 8, wherein the binder resin contains a butyral resin. As the conductive paste described in any one of items 1 to 9 in the scope of the patent application, the viscosity of the aforementioned conductive paste at a shear rate of 100sec ^-1 is 0.8Pa. Below S, the viscosity at a shear rate of 10000sec ^-1 is 0.18Pa. Below S. The conductive paste described in any one of items 1 to 10 in the scope of patent application, wherein the conductive paste is used for internal electrodes of laminated ceramic parts. An electronic component characterized in that it is an electronic component formed using the conductive paste described in any one of items 1 to 10 in the scope of the patent application. A multilayer ceramic capacitor characterized by having at least a multilayer body in which a dielectric layer and an internal electrode are laminated, and the internal electrode is formed using the conductive paste described in claim 11.

Images