TW202115743A - Electroconductive composition, electroconductive paste, electronic component, and laminated ceramic capacitor - Google Patents

Abstract

Provided, inter alia, is an electroconductive composition that exhibits an excellent dispersibility. The electroconductive composition contains electroconductive powder and a dispersant wherein the dispersant comprises a first acidic dispersant, which has an average molecular weight of greater than 500 and not greater than 2000 and has one or more hydrocarbon group-containing branch chains per main chain, and comprises a carboxyl group-bearing second acidic dispersant which is other than the first dispersant.

Description

Conductive composition, conductive paste, electronic parts, and multilayer ceramic capacitors

The present invention relates to conductive compositions, conductive pastes, 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. Multilayer ceramic capacitors have 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 in the following manner. First, a conductive paste for internal electrodes is printed (coated) with a predetermined electrode pattern on the surface of a dielectric green sheet containing dielectric powder such as barium titanate (BaTiO _{3) and a binder resin, and dried to form a dry} membrane. Next, the dry film and the green sheet are laminated alternately to obtain a laminated body. Next, the laminated body is heated and pressure-bonded to be integrated 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. Next, the external electrode slurry is applied to both ends of the fired wafer, and after firing, nickel plating or the like is applied to the surface of the external electrode to obtain a multilayer ceramic capacitor.

Generally, the conductive paste for forming the internal electrode layer contains conductive powder, ceramic powder, binder resin, and organic solvent. In addition, in order to improve the dispersibility of conductive powder and the like, the conductive paste may contain a dispersant. Along with the thinning of the internal electrode layer in recent years, the conductive powder also tends to have a smaller particle size. When the particle size of the conductive powder is small, the specific surface area of the particle surface becomes larger, so the surface activity of the conductive powder (metal powder) becomes higher, and the dispersibility may be lowered and the viscosity characteristics may be lowered.

Therefore, an attempt was made to improve the viscosity characteristics of the conductive paste over time. For example, Patent Document 1 describes a conductive paste that contains at least a metal component, an oxide, a dispersant, and a binder resin. The metal component is Ni powder whose surface composition has a specific composition ratio. The amount of spots is 500~2000μmol/g, and the amount of acid sites of the adhesive resin is 15~100μmol/g. Furthermore, according to Patent Document 2, the conductive paste has good dispersibility and viscosity stability.

In addition, Patent Document 2 describes a conductive paste for internal electrodes, which is composed of conductive powder, resin, organic solvent, _{a common material of ceramic powder mainly made of BaTiO 3} and an aggregation inhibitor, wherein the aggregation inhibitor is The content of the agent is 0.1% by weight or more and 5% by weight or less, and the aforementioned aggregation inhibitor is a tertiary amine or a secondary amine represented by a specific structural formula. According to Patent Document 2, the conductive paste for internal electrodes suppresses aggregation of common material components, has excellent long-term storage properties, and can achieve thin-film multilayer ceramic capacitors.

On the other hand, when the internal electrode layer is thinned, it is required that a dry film obtained by printing and drying a conductive paste for internal electrodes on the surface of a dielectric green sheet has a high density. For example, Patent Document 3 proposes a metal ultrafine powder slurry, which contains an organic solvent, a surfactant, and metal ultrafine particles, wherein the surfactant is sarcosine, and the metal ultrafine powder slurry contains , Containing 70% by mass or more and 95% by mass or less of the aforementioned metal superfine powder, based on 100 parts by mass of the aforementioned metal superfine powder, containing more than 0.05 parts by mass and less than 2.0 parts by mass Parts of the aforementioned surfactant. According to Patent Document 3, by preventing the aggregation of ultrafine particles, it is possible to obtain a metal ultrafine powder slurry that is free of aggregated particles and is excellent in dispersibility and dry film density.

【Prior Technical Literature】

【Patent Literature】

[Patent Document 1] Japanese Patent Application Publication No. 2015-216244

[Patent Document 2] JP 2013-149457 A

[Patent Document 3] JP 2006-063441 A

With the thinning of electrode patterns and dielectric layers in recent years, in order to maintain the gaps between the electrode patterns with high accuracy, it is required that there is no surface roughness caused by the agglomeration of coarse particles of conductive powder, etc., and that it has a smoother surface than before. The electrode surface, the inner electrode layer with a denser electrode density.

In view of such a situation, the object of the present invention is to provide a conductive composition with a high dry film density that is excellent in the dispersibility of conductive powder and is the basis of electrode density.

The first aspect of the present invention is a conductive composition containing a conductive powder and a dispersant. The dispersant includes a first acid-based dispersant and a second acid-based dispersant. The first acid-based dispersant has an average molecular weight of more than 500 and It is an acid-based dispersant that is 2000 or less and has one or more branched chains composed of hydrocarbon groups with respect to the main chain. The second acid-based dispersant system is excluding the first acid-based dispersant, Acid-based dispersant with carboxyl group.

In addition, the second acid-based dispersant may be a linear acid-based dispersant. In addition, the second acid-based dispersant may be an acid-based dispersant having a branch and having a molecular weight of 250 or more and 1400 or less. In addition, the first acid-based dispersant desirably has a carboxyl group. In addition, the first acid-based dispersant is desirably a hydrocarbon-based graft copolymer having a polycarboxylic acid as the main chain. In addition, it is desirable that the first acid dispersant is contained in an amount of 0.2 to 2 parts by mass based on 100 parts by mass of the conductive powder, and 0.3 to 2 parts by mass of the conductive powder is contained in 100 parts by mass. The following second acid-based dispersant. In addition, the conductive powder desirably contains at least one metal powder selected from the group consisting of Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. In addition, the average particle size of the conductive powder is desirably 0.05 μm or more and 1.0 μm or less.

A second aspect of the present invention provides a conductive paste containing the above-mentioned conductive composition, a binder resin, and an organic solvent.

The conductive paste preferably further contains ceramic powder. 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 at least one of a cellulose resin, an acrylic resin, and a butyral resin. In addition, the above-mentioned conductive paste is ideally used for internal electrodes of laminated ceramic parts.

A third aspect of the present invention provides an electronic component formed using the above-mentioned conductive paste.

A fourth aspect of the present invention provides a multilayer ceramic capacitor 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 above-mentioned conductive paste.

According to the conductive composition (conductive paste) of the present invention, since the dispersibility of the conductive powder is excellent, it has a high dry film density. In addition, when the electrode patterns of electronic parts such as multilayer ceramic capacitors formed using the conductive paste of the present invention are formed into thin-film electrodes, the conductive paste also has excellent printability, and can have a uniform width with high accuracy. 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] shows a perspective view and a cross-sectional view of the multilayer ceramic capacitor of the embodiment.

[Conductive composition and conductive paste]

The conductive composition of this embodiment contains conductive powder and a dispersant. In addition, the conductive paste concerning this embodiment contains the above-mentioned conductive powder, a dispersant, a binder resin, and an organic solvent. In addition, the conductive paste may contain ceramic powder. Hereinafter, each component contained in the conductive powder or the conductive paste will be described 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 thereof can be used. Among them, from the viewpoints of electrical conductivity, corrosion resistance, and cost, it is desirable to be powder of Ni or its alloy (hereinafter, both may be collectively 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 prevent the part from the binder resin during the debinding process The violent gas generation caused by the thermal decomposition of Ni powder can also contain about several hundred ppm of element S.

The average particle size of the conductive powder is desirably 0.05 μm or more and 1.0 μm or less, and more desirably 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 by observation based on a scanning electron microscope (SEM), and an average value obtained by measuring the particle size of a plurality of particles one by one from an image obtained by observation with SEM at a magnification of 10,000 times value.

The content of the conductive powder is desirably 30% by mass or more and less than 70% by mass relative to the total amount of the conductive paste, and more desirably 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 slurry for internal electrodes 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 oxides include oxides of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and one or more rare earth elements. In addition, as the ceramic powder, for example, a perovskite-type oxide ferroelectric ceramic powder 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.}

In the case of using as a slurry 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 step. Such ceramic powder, in addition to the above, for example, ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , R (rare earth element) ₂ O ₃ , TiO ₂ , Nd ₂ O ₃ and other oxides. In addition, one type of ceramic powder may be used, or two or more types may be used.

The average particle size of the ceramic powder is, for example, 0.01 μm 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 it is 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 by observation based on a scanning electron microscope (SEM). It is an average value obtained by measuring the particle size of a plurality of particles one by one from an image obtained by observation with SEM at a magnification of 50,000 times. .

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, and 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 5% 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 ceramic powder is within the above range, conductivity and dispersibility are excellent.

(Binder resin)

The binder resin is not particularly limited, and conventional resins can be used. Examples of the binder resin include cellulose resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, acrylic resins, and butyrals such as polyvinyl butyral. Department of resin and so on. Among them, it is desirable to contain ethyl cellulose from the viewpoints of solubility in a solvent and combustion decomposability. In addition, when used as a slurry for internal electrodes, from the viewpoint of improving the adhesive strength with the green sheet, a butyral-based resin may be contained, or a butyral-based resin may be used alone. One type of binder resin may be used, or two or more types may be used. In addition, from the viewpoint of improving various characteristics, it is desirable to use a mixture of a cellulose resin and a butyral resin for the binder resin. In addition, the molecular weight of the binder resin is, for example, 20,000~200,000 size.

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 20 parts by mass or less, and more desirably 1 part by mass or more and 15 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 1% 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 is not particularly limited, and a conventional organic solvent capable of dissolving the above-mentioned binder resin can be used. Examples of organic solvents include dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, and ethylene glycol monobutyl ether acetate. , Acetate-based solvents such as dipropylene glycol methyl ether acetate, terpene-based solvents such as terpineol and dihydroterpineol, and hydrocarbon-based solvents such as tridecane, nonane, and cyclohexane. Among them, it is desirable to use terpene-based solvents such as terpineol. In addition, one type of organic solvent may be used, or two or more types may be used.

Based on 100 parts by mass of the conductive powder, the content of the organic solvent is desirably 40 parts by mass or more and 100 parts by mass or less, and more desirably 65 parts by mass or more and 95 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 60% by mass or less, and more desirably 35% by mass or more and 55% 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 the conductive composition, and found that by using more than one, ideally a plurality of branches composed of hydrocarbon groups, and the average molecular weight exceeds 500 It is a first acid dispersant of an acid dispersant of 2000 or less and a second acid dispersant having a carboxyl group other than the above-mentioned first acid dispersant, especially Improve the dispersibility of conductive powder and increase the dry film density. Hereinafter, the dispersant of this embodiment will be described in further detail.

(The first acid-based dispersant)

The first acid-based dispersant used in this embodiment has an average molecular weight of more than 500 and 2000 or less, and has one or more branched chains of hydrocarbon groups with respect to the main chain. Regarding the conductive composition of this embodiment, by containing the first acid-based dispersant, compared with the conventional conductive composition that does not contain the first acid-based dispersant, it has a higher dry film density and improves drying. Smoothness of the film surface.

Although the details of the reason are not clear, it is considered that by having one or more branched chains composed of hydrocarbon groups with respect to the main chain, it is possible to effectively form a steric obstacle and suppress aggregation of the powder material. In addition, by setting the average molecular weight of the first acid-based dispersant within the above range, it is possible to maintain a suitable viscosity when the slurry is prepared according to the use of the conductive composition. In addition, the present invention is not restricted by the above-mentioned theory (reason).

In addition, the first 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 desirably has an ester structure.

In addition, it is desirable that the branched hydrocarbon group of the first acid-based dispersant has a chain structure. The hydrocarbyl group may also 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. In addition, it is desirable that the main chain and the hydrocarbon group do not have a ring structure.

(Second acid-based dispersant)

The second acid-based dispersant is an acid-based dispersant having a carboxyl group other than the aforementioned first acid-based dispersant. Regarding the conductive composition of this embodiment, by using the second acid-based dispersant together with the first acid-based dispersant, the dry film density can be further increased.

In addition, the second acid-based dispersant may be a linear acid-based dispersant. That is, the second acid-based dispersant may have a linear structure without having a branched chain composed of a hydrocarbon group with respect to the main chain. In this case, the molecular weight of the second acid-based dispersant is desirably 5000 or less, and may be 250 or more and 1400 or less. In addition, the second acid-based dispersant desirably contains an alkyl group having 10 or more and 20 or less carbon atoms or an alkenyl group having 10 or more and 20 or less carbon atoms. In addition, it is desirable that the molecular weight of the second acid-based dispersing agent is smaller than that of the first acid-based dispersing agent. By using the above-mentioned second acid-based dispersant together with the first acid-based dispersant, the density of the dried film can be increased, and the smoothness of the dried film surface can be further improved.

In addition, the second acid-based dispersant may be an acid-based dispersant having a branch. In this case, the second acid-based dispersant is desirably an acid-based dispersant having a molecular weight of 250 or more and 1400 or less. In addition, the second acid-based dispersant may be a dicarboxylic acid. In addition, the second acid-based dispersant having a branch preferably contains an alkyl group having 15 or more and 100 or less carbon atoms or an alkenyl group having 15 or more and 100 or less carbon atoms, and more preferably has 15 or more and 50 carbon atoms. The following alkyl groups or alkenyl groups having 15 or more and 50 carbon atoms are more desirably an alkyl group having 15 or more and 25 or less carbon atoms or alkenyl groups having 15 or more and 25 or less carbon atoms. In addition, it is desirable that the molecular weight of the second acid-based dispersing agent is smaller than that of the first acid-based dispersing agent. By using the above-mentioned second acid-based dispersant together with the first acid-based dispersant, the density of the dried film can be increased, and the smoothness of the dried film surface can be further improved.

For each acid-based dispersing agent, for example, an acid-based dispersing agent that satisfies the above-mentioned characteristics can be selected from commercially available products. In addition, a conventionally known manufacturing method may be used to manufacture an acid-based dispersant to satisfy the above-mentioned characteristics.

(Proportion of dispersant content)

Based on 100 parts by mass of the conductive powder, for example, containing 0.2 parts by mass or more and 2 parts by mass or less of the first acid-based dispersant, and based on 100 parts by mass of the conductive powder, for example, containing 0.01 parts by mass or more and 2 parts by mass or less of the first Diacid dispersant. When the content of the dispersant is within the above range, compared with the case where the first acid-based dispersant alone contains the same amount, the content of the conductive powder is The dispersibility is improved, the smoothness of the surface of the dried electrode after coating is more excellent, and the density of the dry film is further improved, and the viscosity of the conductive paste can also be adjusted to an appropriate range. In addition, sheet erosion and green sheet peeling failure can be suppressed.

In addition, within the above range, the content of the first acid-based dispersant may be 1 part by mass or less, or 0.5 parts by mass or less. Even if the content of the first acid-based dispersant is small, by using the second acid-based dispersant in combination, higher dispersibility can be achieved. In addition, it is possible to further suppress sheet erosion and green sheet peeling failure caused by the residue of the dispersant.

In addition, the lower limit of the content of the second acid-based dispersant is preferably 0.3 parts by mass or more based on 100 parts by mass of the conductive powder, and may also be 0.5 parts by mass or more. When the lower limit of the content of the second acid-based dispersant is within the above range, the smoothness of the dried film surface can be further improved. In addition, from the viewpoint of having a higher dry film density and further suppressing sheet erosion and green sheet peeling defects caused by the residue of the dispersant, the upper limit of the content of the second acid-based dispersant may be 1.5 parts by mass Below, it may be 1.2 parts by mass or less. In addition, from the viewpoint of further increasing the dry film density, the content of the second acid-based dispersant may be greater than the content of the first acid-based dispersant.

In addition, the total amount of the acid-based dispersant is desirably 3% by mass or less relative to the entire amount of the conductive paste. The upper limit of the content of the dispersant is desirably 2% by mass or less, and more desirably 1% by mass or less. The lower limit of the content of the dispersant is not particularly limited. For example, it is 0.01% by mass or more, and desirably 0.05% by mass or more. When the content of the dispersant is within the above range, the viscosity of the conductive paste can be adjusted to an appropriate range, and sheet erosion and green sheet peeling failure can be suppressed.

In addition, the conductive paste may contain a dispersant other than the above-mentioned acid-based dispersant within a range that does not inhibit the effects of the present invention. As a dispersant other than the above, the conductive paste may contain, for example, an acid-based dispersant including higher fatty acids, polymer surfactants, etc., Alkaline dispersants, amphoteric surfactants, polymer dispersants, etc., preferably contain alkali dispersants. In addition, one of these dispersants can be used or two or more of them can be used in combination.

In the case of containing a dispersant other than an acid-based dispersant, the content of the entire dispersant (total content) in total with the main added acid-based dispersant based on 100 parts by mass of the aforementioned conductive powder is preferably 0.01 mass Part or more and 3 parts by mass or less, may be 2.5 parts by mass or less, may be 2.0 parts by mass or less, or may be 1.5 parts by mass or less.

(Conductive paste)

The above-mentioned materials can be mixed (stirred, kneaded) to produce the conductive paste related to the present embodiment. Specifically, it can be manufactured by preparing each of the above-mentioned components, stirring and kneading with a mixer.

The above-mentioned materials can be mixed at the same time. For example, a conductive powder slurry can be prepared by mixing a conductive powder, a dispersant, and an organic solvent in advance. Thereby, the dispersant can be applied to the surface of the conductive powder in advance. If a dispersant is applied to the surface of the conductive powder in advance, even when the conductive powder is mixed with other materials to produce a conductive paste, the conductive powder does not aggregate and maintains a sufficiently dispersed state, and it is easy to obtain a uniform conductive paste.

As the conductive powder slurry (/coating of the dispersant on the surface of the conductive powder), for example, based on 100 parts by mass of the conductive powder, 0.01 parts by mass or more and less than 5 parts by mass, ideally 0.1 parts by mass or more and 3 parts by mass The dispersant is mixed in an amount less than 1 part to prepare (/coating).

In addition, for example, a ceramic powder, a dispersant, and an organic solvent may be mixed in advance to prepare a ceramic powder slurry. Thereby, a dispersant can be applied to the ceramic powder in advance. If a dispersant is applied to the surface of the ceramic powder in advance, even when it is mixed with other materials to produce a conductive slurry, the ceramic powder does not aggregate and maintains a sufficiently dispersed state, and it is easy to obtain a uniform conductive slurry.

As the ceramic powder slurry (/coating of the dispersant to the ceramic powder), for example, The conductive powder is based on 100 parts by mass, and the dispersant is mixed in an amount of 0.01 part by mass or more and 10 parts by mass or less, ideally 0.1 part by mass or more and 5 parts by mass or less to produce (/coating).

In addition, it is also possible to dissolve the binder resin in the organic solvent for the carrier to make an organic vehicle, add conductive powder, ceramic powder, organic vehicle, and dispersant to the organic solvent for the slurry, and then stir it with a mixer. Kneaded to produce a conductive paste.

In addition, among the organic solvents, as the organic solvent for the carrier, it is desirable to use the same solvent as the organic solvent for the slurry that adjusts the viscosity of the conductive paste in order to improve the fusion of the organic vehicle. The content of the organic solvent for the carrier is, for example, 5 parts by mass or more and 80 parts by mass or less based on 100 parts by mass of the conductive powder. In addition, the content of the organic solvent for the carrier is desirably 10% by mass or more and 40% by mass or less with respect to the entire amount of the conductive paste.

The viscosity of the conductive paste after 24 hours from the manufacture of the conductive paste is ideally 10Pa. 50Pa above s. s or less. In addition, the viscosity of the conductive paste can be measured under the conditions of ^{10 rpm (shear rate=4sec -1) using a B-type viscometer manufactured by Brookfield Corporation.}

In addition, after the conductive paste is screen-printed, the dry film density (DFD) of the dried film obtained by drying is desirably more than 5.0 g/cm ³ , more desirably more than 5.5 g/cm ³ , particularly desirably 5.6 g/cm ³ or more. In addition, the upper limit of the dry film density is not particularly limited. For example, it may be 6.5 g/cm ³ or less. In addition, the upper limit of the dry film density does not exceed the true density of the conductive powder used (for example, in the case of metallic nickel: 9.8 g/cm ³ )

In addition, the surface roughness Ra (arithmetic mean roughness) when a dried film of 20 mm square and a film thickness of 1 μm to 3 μm is produced by screen printing the conductive paste and drying in the air at 120°C for 1 hour is ideally 0.045 μm or less, more preferably 0.04 μm or less. In addition, the lower limit of the surface roughness Ra (arithmetic mean roughness) is desirably a flat surface and is not particularly limited, but it is a value exceeding 0 and the smaller the value, the better.

In addition, the Rt (maximum cross-sectional height) of the above-mentioned dry film is desirably 0.4 μm or less. In addition, the lower limit of the surface roughness Ra (arithmetic mean roughness) is desirably a flat surface and is not particularly limited, but it is a value exceeding 0 and the smaller the value, the better.

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.

In a multilayer ceramic capacitor (electronic component), it is desirable that the dielectric ceramic powder contained in the dielectric green sheet and the ceramic powder contained in the conductive paste are powders of the same composition. In the laminated ceramic device manufactured using the conductive paste of this embodiment, even when the thickness of the dielectric green sheet is 3 μm or less, for example, sheet erosion and green sheet peeling failure can be suppressed.

〔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 and the scale may be changed as appropriate. In addition, the position, direction, etc. of the parts will be described 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 a vertical direction (up and down direction).

The electronic component of this embodiment is formed using the above-mentioned conductive paste of this embodiment. FIG. 1A and FIG. 1B are diagrams showing a multilayer ceramic capacitor 1 as an example of an electronic component related to an embodiment. The multilayer ceramic capacitor 1 includes a multilayer body 10 and external electrodes 20 in which dielectric layers 12 and internal electrode layers 11 are alternately laminated. The multilayer ceramic capacitor 1 is formed using the above-mentioned conductive paste of this embodiment.

Hereinafter, a method of manufacturing a multilayer ceramic capacitor using the above-mentioned conductive paste will be described. First, a conductive paste is printed on a dielectric layer made of a ceramic green sheet and dried to form a dry film. The plurality of dielectric layers having the dry film on the upper surface are bonded by pressing After laminating to obtain a laminated body, the laminated body is fired and integrated, thereby preparing a ceramic laminated body 10 in which internal electrode layers 11 and dielectric layers 12 are alternately laminated. After that, by forming a pair of external electrodes on both ends of the ceramic laminate 10, the multilayer ceramic capacitor 1 is manufactured. Hereinafter, a more detailed description will be given.

First, a ceramic green sheet as an unfired ceramic sheet is prepared. The ceramic green sheet includes, 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 in PET A support film such as a film is coated in a sheet form and dried to remove the solvent to form a film. In addition, the thickness of the dielectric layer composed of the ceramic green sheet is not particularly limited, but from the viewpoint of miniaturization of multilayer ceramic capacitors, it is desirably 0.05 μm or more and 3 μm or less.

Next, a plurality of sheets in which the above-mentioned conductive paste is printed (coated) on one surface of the ceramic green sheet by a conventional method such as a screen printing method and dried to form a dry film are prepared. In addition, from the viewpoint of the requirement for thinning of the internal electrode layer 11, the thickness of the conductive paste (dried film) after printing is desirably 1 μm or less after drying.

Next, the ceramic green sheet is peeled from the supporting film, and the dielectric layer composed of the ceramic green sheet and the dry film formed on one surface of the dielectric layer are laminated alternately, and then heated and pressurized Processed to obtain a laminate. Moreover, it can also be comprised so that the ceramic green sheet for protection which is not coated with a conductive paste may be further arrange|positioned 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 the ceramic laminated body 10. In addition, the gas environment in the debinding agent treatment is ideally atmospheric or N ₂ gas. 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 retention 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 the oxidation of the metal used in the internal electrode layer, firing is performed in a reducing gas atmosphere. In addition, the temperature at which the laminate is fired is, for example, 1000°C or more and 1350°C or less, which is the temperature during firing. The retention time of, for example, is 0.5 hour or more and 8 hours or less.

By firing the green wafer, the organic binder in the green wafer is completely removed and the ceramic raw material powder is fired, thereby forming the dielectric layer 12 made of ceramic. In addition, the organic carrier in the dry film is removed and the nickel powder or the alloy powder with nickel as the main component is sintered or melted to be integrated to form internal electrodes, thereby forming a multilayer alternately stacked dielectric layer 12 and internal electrode layer 11 Laminated ceramic fired body. In addition, from the viewpoint of bringing oxygen into the dielectric layer to improve reliability and suppress re-oxidation of the internal electrodes, annealing treatment may be performed on the laminated ceramic fired body after firing.

Next, a pair of external electrodes 20 are provided to the produced laminated ceramic fired body, thereby producing a laminated ceramic capacitor 1. For example, the external electrode 20 includes an external electrode layer 21 and a plating layer 22. The external electrode layer 21 is electrically connected to the internal electrode layer 11. In addition, as the material of the external electrode 20, for example, copper, nickel, or alloys thereof can be applied. In addition, as electronic components, electronic components other than multilayer ceramic capacitors may also be used.

[Examples]

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

[Evaluation method]

(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 drying the obtained PET film at 120°C for 40 minutes to form a dried body, the dried body was cut into four pieces of 2.54 cm (1 inch) square. After the PET film was peeled off, the four pieces were dried. The thickness and weight of the film are measured Determine and calculate the dry film density (average value).

(Surface roughness)

The prepared conductive paste was screen printed on 2.54 cm (1 inch) square heat-resistant tempered glass, and dried at 120°C for 1 hour in the atmosphere to produce a dried film of 20 mm square and a film thickness of 1 μm to 3 μm. . Based on the standard of JIS B0601-2001, the surface roughness Ra (arithmetic mean roughness) and Rt (maximum cross-sectional height) of the produced dry film were measured.

〔Materials used〕

(Conductive powder)

As the conductive powder, Ni powder (SEM average particle size 0.2 μm) was used.

(Binder resin)

As the binder resin, ethyl cellulose (EC resin) and polyvinyl butyral resin (PVB resin) are used. In addition, when preparing the conductive paste, it was used as a product obtained by dissolving 12 parts by mass of a binder resin (a resin obtained by mixing EC resin and PVB resin at 2:1) in 88 parts by mass of terpineol in advance A substance prepared as an organic carrier.

(Dispersant)

As the first acid-based dispersant, (i) an acid-based dispersant A with an average molecular weight of 800 as a hydrocarbon-based graft copolymer with polycarboxylic acid as the main chain, and (ii) as a polycarboxylic acid as the main An acid-based dispersant B having a chain hydrocarbon-based graft copolymer and an average molecular weight of 1500.

In addition, as the second acid-based dispersant, (i) an acid-based dispersant C having an average molecular weight of 350 as a linear dispersant having a carboxyl group, and (ii) an acid-based dispersant C having an average molecular weight of 350 as a linear dispersant having a carboxyl group and an average molecular weight were used The acid-based dispersant D of 290 and (iii) the acid-based dispersant F having an average molecular weight of 370 as a dispersant having two carboxyl groups and having a branch with respect to the main chain.

In addition, as the second acid-based dispersant, (iv) In Example 12, an acid-based dispersant B having an average molecular weight of 1500 as a hydrocarbon-based graft copolymer with a polycarboxylic acid as the main chain was used (Corresponding to the first acid-based dispersant), (v) In Example 13, an acid-based dispersant E with an average molecular weight of 230 was used as an acid-based dispersant having two carboxyl groups and a branch with respect to the main chain .

(Organic solvents)

As the organic solvent, terpineol (terpene-based solvent) is used.

(Example 1)

Based on 100 parts by mass of the conductive powder (Ni powder), 50 parts by mass of the organic vehicle containing the binder resin obtained by mixing EC resin and PVB resin at 2:1, and the acid as the first acid-based dispersant 0.5 parts by mass of dispersant A and 1 part by mass of acid dispersant C as the second acid dispersant were mixed, and an organic solvent was added to make the above-mentioned mixed material 85.5% by mass to prepare evaluation Conductive paste. The types of dispersants used in the conductive paste are shown in Table 1.

In addition, using the obtained conductive paste, a dry film was produced by the method described in the above-mentioned evaluation method, and the dry film density and the surface roughness of the dry film were evaluated by the above-mentioned method. The evaluation results are shown in Table 1.

(Examples 2~13)

A conductive paste was produced under the same conditions as in Example 1, except that the dispersant was set to a combination of the type and content described in Table 1. The dry film density and the surface roughness of the dry film produced using this conductive paste were evaluated by the above-mentioned method. The evaluation results are shown in Table 1 together with the type and content of the acid-based dispersant used.

(Reference example 1~3)

A conductive paste was produced under the same conditions as in Example 1, except that the dispersant was set to a combination of the type and content described in Table 1. The dry film density and the surface roughness of the dry film produced using this conductive paste were evaluated by the above-mentioned method. Compare the evaluation results with The type and content of the acid-based dispersant used are shown in Table 1 together.

【Table 1】

(Evaluation results)

From the results in Table 1, it was confirmed that the conductive paste containing the first acid-based dispersant and the second acid-based dispersant of Example 1, Examples 4 to 13 had the same content as the first acid-based dispersant Compared with the conductive paste of Reference Example 1 which does not contain the second acid-based dispersant, the dry film density is higher, and the surface roughness of the dry film is smaller and smoother.

In addition, the conductive pastes of Example 2 and Example 3 produced under the same conditions as Example 1 except that the content of the first acid-based dispersant was changed to 0.2 parts by mass or 2.0 parts by mass were also compared with other conductive pastes. In the same manner, the dry film has a higher density and a lower surface roughness (Ra and Rt) of the dry film.

In addition, it was confirmed that when comparing Examples 4 to 7 in which the content of the second acid-based dispersant was changed within the range of 0.01 parts by mass to 2.0 parts by mass, it was particularly In the conductive pastes of Example 6 and Example 7 in which the content of the second acid-based dispersant is 0.3 parts by mass or more, the surface roughness (Ra and Rt) of the dried film is further reduced, and it has higher smoothness (also That is, it is satisfied that Ra is 0.045 μm or less and Rt is 0.4 μm or less).

On the other hand, in the conductive paste of Reference Example 2 in which the content of the first acid-based dispersant alone is the same as that of the entire dispersant of Examples 1, 8 to 10 (1.5 parts by mass), although the dry film density increases However, compared with these examples, the dry film density is lower, and the improvement of smoothness (especially the reduction of Rt) is also insufficient.

In addition, in the conductive paste of Reference Example 3 in which the content of the second acid-based dispersant alone was the same amount (1.5 parts by mass) of the dispersion amount of Examples 1, 8 to 10 as a whole, it was the same as Reference Example 2. Although the density of the dried film is increased, the density of the dried film is lower compared to these examples, and the improvement in smoothness (especially the reduction in Rt) is also insufficient.

In addition, in the conductive pastes of Examples 12 and 13 in which a dispersant having a branched chain and a molecular weight of more than 1400 or a molecular weight of less than 250 was used as the second acid-based dispersant, although compared with Comparative Example 2, the conductive paste was dry The film density was increased, but the reduction in the surface roughness (Ra and Rt) of the dried film was insufficient compared with other Examples. Therefore, from the viewpoint of further improving the smoothness, as the second acid-based dispersant, it is desirable to use an acid-based dispersant having a linear structure as in Example 1, or the molecular weights as in Example 10 and Example 11. It is an acid-based dispersant that is 250 or more and 1400 or less and has a branch.

In addition, the technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments and the like. For example, the conductive paste used for printing electrodes, wiring, etc. on electronic parts can be used as it is. The above-mentioned conductive paste prepared in the examples can be used as it is. However, in order to improve the adhesion to the dielectric layer, ceramic powder may be further included. It has been confirmed that the inclusion of ceramic powder does not hinder the dispersibility of the above-mentioned conductive paste. Therefore, the conductive paste of this embodiment can also be flexibly applied to conductive pastes for electrodes such as internal electrodes of multilayer ceramic capacitors.

【Industrial Utilization】

Regarding the conductive paste of this embodiment, the dispersibility is excellent, so the dry film density after coating and the dry film surface smoothness are very excellent, and it can be particularly suitably used as a miniaturized electronics for mobile phones, digital devices, etc. It is a raw material for the internal electrodes of multilayer ceramic capacitors, which are chip parts of equipment.

In addition, one or more of the requirements described in the above-mentioned embodiments and the like may be 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 disclosure content of all the documents cited in the above-mentioned implementation types and the like is cited and used as a part of the description of this specification. In addition, as long as permitted by law, the content of Japanese Patent Application No. 2019-175455, which is a Japanese patent application, is cited as a part of the description in this specification.

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

Claims (16)

A conductive composition, which contains conductive powder and a dispersant, and is characterized by: The dispersant includes a first acid-based dispersant and a second acid-based dispersant, The first acid-based dispersant is an acid-based dispersant having an average molecular weight exceeding 500 and 2000 or less, and having at least one branched chain composed of a hydrocarbon group with respect to the main chain, The second acid-based dispersing agent is an acid-based dispersing agent having a carboxyl group other than the first acid-based dispersing agent. The conductive composition according to claim 1, wherein the second acid-based dispersant is a linear acid-based dispersant. The conductive composition according to claim 1, wherein the second acid-based dispersant is an acid-based dispersant having a branch and a molecular weight of 250 or more and 1400 or less. The conductive composition according to any one of claims 1 to 3, wherein the first acid-based dispersant has a carboxyl group. The conductive composition according to any one of claims 1 to 4, wherein the first acid-based dispersant is a hydrocarbon-based graft copolymer whose main chain is polycarboxylic acid. The conductive composition according to any one of claims 1 to 5, wherein, based on 100 parts by mass of the conductive powder, the first acid-based dispersant is contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less. The conductive powder is based on 100 parts by mass and contains 0.3 parts by mass or more and 2 parts by mass or less of the second acid-based dispersant. The conductive composition according to any one of claims 1 to 6, wherein the conductive powder contains at least one metal powder selected from the group consisting of Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. The conductive composition according to any one of claims 1 to 7, wherein the conductive The average particle size of the powder is 0.05 μm or more and 1.0 μm or less. A conductive paste, its characteristics are: The conductive paste contains the conductive composition according to any one of claims 1 to 8, a binder resin, and an organic solvent. The conductive paste according to claim 9, wherein the conductive paste further contains ceramic powder. The conductive paste according to claim 10, wherein the ceramic powder contains a perovskite-type oxide. The conductive paste according to claim 10 or 11, wherein the average particle size of the ceramic powder is 0.01 μm or more and 0.5 μm or less. The conductive paste according to any one of claims 9 to 12, wherein the binder resin contains at least one of a cellulose resin, an acrylic resin, and a butyral resin. The conductive paste according to any one of claims 9 to 13, wherein the conductive paste is used for internal electrodes of laminated ceramic parts. An electronic component, characterized in that: the electronic component is formed using the conductive paste described in any one of claims 9-13. A type of multilayer ceramic capacitor, its characteristics are: This multilayer ceramic capacitor has at least a multilayer body formed by laminating a dielectric layer and internal electrodes, The internal electrode is formed using the conductive paste described in claim 14.

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