TWI858145B - Conductive composition, conductive slurry, electronic component, and multilayer ceramic capacitor - Google Patents

Abstract

The present invention provides a conductive composition with excellent dispersibility. The conductive composition of the present invention contains a conductive powder and a dispersant, wherein the dispersant contains a first acid-based dispersant having an average molecular weight greater than 500 and less than 2000 and having one or more side chains composed of hydroxyl groups relative to the main chain, and a second acid-based dispersant having a carboxyl group other than the first acid-based dispersant.

Description

Conductive composition, conductive slurry, electronic component, and multilayer ceramic capacitor

The present invention relates to a conductive composition, a conductive slurry, an electronic component, and a multilayer ceramic capacitor.

As electronic devices such as mobile phones and digital devices become smaller and more powerful, electronic components such as multilayer ceramic capacitors are also expected to become smaller and more powerful. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked. Miniaturization and higher capacity can be achieved by thinning the dielectric layers and internal electrode layers.

For example, a laminated ceramic capacitor can be manufactured as follows. First, a conductive slurry for an internal electrode is printed (applied) in a predetermined electrode pattern on the surface of a dielectric green sheet containing a dielectric powder such as _barium titanium oxide (BaTiO 3) and a binder resin, and dried to form a dry film. Next, the dry film and the green sheet are laminated in an alternating manner to obtain a laminate. Next, the laminate is heated and pressed to form a press-bonded body. The press-bonded body is cut, subjected to an organic binder removal treatment in an oxidizing gas environment or an inert gas environment, and then fired to obtain a fired chip. Next, external electrode slurry is applied to both ends of the fired wafer, and after firing, nickel or the like is plated on the surface of the external electrode to obtain a multilayer ceramic capacitor.

Generally speaking, the conductive slurry used to form the internal electrode layer contains conductive powder, ceramic powder, binder resin, and organic solvent. In addition, in order to improve the dispersibility of the conductive powder, etc., the conductive slurry sometimes contains a dispersant. With the thin film formation 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 smaller, the specific surface area of the particle surface becomes larger, so the surface activity of the conductive powder (metal powder) becomes higher, and there is a possibility that the dispersibility is reduced and the viscosity characteristics are reduced.

Therefore, attempts have been made to improve the viscosity characteristics of conductive slurries over time. For example, Patent Document 1 describes a conductive slurry that contains at least a metal component, an oxide, a dispersant, and a binder resin, wherein the metal component is Ni powder having a specific composition ratio on its surface composition, the acidic site amount of the dispersant is 500-2000 μmol/g, and the acidic site amount of the binder resin is 15-100 μmol/g. Moreover, according to Patent Document 2, the conductive slurry has good dispersibility and viscosity stability.

In addition, Patent Document 2 describes a conductive slurry for an internal electrode, which is composed of a conductive powder, a resin, an organic solvent, a common material of a ceramic powder mainly composed of BaTiO ₃ , and an agglomeration inhibitor, wherein the content of the agglomeration inhibitor is 0.1% by weight or more and 5% by weight or less, and the agglomeration inhibitor is a tertiary amine or a diamine represented by a specific structural formula. According to Patent Document 2, the conductive slurry for an internal electrode inhibits the agglomeration of the common material components, has excellent long-term storage properties, and can realize the thin film of a multilayer ceramic capacitor.

On the other hand, when the inner electrode layer is made thinner, the dried film obtained by printing the conductive paste for the inner electrode on the surface of the dielectric green sheet and drying it is required to have a higher density. For example, Patent Document 3 proposes a metal ultrafine powder paste, which contains an organic solvent, a surfactant and metal ultrafine particles, wherein the surfactant is oleyl sarcosine, and the metal ultrafine powder paste contains 70 mass % or more and 95 mass % or less of the metal ultrafine powder, and the surfactant is contained in an amount of more than 0.05 mass parts and less than 2.0 mass parts based on 100 mass parts of the metal ultrafine powder. According to Patent Document 3, by preventing the aggregation of ultrafine particles, it is possible to obtain a metal ultrafine powder slurry with no agglomerated particles and excellent dispersibility and dry film density.

[Prior Technical Literature]

【Patent Literature】

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

[Patent Document 2] Japanese Patent Publication No. 2013-149457

[Patent Document 3] Japanese Patent Publication No. 2006-063441

With the recent thinning of electrode patterns and dielectric layers, in order to maintain the gaps between electrode patterns with high precision, there is a demand for an internal electrode layer with a smoother electrode surface and a denser electrode density than before, without surface roughness caused by coarse particles formed by agglomeration of conductive powder.

In view of such a situation, the purpose of the present invention is to provide a conductive composition having excellent dispersibility of conductive powder and a high dry film density which serves as the basis of electrode density.

The first aspect of the present invention is a conductive composition containing conductive powder and a dispersant, wherein the dispersant includes a first acid-based dispersant and a second acid-based dispersant, wherein the first acid-based dispersant is an acid-based dispersant having an average molecular weight of more than 500 and less than 2000 and having one or more side chains composed of hydrocarbon groups relative to the main chain, and the second acid-based dispersant is an acid-based dispersant having a carboxyl group other than the first acid-based dispersant.

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 with a branched chain and a molecular weight of 250 or more and 1400 or less. In addition, the first acid-based dispersant preferably has a carboxyl group. In addition, the first acid-based dispersant is preferably a hydrocarbon graft copolymer with polycarboxylic acid as the main chain. In addition, it is ideal that the conductive powder contains 0.2 mass parts or more and 2 mass parts or less of the first acid-based dispersant based on 100 mass parts of the conductive powder, and the conductive powder contains 0.3 mass parts or more and 2 mass parts or less of the second acid-based dispersant based on 100 mass parts of the conductive powder. In addition, the conductive powder preferably contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu and alloys thereof. In addition, the average particle size of the conductive powder is preferably 0.05μm or more and 1.0μm or less.

The second aspect of the present invention provides a conductive slurry, which contains the above-mentioned conductive composition, a binder resin and an organic solvent.

The conductive slurry desirably further contains ceramic powder. In addition, the ceramic powder desirably contains calcium titanate-type oxide. In addition, the average particle size of the ceramic powder desirably is greater than 0.01 μm and less than 0.5 μm. In addition, the binder resin desirably contains at least one of a cellulose-based resin, an acrylic resin, and a butyral-based resin. In addition, the conductive slurry desirably is used for the internal electrode of a laminated ceramic part.

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

The fourth aspect of the present invention provides a multilayer ceramic capacitor, which has at least a multilayer body formed by stacking a dielectric layer and an internal electrode, and the internal electrode is formed using the above-mentioned conductive slurry.

According to the conductive composition (conductive slurry) of the present invention, the conductive powder has excellent dispersibility and thus has a high dry film density. In addition, when the electrode pattern of electronic parts such as multilayer ceramic capacitors formed using the conductive slurry of the present invention is formed into a thin film electrode, the conductive slurry has excellent printability and can have uniform width and thickness with high precision.

1: Multilayer ceramic capacitors

10: Ceramic laminate

11: Internal electrode layer

12: Dielectric layer

20: External electrode

21: External electrode layer

22: Electroplating

[Figure 1] shows an oblique view and a cross-sectional view of a multilayer ceramic capacitor according to an embodiment.

[Conductive composition and conductive slurry]

The conductive composition of this embodiment contains conductive powder and dispersant. In addition, the conductive slurry of this embodiment contains the above-mentioned conductive powder and dispersant, binder resin and organic solvent. In addition, the conductive slurry may also contain ceramic powder. The following is a detailed description of each component contained in the conductive powder or conductive slurry.

(Conductive powder)

There is no particular limitation on the conductive powder, and metal powder can be used, for example, powder of one or more selected from Ni, Pd, Pt, Au, Ag, Cu and alloys thereof. Among them, from the viewpoint of conductivity, corrosion resistance and cost, powder of Ni or its alloy (hereinafter, both are sometimes collectively referred to as "Ni powder") is ideal. As Ni alloy, for example, alloy of Ni and at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt and Pd can be used. The content of Ni in the Ni alloy is, for example, 50% by mass or more, and ideally 80% by mass or more. In addition, in order to suppress the violent gas generation caused by the partial thermal decomposition of the binder resin during the debonding treatment, the Ni powder may also contain about several hundred ppm of element S.

The average particle size of the conductive powder is preferably 0.05 μm to 1.0 μm, and more preferably 0.1 μm to 0.5 μm. When the average particle size of the conductive powder is within the above range, it can be suitably used as a slurry for the internal electrode of a thin-film multilayer ceramic capacitor (multilayer ceramic part), for example, to improve the smoothness and density of the dry film. The average particle size is a value obtained by observation based on a scanning electron microscope (SEM), and is an average value obtained by measuring the particle sizes of multiple particles one by one from an image obtained by observation at a magnification of 10,000 times by SEM.

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

(Ceramic powder)

The ceramic powder is not particularly limited, and for example, when the slurry is used for the internal electrode of a multilayer ceramic capacitor, a known ceramic powder can be appropriately selected according to the type of multilayer ceramic capacitor to be used. Examples of the ceramic powder include a calcium titanate-type oxide containing Ba and Ti, preferably barium titanate (BaTiO ₃ ).

As the ceramic powder, a ceramic powder containing barium titanate as a main component and oxides as a subcomponent can be used. Examples of the 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 calcite-titanic oxide ferroelectric ceramic powder in which Ba atoms and Ti atoms of barium titanate (BaTiO ₃ ) are replaced with other atoms such as Sn, Pb, and Zr can be used.

When used as a slurry for an internal electrode, the ceramic powder may have the same composition as the dielectric ceramic powder constituting the green sheet of the multilayer ceramic capacitor (electronic component). This can suppress the generation of cracks due to shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer in the sintering step. Such ceramic powders include, in addition to the above, oxides such as ZnO, ferrite, PZT, BaO, _Al2O3 , _Bi2O3 , _R (rare earth element) _2O3 , _TiO2 , and _Nd2O3 . In addition, the ceramic powder may be _{one kind} or _two or more kinds.

The average particle size of the ceramic powder is, for example, 0.01 μm to 0.5 μm, and ideally 0.01 μm to 0.3 μm. By making the average particle size of the ceramic powder within the above range, when used as a slurry for an internal electrode, 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), and is an average value obtained by measuring the particle sizes of multiple particles one by one from an image obtained by observation at a magnification of 50,000 times based on the SEM.

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

The content of ceramic powder relative to the total amount of conductive slurry is ideally 1% by mass to 20% by mass, and more ideally 5% by mass to 20% by mass. When the content of ceramic powder is within the above range, the conductivity and dispersibility are excellent.

(Adhesive resin)

The binder resin is not particularly limited, and known 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 butyral resins such as polyvinyl butyral. Among them, from the viewpoints of solubility in solvents and combustion decomposition, it is ideal to contain ethyl cellulose. In addition, when used as an internal electrode slurry, from the viewpoint of improving the bonding strength with the raw sheet, a butyral resin may be contained, or a butyral resin may be used alone. The adhesive resin may be one type or two or more types. In addition, from the viewpoint of improving various properties, the adhesive resin is preferably a mixture of a cellulose-based resin and a butyraldehyde-based resin. In addition, the molecular weight of the adhesive resin is, for example, 20,000 to 200,000.

Based on 100 parts by mass of the conductive powder, the content of the binder resin is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 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 slurry is preferably 0.5 mass% to 10 mass%, and more preferably 1 mass% to 6 mass%. When the content of the binder resin is within the above range, the conductivity and dispersibility are excellent.

(Organic solvent)

As an organic solvent, there is no particular limitation, and a known organic solvent that can dissolve the above-mentioned adhesive resin can be used. As an organic solvent, for example, acetate solvents such as dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, terpene solvents such as terpineol and dihydroterpineol, hydrocarbon solvents such as tridecane, nonane, cyclohexane, etc. can be listed. Among them, it is ideal to use terpene solvents such as terpineol. In addition, one organic solvent can be used, or two or more can be used.

Based on 100 parts by mass of the conductive powder, the content of the organic solvent is preferably 40 parts by mass to 100 parts by mass, and more preferably 65 parts by mass to 95 parts by mass. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

The content of the organic solvent relative to the total amount of the conductive slurry is preferably 20% by mass to 60% by mass, and more preferably 35% by mass to 55% by mass. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

(Dispersant)

The inventors of the present invention have studied various dispersants used in conductive compositions and have found that by using a first acid-based dispersant having one or more, preferably multiple, side chains consisting of hydroxyl groups and an average molecular weight of more than 500 and less than 2000 and a second acid-based dispersant having a carboxyl group other than the first acid-based dispersant, the dispersibility of the conductive powder is particularly improved and the dry film density is increased. The dispersant of this embodiment is described in further detail below.

(First acid dispersant)

The first acid-based dispersant used in this embodiment is an acid-based dispersant having an average molecular weight of more than 500 and less than 2000 and having one or more side chains composed of hydroxyl groups relative to the main chain. The conductive composition of this embodiment has a higher dry film density and improves the smoothness of the dry film surface compared to the conventional conductive composition not containing the first acid-based dispersant by containing the first acid-based dispersant.

Although the details of the reason are not clear, it is believed that by having one or more side chains composed of hydrocarbons relative to the main chain, stereo barriers can be effectively formed to inhibit the aggregation of powder materials. In addition, by setting the average molecular weight of the first acid-based dispersant within the above range, it is possible to maintain an appropriate viscosity when making a slurry according to the use of the conductive composition. In addition, the present invention is not limited to the above theory (reason).

In addition, the first acid-based dispersant preferably has a carboxyl group, and more preferably is a hydrocarbon graft copolymer with a polycarboxylic acid as the main chain. In addition, the polycarboxylic acid preferably has an ester structure.

In addition, the alkyl group as the branched chain of the first acid-based dispersant preferably has a chain structure. The alkyl group may also be an alkyl group. In addition, the alkyl group may be composed only of carbon and hydrogen, and a part of the hydrogen constituting the alkyl group may also be substituted by a substituent. In addition, the main chain and the alkyl group preferably do not have a ring structure.

(Second acid dispersant)

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

In addition, the second acid-based dispersant may also be a linear acid-based dispersant. That is, the second acid-based dispersant may have a linear structure, but does not have a branched chain composed of a hydrocarbon group relative to the main chain. In this case, the molecular weight of the second acid-based dispersant is preferably 5000 or less, and may be 250 or more and 1400 or less. In addition, the second acid-based dispersant preferably contains an alkyl group having a carbon number of 10 or more and 20 or an alkenyl group having a carbon number of 10 or more and 20 or less. In addition, the molecular weight of the second acid-based dispersant is preferably smaller than that of the first acid-based dispersant. By using the second acid-based dispersant as described above together with the first acid-based dispersant, the density of the dry film can be increased, and the smoothness of the dry film surface can be further improved.

In addition, the second acid-based dispersant may also be an acid-based dispersant with a branched chain. In this case, the second acid-based dispersant is preferably an acid-based dispersant with a molecular weight of 250 to 1400. In addition, the second acid-based dispersant may be a dicarboxylic acid. In addition, the second acid-based dispersant with a branched chain is preferably an alkyl group with a carbon number of 15 to 100 or an alkenyl group with a carbon number of 15 to 100, more preferably an alkyl group with a carbon number of 15 to 50 or an alkenyl group with a carbon number of 15 to 50, and further preferably an alkyl group with a carbon number of 15 to 25 or an alkenyl group with a carbon number of 15 to 25. In addition, the molecular weight of the ideal second acid-based dispersant is smaller than that of the first acid-based dispersant. By using the second acid-based dispersant as described above together with the first acid-based dispersant, the density of the dry film can be increased and the smoothness of the dry film surface can be further improved.

For example, each acid-based dispersant can be selected from commercially available products and can satisfy the above-mentioned characteristics. In addition, the acid-based dispersant can be manufactured using a conventionally known manufacturing method to satisfy the above-mentioned characteristics.

(Content ratio of dispersant)

For example, the first acid-based 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 the second acid-based dispersant is contained in an amount of 0.01 to 2 parts by mass based on 100 parts by mass of the conductive powder. When the content of the dispersant is within the above range, compared with the case where the same amount of the first acid-based dispersant is contained alone, the dispersibility of the conductive powder is improved, the smoothness of the dry electrode surface after coating is more excellent, and the dry film density is further improved, and the viscosity of the conductive slurry can also be adjusted to an appropriate range. In addition, sheet erosion and poor peeling of green sheets can be suppressed.

In addition, within the above range, the content of the first acid-based dispersant can be less than 1 part by mass, or less than 0.5 parts by mass. Even if the content of the first acid-based dispersant is small, it can have a higher dispersibility by using the second acid-based dispersant. In addition, sheet erosion and poor peeling of the green sheet caused by the residual dispersant can be further suppressed.

In addition, based on 100 parts by mass of the conductive powder, the lower limit of the content of the second acid-based dispersant is preferably 0.3 parts by mass or more, and may 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 surface of the dry film can be further improved. In addition, from the perspective of having a higher dry film density and further suppressing sheet erosion and poor peeling of the raw sheet caused by the residue of the dispersant, the upper limit of the content of the second acid-based dispersant can be 1.5 parts by mass or less, and may be 1.2 parts by mass or less. In addition, from the perspective of further improving the dry film density, the content of the second acid-based dispersant can be more than the content of the first acid-based dispersant.

In addition, the total amount of the acidic dispersant relative to the total amount of the conductive slurry is preferably 3% by mass or less. The upper limit of the content of the dispersant is preferably 2% by mass or less, and more preferably 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 preferably 0.05% by mass or more. When the content of the dispersant is within the above range, the viscosity of the conductive slurry can be adjusted to an appropriate range, and sheet erosion and poor peeling of the green sheet can be suppressed.

In addition, the conductive slurry may contain dispersants other than the above-mentioned acidic dispersants within the range that does not hinder the effect of the present invention. As dispersants other than the above-mentioned, the conductive slurry may contain, for example, acidic dispersants including higher fatty acids and polymeric surfactants, alkaline dispersants, amphoteric surfactants, and polymeric dispersants, etc., and more preferably, alkaline dispersants. In addition, these dispersants may be used alone or in combination of two or more.

When containing a dispersant other than an acid-based dispersant, the content (total content) of the dispersant as a whole, including the acid-based dispersant mainly added, is preferably 0.01 to 3 parts by mass, based on 100 parts by mass of the conductive powder, and may be 2.5 to 2.0 parts by mass, or 1.5 parts by mass.

(Conductive slurry)

The conductive slurry of this embodiment can be produced by mixing (stirring and kneading) the above-mentioned materials. Specifically, it can be produced by preparing the above-mentioned components and stirring and kneading them using a mixer.

The above materials can be mixed at the same time. For example, conductive powder, dispersant and organic solvent can be mixed in advance to make conductive powder slurry. In this way, the dispersant can be pre-coated on the surface of the conductive powder. If the dispersant is pre-coated on the surface of the conductive powder, even when the conductive slurry is mixed with other materials, the conductive powder will not agglomerate and maintain a fully dispersed state, and a uniform conductive slurry can be easily obtained.

As a conductive powder slurry (/dispersant applied to the surface of the conductive powder), for example, the conductive powder is mixed with a dispersant in an amount of 0.01 mass parts or more and less than 5 mass parts, preferably 0.1 mass parts or more and less than 3 mass parts, to prepare (/apply).

In addition, for example, ceramic powder, dispersant, and organic solvent may be mixed in advance to prepare ceramic powder slurry. In this way, the dispersant can be pre-coated on the ceramic powder. If the dispersant is pre-coated on the surface of the ceramic powder, even when the ceramic powder is mixed with other materials to produce a conductive slurry, the ceramic powder will not agglomerate and maintain a fully dispersed state, and a uniform conductive slurry can be easily obtained.

As a ceramic powder slurry (/application of a dispersant to ceramic powder), for example, the dispersant is mixed in an amount of 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, with respect to 100 parts by mass of the conductive powder to prepare (/application).

Alternatively, the binder resin may be dissolved in an organic solvent for the carrier to produce an organic carrier, and conductive powder, ceramic powder, organic carrier and dispersant may be added to the organic solvent for the slurry, and then stirred and kneaded using a mixer to produce a conductive slurry.

In addition, among the organic solvents, the organic solvent used as the carrier is preferably the same solvent as the organic solvent used to adjust the viscosity of the conductive slurry in order to make the organic carrier have good fusion properties. The content of the organic solvent used as the carrier is, for example, 5 to 80 parts by mass based on 100 parts by mass of the conductive powder. In addition, the content of the organic solvent used as the carrier is preferably 10 to 40% by mass relative to the total amount of the conductive slurry.

The viscosity of the conductive slurry is preferably 10 Pa.s or more and 50 Pa.s or less 24 hours after the conductive slurry is prepared. The viscosity of the conductive slurry can be measured using a B-type viscometer manufactured by Brookfield at 10 rpm (shear rate = 4 sec ^-1 ).

In addition, after screen printing the conductive slurry, the dry film density (DFD) of the dried film obtained is preferably more than 5.0 g/cm ³ , more preferably more than 5.5 g/cm ³ , and particularly preferably more than 5.6 g/cm ^3. In addition, the upper limit of the dry film density is not particularly limited, and for example, it can 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 nickel metal: 9.8 g/cm ³ )

In addition, when a 20 mm square dry film with a film thickness of 1 μm to 3 μm is produced by screen printing a conductive slurry and drying it at 120°C in the atmosphere for 1 hour, the surface roughness Ra (arithmetic mean roughness) is preferably 0.045 μm or less, and more preferably 0.04 μm or less. In addition, the lower limit of the surface roughness Ra (arithmetic mean roughness) is preferably a flat surface, and there is no special limit, 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 preferably less than 0.4μm. In addition, the lower limit of the surface roughness Ra (arithmetic mean roughness) is preferably a flat surface, and there is no particular limit, but it is a value exceeding 0 and the smaller the value, the better.

Conductive slurry can be suitably used in electronic parts such as multilayer ceramic capacitors. Multilayer ceramic capacitors have a dielectric layer formed using a dielectric green sheet and an internal electrode layer formed using a conductive slurry.

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

[Electronic parts]

Hereinafter, the implementation forms of the electronic components of the present invention are described with reference to the drawings. In the drawings, the components are sometimes appropriately represented in a schematic manner or with a changed scale. In addition, the positions and directions of the components are described with reference to the XYZ orthogonal coordinate system shown in FIG. 1, etc. In the 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 conductive slurry of this embodiment described above. FIG. 1A and FIG. 1B are diagrams showing a multilayer ceramic capacitor 1 as an example of an electronic component of this embodiment. The multilayer ceramic capacitor 1 has a multilayer body 10 in which dielectric layers 12 and internal electrode layers 11 are alternately stacked, and an external electrode 20. The multilayer ceramic capacitor 1 is formed using the conductive slurry of this embodiment described above.

The following is a description of a method for manufacturing a multilayer ceramic capacitor using the above-mentioned conductive slurry. First, a conductive slurry is printed on a dielectric layer composed of a ceramic green sheet and dried to form a dry film. After a plurality of dielectric layers having the dry film on the upper surface are laminated by pressing to obtain a laminate, the laminate is fired to be integrated, thereby preparing a ceramic laminate 10 in which internal electrode layers 11 and dielectric layers 12 are alternately laminated. Thereafter, a pair of external electrodes are formed at both ends of the ceramic laminate 10 to manufacture a multilayer ceramic capacitor 1. A more detailed description is given below.

First, a ceramic green sheet as an unfired ceramic sheet is prepared. As the ceramic 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 specified ceramic raw material powder such as barium titanium oxide is coated on a supporting film such as a PET film in a sheet shape and dried to remove the solvent. In addition, there is no particular limitation on the thickness of the dielectric layer composed of the ceramic green sheet, but from the perspective of the miniaturization of the multilayer ceramic capacitor, it is ideally 0.05μm or more and 3μm or less.

Next, prepare a plurality of sheets with dry films formed by printing (applying) the above-mentioned conductive slurry on one surface of the ceramic green sheet by a known method such as screen printing and drying. In addition, from the perspective of the requirement for thinning the internal electrode layer 11, the thickness of the conductive slurry (dry film) after printing is preferably less than 1μm after drying.

Next, the ceramic green sheet is peeled off from the supporting film, and after being laminated in a manner in which a dielectric layer composed of the ceramic green sheet and a dry film formed on one surface of the dielectric layer are alternately arranged, a laminate is obtained by heating and pressurizing. In addition, a protective ceramic green sheet without a conductive slurry coating may be further arranged on both sides of the laminate.

Next, after the laminate is cut into pieces of a predetermined size to form a green wafer, the green wafer is subjected to a debinder treatment and fired in a reducing gas environment, thereby manufacturing a ceramic laminate 10. In addition, the gas environment in the debinder treatment is preferably an atmosphere or a _N2 gas environment. The temperature during the debinder treatment is, for example, 200°C to 400°C. In addition, the holding time of the above temperature during the debinder treatment is preferably 0.5 hours to 24 hours. In order to suppress oxidation of the metal used in the internal electrode layer, sintering is performed in a reducing gas environment. The temperature during sintering of the laminate is, for example, 1000° C. to 1350° C., and the temperature is maintained for, for example, 0.5 hour to 8 hours.

By firing the green sheet, the organic binder in the green sheet is completely removed and the ceramic raw material powder is fired, thereby forming a ceramic dielectric layer 12. 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 form an internal electrode, thereby forming a laminated ceramic sintered body in which multiple layers of dielectric layers 12 and internal electrode layers 11 are alternately stacked. In addition, from the perspective of bringing oxygen into the interior of the dielectric layer to improve reliability and suppressing reoxidation of the internal electrode, the laminated ceramic sintered body after firing can be annealed.

Next, a pair of external electrodes 20 are provided on the manufactured multilayer ceramic sintered body, thereby manufacturing a multilayer ceramic capacitor 1. For example, the external electrode 20 has an external electrode layer 21 and an electroplated layer 22. The external electrode layer 21 is electrically connected to the internal electrode layer 11. In addition, as a material for the external electrode 20, for example, copper, nickel or alloys thereof can be used. In addition, as electronic components, electronic components other than multilayer ceramic capacitors can also be used.

[Implementation Example]

The present invention is described in detail below based on embodiments and reference examples, but the present invention is not limited to the embodiments in any way.

[Evaluation method]

(Dry film density)

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

(Surface roughness)

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

[Materials used]

(Conductive powder)

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

(Adhesive resin)

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

(Dispersant)

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

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

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 graft copolymer with polycarboxylic acid as the main chain was used (equivalent to the first acid-based dispersant), and (v) in Example 13, an acid-based dispersant E having an average molecular weight of 230 as an acid-based dispersant having two carboxyl groups and a branched chain relative to the main chain was used.

(Organic solvent)

As an organic solvent, terpineol (terpene solvent) was used.

(Implementation Example 1)

The conductive powder (Ni powder) was 100 parts by mass, an organic carrier containing an adhesive resin obtained by mixing EC resin and PVB resin at a ratio of 2:1 was 50 parts by mass, an acid dispersant A as the first acid dispersant was 0.5 parts by mass, and an acid dispersant C as the second acid dispersant was 1 part by mass. An organic solvent was added to make the above mixed material 85.5% by mass to prepare a conductive slurry for evaluation. The types of dispersants used in the conductive slurry are shown in Table 1.

In addition, the obtained conductive slurry was used to prepare a dry film by the method described in the above evaluation method, and the dry film density and the surface roughness of the dry film were evaluated by the above method. The evaluation results are shown in Table 1.

(Examples 2 to 13)

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

(Refer to Examples 1~3)

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

【Table 1】

(Evaluation results)

The results in Table 1 show that the conductive slurries containing the first acid-based dispersant and the second acid-based dispersant in Examples 1 and Examples 4 to 13 have higher dry film density and smaller and smoother surface roughness than the conductive slurry of Reference Example 1 having the same content of the first acid-based dispersant and not containing the second acid-based dispersant.

In addition, in the conductive slurries of Examples 2 and 3 manufactured 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, the dry film density was higher and the dry film surface roughness (Ra and Rt) was smaller, as in the other examples.

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 to 2.0 parts by mass, in particular, in the conductive slurry of Examples 6 and 7 in which the content of the second acid-based dispersant was 0.3 parts by mass or more, the surface roughness (Ra and Rt) of the dried film was further reduced, and the film had higher smoothness (i.e., satisfying Ra of 0.045 μm or less and Rt of 0.4 μm or less).

On the other hand, in the conductive slurry of Reference Example 2, in which the content of the first acid-based dispersant alone is the same as that of the dispersants of Examples 1, 8 to 10 (1.5 parts by mass), although the dry film density is improved, it is lower than that of these Examples, and the improvement in smoothness (especially the reduction in Rt) is not sufficient.

In addition, in the conductive slurry of Reference Example 3, in which the content of the second acid-based dispersant alone is the same as that of Examples 1, 8 to 10 (1.5 parts by mass), similarly to Reference Example 2, although the dry film density is improved, the dry film density is lower than that of these Examples, and the improvement in smoothness (especially the reduction in Rt) is not sufficient.

In addition, in the conductive slurry of Example 12 and Example 13, which use a dispersant with a branched chain and a molecular weight of more than 1400 or a molecular weight of less than 250 as the second acid-based dispersant, although the dry film density is improved compared with Comparative Example 2, the reduction of the dry film surface roughness (Ra and Rt) is not sufficient compared with other examples. Therefore, from the perspective of further improving the smoothness, it is ideal to use an acid-based dispersant with a linear chain structure such as Example 1, or an acid-based dispersant with a molecular weight of more than 250 and less than 1400 and a branched chain such as Example 10 and Example 11.

In addition, the technical scope of the present invention is not limited to the embodiments described in the above-mentioned embodiments. For example, the conductive slurry used for printing electrodes, wiring, etc. on electronic parts can directly use the conductive slurry prepared in the embodiment, but in order to improve the adhesion with the dielectric layer, it can also contain ceramic powder. It has been confirmed that the inclusion of ceramic powder does not hinder the dispersibility of the conductive slurry. Therefore, the conductive slurry of this embodiment can also be flexibly used as a conductive slurry for electrodes such as internal electrodes of multilayer ceramic capacitors.

【Industrial Utilization】

The conductive slurry of this embodiment has excellent dispersibility, so the dry film density and dry film surface smoothness after coating are very excellent, and it can be particularly suitable for use as a raw material for internal electrodes of multilayer ceramic capacitors as chip parts of electronic devices such as mobile phones and digital devices that are becoming smaller and smaller.

In addition, one or more of the requirements described in the above embodiments may be omitted. In addition, the requirements described in the above embodiments may be combined appropriately. In addition, as long as the law permits, the disclosure contents of all documents cited in the above embodiments are cited and made part of the description in this specification. In addition, as long as the law permits, the contents of Japanese Patent Application No. 2019-175455, which is a Japanese patent application, are cited and made part of the description in this specification.

1: Multilayer ceramic capacitors

10: Ceramic laminate

11: Internal electrode layer

12: Dielectric layer

20: External electrode

21: External electrode layer

22: Electroplating

Claims (16)

A conductive composition comprises conductive powder and a dispersant, wherein the dispersant comprises a first acidic dispersant and a second acidic dispersant, wherein the first acidic dispersant is an acidic dispersant having an average molecular weight of more than 500 and less than 2000 and having one or more side chains composed of hydrocarbon groups relative to the main chain, and the second acidic dispersant is an acidic dispersant having a carboxyl group other than the first acidic dispersant; after screen printing the conductive slurry containing the conductive composition, the dry film density of the dried film obtained by drying exceeds 5.0 g/cm ³ . The conductive composition as described in claim 1, wherein the second acid-based dispersant is a linear acid-based dispersant. The conductive composition as described in claim 1, wherein the second acid-based dispersant is an acid-based dispersant having a branched chain and a molecular weight of not less than 250 and not more than 1400. A conductive composition as described in any one of claims 1 to 3, wherein the first acid-based dispersant has a carboxyl group. The conductive composition as described in claim 1, wherein the first acid-based dispersant is a hydrocarbon graft copolymer with polycarboxylic acid as the main chain. The conductive composition as described in claim 1, 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 to 2 parts by mass, and based on 100 parts by mass of the conductive powder, the second acid-based dispersant is contained in an amount of 0.3 parts by mass to 2 parts by mass. The conductive composition as described in claim 1, wherein the conductive powder contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu and alloys thereof. The conductive composition as described in claim 1, wherein the average particle size of the conductive powder is greater than 0.05 μm and less than 1.0 μm. A conductive slurry, characterized in that the conductive slurry contains a conductive composition as described in any one of claims 1 to 8, a binder resin and an organic solvent. The conductive slurry as described in claim 9, wherein the conductive slurry further contains ceramic powder. The conductive slurry as described in claim 10, wherein the ceramic powder contains a calcium-titanium oxide. The conductive slurry as described in claim 10 or 11, wherein the average particle size of the ceramic powder is greater than 0.01 μm and less than 0.5 μm. The conductive slurry as described in claim 9, wherein the binder resin contains at least one of a cellulose resin, an acrylic resin, and a butyral resin. The conductive slurry as described in claim 9, wherein the conductive slurry is used for the internal electrode of a laminated ceramic part. An electronic component, characterized in that the electronic component is formed using a conductive slurry as described in any one of claims 9 to 13. A multilayer ceramic capacitor, characterized in that: the multilayer ceramic capacitor has at least a laminated body formed by laminating a dielectric layer and an internal electrode, and the internal electrode is formed using the conductive slurry as described in claim 14.

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