Electroconductive paste, electronic component, and laminated ceramic capacitor

Abstract

To provide an electroconductive paste having a reduced number of projections present in a dry film.SOLUTION: Provided is an electroconductive paste that contains an electroconductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent. The dispersant contains an amino acid dispersant represented by general formula (1) in an amount of 0.01-4 pts.mass (inclusive) with respect to 100 pts.mass of the electroconductive powder, and an amine dispersant represented by a primary amine having a linear hydrocarbon group with 12 to 22 carbon atoms in an amount of 0.01-4 pts.mass (inclusive) with respect to 100 pts.mass of the electroconductive powder. (In general formula (1), R1 represents a linear hydrocarbon group having 10 to 20 carbon atoms).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a conductive paste, an electronic component, and a multilayer ceramic capacitor. [Background technology]

[0002] As electronic devices such as mobile phones and digital devices become smaller and more powerful, there is a demand for smaller electronic components, including multilayer ceramic capacitors, with higher capacitance. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked, and by thinning these dielectric layers and internal electrode layers, it is possible to achieve smaller size and higher capacitance.

[0003] For example, a multilayer ceramic capacitor is manufactured as follows. First, barium titanate (BaTiO 3 A conductive paste for internal electrodes is printed (applied) in a predetermined electrode pattern onto the surface of a dielectric green sheet containing a dielectric powder such as ethylenediaminetetraacetate (EPO) and a binder resin, and then dried to form a dry film. Next, the dry film and the dielectric green sheet are alternately stacked and integrated by heat and pressure bonding to form a compressed body. This compressed body is cut, and an organic binder removal process is performed in an oxidizing atmosphere or an inert atmosphere, and then fired to obtain a fired chip. Next, a paste for external electrodes is applied to both ends of the fired chip, and after firing, nickel plating or the like is performed on the surface of the external electrodes to obtain a multilayer ceramic capacitor.

[0004] Generally, the conductive paste used to form the internal electrode layer contains a conductive powder, a ceramic powder, a binder resin, and an organic solvent. The conductive paste may also contain a dispersant to improve the dispersibility of the conductive powder and the like. In recent years, the thickness of the internal electrode layer has become thinner, and the conductive powder also tends to become smaller in particle size. When the particle size of the conductive powder is small, the specific surface area of ​​the particle surface becomes large, so that the surface activity of the conductive powder (metal powder) becomes high, the dispersibility decreases, and the powders tend to aggregate with each other, forming aggregates. If aggregates exist in the conductive paste, convex parts due to the aggregates are formed on the internal electrode layer, and these convex parts may penetrate the green sheet and cause short circuit defects.

[0005] For example, Patent Document 1 describes the use of nickel powder with an average particle size of 0.2 μm or less to suppress short circuit defects. Even if agglomerates are generated, it is said that it is possible to reduce short circuit defects that penetrate the green sheet because convex parts of the internal conductor layer are unlikely to be formed. Patent Document 1 also describes that by filtering the conductive paste through a filter with an opening of 5 μm or less, agglomerated particles of nickel powder can be removed, the smoothness of the printed internal conductor layer can be obtained, and short circuit defects that penetrate the green sheet can be reduced. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-197019 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in a multilayer ceramic capacitor using a conventional conductive paste, as the electrode pattern becomes thinner, short-circuit defects in the multilayer ceramic capacitor increase, which may cause a problem of reduced reliability.

[0008] According to the investigations of the present inventors, it has been found that, for example, as described in the above Patent Document 1, even if the average particle size of the nickel powder used in the manufacturing process of the conductive paste is set to 2 μm or less, or the conductive paste is filtered with a filter, it may not be possible to sufficiently suppress short-circuit defects in the multilayer ceramic capacitor.

[0009] Therefore, the inventors conducted further investigation and newly discovered that one of the factors causing the above-mentioned problems associated with thinning of the electrode pattern is tiny protrusions that appear on the dried film after printing the conductive paste.

[0010] In other words, if a considerable number of protrusions are present on the dry film, when the dry film and the dielectric green sheets are alternately laminated in the production of a multilayer ceramic capacitor, or when the film thickness is reduced during lamination, these tiny protrusions may cause punch-through into adjacent layers, which may result in reduced reliability such as short circuits in the multilayer ceramic capacitor.

[0011] Furthermore, according to the investigations of the present inventors, it has become clear that the occurrence of the above-mentioned minute protrusions is difficult to detect by ordinary roughness evaluation of a dry film.

[0012] Based on the above findings, an object of the present invention is to provide a conductive paste having a reduced number of protrusions present on a dried film. [Means for solving the problem]

[0013] In a first aspect of the present invention, there is provided a conductive paste comprising a conductive powder, a ceramic powder, a dispersant, a binder resin and an organic solvent, wherein the dispersant comprises an amino acid-based dispersant represented by the following general formula (1) in an amount of 0.01 parts by mass or more and 4 parts by mass or less relative to 100 parts by mass of the conductive powder, and an amine-based dispersant represented by the following general formula (2) in an amount of 0.01 parts by mass or more and 4 parts by mass or less relative to 100 parts by mass of the conductive powder.

[0014] [ka]

[0015] (In the general formula (1), R 1 represents a chain hydrocarbon group having 10 to 20 carbon atoms.

[0016] [ka]

[0017] (In the general formula (2), R 2 represents a chain hydrocarbon group having 12 to 22 carbon atoms.

[0018] In addition, the dispersant further contains an amine-based dispersant represented by the following general formula (3) in an amount of 0.01 parts by mass or more and 4 parts by mass or less per 100 parts by mass of the conductive powder, and preferably contains the conductive powder in an amount of 40% by mass or more and 60% by mass or less with respect to the entire conductive paste.

[0019] [ka]

[0020] (In the general formula (3), R 3 represents an alkyl group, an alkenyl group, or an alkynyl group having 8 to 16 carbon atoms; R 4 represents an oxyethylene group, an oxypropylene group, or a methylene group; R 5 represents an oxyethylene group or an oxypropylene group, R 4 and R 5 may be the same or different. In addition, the N atom and R 4 and R 5 It does not bond directly to the O atom in the ring, and Y is a number from 0 to 2, and Z is a number from 1 to 2.)

[0021] In addition, in the general formula (1), R 1It is preferable that represents a linear hydrocarbon group having 10 to 20 carbon atoms. The dispersant is preferably contained in an amount of 0.01% by mass or more and 4% by mass or less with respect to the entire conductive paste. The conductive powder preferably contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. The conductive powder preferably has an average particle size of 0.05 μm or more and 1.0 μm or less. The ceramic powder preferably contains a perovskite-type oxide. The ceramic powder preferably has an average particle size of 0.01 μm or more and 0.5 μm or less. The binder resin preferably contains at least one of a cellulose-based resin, an acrylic-based resin, and a butyral-based resin. The conductive paste is preferably for use in an internal electrode of a multilayer ceramic component.

[0022] In a second aspect of the present invention, there is provided an electronic component formed using the above-mentioned conductive paste.

[0023] In a third aspect of the present invention, there is provided a multilayer ceramic capacitor having at least a laminate in which dielectric layers and internal electrodes are laminated, the internal electrodes being formed using the above-mentioned conductive paste. Effect of the Invention

[0024] The conductive paste according to the present invention produces a small number of minute protrusions on the dried film after printing, and therefore the conductive paste according to the present invention can be suitably used for, for example, thin-film electrodes. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a perspective view and a cross-sectional view showing a multilayer ceramic capacitor according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The conductive paste of the present embodiment contains a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent. Each component will be described in detail below.

[0027] (conductive powder) The conductive powder is not particularly limited, and a metal powder can be used, for example, a powder of one or more selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. Among these, from the viewpoints of conductivity, corrosion resistance, and cost, a powder of Ni or its alloy is preferable. As the Ni alloy, for example, an alloy of Ni and at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd (Ni alloy) can be used. The Ni content in the Ni alloy is, for example, 50 mass% or more, preferably 80 mass% or more. In addition, the Ni powder may contain about several hundred ppm of S in order to suppress rapid gas generation due to partial thermal decomposition of the binder resin during the binder removal process.

[0028] The average particle size of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.5 μm or less. When the average particle size of the conductive powder is within the above range, it can be suitably used as an internal electrode paste for a thin multilayer ceramic capacitor, and for example, the smoothness and density of the dry film are improved. The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the average value obtained by measuring the particle size of each of a plurality of particles from an image observed with an SEM at a magnification of 10,000 times.

[0029] The content of the conductive powder is preferably 30% by mass or more and less than 70% by mass, more preferably 40% by mass or more and 60% by mass or less, based on the total amount of the conductive paste. When the content of the conductive powder is within the above range, the conductive paste has excellent conductivity and dispersibility.

[0030] (ceramic powder) The ceramic powder is not particularly limited, and for example, in the case of a paste for an internal electrode of a multilayer ceramic capacitor, a known ceramic powder is appropriately selected depending on the type of multilayer ceramic capacitor to be applied. Examples of the ceramic powder include perovskite oxides containing Ba and Ti, and preferably barium titanate (BaTiO 3 ).

[0031] The ceramic powder may be a ceramic powder containing barium titanate as a main component and an oxide as a subcomponent. The oxide may be one or more oxides selected from Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and rare earth elements. The ceramic powder may be, for example, barium titanate (BaTiO 3 Also included is a ceramic powder of a perovskite-type oxide ferroelectric in which the Ba atoms and Ti atoms of the above-mentioned compound are replaced by other atoms such as Sn, Pb, Zr, etc.

[0032] The ceramic powder in the internal electrode paste may be powder of the same composition as the dielectric ceramic powder constituting the dielectric green sheet of the multilayer ceramic capacitor. This suppresses the occurrence of cracks due to a mismatch in shrinkage at the interface between the dielectric layer and the internal electrode layer during the sintering process. In addition to the perovskite oxides containing Ba and Ti, other ceramic powders such as ZnO, ferrite, PZT, BaO, Al 2 O 3 , Bi 2 O 3 , R (rare earth elements) 2 O 3 , TiO 2 , Nd 2 O 3 The ceramic powder may be one type or two or more types.

[0033] The average particle size of the ceramic powder is, for example, 0.01 μm to 0.5 μm, preferably 0.01 μm to 0.3 μm. When the average particle size of the ceramic powder is in the above range, it is possible to form a sufficiently fine, thin, and uniform internal electrode when used as an internal electrode paste. The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the average value obtained by measuring the particle size of each of a plurality of particles from an image observed with an SEM at a magnification of 50,000 times.

[0034] 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, relative to 100 parts by mass of the conductive powder.

[0035] The content of the ceramic powder is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 20% by mass or less, based on the total amount of the conductive paste. When the content of the ceramic powder is within the above range, the conductive paste has excellent conductivity and dispersibility.

[0036] (binder resin) The binder resin is not particularly limited, and known resins can be used. Examples of the binder resin include cellulose-based resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, acrylic resins, and butyral-based resins such as polyvinyl butyral. Among them, it is preferable to contain ethyl cellulose from the viewpoint of solubility in a solvent and combustion decomposition. In addition, when used as an internal electrode paste, a butyral-based resin may be contained or a butyral-based resin may be used alone from the viewpoint of improving the adhesive strength with the dielectric green sheet. One type of binder resin may be used, or two or more types may be used.

[0037] The binder resin may be, for example, a cellulose-based resin and a butyral-based resin. When the conductive paste contains a cellulose-based resin and a butyral-based resin, the number of protrusions on the dried film tends to decrease. The content ratio of the cellulose-based resin and the butyral-based resin is not particularly limited, and is, for example, cellulose-based resin:butyral-based resin=10-90:90-10 (weight ratio, the total of the cellulose-based resin and the butyral-based resin is 100), and preferably 30-70:70-30.

[0038] The weight average molecular weight Mw of the butyral resin is not particularly limited and is, for example, 20,000 to 200,000, and preferably 30,000 to 150,000. When the weight average molecular weight Mw is within the above range, when used in a conductive paste, it is possible to reduce the number of protrusions on a dried film while providing excellent dispersibility of conductive powder and the like and providing a suitable paste viscosity.

[0039] The content of the binder resin is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the conductive powder.

[0040] The content of the binder resin is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 6% by mass or less, based on the total amount of the conductive paste. When the content of the binder resin is within the above range, the conductive paste has excellent conductivity and dispersibility.

[0041] (Organic solvent) The organic solvent is not particularly limited, and any known organic solvent capable of dissolving the binder resin can be used. Examples of the organic solvent include acetate-based solvents such as dihydroterpineyl acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, and dipropylene glycol methyl ether acetate, terpene-based solvents such as terpineol and dihydroterpineol, and hydrocarbon-based solvents such as tridecane, nonane, and cyclohexane. The organic solvent may be used alone or in combination of two or more.

[0042] The content of the organic solvent is preferably 40 parts by mass or more and 100 parts by mass or less, more preferably 65 parts by mass or more and 95 parts by mass or less, relative to 100 parts by mass of the conductive powder. When the content of the organic solvent is within the above range, the conductive powder has excellent conductivity and dispersibility.

[0043] The content of the organic solvent is preferably 20% by mass or more and 60% by mass or less, and more preferably 35% by mass or more and 55% by mass or less, based on the total amount of the conductive paste. When the content of the organic solvent is within the above range, the conductive paste has excellent conductivity and dispersibility.

[0044] (Dispersant) The conductive paste according to the present embodiment includes a dispersant. The dispersant includes an amino acid-based dispersant (amino acid-based surfactant) represented by the following general formula (1) and an amine-based dispersant (amine-based surfactant) represented by the following general formula (2). The amine-based dispersant represented by the general formula (2) is a primary amine.

[0045] [ka]

[0046] In the above general formula (1), R 1 represents a chain hydrocarbon group having 10 to 20 carbon atoms. 1 preferably represents a linear hydrocarbon group having 10 to 20 carbon atoms.

[0047] [ka]

[0048] In the above general formula (2), R 2 represents a chain hydrocarbon group having 12 to 22 carbon atoms. 2 may represent a linear hydrocarbon group having 12 to 22 carbon atoms, may be a linear alkenyl group, and may have a double bond.

[0049] As described above, the present inventors have newly discovered that one of the factors that causes the above problems associated with the thinning of the electrode pattern is the protrusions that form on the dried film after printing the conductive paste. Based on this knowledge, the present inventors have investigated various dispersants for use in the conductive paste, and have further discovered that, in particular, the conductive paste containing the amino acid-based dispersant represented by the above general formula (1) tends to easily form protrusions on the dried film, and that by combining the above dispersants, the number of protrusions present on the dried film after printing the conductive paste can be reduced.

[0050] Here, the protrusions on the dried film refer to convex portions (protrusions) formed on the dried film, and more specifically, refer to protrusions whose major axis direction (longest diameter) is 5 μm or more when the dried film obtained by filtering the obtained conductive paste, applying it, and drying it is observed from above.

[0051] Furthermore, the present inventors analyzed the components inside the protrusions (convex portions) and found that organic matter was present. For example, the above-mentioned Patent Document 1 describes the removal of aggregates by filtering the conductive paste with a filter. However, when protrusions (aggregates) caused by organic matter are present in the conductive paste, even if filtration is performed with a filter as described in Patent Document 1, aggregates larger than the mesh size of the filter pass through because the aggregates have flexibility, making it difficult to reduce the number of protrusions on the dry film. Although the details of the mechanism by which protrusions containing organic matter are generated on the dry film are unknown, for example, the following mechanism is considered.

[0052] For example, when the dispersant contains an amino acid-based dispersant represented by general formula (1), this amino acid-based dispersant may react with other components in the conductive paste to produce compounds that are insoluble in the conductive paste, which may result in protrusions on the dried film after the conductive paste is printed and dried.

[0053] In addition, as described later, when the conductive paste contains an amino acid-based dispersant represented by general formula (1) and an amine-based dispersant represented by general formula (3), the amino acid-based dispersant and the amine-based dispersant may react to generate a compound that is insoluble in the conductive paste. For example, when the conductive paste contains only the amino acid-based dispersant represented by general formula (1) and the amine-based dispersant represented by general formula (3) as dispersants, the number of protrusions on the dried film tends to increase as the content of the amine-based dispersant represented by general formula (3) increases (see the conductive pastes of Comparative Examples 1 and 2 described later).

[0054] In the conductive paste according to the present embodiment, the number of protrusions on the dry film can be reduced by including the amine-based dispersant represented by general formula (2). Although the details of the reason for this are unclear, it is considered that, for example, the amine-based dispersant represented by general formula (2) suppresses the reaction between the amino acid-based dispersant represented by general formula (1) and other components, thereby suppressing the generation of insoluble compounds, or that the amine-based dispersant reacts with the amino acid-based dispersant represented by general formula (1) and other components to improve the solubility of the product, so that the product does not exist as a mass, thereby reducing the number of protrusions on the dry film.

[0055] In the conductive paste, the amino acid dispersant represented by the general formula (1) is contained in an amount of 0.01 to 4 parts by mass, preferably 0.02 to 3 parts by mass, more preferably 0.03 to 2 parts by mass, relative to 100 parts by mass of the conductive powder. The amino acid dispersant represented by the formula (1) may be contained in an amount of 0.03 to 0.6 parts by mass, or 0.1 to 0.6 parts by mass.

[0056] When the amino acid-based dispersant represented by the general formula (1) is contained within the above range, the dry film density can be improved. Also, when the amino acid-based dispersant is increased within the above range, for example, when the amino acid-based dispersant is contained in an amount of 0.1 to 2 parts by mass, preferably 0.1 to 1.5 parts by mass, relative to 100 parts by mass of the conductive powder, the dry film density and surface roughness can be improved.

[0057] In addition, when the content of the amino acid-based dispersant represented by the general formula (1) exceeds 2 parts by mass per 100 parts by mass of the conductive powder, the drying properties deteriorate, and after the conductive paste is printed on the dielectric green sheet and dried, an undried dried film is formed. This may cause the internal electrode layer to be crushed during stacking, resulting in a deterioration in the chip shape or an increase in protrusions on the dried film.

[0058] The amino acid-based dispersant represented by the general formula (1) may be selected from commercially available products that satisfy the above-mentioned characteristics. The amino acid-based dispersant may also be produced by a conventionally known production method so as to satisfy the above-mentioned characteristics.

[0059] In the conductive paste, the amine-based dispersant represented by the general formula (2) is contained in an amount of 0.01 to 4 parts by mass, preferably 0.02 to 3 parts by mass, more preferably 0.04 to 2 parts by mass, and may be contained in an amount of 0.1 to 1 part by mass, relative to 100 parts by mass of the conductive powder. When the content of the amine-based dispersant represented by the general formula (2) is within the above range, the dispersibility can be improved and protrusions on the dried film can be effectively suppressed. When the content of the amine-based dispersant represented by the general formula (2) is greater than the above range, the drying property is deteriorated, so that after the conductive paste is printed on the dielectric green sheet and dried, it becomes an undried dried film, which may cause the internal electrode layer to be crushed during lamination, etc., and may cause the chip shape to deteriorate or the protrusions on the dried film to increase.

[0060] In addition, when the conductive paste contains both an amino acid-based dispersant represented by general formula (1) and an amine-based dispersant represented by general formula (2), the content of the amine-based dispersant represented by general formula (2) may be, in mass ratio, 0.1 to 3 times, 0.5 to 2.5 times, or 0.8 to 1.5 times the content of the amino acid-based dispersant represented by general formula (1).

[0061] Furthermore, as described later, when the conductive paste contains an amino acid-based dispersant represented by general formula (1), an amine-based dispersant represented by general formula (2), and an amine-based dispersant represented by general formula (3), the content of the amine-based dispersant represented by general formula (2) may be, in mass ratio, 0.1 to 3 times, 0.2 to 2 times, or 0.3 to 1.5 times the total content of the amino acid-based dispersant represented by general formula (1) and the amine-based dispersant represented by general formula (3).

[0062] The dispersant may be composed of an amino acid-based dispersant represented by the general formula (1) and an amine-based dispersant represented by the general formula (2), or may contain other dispersants.

[0063] For example, when the dispersant contains only the amino acid-based dispersant represented by the general formula (1) and the amine-based dispersant represented by the general formula (2), R 2 has a carbon number of 15 to 22. In this case, the content of the amine-based dispersant represented by general formula (2) may be 0.8 to 1.5 times, in terms of mass ratio, the content of the amino acid-based dispersant represented by general formula (1).

[0064] The conductive paste according to this embodiment may further contain, as a dispersant, an amine-based dispersant represented by the following general formula (3).

[0065] [ka]

[0066] In the above general formula (3), R 3 represents an alkyl group, an alkenyl group, or an alkynyl group having 8 to 16 carbon atoms; R 4 represents an oxyethylene group, an oxypropylene group, or a methylene group; R 5 represents an oxyethylene group or an oxypropylene group. 4 and R 5 may be the same or different. In addition, the N atom and R 4 and R 5 and Y is a number from 0 to 2, and Z is a number from 1 to 2.

[0067] The amine-based dispersant represented by general formula (3) is a tertiary amine or secondary amine, and has a structure in which an amine group is bonded to one or two oxyalkylene groups.

[0068] When an amine-based dispersant represented by general formula (3) is contained in addition to an amino acid-based dispersant represented by general formula (1) and an amine-based dispersant represented by general formula (2), the resulting conductive paste has excellent printability even when forming thin-film electrodes, and the electrode patterns of electronic components such as multilayer ceramic capacitors formed using this conductive paste can have precisely uniform widths and thicknesses.

[0069] In general formula (3), R 3 R represents an alkyl group, an alkenyl group, or an alkynyl group having 8 to 16 carbon atoms. 3 When the number of carbon atoms of R is within the above range, the powder in the conductive paste has sufficient dispersibility and excellent solubility in the solvent. 3 is preferably a straight-chain hydrocarbon group.

[0070] In general formula (3), R 4 represents an oxyethylene group, an oxypropylene group, or a methylene group; R 5 represents an oxyethylene group or an oxypropylene group, R 4 and R 5 may be the same or different. In addition, the N atom and R 4 and R 5 It does not bond directly to the O atom in the ring, Y is a number between 0 and 2, and Z is a number between 1 and 2.

[0071] For example, in the general formula (3), R 4 is an oxyalkylene group represented by -AO-, and when Y is 1 to 2, the O atom in the terminal oxyalkylene group is (R 4 ) Y and the adjacent H atom. Also, R 4 When R is a methylene group, 4 ) Y is -(CH 2 ) Y When Y is 1 or 2, it bonds with the adjacent H element to form a methyl group (-CH 3 ), or an ethyl group (-CH 2 -CH 3 ) is formed. Also, R5 is an oxyalkylene group represented by -AO-, the O atom in the terminal oxyalkylene group is (R 5 ) Z and bonds to the adjacent H atom.

[0072] In the general formula (3), when Y is 0, the amine-based dispersant is -R 3 and one hydrogen group, -(R 5 ) Z For example, when Y is 0 and Z is 2, the amine dispersant has an alkyl group, an alkenyl group, or an alkynyl group having 8 to 16 carbon atoms, one hydrogen group, and either a dioxyethylene group or a dioxypropylene group and an H element bonded thereto, i.e., -(AO) 2 H and a secondary amine composed of.

[0073] In addition, in the general formula (3), when Y is 1, the amine-based dispersant is -R 3 and -R 4 H and -(R 5 ) Z When Y is 2, the amine dispersant is a tertiary amine having -R 3 And, -(R 4 ) 2 H, a dioxyethylene group, a dioxypropylene group, or an ethylene group bonded to an H element -(AO) 2 H or -C 2 H 5 And, -(R 5 ) Z H and becomes a tertiary amine.

[0074] In the conductive paste, the amine-based dispersant represented by the general formula (3) may be contained in an amount of 0.01 to 4 parts by mass, preferably 0.02 to 2.5 parts by mass, more preferably 0.03 to 2 parts by mass, or 0.05 to 0.6 parts by mass, relative to 100 parts by mass of the conductive powder. When the amine-based dispersant represented by the general formula (3) is contained in the above range, the viscosity change over time can be suppressed and the viscosity stability can be improved.

[0075] In addition, when the conductive paste does not contain the amine-based dispersant represented by general formula (2) and contains only the amino acid-based dispersion represented by general formula (1) and the amine-based dispersant represented by general formula (3), the viscosity stability and dispersibility improve as the content of the amine-based dispersant represented by general formula (3) increases, but the number of protrusions on the dry film also tends to increase. However, in the conductive paste according to the present embodiment, by containing the amine-based dispersion represented by general formula (2), even when the amine-based dispersant represented by general formula (3) is contained in a large amount (for example, when the amine-based dispersant is contained in an amount of 0.5 parts by mass or more or 0.6 parts by mass or more relative to 100 parts by mass of the conductive powder), the viscosity stability and dispersibility can be improved and the occurrence of protrusions on the dry film can be suppressed.

[0076] In addition, when the content of the amine-based dispersant represented by the general formula (3) exceeds 2 parts by mass, the drying property is deteriorated, and after the conductive paste is printed on the dielectric green sheet and dried, an undried dried film is formed. This may cause the internal electrode layer to be crushed during lamination, etc., and may result in deterioration of the chip shape or an increase in protrusions on the dried film.

[0077] The amine-based dispersant represented by the general formula (3) may be selected from commercially available products that satisfy the above-mentioned characteristics. The amine-based dispersant may be produced by a conventionally known production method so as to satisfy the above-mentioned characteristics.

[0078] In the conductive paste, the total content of the dispersant is preferably 0.01 to 5 parts by mass, more preferably 0.04 to 3 parts by mass, and may be 0.2 to 2 parts by mass, relative to 100 parts by mass of the conductive powder. 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 attack and peeling failure of the dielectric green sheet can be suppressed.

[0079] The total content of the dispersant is preferably 4% by mass or less based on the total amount of the conductive paste. The upper limit of the content of the dispersant is preferably 3% by mass or less, more preferably 2% by mass or less, and may be 1% by mass or less. The lower limit of the content of the dispersant is not particularly limited, but is, for example, 0.01% by mass or more, preferably 0.05% by mass or more, and may be 0.1% 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 while suppressing sheet attack and peeling failure of the dielectric green sheet.

[0080] The conductive paste may contain a dispersant other than the amino acid-based dispersant and the amine-based dispersant as long as the effect of the present invention is not impaired. Examples of dispersants other than the above include acid-based dispersants including higher fatty acids and polymeric surfactants, cationic dispersants other than acid-based dispersants, nonionic dispersants, amphoteric surfactants, and polymeric dispersants. These dispersants may be used alone or in combination of two or more.

[0081] (Conductive paste) The method for producing the conductive paste according to the present embodiment is not particularly limited, and a conventionally known method can be used. For example, the conductive paste according to the present embodiment can be produced by preparing the above-mentioned components and stirring and kneading the components with a three-roll mill, a ball mill, a mixer, or the like. In this case, if a dispersant is applied to the surface of the conductive powder in advance, the conductive powder is sufficiently loosened without agglomeration, and the dispersant is distributed over the surface, making it easy to obtain a uniform conductive paste. In addition, the binder resin may be dissolved in an organic solvent for a vehicle to produce an organic vehicle, and then the conductive powder, ceramic powder, organic vehicle, and dispersant may be added to the organic solvent for the paste, and the conductive paste may be produced by stirring and kneading.

[0082] In addition, among the organic solvents, the organic solvent for the vehicle is preferably the same as the organic solvent for the paste that adjusts the viscosity of the conductive paste in order to improve the compatibility of the organic vehicle. The content of the organic solvent for the vehicle is, for example, 5 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the conductive powder. The content of the organic solvent for the vehicle is preferably 10% by mass or more and 40% by mass or less with respect to the total amount of the conductive paste.

[0083] Hereinafter, preferred characteristics of the conductive paste according to this embodiment will be described.

[0084] [Dry film density: DFD] After printing the conductive paste, the density of the dried film (DFD) obtained by drying is 4.8g / cm 3 It is preferable that the density exceeds 5.0 g / cm 3 More preferably, it is 5.2 g / cm or more. 3 More preferably, 5.4 g / cm 3 More preferably, the above is the case.

[0085] [Surface roughness of dry film] The conductive paste is screen-printed and dried in air at 120°C for 1 hour to produce a dried film 20 mm square and 1 to 3 μm thick. The surface roughness Ra (arithmetic mean roughness) is preferably 0.10 μm or less, or may be 0.07 μm or less, or may be 0.06 μm or less. The lower limit of the surface roughness Ra (arithmetic mean roughness) is not particularly limited, and it is preferable that the surface is flat, but a value exceeding 0 and a smaller value are preferable.

[0086] [Number of protrusions on dry film] The number of protrusions on a dry film produced using the conductive paste under the following conditions is preferably 100 or less, more preferably 50 or less, and even more preferably 20 or less. When the number of protrusions on the dry film is within the above range, short-circuit defects in electronic components such as multilayer ceramic capacitors formed using the conductive paste can be suppressed.

[0087] - Dry film manufacturing conditions The conductive paste, which has been filtered through a 6 μm mesh filter and is 1.5 cm wide and 4 cm long, is applied to a 2-inch square, 1 mm thick glass substrate with a thickness of 35 μm using an applicator, and dried at 120°C for 10 minutes to obtain a dry film. In addition, the entire surface of the applied film (1.5 cm wide x 4 cm long) is observed with a 10x lens using an optical microscope, and the number of protrusions 5 μm or larger in size is counted when viewed from above (planar view) to calculate the number of protrusions on the dry film.

[0088] The conductive paste can be suitably used in electronic components such as multilayer ceramic capacitors. A multilayer ceramic capacitor has dielectric layers formed using dielectric green sheets and internal electrode layers formed using the conductive paste.

[0089] In the multilayer ceramic capacitor, it is preferable that the dielectric ceramic powder contained in the dielectric green sheet and the ceramic powder contained in the conductive paste are powders of the same composition. In the multilayer ceramic capacitor manufactured using the conductive paste of this embodiment, even if the thickness of the green sheet is, for example, 3 μm or less, sheet attack and peeling failure of the green sheet are suppressed.

[0090] (Electronic Components) Hereinafter, embodiments of electronic components and the like of the present invention will be described with reference to the drawings. In the drawings, the components may be shown diagrammatically or at a different scale as appropriate. The positions and directions of components will be described with reference to an XYZ orthogonal coordinate system shown in FIG. 1 as appropriate. In this XYZ orthogonal coordinate system, the X and Y directions are horizontal directions, and the Z direction is vertical (up-down direction).

[0091] 1A and 1B are diagrams showing a multilayer ceramic capacitor 1, which is an example of an electronic component according to an embodiment. The multilayer ceramic capacitor 1 includes an external electrode 20 and a laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately laminated.

[0092] A method for manufacturing a multilayer ceramic capacitor using the conductive paste is described below. First, the conductive paste is printed on a dielectric layer made of a dielectric green sheet, and dried to form a dry film. A plurality of dielectric layers having this dry film on the upper surface are laminated by pressure bonding, and then fired to be integrated, thereby producing a ceramic laminate 10 (laminate 10) in which internal electrode layers 11 and dielectric layers 12 are alternately laminated. Then, a pair of external electrodes 20 is formed on both ends of the ceramic laminate 10, thereby producing a multilayer ceramic capacitor 1. A more detailed description is given below.

[0093] First, a green sheet, which is an unfired ceramic sheet, is prepared. For example, the green sheet is prepared by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a raw powder of a specific ceramic such as barium titanate, applying the dielectric layer paste to a support film such as a PET film in a sheet form, and drying to remove the solvent. The thickness of the dielectric layer made of the green sheet is not particularly limited, but is preferably 0.05 μm or more and 3 μm or less from the viewpoint of the demand for miniaturization of the multilayer ceramic capacitor.

[0094] Next, the above-mentioned conductive paste is printed (applied) on one side of the green sheet by a known method such as screen printing, and dried to form a dry film, to prepare a plurality of sheets. Note that, from the viewpoint of the requirement to make the internal electrode layer 11 thin, it is preferable that the thickness of the printed conductive paste (dry film) is 1 μm or less after drying.

[0095] Next, the green sheet is peeled off from the support film, and the dielectric layer made of the green sheet and the dry film formed on one side thereof are alternately laminated, and then a laminate (compressed body) is obtained by heat and pressure treatment. Note that a configuration in which protective green sheets not coated with the conductive paste are further arranged on both sides of the laminate (compressed body) may be adopted.

[0096] Next, the laminate (bonded body) is cut to a predetermined size to form a green chip, and then the green chip is subjected to a binder removal treatment and fired in a reducing atmosphere to produce the ceramic laminate 10. The binder removal treatment is performed in an atmosphere of air or N 2 It is preferable to use a gas atmosphere. The temperature during the binder removal treatment is, for example, 200°C or higher and 400°C or lower. It is also preferable to hold the above temperature for 0.5 hours or higher and 24 hours or lower during the binder removal treatment. The firing is performed in a reducing atmosphere to suppress oxidation of the metal used in the internal electrode layers, and the temperature during firing of the laminate (bonded body) is, for example, 1000°C or higher and 1350°C or lower, and the temperature holding time during firing is, for example, 0.5 hours or higher and 8 hours or lower.

[0097] By firing the green chip, the organic binder in the green sheet is completely removed, and the ceramic raw material powder is fired to form the ceramic dielectric layer 12. The organic vehicle in the dried film is also removed, and the nickel powder or the alloy powder mainly composed of nickel is sintered or melted and integrated to form the internal electrodes, forming the ceramic laminate 10 in which the dielectric layers 12 and the internal electrode layers 11 are alternately laminated. Note that the fired ceramic laminate 10 may be subjected to an annealing treatment from the viewpoint of taking oxygen into the dielectric layers to increase reliability and suppressing reoxidation of the internal electrodes.

[0098] A pair of external electrodes 20 is then provided on the produced ceramic laminate 10 to manufacture the multilayer 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. Note that, for example, copper, nickel, or an alloy thereof can be suitably used as the material for the external electrode 20. Note that the electronic component is not limited to a multilayer ceramic capacitor, and may be an electronic component other than a multilayer ceramic capacitor. EXAMPLES

[0099] The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to these examples.

[0100] [Evaluation method] (Number of conductive paste protrusions) A conductive paste was prepared and filtered through a filter with 6 μm openings. The filtered conductive paste was then applied to a 2-inch square, 1 mm thick glass substrate with an applicator to a thickness of 35 μm, width of 1.5 cm, and length of 4 cm, and dried at 120°C for 10 minutes to prepare a sample (dried film). Then, using an Olympus optical microscope with a 10x lens, the entire surface of the resulting dried film (1.5 cm x 4 cm) was observed from above, and the number of protrusions with a size (length in the longest axial direction) of 5 μm or more was counted. The fewer the number of protrusions, the better.

[0101] (Dry film density DFD) The conductive paste thus prepared was placed on a PET film and stretched to a length of approximately 100 mm using an applicator with a width of 50 mm and a gap of 125 μm. The resulting PET film was dried at 120°C for 40 minutes to form a dried body, which was then cut into four pieces measuring 2.54 cm (1 inch) square. After removing the PET film, the thickness and weight of each of the four dried films were measured to calculate the dry film density (average value).

[0102] (Surface roughness) The conductive paste was screen-printed onto a 2.54 cm (1 inch) square piece of heat-resistant tempered glass and dried in air at 120°C for 1 hour to produce a 20 mm square dry film with a thickness of 1 to 3 μm. The surface roughness Ra (arithmetic mean roughness) of the dry film was measured according to the JIS B0601-2001 standard.

[0103] (comprehensive evaluation) As an overall evaluation of the dried film, those with 20 or less protrusions and a surface roughness Ra of 0.1 μm or less were rated as "O", those with more than 20 but not more than 99 protrusions and a surface roughness Ra of 0.1 μm or less were rated as "△", and those with more than 100 protrusions and / or a surface roughness Ra of more than 0.1 μm were rated as "X".

[0104] [Materials used] (conductive powder) As the conductive powder, Ni powder (SEM average particle size: 0.2 μm) was used.

[0105] (ceramic powder) The ceramic powder is barium titanate (BaTiO 3 (SEM average particle size 0.10 μm) was used.

[0106] (binder resin) The binder resin used was ethyl cellulose resin (EC resin) and / or polyvinyl butyral resin (PVB resin). The binder resin was prepared as a vehicle by dissolving it in isobornyl acetate (organic solvent).

[0107] (Dispersant) The following dispersants were used: (1) As the dispersant a, in the above general formula (1), R 1 =C 17 H 33 An amino acid-based dispersant represented by (straight-chain hydrocarbon group) was used. (2) As the dispersant b, in the above general formula (2), R 2 =C 18 H 35 An amine-based dispersant represented by (straight-chain hydrocarbon group) was used. (3) As the dispersant b2, in the above general formula (2), R 2 =C 12 H 25 An amine-based dispersant represented by (straight-chain hydrocarbon group) was used. (4) As the dispersant c, in the above general formula (3), R 3 =C 12 H25 , R 4 =C 2 H 4 O, R 5 =C 2 H 4 An amine-based dispersant with O, Y=1, and Z=1 was used.

[0108] (Organic solvent) As the organic solvent, isobornyl acetate (IBA) or terpineol (TPO) was used.

[0109] [Example 1] A conductive paste was prepared by mixing 50% by mass of conductive powder, 10% by mass of ceramic powder, a total of 3% by mass of binder resin in a vehicle consisting of ethyl cellulose resin and polyvinyl butyral resin (ethyl cellulose resin: polyvinyl butyral resin = 60:40 (weight ratio)), a total of 0.62% by mass of dispersants mixed in the ratios shown in Table 1, and an organic solvent so that the total was 100% by mass, and mixing these materials. The surface roughness and number of protrusions of the dried film of the prepared conductive paste were evaluated using the methods described above. The evaluation results are shown in Table 1.

[0110] [Examples 2 to 12, Comparative Examples 1 to 3] A conductive paste was prepared under the same conditions as in Example 1, except that the content of the dispersant was changed to the amount shown in Table 1. The surface roughness, number of protrusions, etc. of the prepared conductive paste were evaluated by the above-mentioned methods. The evaluation results are shown in Table 1.

[0111] In the table, the "parts by mass" indicating the content of each dispersant is the ratio to 100 parts by mass of the conductive powder, and the "% by mass" indicating the content of each dispersant is the ratio to 100% by mass of the conductive paste.

[0112] [Table 1]

[0113] [Examples 13 to 16, Comparative Examples 3 and 4] A conductive paste was prepared under the same conditions as in Example 1, except that the type and content of each material were the types and amounts shown in Table 2. Using the prepared conductive paste, the surface roughness, number of protrusions, and the like were evaluated by the above-mentioned methods. The evaluation results are shown in Table 2. Note that Comparative Example 3 in Table 2 is the same as Comparative Example 3 in Table 1 (shown for comparison).

[0114] [Table 2]

[0115] [Evaluation Results] As shown in Table 1, the conductive pastes of the examples containing amino acid-based dispersant a, amine-based dispersant b, and amine-based dispersant c had a surface roughness Ra (arithmetic mean roughness) of 0.10 μm or less and a small number of protrusions of 100 or less on the dry film. In addition, the dry film density (DFD) of the conductive pastes of the examples was 5.5 g / cm 3 As described above, it was demonstrated that the dispersibility was excellent.

[0116] On the other hand, in the conductive pastes of Comparative Examples 1 to 3 not containing the amine-based dispersant b, the number of protrusions on the dried film increased compared to Examples 1, 4, and 7 produced under similar conditions except that the amine-based dispersant b was not contained. In addition, in the conductive paste of Comparative Example 2, since the content of the amine-based dispersant c was small, the number of protrusions on the dried film was somewhat small, but the surface roughness Ra of the dried film exceeded 0.10 μm. In addition, in the conductive paste of Comparative Example 3, since the content of the entire dispersant was sufficiently large, many protrusions were generated on the dried film, although the surface roughness Ra of the dried film was 0.10 μm or less.

[0117] Furthermore, as shown in Table 2, the conductive pastes of Examples 13 to 16 containing the amino acid-based dispersant a and the amine-based dispersant b or b2 also showed a surface roughness Ra of the dried film of 0.10 μm or less, and the number of protrusions of the dried film was as small as 100 or less. In particular, the conductive paste of Example 16 containing ethyl cellulose resin (EC) and polyvinyl butyral resin (PVB) as the binder resin showed a greater reduction in the number of protrusions of the dried film compared to the conductive paste of Example 15 (binder resin: EC only).

[0118] On the other hand, in the conductive paste of Comparative Example 4 containing only the amino acid-based dispersant a, the surface roughness Ra of the dried film exceeded 0.10 μm, and many protrusions were formed on the dried film.

[0119] The technical scope of the present invention is not limited to the aspects described in the above embodiments. One or more of the requirements described in the above embodiments may be omitted. The requirements described in the above embodiments may be combined as appropriate. In addition, to the extent permitted by law, the disclosures of all documents cited in the above embodiments are incorporated as part of the description in this text. In addition, to the extent permitted by law, the contents of Japanese Patent Application No. 2020-036584 are incorporated as part of the description in this text. [Explanation of symbols]

[0120] 1. Multilayer ceramic capacitors 10 Ceramic laminate 11 Internal electrode layer 12 Dielectric layer 20 External electrode 21 External electrode layer 22 Plating layer

Claims

[Claim 1] A conductive paste comprising a conductive powder, a ceramic powder, a dispersant, a binder resin and an organic solvent, The dispersant contains an amino acid-based dispersant represented by the following general formula (1) in an amount of 0.01 parts by mass or more and 4 parts by mass or less relative to 100 parts by mass of the conductive powder, and an amine-based dispersant represented by the following general formula (2) in an amount of 0.01 parts by mass or more and 4 parts by mass or less relative to 100 parts by mass of the conductive powder: Conductive paste. 【Chemistry 1】 (In the general formula (1), R １ represents a chain hydrocarbon group having 10 to 20 carbon atoms. 【Chemistry 2】 (In the general formula (2), R ２ represents a chain hydrocarbon group having 12 to 22 carbon atoms.

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