Conductive paste, electronic components, and multilayer ceramic capacitors

Abstract

To provide a conductive paste etc. with excellent dispersibility.SOLUTION: A conductive paste includes a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent, and the dispersant includes an acid-based dispersant having a molecular weight of more than 500 and less than 2000, and the acid-based dispersant has one or more branched chains consisting of a hydrocarbon group.SELECTED DRAWING: Figure 1

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 reducing the thickness of these dielectric layers and internal electrode layers, it is possible to achieve smaller size and higher capacitance.

[0003] Multilayer ceramic capacitors are manufactured, for example, as follows. First, 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 barium titanate (BaTiO) and a binder resin, and then dried to form a dry film. This dry film and the dielectric green sheet are alternately stacked and integrated by heat and pressure to form a pressed body. This pressed body is cut, subjected to an organic binder removal process in an oxidizing or inert atmosphere, and then fired to obtain a fired chip (laminate). Next, a paste for external electrodes is applied to both ends of the fired chip (laminate), and after firing, the surfaces of the external electrodes are nickel-plated or the like to obtain a multilayer ceramic capacitor.

[0004] Generally, the conductive paste used to form the internal electrodes contains conductive powder, ceramic powder, binder resin, and organic solvent. The conductive paste may also contain a dispersant to improve the dispersibility of the conductive powder. With the recent trend toward thinner internal electrode layers, the particle size of the conductive powder also tends to become smaller. When the particle size of the conductive powder is small, the specific surface area of ​​the particle surface increases, which increases the surface activity of the conductive powder (metal powder), which may result in a decrease in dispersibility and a decrease in viscosity characteristics.

[0005] Therefore, attempts have been made to improve the viscosity characteristics of conductive pastes over time. For example, Patent Document 1 describes a conductive paste containing at least a metal component, an oxide, a dispersant, and a binder resin, in which the metal component is Ni powder whose surface composition has a specific composition ratio, the dispersant has an acid site number of 500 to 2000 μmol / g, and the binder resin has an acid site number of 15 to 100 μmol / g. According to Patent Document 1, this conductive paste is said to have good dispersibility and viscosity stability.

[0006] Furthermore, Patent Document 2 describes a conductive paste for internal electrodes that is composed of conductive powder, resin, organic solvent, co-materials of ceramic powder mainly composed of BaTiO3, and an aggregation inhibitor, wherein the content of the aggregation inhibitor is 0.1% by weight or more and 5% by weight or less, and the aggregation inhibitor is a tertiary amine or secondary amine represented by a specific structural formula. According to Patent Document 2, this conductive paste for internal electrodes inhibits aggregation of the co-material components, has excellent long-term storage properties, and enables the thinning of multilayer ceramic capacitors.

[0007] On the other hand, when thinning the internal electrode layer, a high density is required for the dried film obtained by printing a conductive paste on the surface of a dielectric green sheet and drying it. For example, Patent Document 3 proposes an ultrafine metal powder slurry containing an organic solvent, a surfactant, and ultrafine metal particles, where the surfactant is oleoyl sarcosine, the ultrafine metal powder is contained in the ultrafine metal powder slurry at 70 mass% to 95 mass% and the surfactant is contained at more than 0.05 mass parts and less than 2.0 mass parts per 100 mass parts of the ultrafine metal powder. Patent Document 3 claims that by preventing aggregation of the ultrafine particles, an ultrafine metal powder slurry can be obtained that is free of aggregated particles and has excellent dispersibility and dry film density. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-216244 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-149457 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-063441 Summary of the Invention [Problem to be solved by the invention]

[0009] As electrode patterns and dielectric layers have become thinner in recent years, smoother electrode surfaces are required that are free from surface roughness caused by coarse particles formed by agglomeration of conductive powder in order to maintain accurate clearances between each electrode pattern.

[0010] In view of the above circumstances, an object of the present invention is to provide a conductive paste in which the dispersibility of the conductive powder and the ceramic powder is further improved. [Means for solving the problem]

[0011] A first aspect of the present invention provides a conductive paste comprising a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent, wherein the dispersant comprises an acid-based dispersant, and the acid-based dispersant has an average molecular weight of more than 500 and not more than 2000, and has one or more branched chains consisting of hydrocarbon groups attached to the main chain.

[0012] The acid dispersant is preferably an acid dispersant having a carboxyl group, and more preferably a hydrocarbon graft copolymer having a polycarboxylic acid backbone. The acid dispersant is preferably contained in an amount of 0.01 to 5 parts by mass relative to 100 parts by mass of the conductive powder. The dispersant preferably further contains a basic dispersant. The basic dispersant is preferably one or a mixture of two selected from aliphatic amines and polyether amines. The basic dispersant is preferably contained in an amount of 0.01 to 3 parts by mass relative to 100 parts by mass of the conductive powder. 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 to 1.0 μm. The ceramic powder preferably contains a perovskite-type oxide. The ceramic powder preferably has an average particle size of 0.01 μm to 0.5 μm. 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 internal electrodes of a multilayer ceramic component.

[0013] In a second aspect of the present invention, there is provided an electronic component formed using the conductive paste.

[0014] 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. [Effects of the Invention]

[0015] The conductive paste of the present invention improves the dispersibility of the powder materials, such as conductive powder and ceramic powder, and improves the smoothness of the dried electrode surface after application. Furthermore, the electrode pattern of an electronic component such as a multilayer ceramic capacitor formed using the conductive paste of the present invention exhibits excellent printability of the conductive paste even when forming thin electrodes, and can have a precise, uniform width and thickness. [Brief explanation of the drawings]

[0016] [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 INVENTION

[0017] The conductive paste of this 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.

[0018] (conductive powder) The conductive powder is not particularly limited, and known metal powders can be used. Examples of the conductive powder include powders of one or more elements selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. Among these, powders of Ni or its alloys (hereinafter sometimes referred to as "Ni powder") are preferred from the viewpoints of conductivity, corrosion resistance, and cost. Examples of Ni alloys that can be used include alloys of Ni with at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd. The Ni content in the Ni alloy is, for example, 50% by mass or more, preferably 80% by mass or more. Furthermore, the Ni powder may contain several hundred ppm of the element S to suppress rapid gas generation due to partial thermal decomposition of the binder resin during binder removal.

[0019] 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 in pastes for internal electrodes of thin-film multilayer ceramic capacitors (multilayer ceramic components), and for example, the smoothness and density of the dried film are improved. The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the number-average value obtained by measuring the particle size of each of multiple particles in an image observed with the SEM at 10,000x magnification.

[0020] 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 conductivity and dispersibility are excellent.

[0021] (ceramic powder) The ceramic powder is not particularly limited, and when used in a paste for internal electrodes of a multilayer ceramic capacitor, a known ceramic powder is appropriately selected depending on the type of multilayer ceramic capacitor to be used. Examples of the ceramic powder include perovskite oxides containing Ba and Ti, and preferably barium titanate (BaTiO).

[0022] The ceramic powder may be composed primarily of barium titanate and secondary oxides, such as oxides of one or more elements selected from the group consisting of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and rare earth elements.

[0023] Furthermore, the ceramic powder may be, for example, a perovskite-type oxide ferroelectric ceramic powder in which the Ba atoms or Ti atoms of barium titanate (BaTiO3) are substituted with other atoms such as Sn, Pb, or Zr.

[0024] When used as an internal electrode paste, the ceramic powder may have the same composition as the dielectric ceramic powder constituting the dielectric green sheets of a multilayer ceramic capacitor (electronic component). This prevents cracks from occurring at the interface between the dielectric layer and the internal electrode layer during the sintering process due to a shrinkage mismatch. Examples of such ceramic powders include perovskite oxides containing Ba and Ti, as well as oxides such as ZnO, ferrite, PZT, BaO, Al2O3, Bi2O3, R (rare earth element)2O3, TiO2, and Nd2O3. One type of ceramic powder may be used, or two or more types may be used.

[0025] The average particle size of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, and preferably 0.01 μm or more and 0.3 μm or less. When the average particle size of the ceramic powder is in the above range, when used as an internal electrode paste, a sufficiently fine, thin, and uniform internal electrode can be formed. The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the number-average value obtained by measuring the particle size of each of multiple particles in an image observed with the SEM at a magnification of 50,000 times.

[0026] 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.

[0027] The content of the ceramic powder is preferably 1% by mass or more and 20% by mass or less, and more preferably 3% by mass or more and 20% by mass or less, based on the total amount of the conductive paste.

[0028] (binder resin) The binder resin is not particularly limited, and known resins can be used. Examples of binder resins include cellulose-based resins such as methyl cellulose, ethyl cellulose, ethylhydroxyethyl cellulose, and nitrocellulose, acrylic resins, and butyral-based resins such as polyvinyl butyral. Among them, it is preferable to contain ethyl cellulose from the viewpoints of solubility in solvents and combustion decomposition properties. Furthermore, when used in an internal electrode paste, a butyral-based resin may be contained or 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. Furthermore, it is preferable to use a mixture of a cellulose-based resin and a butyral-based resin as the binder resin from the viewpoint of improving various properties. Furthermore, the molecular weight of the binder resin is, for example, about 20,000 to 200,000.

[0029] 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, relative to 100 parts by mass of the conductive powder.

[0030] 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.

[0031] (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 organic solvents include acetate-based solvents such as dihydroterpineol 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. Among these, terpene-based solvents such as terpineol are preferred. One or more organic solvents may be used.

[0032] 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 conductivity and dispersibility are excellent.

[0033] 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.

[0034] (dispersant) The inventors have investigated various dispersants for use in conductive pastes and found that using an acid-based dispersant with an average molecular weight greater than 500 and less than 2000 and having one or more hydrocarbon-based branched chains on the main chain improves the dispersibility of the powder materials (conductive powder and ceramic powder) contained in the conductive paste and improves the smoothness of the dried film surface. While the exact reasons for this are unclear, it is believed that the hydrocarbon-based branched chains in the acid-based dispersant effectively create steric hindrance, suppressing the aggregation of the powder materials, and the specific molecular weight allows the acid-based dispersant to maintain a viscosity suitable for the conductive paste. The acid-based dispersant used in this embodiment will be described in more detail below.

[0035] The acid dispersant has one or more, preferably a plurality of, branched chains made of hydrocarbon groups on the main chain, and preferably has a carboxyl group, and is more preferably a hydrocarbon graft copolymer having a polycarboxylic acid main chain.

[0036] The molecular weight of the acid dispersant is more than 500 and not more than 2000. When the molecular weight is within the above range, the dispersibility of the conductive powder and ceramic powder is excellent, and the density and smoothness of the dried film surface are excellent.

[0037] The acid-based dispersant may be selected from commercially available products that satisfy the above-mentioned properties, or may be produced using a conventionally known production method so as to satisfy the above-mentioned properties.

[0038] The acid dispersant is preferably contained in an amount of 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, per 100 parts by mass of the conductive powder. When the content of the acid dispersant is within the above range, the dispersibility of the conductive powder and ceramic powder and the smoothness of the dried film surface are improved. In addition, the viscosity of the conductive paste can be adjusted within an appropriate range, thereby suppressing sheet attack and poor peeling of the green sheet.

[0039] The lower limit of the content of the acid-based dispersant may be more than 0.1 parts by mass or more than 0.5 parts by mass relative to 100 parts by mass of the conductive powder. When the lower limit of the content of the acid-based dispersant is within the above range, the dispersibility of the conductive powder and ceramic powder and the smoothness of the dried film surface are superior.

[0040] The upper limit of the content of the acidic dispersant may be 1.5 parts by mass or less, or may be 1 part by mass or less, per 100 parts by mass of the conductive powder. Even when the upper limit of the content of the acidic dispersant is within the above range, the dispersibility of the conductive powder and ceramic powder and the smoothness of the dried film surface are sufficiently excellent, and sheet attack and peeling problems of the green sheet can be suppressed.

[0041] The acid dispersant is preferably contained in an amount of 3 mass% or less relative to the total amount of the conductive paste. The upper limit of the content of the acid dispersant is preferably 2 mass% or less, more preferably 1 mass% or less. The lower limit of the content of the acid dispersant is not particularly limited, but is, for example, 0.01 mass% or more, preferably 0.05 mass% or more. When the content of the acid dispersant is within the above range, the viscosity of the conductive paste can be adjusted to an appropriate range, and sheet attack and poor peeling of the green sheet can be suppressed.

[0042] The conductive paste according to this embodiment may further contain a basic dispersant as a dispersant. The type of basic dispersant is not particularly limited, but it is more preferable to use one or more basic dispersants selected from aliphatic amines and polyether amines.

[0043] The basic dispersant is preferably contained in an amount of 0.01 to 3 parts by mass, more preferably 0.01 to 1 part by mass, and even more preferably 0.05 to 1 part by mass, per 100 parts by mass of the conductive powder. When the content of the basic dispersant is within the above range, the viscosity of the conductive paste can be adjusted to an appropriate range, while the dispersibility of the conductive powder and ceramic powder and the smoothness of the dried film surface can be further improved. Furthermore, sheet attack and peeling problems of the green sheet can be further suppressed.

[0044] Furthermore, for example, even if the acid-based dispersant is contained in an amount of 1 part by mass or less per 100 parts by mass of the conductive powder, by containing 0.01 parts by mass or more and 0.3 parts by mass or less, preferably 0.01 parts by mass or more and 0.2 parts by mass or less, of the basic dispersant, the dispersibility of the conductive powder and ceramic powder and the smoothness of the dried film can be excellent, and the viscosity of the conductive paste can be adjusted to an appropriate range.

[0045] The basic dispersant is preferably contained in an amount of 2% by mass or less based on the total amount of the conductive paste. The upper limit of the content of the basic dispersant is preferably 1.5% by mass or less, more preferably 1% by mass or less. The upper limit of the content of the basic dispersant may be 0.5% by mass or less, or may be 0.2% by mass or less. The lower limit of the content of the basic dispersant is not particularly limited, but may be, for example, 0.01% by mass or more, preferably 0.02% by mass or more, or may be 0.05% by mass or more. When the content of the basic dispersant is within the above range, the viscosity of the conductive paste can be adjusted to an appropriate range, while the dispersibility of the conductive powder and ceramic powder and the smoothness of the dried electrode surface after application can be further improved. Furthermore, sheet attack and poor peeling of the green sheet can be further suppressed.

[0046] The conductive paste may contain a dispersant other than the above-mentioned acidic dispersant or basic dispersant, provided that the effects of the present invention are not impaired. Examples of dispersants other than the above include acidic dispersants containing higher fatty acids and polymeric surfactants, amphoteric surfactants, and polymeric dispersants. These dispersants may be used alone or in combination.

[0047] When a dispersant other than the above-mentioned acid-based dispersant or base-based dispersant is added, the total content of the dispersants is preferably 0.01 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the conductive powder. The total content of the dispersants may be 5 parts by mass or less, 3 parts by mass or less, or even 1 part by mass or less. By including the above-mentioned acid-based dispersant, the conductive paste according to this embodiment can achieve superior dispersibility, smoothness, and paste viscosity, even when the total content of the dispersants is within the above-mentioned range.

[0048] (Conductive paste) The method for producing the conductive paste of this embodiment is not particularly limited, and any conventionally known method can be used. The conductive paste can be produced, for example, by mixing (stirring and kneading) the above-mentioned components (conductive powder, ceramic powder, dispersant, binder resin, organic solvent, etc.). The device used for mixing (stirring and kneading) is not particularly limited, and for example, a three-roll mill, a ball mill, a mixer, etc. can be used.

[0049] The above materials may be mixed simultaneously, or, for example, the conductive powder, some or all of the dispersant, and some of the organic solvent may be mixed in advance to prepare a conductive powder slurry, and then the remaining materials may be mixed. This allows the dispersant to be applied to the surface of the conductive powder in advance. If the dispersant is applied in advance to the surface of the conductive powder, the conductive powder will remain well dispersed without agglomeration even when mixed with other materials to produce a conductive paste, making it easier to obtain a uniform conductive paste.

[0050] The conductive powder slurry may be prepared, for example, by mixing 0.01 to less than 5 parts by mass, preferably 0.1 to 3 parts by mass, of dispersant with 100 parts by mass of conductive powder. The contents of the dispersant and organic solvent in the conductive powder slurry can be adjusted appropriately depending on the particle size and content of the conductive powder slurry. The method for producing the conductive powder slurry is not particularly limited, and a general kneading method can be used.

[0051] Alternatively, for example, ceramic powder, a portion of the dispersant, and a portion of the organic solvent may be mixed in advance to prepare a ceramic powder slurry, and then the remaining materials may be mixed in. This allows the dispersant to be applied to the ceramic powder in advance. If the dispersant is applied in advance to the surface of the ceramic powder, the ceramic powder will remain well dispersed without agglomeration when mixed with other materials to produce a conductive paste, making it easier to obtain a uniform conductive paste.

[0052] The ceramic powder slurry may be prepared, for example, by mixing 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, of a dispersant with respect to 100 parts by mass of ceramic powder. The contents of the dispersant and organic solvent in the ceramic powder slurry can be adjusted appropriately depending on the particle size and content of the ceramic powder. The method for producing the ceramic powder slurry is not particularly limited, and a general kneading method can be used.

[0053] The viscosity of the conductive powder slurry and ceramic powder slurry used to prepare the conductive paste is practically acceptable as long as it is approximately 120 Pa·S or less. The viscosity of the conductive powder slurry and ceramic powder slurry can be adjusted by the amount of organic solvent contained. When the above-mentioned acid-based dispersant is used as the dispersant, it has excellent dispersibility for the conductive powder and ceramic powder, so large amounts of organic solvent are not required to adjust the slurry viscosity. This shortens the drying time when preparing the internal electrodes and reduces the problem of residual organic solvent.

[0054] Alternatively, a binder resin may be dissolved in an organic solvent for a vehicle to prepare an organic vehicle, and then conductive powder, ceramic powder, the organic vehicle, and a dispersant may be added to the organic solvent for a paste, followed by stirring and kneading with a mixer to prepare a conductive paste.

[0055] Furthermore, among the organic solvents, it is preferable to use the same organic solvent for the vehicle 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 per 100 parts by mass of the conductive powder. Furthermore, 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.

[0056] The conductive paste preferably has a viscosity of 10 Pa·s or more and 50 Pa·s or less 24 hours after production.

[0057] In addition, the dry film density (DFD) of the dried film obtained by printing and drying the conductive paste is 5.0 g / cm 3 It is preferable that the density is greater than 5.3 g / cm 3 More preferably, it is 5.5 g / cm or more. 3 More preferably, 5.6 g / cm 3 The upper limit of the dry film density (DFD) is not particularly limited, but is preferably 6.5 g / cm. 3 It may be the following:

[0058] Furthermore, when 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 0.04 μm or less, more preferably 0.03 μm or less. The lower limit of the surface roughness Ra (arithmetic mean roughness) is not particularly limited, and a flat surface is preferred, but a value above 0 and a smaller value is preferred.

[0059] The Rt (maximum cross-sectional height) of the above-mentioned dry film is preferably 0.4 μm or less, more preferably 0.3 μm or less. The lower limit of the surface roughness Ra (arithmetic mean roughness) is not particularly limited, and the surface is preferably flat, but a value exceeding 0 and a smaller value is preferable.

[0060] 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.

[0061] In a multilayer ceramic capacitor (electronic component), 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 a multilayer ceramic device manufactured using the conductive paste of this embodiment, sheet attack and peeling failure of the green sheet are suppressed even when the thickness of the dielectric green sheet is, for example, 3 μm or less.

[0062] [Electronic Components] Hereinafter, embodiments of electronic components and the like of the present invention will be described with reference to the drawings. The drawings may be used in schematic form or with a different scale, as appropriate. The positions and directions of components will be described with reference to an XYZ Cartesian coordinate system, as shown in FIG. 1, as appropriate. In this XYZ Cartesian coordinate system, the X and Y directions are horizontal, and the Z direction is vertical (up-down).

[0063] The electronic component according to this embodiment is formed using the conductive paste of this embodiment described above. Figures 1A and 1B are diagrams showing a multilayer ceramic capacitor 1, which is an example of the electronic component according to this embodiment. The multilayer ceramic capacitor 1 includes a laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately stacked, and external electrodes 20.

[0064] A method for manufacturing a multilayer ceramic capacitor 1 having internal electrode layers 11 formed using the above-mentioned conductive paste will be described below. First, the conductive paste is printed on a dielectric green sheet and dried to form a dry film. Next, a plurality of dielectric green sheets having this dry film on their upper surfaces are laminated by pressure bonding and then fired to form a fired multilayer ceramic body (laminate 10) that will become the ceramic capacitor body. After that, a pair of external electrodes 20 is formed on both ends of the laminate 10, thereby manufacturing the multilayer ceramic capacitor 1. A more detailed description will be given below.

[0065] First, a dielectric green sheet (ceramic green sheet), which is an unfired ceramic sheet, is prepared. Examples of this dielectric green sheet include a dielectric layer paste obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a predetermined ceramic raw material powder such as barium titanate, and then coating the paste on a support film such as a PET film in a sheet form and drying it to remove the solvent. The thickness of the dielectric layer made of the dielectric green sheet is not particularly limited, but is preferably 0.05 μm or more and 3 μm or less in view of the demand for miniaturization of the multilayer ceramic capacitor 1.

[0066] Next, the above-mentioned conductive paste is printed and applied to one side of this dielectric green sheet by a known method such as screen printing, and then dried to form a dry film, to prepare multiple sheets. Note that the printing method for the conductive paste may be other than screen printing, and can be appropriately selected depending on the line width, thickness, production speed, etc. of the electrode pattern to be formed. Note that the thickness of the printed conductive paste (dry film) after drying is preferably 1 μm or less from the viewpoint of the requirement for thin internal electrode layers 11.

[0067] Next, the dielectric green sheets are peeled off from the support film, and the dielectric green sheets and the conductive paste (dry film) formed on one side thereof are stacked alternately, and then a laminate (compressed body) is obtained by heat and pressure treatment. Note that a configuration may also be adopted in which protective dielectric green sheets not coated with conductive paste are further placed on both sides of the laminate.

[0068] Next, the laminate is cut to a predetermined size to form green chips, and the green chips are then subjected to a binder removal treatment and fired in a reducing atmosphere to produce a fired laminated ceramic body (laminate 10). The binder removal treatment is preferably performed in air or an N2 gas atmosphere. The temperature during the binder removal treatment is, for example, 200°C or higher and 400°C or lower. The temperature is preferably maintained 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 11. The temperature during firing of the laminate 10 is, for example, 1000°C or higher and 1350°C or lower, and the temperature is preferably maintained for 0.5 hours or higher and 8 hours or lower during the firing treatment.

[0069] By firing the green chip, the organic binder in the dielectric green sheet is completely removed, and the ceramic raw material powder is fired to form the ceramic dielectric layer 12. Also, the organic vehicle in the dried film is removed, and the nickel powder or the alloy powder mainly composed of nickel is sintered or melted and integrated to form the internal electrode layer 11, and a multilayer ceramic fired body (laminate 10) is formed in which a plurality of dielectric layers 12 and internal electrode layers 11 are alternately stacked. Note that, from the viewpoint of taking oxygen into the dielectric layer 12 to increase reliability and suppressing reoxidation of the internal electrode layer 11, the fired multilayer ceramic fired body (laminate 10) may be subjected to an annealing treatment.

[0070] Then, a pair of external electrodes 20 is provided on the produced fired laminated ceramic body (laminate 10), thereby producing a multilayer ceramic capacitor 1. For example, the external electrodes 20 include 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 electrodes 20. Note that, electronic components other than a multilayer ceramic capacitor can also be used. [Example]

[0071] EXAMPLES 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.

[0072] [Evaluation method] (Dispersibility of conductive powder slurry) Conductive powder slurries for evaluation were prepared from conductive powder, dispersant, and organic solvent, and their viscosity was measured to evaluate dispersibility. Conductive powder slurries for evaluation were prepared using the formulation described in Test 1 below, and the viscosity was measured one hour after preparation using a Brookfield B-type viscometer at 10 rpm (shear rate = 4 sec -1 ) conditions. If the dispersibility of the conductive powder slurry is insufficient, the conductive powder (powder material) will aggregate to form agglomerated particles, and the viscosity of the conductive powder slurry will increase due to the influence of these agglomerated particles. Therefore, the lower the viscosity of the conductive powder slurry, the better the dispersibility.

[0073] (Dispersibility of ceramic powder slurry) A ceramic powder slurry for evaluation was prepared from ceramic powder, a dispersant, and an organic solvent, and its viscosity was measured to evaluate dispersibility. A ceramic powder slurry for evaluation was prepared according to the formulation described in Test 1 below, and the viscosity was measured one hour after preparation using a Brookfield B-type viscometer at 10 rpm (shear rate = 4 sec -1) conditions. If the dispersibility of the ceramic powder slurry is insufficient, the ceramic powder (powder material) will aggregate to form agglomerated particles, increasing the viscosity of the ceramic powder slurry. Therefore, the lower the viscosity of the ceramic powder slurry, the better the dispersibility.

[0074] (Dispersibility of conductive paste: viscosity) Conductive paste was prepared, and the viscosity after 24 hours was measured using a Brookfield B-type viscometer at 10 rpm (shear rate = 4 sec -1 ) conditions. If the dispersibility of the conductive paste is insufficient, the conductive powder and ceramic powder (powder material) will aggregate to form agglomerated particles, increasing the viscosity of the conductive paste. Therefore, the lower the viscosity of the conductive paste within the viscosity range suitable for printing, the better the dispersibility.

[0075] (Dry film density) The conductive paste was placed on a PET film and spread 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 dry film, which was then cut into four 2.54 cm (1 inch) square pieces. The PET film was then peeled off, and the thickness and weight of each of the four dry films were measured to calculate the dry film density (average value).

[0076] (surface roughness) The conductive paste was applied to a 2.54 cm (1 inch) square piece of heat-resistant tempered glass. By printing the film and drying it in air at 120°C for 1 hour, a film measuring 20mm square and 1-3μm thick is obtained. The surface roughness Ra (arithmetic mean roughness) and Rt (maximum cross-sectional height) of the dried film were measured in accordance with the standard JIS B0601-2001.

[0077] [Materials used] (conductive powder) As the conductive powder, Ni powder (SEM average particle size: 0.2 μm) was used.

[0078] (ceramic powder) Barium titanate (BaTiO3; SEM average particle size 0.05 μm) was used as the ceramic powder.

[0079] (binder resin) Ethyl cellulose resin and polyvinyl butyral resin (PVB resin) were used as binder resins. An organic vehicle was prepared in advance by dissolving 50% by mass of ethyl cellulose resin and 50% by mass of polyvinyl butyral resin in terpineol (total amount of binder resin: 100% by mass), and this organic vehicle was used when producing the conductive paste.

[0080] (dispersant) As the acid dispersant, the following acid dispersants A to E were used. Acid-based dispersants A and B: Hydrocarbon-based graft copolymers with a polycarboxylic acid backbone, with average molecular weights of 1500 (acid-based dispersant A) and 800 (acid-based dispersant B), respectively. Acid Dispersants C and D: Average molecular weights are 370 (Acid Dispersant C) and 230 (Acid Dispersant D), respectively, and contain a hydrocarbon group and two carboxyl groups. Acid-based dispersant E: An acid-based dispersant with an average molecular weight of 350, a linear hydrocarbon group (not branched), and one carboxyl group (an acid-based dispersant used in conventional conductive pastes).

[0081] As the basic dispersant, the following basic dispersants F and G were used. Base-based dispersant F: Polyetheramine-based dispersant (polyoxyethylene laurylamine) Base-based dispersant G: Aliphatic amine-based dispersant (rosin amine)

[0082] (organic solvent) Terpineol (a terpene-based solvent) was used as the organic solvent.

[0083] (Test 1) [Dispersibility of conductive powder slurry] Conductive powder slurries for evaluation were prepared containing 100 parts by mass of conductive powder (Ni powder), 0.2 parts by mass of dispersant, and 34 parts by mass of organic solvent (terpineol), and the dispersibility (viscosity) was evaluated using the method described above. Acid-based dispersants A to E were used as dispersants. The evaluation results for each acid-based dispersant are shown in Table 1.

[0084] [Dispersibility of ceramic powder slurry] A ceramic powder slurry for evaluation was prepared containing 100 parts by mass of ceramic powder (barium titanate), 0.6 parts by mass of dispersant, and 33 parts by mass of organic solvent (terpineol), and the dispersibility (viscosity) was evaluated using the method described above. Acid-based dispersants A to E were used as dispersants. The evaluation results for each acid-based dispersant are shown in Table 1.

[0085] [Table 1]

[0086] As shown in Table 1, acid-based dispersants A and B, which have an average molecular weight exceeding 500, produced conductive powder slurries with lower viscosities and exhibited better dispersibility than the conventionally used acid-based dispersant E. On the other hand, acid-based dispersants C and D, which have an average molecular weight of 500 or less, produced conductive powder slurries with higher viscosities and exhibited lower dispersibility than the conventionally used acid-based dispersant E.

[0087] (Test 2) Conductive pastes were prepared by the following method and evaluated in more detail.

[0088] [Example 1] A conductive paste was prepared by mixing 50% by mass of Ni powder, 3.8% by mass of ceramic powder, a total of 6% by mass of binder resin consisting of ethyl cellulose resin and polyvinyl butyral resin (ethyl cellulose resin:polyvinyl butyral resin (mass ratio) = 1:1), 0.05% by mass of acid-based dispersant B, and the remainder consisting of terpineol, based on the total amount of conductive paste (100% by mass). The dispersibility (viscosity), dry film density, and surface roughness of the dry film of the prepared conductive paste were evaluated using the methods described above. The evaluation results are shown in Table 2. It should be noted that Example 1 is a reference example.

[0089] [Examples 2 to 6] Conductive pastes were prepared under the same conditions as in Example 1, except that the type and content of the acid dispersant were changed to the amounts shown in Table 2. The viscosity, dry film density, and surface roughness of the prepared conductive pastes were evaluated using the methods described above. The evaluation results are shown in Table 2.

[0090] [Examples 7 to 9] Conductive pastes were prepared under the same conditions as in Example 1, except that acidic dispersant B and basic dispersant F were added as dispersants in the amounts shown in Table 3. The viscosity, dry film density, and surface roughness of the prepared conductive pastes were evaluated using the methods described above. The evaluation results are shown in Table 3.

[0091] [Examples 10 to 13] Conductive pastes were prepared under the same conditions as in Example 2, except that, in addition to acidic dispersant B, basic dispersant F or basic dispersant G was added in the amounts shown in Table 4. The viscosity, dry film density, and surface roughness of the prepared conductive pastes were evaluated using the methods described above. The evaluation results are shown in Table 4.

[0092] [Comparative Example 1] A conductive paste was prepared under the same conditions as in Example 1, except that the dispersant was changed to acid-based dispersant E. The viscosity, dry film density, and surface roughness of the prepared conductive paste were evaluated using the methods described above. The evaluation results are shown in Table 2. Comparative Example 2 A conductive paste was prepared under the same conditions as in Example 3, except that the dispersant was changed to acid-based dispersant E. The viscosity, dry film density, and surface roughness of the prepared conductive paste were evaluated using the methods described above. The evaluation results are shown in Tables 2 to 4. Comparative Example 3 A conductive paste was prepared under the same conditions as in Example 3, except that the dispersant was changed to acid-based dispersant C. The viscosity, dry film density, and surface roughness of the prepared conductive paste were evaluated using the methods described above. The evaluation results are shown in Table 2. Comparative Example 4 A conductive paste was prepared under the same conditions as in Example 2, except that the dispersant was changed to acid-based dispersant E. The viscosity, dry film density, and surface roughness of the prepared conductive paste were evaluated using the methods described above. The evaluation results are shown in Table 4.

[0093] [Table 2]

[0094] [Table 3]

[0095] [Table 4]

[0096] (Evaluation results) When compared with the conductive paste of the comparative example in which the acid-based dispersants C and E were used in the same amounts as those used in the examples, it was confirmed that the conductive paste of the examples had a lower viscosity and better dispersibility, improved dry film density, and a smoother dry film surface.

[0097] The technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments. One or more of the requirements described in the above-mentioned embodiments may be omitted. The requirements described in the above-mentioned embodiments may be combined as appropriate. Furthermore, to the extent permitted by law, the disclosures of all documents cited in the above-mentioned embodiments are incorporated by reference and are included as part of the description in this document. [Industrial Applicability]

[0098] The conductive paste of the present invention has improved dispersibility, dry film density after application, and dry film surface smoothness, and can be suitably used as a raw material for internal electrodes of multilayer ceramic capacitors, which are chip components in electronic devices such as mobile phones and digital devices that are becoming increasingly miniaturized. [Explanation of symbols]

[0099] 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

1. A conductive paste comprising a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent, the dispersant comprises an acid-based dispersant; the acid dispersant is a hydrocarbon graft copolymer having a polycarboxylic acid main chain, an average molecular weight of more than 500 and not more than 2000, and having one or more branched chains composed of hydrocarbon groups on the main chain; The acid-based dispersant is contained in an amount of 0.2 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the conductive powder. Conductive paste.

2. The conductive paste according to claim 1 , wherein the dispersant further comprises a basic dispersant.

3. The conductive paste according to claim 2 , wherein the basic dispersant is one or more selected from the group consisting of aliphatic amines and polyether amines.

4. The conductive paste according to claim 2 , wherein the basic dispersant is contained in an amount of 0.01 parts by mass or more and 3 parts by mass or less relative to 100 parts by mass of the conductive powder.

5. The conductive paste according to any one of claims 1 to 4, wherein the conductive powder contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof.

6. The conductive paste according to any one of claims 1 to 5, wherein the conductive powder has an average particle size of 0.05 µm or more and 1.0 µm or less.

7. The conductive paste according to any one of claims 1 to 6, wherein the ceramic powder contains a perovskite oxide.

8. The conductive paste according to any one of claims 1 to 7, wherein the ceramic powder has an average particle size of 0.01 µm or more and 0.5 µm or less.

9. The conductive paste according to any one of claims 1 to 8, wherein the binder resin includes at least one of a cellulose-based resin, an acrylic-based resin, and a butyral-based resin.

10. The conductive paste according to any one of claims 1 to 9, which is used for internal electrodes of multilayer ceramic parts.

11. An electronic component formed using the conductive paste according to any one of claims 1 to 10.

12. The laminate has at least a laminate of dielectric layers and internal electrode layers, A multilayer ceramic capacitor, wherein the internal electrode layers are formed using the conductive paste according to any one of claims 1 to 10.

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