Conductive composition, conductive paste, electronic component, and laminated ceramic capacitor

Abstract

Provided is a conductive composition having excellent dispersibility, for example. The conductive composition includes conductive powder and a dispersant. The dispersant includes a first acidic dispersant having an average molecular weight of more than 500 and 2,000 or less and having one or more hydrocarbon groups as branched chains on a main chain, and a second acidic dispersant containing a carboxy group and being distinct from the first dispersant.

Description

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

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

[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] 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 ethylenediaminetetraacetic acid (EPO) and a binder resin, and then dried to form a dry film. The dried film and green sheets are then alternately stacked to obtain a laminate. This laminate is then integrated by heat and pressure to form a pressed body. This pressed body is then cut, subjected to an organic binder removal treatment in an oxidizing or inert atmosphere, and then fired to obtain fired chips. Next, a paste for external electrodes is applied to both ends of the fired chip, 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 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. 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 having a surface composition with 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 2, this conductive paste is said to have good dispersibility and viscosity stability.

[0006] In addition, Patent Document 2 discloses a method for manufacturing a conductive material using a conductive powder, a resin, an organic solvent, BaTiO ３ Patent Document 2 describes a conductive paste for internal electrodes that is composed of a ceramic powder co-material mainly composed of the above 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 a secondary amine represented by a specific structural formula. According to Patent Document 2, this conductive paste for internal electrodes is said to inhibit 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 for the internal electrode on the surface of a dielectric green sheet and drying it. For example, Patent Document 3 proposes a metal ultrafine powder slurry containing an organic solvent, a surfactant, and metal ultrafine particles, where the surfactant is oleoyl sarcosine, the metal ultrafine powder is contained in the metal ultrafine 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 metal ultrafine powder. According to Patent Document 3, by preventing aggregation of the ultrafine particles, a metal ultrafine powder slurry without agglomerated particles is obtained, and the metal ultrafine powder slurry has excellent dispersibility and dry film density.

[0008] JP 2015-216244 A JP 2013-149457 A JP 2006-063441 A

[0009] With the recent trend toward thinner electrode patterns and dielectric layers, there is a demand for smoother electrode surfaces and internal electrode layers with denser electrode densities than ever before, free from surface roughness caused by coarse particles formed by agglomeration of conductive powder, in order to maintain precise clearances between each electrode pattern.

[0010] In view of the above circumstances, an object of the present invention is to provide a conductive composition that has excellent dispersibility of conductive powder and a high dry film density, which is the basis for electrode density.

[0011] In a first aspect of the present invention, there is provided a conductive composition containing a conductive powder and a dispersant, wherein the dispersant comprises a first acid-based dispersant and a second acid-based dispersant, the first acid-based dispersant having 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 a main chain, and the second acid-based dispersant is an acid-based dispersant other than the first dispersant and having a carboxyl group.

[0012] The second acid-based dispersant may be a linear acid-based dispersant. The second acid-based dispersant may be a branched-chain acid-based dispersant with a molecular weight of 250 to 1400. The first acid-based dispersant preferably has a carboxyl group. The first acid-based dispersant is preferably a hydrocarbon graft copolymer with a polycarboxylic acid main chain. The first acid-based dispersant is preferably contained in an amount of 0.2 to 2 parts by mass per 100 parts by mass of the conductive powder, and the second acid-based dispersant is preferably contained in an amount of 0.3 to 2 parts by mass per 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.

[0013] In a second aspect of the present invention, there is provided a conductive paste containing the above-mentioned conductive composition, a binder resin, and an organic solvent.

[0014] The conductive paste preferably further contains a ceramic powder. The ceramic powder preferably contains a perovskite 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 internal electrodes of a multilayer ceramic component.

[0015] In a third aspect of the present invention, there is provided an electronic component formed using the conductive paste.

[0016] In a fourth 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.

[0017] The conductive composition (conductive paste) of the present invention has excellent dispersibility of the conductive powder, and therefore has a high dry film density. Furthermore, the electrode pattern of an electronic component such as a multilayer ceramic capacitor formed using the conductive paste of the present invention has excellent printability of the conductive paste even when forming a thin electrode, and can have a precisely uniform width and thickness.

[0018] FIG. 1 is a perspective view and a cross-sectional view showing a multilayer ceramic capacitor according to an embodiment.

[0019] [Conductive Composition and Conductive Paste] The conductive composition according to this embodiment contains a conductive powder and a dispersant. The conductive paste according to this embodiment contains the conductive powder and dispersant, a binder resin, and an organic solvent. The conductive paste may further contain a ceramic powder. Each component contained in the conductive powder or conductive paste will be described in detail below.

[0020] (Conductive Powder) The conductive powder is not particularly limited, and metal powders can be used. For example, powders of one or more elements selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof can be used. Among these, powders of Ni or its alloys (hereinafter, both may be collectively 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 element S to suppress rapid gas generation due to partial thermal decomposition of the binder resin during binder removal treatment.

[0021] 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-film multilayer ceramic capacitor (multilayer ceramic component), 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 average value obtained by measuring the particle size of each of a plurality of particles in an image observed with the SEM at a magnification of 10,000 times.

[0022] 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 in the above range, the conductive paste has excellent conductivity and dispersibility.

[0023] (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-type oxides containing Ba and Ti, and preferably barium titanate (BaTiO ３ )

[0024] The ceramic powder may be a ceramic powder containing barium titanate as a main component and an oxide as a secondary component. Examples of the oxide include oxides of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and one or more rare earth elements. Examples of the ceramic powder include barium titanate (BaTiO ３ Alternatively, a ceramic powder of a perovskite-type oxide ferroelectric may be used in which the Ba atoms or Ti atoms of the above-mentioned ferroelectric material are substituted with other atoms such as Sn, Pb, or Zr.

[0025] When used as an internal electrode paste, the ceramic powder may have the same composition as the dielectric ceramic powder constituting the green sheet 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 mismatch in shrinkage. Examples of such ceramic powders include, in addition to those mentioned above, ZnO, ferrite, PZT, BaO, and Al. ２ O ３ , Bi ２ O ３ , R (rare earth element) ２ O ３ , TiO ２ , Nd ２ O ３ The ceramic powder may be one type or two or more types.

[0026] The average particle size of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, 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 average value obtained by measuring the particle size of each of multiple particles from an image observed with the SEM at a magnification of 50,000 times.

[0027] 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.

[0028] 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 conductive powder is in the above range, the conductive paste has excellent conductivity and dispersibility.

[0029] (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, ethyl hydroxyethyl cellulose, and nitrocellulose; acrylic resins; and butyral-based resins such as polyvinyl butyral. Among these, ethyl cellulose is preferred from the viewpoints of solubility in solvents and combustion decomposition. When used as an internal electrode paste, a butyral-based resin may be included or used alone to improve the adhesive strength with the green sheet. One type of binder resin may be used, or two or more types may be used. A mixture of a cellulose-based resin and a butyral-based resin is preferred from the viewpoint of improving various properties. The molecular weight of the binder resin is, for example, approximately 20,000 to 200,000.

[0030] 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.

[0031] 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 in the above range, the conductive paste has excellent conductivity and dispersibility.

[0032] (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 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.

[0033] 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.

[0034] 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 in the above range, the conductive paste has excellent conductivity and dispersibility.

[0035] (Dispersant) The present inventors have investigated various dispersants for use in the conductive composition and found that the dispersibility of the conductive powder is particularly improved and the dry film density is improved by using a first dispersant containing an acid-based dispersant having one or more, preferably multiple, branched chains consisting of hydrocarbon groups and having an average molecular weight of more than 500 and not more than 2000, and a second acid-based dispersant other than the first acid-based dispersant and having a carboxyl group. The dispersant according to this embodiment will be described in more detail below.

[0036] (First Acid-Based Dispersant) The first acid-based dispersant used in this embodiment is an acid-based dispersant having an average molecular weight of more than 500 and not more than 2000, and having one or more branched chains consisting of hydrocarbon groups on the main chain. By containing the first acid-based dispersant, the conductive composition according to this embodiment has a higher dry film density and improved smoothness of the dried film surface, compared to conventional conductive compositions that do not contain the first acid-based dispersant.

[0037] Although the details of the reason for this are unclear, it is believed that the presence of one or more branched chains consisting of hydrocarbon groups in the main chain effectively forms steric hindrance, thereby suppressing aggregation of the powder material. Furthermore, by setting the average molecular weight of the first dispersant within the above range, it is possible to maintain a suitable viscosity when made into a paste depending on the application of the conductive composition. The present invention is not limited by the above theory (reason).

[0038] The first acid dispersant preferably has a carboxyl group, and more preferably is a hydrocarbon graft copolymer having a polycarboxylic acid as the main chain. The polycarboxylic acid preferably has an ester structure.

[0039] The hydrocarbon group of the branched chain of the first acid-based dispersant preferably has a chain structure. The hydrocarbon group may be an alkyl group. The alkyl group may be composed of only carbon and hydrogen, or a portion of the hydrogen atoms constituting the alkyl group may be substituted with a substituent. The main chain and the hydrocarbon group preferably do not have a ring structure.

[0040] (Second Acid-Based Dispersant) The second acid-based dispersant is an acid-based dispersant having a carboxyl group other than the first dispersant. By using the second acid-based dispersant together with the first acid-based dispersant, the conductive composition according to this embodiment can further improve the dry film density.

[0041] The second acid-based dispersant may be a straight-chain acid-based dispersant. That is, the second acid-based dispersant has a straight-chain structure and may not have a branched chain consisting of a hydrocarbon group in the main chain. In this case, the molecular weight of the second acid-based dispersant is preferably 5,000 or less, and may be 250 to 1,400. The second acid-based dispersant preferably contains an alkyl group having 10 to 20 carbon atoms or an alkenyl group having 10 to 20 carbon atoms. The second acid-based dispersant preferably has a smaller molecular weight than the first acid-based dispersant. By using the second acid-based dispersant as described above together with the first acid-based dispersant, the dry film density can be increased and the smoothness of the dry film surface can be further improved.

[0042] The second acid-based dispersant may also be a branched-chain acid-based dispersant. In this case, the second acid-based dispersant is preferably an acid-based dispersant having a molecular weight of 250 to 1400. The second acid-based dispersant may also be a dicarboxylic acid. The branched-chain second acid-based dispersant preferably contains an alkyl group having 15 to 100 carbon atoms or an alkenyl group having 15 to 100 carbon atoms, more preferably an alkyl group having 15 to 50 carbon atoms or an alkenyl group having 15 to 50 carbon atoms, and even more preferably an alkyl group having 15 to 25 carbon atoms or an alkenyl group having 15 to 25 carbon atoms. The second acid-based dispersant preferably has a smaller molecular weight than the first acid-based dispersant. By using the second acid-based dispersant as described above together with the first acid-based dispersant, the dry film density can be increased and the smoothness of the dry film surface can be further improved.

[0043] Each acid-based dispersant can be selected from commercially available products that satisfy the above-mentioned properties. Alternatively, the acid-based dispersant may be produced using a conventionally known production method so as to satisfy the above-mentioned properties.

[0044] (Dispersant Content) The first acid-based dispersant is contained in an amount of, for example, 0.2 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the conductive powder, and the second acid-based dispersant is contained in an amount of, for example, 0.01 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the conductive powder. When the dispersant content is within the above range, compared to when the same amount of the first acid-based dispersant is contained alone, the dispersibility of the conductive powder is improved, the smoothness of the dried electrode surface after application is superior, the dry film density is also improved, and the viscosity of the conductive paste can be adjusted to an appropriate range. In addition, sheet attack and poor peeling of the green sheet can be suppressed.

[0045] The content of the first acid-based dispersant may be 1 part by mass or less, or 0.5 parts by mass or less, within the above range. Even if the content of the first acid-based dispersant is small, high dispersibility can be achieved by using the second acid-based dispersant in combination. Furthermore, sheet attack and peeling problems of the green sheet caused by residual dispersant are further suppressed.

[0046] The lower limit of the content of the second acid-based dispersant is preferably 0.3 parts by mass or more, and may be 0.5 parts by mass or more, per 100 parts by mass of the conductive powder. When the lower limit of the content of the second dispersant is within the above range, the smoothness of the dried film surface can be further improved. The upper limit of the content of the second acid-based dispersant may be 1.5 parts by mass or less, or may be 1.2 parts by mass or less, from the viewpoint of achieving a higher dry film density and further suppressing sheet attack and green sheet peeling problems caused by residual dispersant. The content of the second dispersant may be greater than the content of the first dispersant, from the viewpoint of further improving the dry film density.

[0047] The total amount of the acid dispersant is preferably 3% by mass or less relative to the total amount of the conductive paste. The upper limit of the dispersant content is preferably 2% by mass or less, more preferably 1% by mass or less. The lower limit of the dispersant content is not particularly limited, but is, for example, 0.01% by mass or more, preferably 0.05% by mass or more. When the dispersant content 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.

[0048] The conductive paste may contain a dispersant other than the above-mentioned acid-based dispersant, provided that the effects of the present invention are not impaired. Examples of dispersants other than the above-mentioned dispersants include acid-based dispersants containing higher fatty acids and polymeric surfactants, basic dispersants, amphoteric surfactants, and polymeric dispersants, with basic dispersants being more preferred. These dispersants may be used alone or in combination of two or more.

[0049] When a dispersant other than an acid-based dispersant is contained, the content of the entire dispersant (total content), including the acid-based dispersant that is mainly added, is preferably 0.01 parts by mass or more and 3 parts by mass or less, and may be 2.5 parts by mass or less, 2.0 parts by mass or less, or 1.5 parts by mass or less, relative to 100 parts by mass of the conductive powder.

[0050] (Conductive Paste) The conductive paste according to this embodiment can be produced by mixing (stirring and kneading) the above-described materials. Specifically, the conductive paste can be produced by preparing the above-described components and stirring and kneading them in a mixer.

[0051] The above materials may be mixed simultaneously, or, for example, a conductive powder, a dispersant, and an organic solvent may be mixed in advance to prepare a conductive powder slurry. This allows the dispersant to be applied to the surface of the conductive powder in advance. If the dispersant is applied to the surface of the conductive powder in advance, the conductive powder remains well dispersed without agglomeration even when mixed with other materials to produce a conductive paste, making it easier to obtain a uniform conductive paste.

[0052] The conductive powder slurry ( / application of a dispersant to the surface of a conductive powder) is prepared ( / applied) by, for example, mixing 0.01 parts by mass or more and less than 5 parts by mass, preferably 0.1 parts by mass or more and 3 parts by mass or less, of a dispersant with respect to 100 parts by mass of the conductive powder.

[0053] Alternatively, for example, ceramic powder, a dispersant, and an organic solvent may be mixed in advance to prepare a ceramic powder slurry. 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 sufficiently dispersed without agglomeration when mixed with other materials to produce a conductive paste, making it easier to obtain a uniform conductive paste.

[0054] The ceramic powder slurry ( / application of a dispersant to a ceramic powder) is prepared ( / applied) by, for example, mixing 0.01 parts by mass or more and 10 parts by mass or less, preferably 0.1 parts by mass or more and 5 parts by mass or less, of a dispersant with respect to 100 parts by mass of the conductive powder.

[0055] Alternatively, a binder resin may be dissolved in an organic solvent for a vehicle to prepare an organic vehicle, and then a conductive powder, a ceramic powder, an 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.

[0056] 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 relative to 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 relative to the total amount of the conductive paste.

[0057] The viscosity of the conductive paste 24 hours after production is preferably 10 Pa s or more and 50 Pa s or less. The viscosity of the conductive paste can be measured using a Brookfield B-type viscometer at 10 rpm (shear rate = 4 sec-1).

[0058] The dry film density (DFD) of the dried film obtained by screen printing the conductive paste and then drying it was 5.0 g / cm ３ and preferably exceeds 5.5 g / cm ３ More preferably, it exceeds 5.6 g / cm ３ The upper limit of the dry film density is not particularly limited, and is, for example, 6.5 g / cm. ３ The upper limit of the dry film density is the true density of the conductive powder used (e.g., in the case of metallic nickel: 9.8 g / cm ３ ) shall not exceed.

[0059] 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 0.045 μm or less, and more preferably 0.04 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 greater than 0 and a smaller value is more preferred.

[0060] The Rt (maximum cross-sectional height) of the dry film is preferably 0.4 μm or less. The lower limit of the surface roughness Ra (arithmetic mean roughness) is not particularly limited, but the surface is preferably flat, and a value exceeding 0 and a smaller value is more preferable.

[0061] 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.

[0062] 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 defects of the green sheet are suppressed even when the thickness of the dielectric green sheet is, for example, 3 μm or less.

[0063] [Electronic Component] Hereinafter, embodiments of electronic components and the like of the present invention will be described with reference to the drawings. The drawings may be represented schematically or at a different scale as appropriate. Furthermore, the positions and directions of components will be described with reference to an XYZ Cartesian coordinate system as shown in FIG. 1 and the like as appropriate. In this XYZ Cartesian coordinate system, the X and Y directions are horizontal, and the Z direction is vertical (up-down).

[0064] The electronic component of 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 an 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. The multilayer ceramic capacitor 1 is formed using the conductive paste of this embodiment described above.

[0065] 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 ceramic green sheet and dried to form a dry film. A plurality of dielectric layers, each having this dry film on its upper surface, are laminated by pressure bonding to obtain a laminate, which is then fired and integrated to produce a ceramic laminate 10 in which internal electrode layers 11 and dielectric layers 12 are alternately laminated. A pair of external electrodes is then formed on both ends of the ceramic laminate 10 to produce a multilayer ceramic capacitor 1. This method is described in more detail below.

[0066] First, a ceramic green sheet, which is an unfired ceramic sheet, is prepared. Examples of the ceramic 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 ceramic 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 multilayer ceramic capacitors.

[0067] Next, the above-mentioned conductive paste is printed (applied) on one side of this ceramic green sheet by a known method such as screen printing, and then dried to form a dry film, to prepare a plurality of sheets. Note that, from the viewpoint of the requirement for thinning of the internal electrode layer 11, it is preferable that the thickness of the printed conductive paste (dry film) is 1 μm or less after drying.

[0068] Next, the ceramic green sheets are peeled off from the support film, and the dielectric layers made of the ceramic green sheets and the dry film formed on one side thereof are stacked alternately, followed by a heat and pressure treatment to obtain a laminate. Note that protective ceramic green sheets not coated with the conductive paste may be further placed on both sides of the laminate.

[0069] 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 the ceramic laminate 10. The binder removal treatment is performed in an atmosphere of air or N ２ It is preferable to carry out the debinding treatment in a gas atmosphere. The temperature during the debinding treatment is, for example, 200°C or higher and 400°C or lower. Furthermore, it is preferable to hold the above temperature for 0.5 hours or higher and 24 hours or lower during the debinding treatment. Furthermore, the firing is carried out in a reducing atmosphere to suppress oxidation of the metal used in the internal electrode layers, and the temperature during firing of the laminate 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.

[0070] 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 nickel-based alloy powder is sintered or melted and integrated to form internal electrodes, forming a multilayer ceramic sintered body in which multiple dielectric layers 12 and internal electrode layers 11 are alternately stacked. Note that, from the viewpoint of incorporating oxygen into the dielectric layers to increase reliability and suppressing reoxidation of the internal electrodes, the sintered multilayer ceramic sintered body may be subjected to an annealing treatment.

[0071] A pair of external electrodes 20 is then provided on the produced fired multilayer ceramic body, thereby producing the 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. Suitable materials for the external electrodes 20 include, for example, copper, nickel, or an alloy thereof. Electronic components other than multilayer ceramic capacitors may also be used.

[0072] The present invention will be described in detail below based on examples and reference examples, but the present invention is not limited to these examples.

[0073] [Evaluation Method] (Dry Film Density) The prepared 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 obtained PET film was dried at 120° C. for 40 minutes to form a dried body, which was then cut into four pieces of 2.54 cm (1 inch) square. The PET film was peeled off, and the thickness and weight of each of the four dried films were measured to calculate the dry film density (average value).

[0074] (Surface Roughness) The prepared 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 prepare a 20 mm square dry film with a film thickness of 1 to 3 µm. The surface roughness Ra (arithmetic mean roughness) and Rt (maximum cross-sectional height) of the prepared dry film were measured based on the standard of JIS B0601-2001.

[0075] [Materials Used] (Conductive Powder) Ni powder (SEM average particle size: 0.2 μm) was used as the conductive powder.

[0076] (Binder Resin) Ethyl cellulose resin (EC resin) and polyvinyl butyral resin (PVB resin) were used as the binder resin. When preparing the conductive slurry, an organic vehicle prepared in advance by dissolving 12 parts by mass of the binder resin (a 2:1 mixture of EC resin and PVB resin) in 88 parts by mass of terpineol was used.

[0077] (Dispersant) As the first acid-based dispersant, (i) Acid-based dispersant A, which is a hydrocarbon-based graft copolymer having a polycarboxylic acid main chain and an average molecular weight of 800, and (ii) Acid-based dispersant B, which is a hydrocarbon-based graft copolymer having a polycarboxylic acid main chain and an average molecular weight of 1500, were used.

[0078] Furthermore, as the second acid-based dispersants, (i) acid-based dispersant C, which is a linear dispersant having a carboxyl group and has an average molecular weight of 350, (ii) acid-based dispersant D, which is a linear dispersant having a carboxyl group and has an average molecular weight of 290, and (iii) acid-based dispersant F, which has two carboxyl groups and a branched chain relative to the main chain and has an average molecular weight of 370, were used.

[0079] Furthermore, as the second acid-based dispersant, (iv) in Example 12, an acid-based dispersant B (corresponding to the first dispersant) which is a hydrocarbon-based graft copolymer having a polycarboxylic acid main chain and an average molecular weight of 1,500 was used, and (v) in Example 13, an acid-based dispersant E which has two carboxyl groups and a branched chain on the main chain and has an average molecular weight of 230 was used.

[0080] (Organic Solvent) Terpineol (a terpene-based solvent) was used as the organic solvent.

[0081] (Example 1) 100 parts by mass of conductive powder (Ni powder) was mixed with 50 parts by mass of an organic vehicle containing a binder resin made of a 2:1 blend of EC resin and PVB resin, 0.5 parts by mass of acid-based dispersant A as a first acid-based dispersant, and 1 part by mass of acid-based dispersant C as a second acid-based dispersant, and an organic solvent was added so that the mixed material was 85.5 mass% to prepare a conductive paste for evaluation. The types of dispersants used in the conductive paste are shown in Table 1.

[0082] Furthermore, a dry film was prepared using the obtained conductive paste according to the method described in the evaluation method above, and the dry film density and surface roughness of the dry film were evaluated according to the method described above. The evaluation results are shown in Table 1.

[0083] (Examples 2 to 13) Conductive pastes were prepared under the same conditions as in Example 1, except that the dispersants were used in the combinations of type and content shown in Table 1. The dry film density and surface roughness of the dry film prepared using the conductive paste were evaluated using the above-mentioned methods. The evaluation results, along with the type and content of the acid-based dispersant used, are shown in Table 1.

[0084] (Reference Examples 1 to 3) Conductive pastes were prepared under the same conditions as in Example 1, except that the dispersants were used in the combinations of type and content shown in Table 1. The dry film density and surface roughness of the dry film prepared using the conductive paste were evaluated using the above-mentioned methods. The evaluation results are shown in Table 1, along with the type and content of the acid-based dispersant used.

[0085]

[0086] (Evaluation Results) From the results in Table 1, it was confirmed that the conductive pastes of Examples 1 and 4 to 13 containing the first acid-based dispersant and the second acid-based dispersant had higher dry film density and smaller dry film surface roughness, making them smoother, compared to the conductive paste of Reference Example 1, which had the same content of the first acid-based dispersant but did not contain the second acid-based dispersant.

[0087] In addition, the conductive pastes of Examples 2 and 3, which were manufactured under the same conditions as Example 1 except that the content of the first acid-based dispersant was changed to 0.2 parts by mass or 2.0 parts by mass, also had high dry film density and small dry film surface roughness (Ra and Rt), similar to the other Examples.

[0088] Furthermore, when comparing Examples 4 to 7 in which the content of the second acid-based dispersant was varied within the range of 0.01 parts by mass to 2.0 parts by mass, it was confirmed that the surface roughness (Ra and Rt) of the dried film was further reduced and had high smoothness (i.e., Ra: 0.045 μm or less and Rt: 0.4 μm or less) in the conductive pastes of Examples 6 and 7 in which the content of the second acid-based dispersant was 0.3 parts by mass or more.

[0089] On the other hand, in the conductive paste of Reference Example 2, in which the content of only the first acid-based dispersant was the same as the total amount of the dispersants in Examples 1 and 8 to 10 (1.5 parts by mass), although the dry film density was improved, the dry film density was lower than those in these Examples, and the improvement in smoothness (particularly the reduction in Rt) was not sufficient.

[0090] In addition, in the conductive paste of Reference Example 3, in which the content of only the second acid-based dispersant was the same as the total dispersion amount of Examples 1 and 8 to 10 (1.5 parts by mass), the dry film density was improved as in Reference Example 2, but the dry film density was lower than those of these Examples, and the improvement in smoothness (particularly the reduction in Rt) was not sufficient.

[0091] The conductive pastes of Examples 12 and 13, which used a dispersant having a branched chain and a molecular weight of more than 1400 or less than 250 as the second dispersant, had improved dry film density compared to Comparative Example 2, but did not show sufficient reduction in dry film surface roughness (Ra and Rt) compared to the other Examples. Therefore, from the viewpoint of further improving smoothness, it is preferable to use, as the second acid-based dispersant, an acid-based dispersant having a linear structure, as in Example 1, or an acid-based dispersant having a molecular weight of 250 or more and 1400 or less, and having a branched chain, as in Examples 10 and 11.

[0092] The technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments. For example, the conductive paste prepared in the examples can be used as is for printing electrodes, wiring, etc. on electronic components. However, ceramic powder may be further added to enhance adhesion with the dielectric layer. It has been confirmed that the inclusion of ceramic powder does not impair the dispersibility of the conductive paste. Therefore, the conductive paste according to this embodiment can also be used as a conductive paste for electrodes, such as internal electrodes of multilayer ceramic capacitors.

[0093] The conductive paste according to this embodiment has excellent dispersibility, and therefore has excellent dry film density and surface smoothness after application, and can be suitably used as a raw material for the 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.

[0094] Note that one or more of the requirements described in the above embodiments may be omitted. Furthermore, the requirements described in the above embodiments may be combined as appropriate. Furthermore, to the extent permitted by law, the disclosures of all documents cited in the above embodiments are incorporated by reference into this text. Furthermore, to the extent permitted by law, the contents of Japanese Patent Application No. 2019-175455 are incorporated by reference into this text.

[0095] REFERENCE SIGNS LIST 1 Multilayer ceramic capacitor 10 Ceramic laminate 11 Internal electrode layer 12 Dielectric layer 20 External electrode 21 External electrode layer 22 Plated layer

Claims

1. A conductive composition containing conductive powder and a dispersant, wherein the dispersant includes a first acid-based dispersant and a second acid-based dispersant, the first acid-based dispersant is an acid-based dispersant having an average molecular weight exceeding 500 and not exceeding 2000, and having one or more branched chains composed of hydrocarbon groups with respect to the main chain, and the second acid-based dispersant is an acid-based dispersant having a carboxyl group other than the first acid-based dispersant.

2. The conductive composition according to claim 1, wherein the second acid-based dispersant is a linear acid-based dispersant.

3. The conductive composition according to claim 1, wherein the second acid-based dispersant has a branched chain and has an acid-based dispersant with a molecular weight of 250 or more and 1400 or less.

4. The conductive composition according to any one of claims 1 to 3, wherein the first acid-based dispersant has a carboxyl group.

5. The conductive composition according to any one of claims 1 to 4, wherein the first acid-based dispersant is a hydrocarbon-based graft copolymer having a polycarboxylic acid as the main chain.

6. The first acid-based dispersant is contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder, and the second acid-based dispersant is contained in an amount of 0.3 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder. The conductive composition according to any one of claims 1 to 5.

7. The conductive composition according to any one of claims 1 to 6, wherein the conductive powder contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof.

8. The conductive composition according to any one of claims 1 to 7, wherein the conductive powder has an average particle size of 0.05 μm or more and 1.0 μm or less.

9. A conductive paste containing the conductive composition according to any one of claims 1 to 8, a binder resin, and an organic solvent.

10. The conductive paste according to claim 9, further containing ceramic powder.

11. The conductive paste according to claim 10, wherein the ceramic powder contains a perovskite-type oxide.

12. The conductive paste according to claim 10 or 11, wherein the ceramic powder has an average particle size of 0.01 μm or more and 0.5 μm or less.

13. The conductive paste according to any one of claims 9 to 12, wherein the binder resin contains at least one of a cellulose-based resin, an acrylic-based resin, and a butyral-based resin.

14. The conductive paste according to any one of claims 9 to 13, which is for an internal electrode of a multilayer ceramic component.

15. An electronic component formed using the conductive paste according to any one of claims 9 to 13.

16. A multilayer ceramic capacitor having at least a laminate in which a dielectric layer and an internal electrode are laminated, wherein the internal electrode is formed using the conductive paste according to claim 14.