JP-7857079-B2 - Conductive paste and multilayer ceramic capacitors

Inventors

• 鈴木 伸寿

Assignees

• 住友金属鉱山株式会社

Dates

Publication Date

20260512

Application Date

20201126

Claims (11)

1. In a conductive paste containing conductive powder, ceramic powder, binder resin, organic solvent and dispersant, The conductive powder has an H₂O adsorption amount per unit area of 0.30 mg/ m² or more and 0.60 mg/ m² or less at a relative pressure P/P₀ = 0.5 , and an average particle size of 0.05 μm or more and 5 μm or less calculated using the specific surface area based on the BET method. The ceramic powder has an average particle size of 0.01 μm or more and 0.5 μm or less, calculated using the specific surface area based on the BET method. The dispersant has a dielectric constant of 10 or more and contains at least one compound selected from the group consisting of 1) compounds having an acid group and 2) compounds having an amine group. Conductive paste.
2. The conductive paste according to claim 1, wherein the compound having the acid group is a compound containing at least one of a carboxyl group and a phosphate group.
3. The conductive paste according to claim 1 or claim 2, wherein the binder resin contains one or more selected from the group consisting of cellulose-based resins and butyral-based resins.
4. The conductive paste according to any one of claims 1 to 3, wherein the content of the binder resin is 0.5% by mass or more and 10% by mass or less based on 100% by mass of the conductive paste.
5. The conductive paste according to any one of claims 1 to 4, wherein the conductive powder contains one or more metal powders selected from the group consisting of Ni, Cu, Ag, Pd, Au, Pt powders, and alloy powders thereof.
6. The conductive paste according to any one of claims 1 to 5, wherein the conductive powder is nickel powder.
7. The conductive paste according to claim 6, wherein the surface composition of the nickel powder contains 20 mol% to 90 mol% NiO.
8. The conductive paste according to any one of claims 1 to 7, wherein the content of the conductive powder is 30% by mass or more and 70% by mass or less based on 100% by mass of the conductive paste.
9. The conductive paste according to any one of claims 1 to 8, wherein the ceramic powder is at least one selected from the group consisting of barium titanate-based and strontium zirconate-based materials.
10. A conductive paste according to any one of claims 1 to 9, wherein the rate of change in viscosity of the conductive paste, measured at 25°C and 10 rpm using a Brookfield viscometer after standing at 25°C for 30 days after manufacturing, is ±10% or less compared to the viscosity of the conductive paste 8 hours after manufacturing.
11. The laminate comprises at least a dielectric layer and an internal electrode layer, A multilayer ceramic capacitor in which the internal electrode layer is formed using the conductive paste described in any one of claims 1 to 10.

Description

This invention relates to conductive paste and multilayer ceramic capacitors. With the miniaturization and increased performance of electronic devices such as mobile phones and digital equipment, there is a growing demand for smaller and higher-capacitance electronic components, including multilayer ceramic capacitors. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked. By thinning these dielectric and internal electrode layers, miniaturization and increased capacitance can be achieved. Multilayer ceramic capacitors are manufactured, for example, as follows: First, a conductive paste for internal electrodes is printed (coated) in a predetermined electrode pattern onto the surface of a dielectric green sheet containing dielectric powder such as barium titanate ( BaTiO3 ) and a binder resin, and then dried to form a dry film. Next, the dry film and the green sheet are stacked alternately to obtain a laminate. Then, this laminate is heated and compressed to form a bonded body. This bonded body is cut, subjected to a de-organic binder treatment in an oxidizing or inert atmosphere, and then fired to obtain a fired chip. Next, paste for external electrodes is applied to both ends of the fired chip, and after firing, nickel plating or the like is applied to the surface of the external electrodes to obtain a multilayer ceramic capacitor. The conductive paste used to form the internal electrode layer includes, for example, 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 and other components. With the recent trend towards thinner internal electrode layers, the conductive powder contained in conductive pastes also tends to become smaller in particle size (micronized). As the particle size of conductive powder decreases, the surface area per unit volume increases, making the properties of the particle surface dominant. In particular, when the particles constituting the conductive powder reach the submicron level, they tend to adhere to each other due to intermolecular forces and electrostatic forces, forming coarse aggregates. If such aggregates are present in the conductive powder, during the manufacturing of multilayer ceramic capacitors, they can form convex portions on the surface of the internal electrode layer, potentially penetrating the ceramic dielectric layer and causing a short circuit between the internal electrode layers. Conductive pastes are manufactured, for example, by incorporating other materials such as conductive powder into an organic vehicle, which is prepared by dissolving a binder resin in an organic solvent, and then kneading and dispersing the mixture. Conventional kneading methods in the manufacturing process of conductive pastes include using equipment such as high-speed shear mixers or twin-shaft or more planetary mixers to mix (knead) conductive powder, inorganic powders such as ceramic powder, dispersants, and organic solvents into the organic vehicle. However, with conventional mixing methods, as the particle size of conductive powder decreases, problems such as insufficient mixing of the organic vehicle and inadequate wetting of the conductive powder and ceramic powder surfaces can occur. Furthermore, even when dispersion treatment is performed after mixing using a three-roll mill or similar equipment, problems such as poor dispersion of conductive powder (metal fine powder) and flake formation can occur. Furthermore, conductive powder produced by the wet manufacturing method, a common method for producing fine metal powders, is prone to aggregation during the drying process. By the time the conductive powder is mixed with the organic vehicle, many aggregates (secondary particles) have already formed, making the above-mentioned problem likely to occur. In the manufacturing process of a conductive paste containing a dispersant, focusing on the dispersion process of conductive powder and ceramic powder (hereinafter collectively referred to as "inorganic powder"), the process by which the particles constituting the inorganic powder are dispersed in the paste can be divided into the following steps, for example: (1) A step in which the surface of the particles (including secondary particles) constituting the inorganic powder is "wetted" (2) A step in which the secondary particles are crushed and the crushed particles are dispersed in the paste (3) A step in which the "re-aggregation" of the crushed particles is suppressed The wetting process described in (1) above is a process in which an organic vehicle/organic solvent adheres to the surface of the particles constituting the conductive powder and ceramic powder. In a conductive paste containing a dispersant, during this process, the dispersant is adsorbed onto the surface of the secondary particles (aggregates), and at