Conductive paste and multilayer ceramic electronic component provided with external electrode formed using same

Abstract

A conductive paste containing (A) conductive particles, (B) a thermosetting resin, and (C) rubber particles containing rubber particles having an average particle diameter of less than 1 [mu] m and having a carbon-carbon bond in the main chain skeleton thereof. According to the present invention, it is possible to provide a conductive paste having improved adhesion to a copper substrate.

Description

Technical Field

[0001] The present invention relates to conductive pastes and laminated ceramic electronic components having external electrodes formed using the conductive pastes. Background Technology

[0002] Chip-type laminated ceramic electronic components, which stack multiple layers of dielectrics and electrodes, are widely used in electronic circuits, especially in small devices such as mobile phones and tablet computers where there is a strong demand for low cost and miniaturization. Regarding previous laminated ceramic electronic components, ... Figure 1 The multilayer ceramic capacitor shown is used as an example for explanation. In multilayer ceramic capacitors, an external electrode layer is provided instead of leads, miniaturizing the structure of multiple layers of dielectric and internal electrodes, thus making a significant contribution to the miniaturization and weight reduction of electronic devices. The multilayer ceramic capacitor 1 has the following structure: an external electrode layer 4 is provided on the internal electrode lead surface of a ceramic composite formed by alternating layers of ceramic dielectric 2 and internal electrode layers 3. Typically, the external electrode has a structure in which a plating layer 5 is applied to the external electrode layer 4. The plating layer 5 typically includes a nickel plating layer, and may even further include a tin plating layer. When the multilayer ceramic capacitor is mounted on a circuit board 7, the external electrode of the multilayer ceramic capacitor is connected to the wiring electrodes of the circuit board via a solder layer 6.

[0003] As a cause of failure in electronic circuits utilizing multilayer ceramic capacitors, physical factors such as applying external force to the circuit board on which the multilayer ceramic capacitor is mounted, or bending of the circuit board, can be cited. This external force is transmitted to the multilayer composite portion in the form of stress through the solder layer and external electrodes, potentially leading to the peeling of the external electrodes from the ceramic composite or the formation of cracks in the ceramic composite. As a means to improve the reliability of electronic circuits against external physical forces, a scheme has been proposed that includes an electrode layer as a buffer material in the external electrode layer 4 (Patent Document 1). In this method, a copper substrate is used as the first conductor layer 11, which is connected to the internal electrodes of the multilayer capacitor, and a conductive paste containing resin is used as the second conductor layer 12 on top of it as a buffer material, thus forming an external electrode composed of multiple layers.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-233452 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] For conductive pastes constituting external electrodes of electronic components, safety and high reliability are required, thus necessitating flexibility to withstand substrate flexural stress. Methods such as those described in Patent Document 1 have been used to achieve this; however, in the method described in Patent Document 1, multiple layers are required to form external electrodes, necessitating good interlayer adhesion. If the conductive paste described in Patent Document 1 is used as the second conductor layer constituting the external electrode layer, there is still room for improvement in its adhesion to the copper substrate, which is the first conductor layer.

[0009] Therefore, the objective of this invention is to provide a conductive paste that improves adhesion to a copper substrate.

[0010] Methods for solving problems

[0011] In order to solve the above-mentioned problems, the inventors conducted repeated and in-depth research and finally completed the present invention. That is, the present invention is not limited to the following, but includes the following invention.

[0012] 1. A conductive paste comprising:

[0013] (A) Conductive particles,

[0014] (B) Thermosetting resins, and

[0015] (C) Rubber particles,

[0016] The rubber particles mentioned above (C) include rubber particles whose main chain backbone contains carbon-carbon bonds and whose average particle diameter is less than 1 μm.

[0017] 2. The conductive paste described in paragraph 1 above, wherein the rubber particles (C) comprise at least one selected from diene rubber, (meth)acrylate rubber, urethane rubber, isoprene rubber, fluorinated rubber, and chloroprene rubber.

[0018] 3. The conductive paste described in paragraph 1 or 2 above, wherein the rubber particles (C) above comprise core-shell type rubber particles.

[0019] 4. The conductive paste described in paragraph 3 above, wherein the core of the aforementioned core-shell type rubber particle is a rubber particle whose main chain skeleton contains carbon-carbon bonds.

[0020] 5. The conductive paste according to paragraph 3 or 4 above, wherein the shell portion of the core-shell type rubber particle is a shell portion containing a polymer having an epoxy group structural unit at a content of 10 parts by mass or more.

[0021] 6. The conductive paste according to any one of the preceding items 1 to 5, wherein the amount of the rubber particles in (C) is in the range of 0.1 to 10 parts by mass relative to 100 parts by mass of component (A).

[0022] 7. The conductive paste according to any one of items 1 to 6 above, wherein the thermosetting resin (B) above comprises an epoxy resin and the epoxy equivalent relative to the total mass of the thermosetting resin is 2000 g / eq or less.

[0023] 8. The conductive paste according to any one of the preceding items 1 to 7, wherein (A) above comprises spherical silver particles and flake-shaped silver particles.

[0024] 9. The conductive paste according to any one of the preceding items 1 to 8, wherein the content of the above-mentioned component (B) is 3 to 25 parts by mass relative to 100 parts by mass of the above-mentioned component (A).

[0025] 10. The conductive paste described in any one of items 1 to 9 above, wherein after drying at 120°C for 60 minutes, it is cured in the atmosphere at 180°C for 30 minutes using a blower dryer, and the flexural modulus at this time is 3 GPa to 15 GPa.

[0026] 11. The conductive paste described in any one of items 1 to 9 above, wherein after drying at 120°C for 60 minutes, it is cured in the atmosphere at 180°C for 30 minutes using a blower dryer, and the adhesion strength to the copper substrate is 1.0 kN / cm. 2 above.

[0027] 12. The conductive paste described in any one of the preceding items 1 to 11, wherein the thixotropic index value, measured by an HB type viscometer at 25°C, is 7 or less as the ratio of viscosity at 10 rpm to viscosity at 100 rpm.

[0028] 13. The conductive paste according to any one of the preceding items 1 to 12 is used to form a second conductive layer of an external electrode, wherein the external electrode has a first conductive layer connected to an internal electrode and a second conductive layer stacked on the first conductive layer.

[0029] 14. A stacked ceramic electronic component having external electrodes formed using the conductive paste described in paragraph 13 above.

[0030] Invention Effects

[0031] The conductive paste of the present invention can be used as a second conductive layer for external electrodes, which improves adhesion to copper substrates. This provides a safe and highly reliable conductive paste for external electrodes, as well as laminated ceramic electronic components. Attached Figure Description

[0032] Figure 1 This is a schematic diagram showing the structure of a ceramic capacitor, which has an external electrode consisting of multiple conductor layers, formed by stacking a second conductor layer containing resin on a first conductor layer connected to the internal electrode. Detailed Implementation

[0033] The embodiments of the present invention will now be described in detail. In the present invention, the term "first conductor layer" refers to a conductor layer that constitutes an external electrode and is directly connected to an internal electrode. Furthermore, the term "second conductor layer" refers to a conductor layer that constitutes an external electrode and is stacked on top of the first conductor layer.

[0034] The conductive paste for external electrodes of the present invention comprises (A) conductive particles, (B) thermosetting resin, and (C) rubber particles, wherein the rubber particles of component (C) comprise rubber particles whose main chain backbone contains carbon-carbon bonds and whose average particle diameter is less than 1 μm. Components (A) to (C) will be described in detail below.

[0035] (A) Conductive particles

[0036] Conductive particles are components used to impart conductivity to external electrodes, and metal particles are used. Examples of metal particles include Ag, Cu, Ni, Pd, Au, and Pt. From the perspective of easily obtaining excellent conductivity, Ag metal particles are preferred.

[0037] The conductive particles are preferably metal particles with a melting point of 700°C or higher. More preferably, the melting point of the conductive particles is 800°C or higher. There is no particular upper limit to the melting point, but it is generally below 1800°C, and preferably below 1600°C. The conductive particles can be used alone or in combination of two or more types.

[0038] Furthermore, alloys of Ag, Cu, Ni, Pd, Au, and Pt can be cited as conductive particles, with metal particles having a melting point of 700°C or higher being preferred. From the perspective of easily obtaining excellent conductivity, Ag alloy particles are preferred.

[0039] As alloy particles, examples include metallic particles composed of two or more elements selected from Ag, Cu, Ni, Pd, Au, and Pt. Examples of binary Ag alloys include AgCu alloy, AgAu alloy, AgPd alloy, and AgNi alloy. Examples of ternary Ag alloys include AgPdCu alloy and AgCuNi alloy.

[0040] Furthermore, as alloying particles, examples include metallic particles composed of alloys made of one or more elements selected from Ag, Cu, Ni, Pd, Au, and Pt, and one or more other elements, among which metallic particles with a melting point of 700°C or higher after alloying are preferred. Examples of other elements include Zn, Al, and Sn. In the case of a binary alloy of Sn and Ag, an AgSn alloy with a higher Ag ratio relative to the Sn:Ag mass ratio of 25.5:74.5 can be used.

[0041] Furthermore, as conductive particles, multilayered particles in which other metal atoms or metal compounds are coated on the surface of metal particles can be used. By depositing expensive metals such as Ag, Pd, Au, and Pt on the surface of relatively inexpensive metal particles such as Cu, it is possible to effectively utilize the high conductivity, migration resistance, and corrosion resistance of these metals while reducing the overall cost of the conductive particles. Multilayered particles can be manufactured using known methods according to the shape of the particles. For example, a metal precipitation reaction based on a reduction reaction of a metal-containing compound on the outer layer can be used to precipitate metal on the surface of the metal particles on the inner layer. By such means, core-shell type particles with a certain thickness ratio of the outer layer to the overall particle can be produced. Alternatively, particles with a thin coating film formed on the surface of the inner metal particles can be produced by impregnating the inner metal particles with a solution of a metal compound and then drying them.

[0042] There are no particular limitations on the thickness and mass ratio of the outer and inner layers of multilayer particles. From the viewpoint of prioritizing the properties of the outer layer metal, a larger outer layer thickness and mass ratio are preferred; from a cost perspective, a smaller outer layer thickness and mass ratio are preferred. The thickness of the outer layer is preferably 1–100 nm or less, and can be controlled by the manufacturing process. Furthermore, the outer layer does not need to cover the entire surface of the inner layer metal; particularly in coating-type particles, the outer layer metal can cover only a portion of the inner layer metal particles. Regarding the mass ratio of the outer layer, in the case of a coating, it is preferably 0.01 parts by mass or more and 1.0 parts by mass or less relative to 100 parts by mass of conductive particles. In the case of core-shell type particles, it is preferably 5 parts by mass or more and 40 parts by mass or less relative to 100 parts by mass of conductive particles.

[0043] In addition, as conductive particles, low-melting-point metal particles of Sn, In, and Bi with melting points above 200°C and below 700°C can be used. Lead-free low-melting-point metal particles are preferred.

[0044] Furthermore, as low-melting-point metal particles, alloys of Sn, In, and Bi with melting points above 200°C and below 700°C can also be used. From the perspective of easily obtaining excellent electrical conductivity, Sn alloys are preferred. Examples of alloy particles include metal particles composed of alloys of two or more elements selected from Sn, In, and Bi; examples of binary alloys include SnIn alloys.

[0045] The conductive particles can be spherical, flake-like, scaly, needle-like, or any other shape. Regarding their average particle diameter, from the perspective of good surface finish after printing or coating, and the ability to impart excellent conductivity to the formed electrode layer, a diameter of 0.015 to 30 μm is preferred. When the conductive particles are spherical, the average particle diameter is more preferably in the range of 0.2 to 5 μm. Furthermore, when the metal particles are flake-like, the average particle diameter is more preferably in the range of 5 to 30 μm. It should be noted that, in this specification, the term "average particle diameter" refers to the particle diameter in the case of spherical particles, the diameter of the longest portion in the case of flake-like particles, the major axis of the particle flake in the case of scaly particles, and the average of all lengths in the case of needle-like particles. Here, the average particle diameter of the metal particles is set as a value obtained by observation using a scanning electron microscope (SEM) and image analysis.

[0046] The conductive particles preferably consist of (A1) spherical silver particles and (A2) flake-shaped silver particles. The mass ratio of (A1) to (A2) silver particles is preferably 5:95 to 95:5. By setting the ratio of spherical silver powder to flake-shaped silver powder within the above range, the resistivity value can be reduced, and the thixotropic index (TI) value can be reduced, resulting in good coating shape and coating adhesion, which is therefore preferred. More preferably, it is 20:80 to 85:15, and even more preferably, it is 40:60 to 80:20. It should be noted that the metal particles used in this invention can be commercially available metal particles or metal particles prepared using methods known to those skilled in the art.

[0047] (B) Thermosetting resins

[0048] Thermosetting resins function as adhesives. There are no particular limitations on thermosetting resins; any resin that undergoes polymerization and curing upon heating can be used. Examples include amino resins such as epoxy resins, urea-formaldehyde resins, melamine resins, and guanidine resins; oxetane resins; phenolic resins such as methyl-phenolic, alkyl-methyl-phenolic, linear phenolic, alkyl-linear phenolic, and aralkyl-linear phenolic resins; phenoxy resins; silicone-modified organic resins such as silicone epoxy and silicone polyester; bismaleimide and polyimide resins, etc. BT resin can also be used, for example. One or more of these resins can be used.

[0049] As a thermosetting resin, it is preferable to use a thermosetting resin that is liquid at room temperature, as this reduces the amount of organic solvent used as a diluent. Examples of such liquid thermosetting resins include liquid epoxy resins and liquid phenolic resins. Furthermore, a resin that is compatible with these liquid resins and exhibits solidity or ultra-high viscosity at room temperature can be added to the mixture within a range where the mixture exhibits fluidity. Examples of such resins include high molecular weight bisphenol A type epoxy resins, diglycidyl biphenyl, linear phenolic epoxy resins, tetrabromobisphenol A type epoxy resins, methyl phenolic resins, linear phenolic resins, and aralkyl linear phenolic resins.

[0050] From the viewpoints of dimensional stability, insulation, and chemical resistance, epoxy resins are preferred as thermosetting resins. Epoxy resins are a general term for thermosetting resins that can be cured by cross-linking and networking using epoxy groups present in the compound, including prepolymer compounds before cross-linking and networking. The type of epoxy resin is not particularly limited as long as it has two or more epoxy groups. From the viewpoints of curing speed and reliability, compounds having 2 to 6 epoxy groups are more preferred, and difunctional epoxy resins having 2 epoxy groups are even more preferred.

[0051] When the thermosetting resin (B) contains epoxy resin, it is preferable to use the epoxy resin such that the epoxy equivalent relative to the total mass of the thermosetting resin is 2000 g / eq or less. Here, "epoxy equivalent" refers to the value obtained by dividing the molecular weight of the resin by the number of epoxy groups in the molecule. Furthermore, the epoxy equivalent value "relative to the total mass of the thermosetting resin" is obtained by multiplying the epoxy equivalent of the epoxy resin itself by the mass proportion of epoxy resin contained in the thermosetting resin (B). By setting the epoxy equivalent within this range, the resistivity value can be reduced, and the bond strength can also be improved. The epoxy equivalent range is preferably 50 to 2000 g / eq, more preferably 70 to 1000 g / eq, and even more preferably 80 to 700 g / eq.

[0052] Examples of epoxy resins include bisphenol A type epoxy resins with an average molecular weight of approximately 400 or less; branched multifunctional bisphenol A type epoxy resins such as glycidoxyphenyl dimethyl tribisphenol A diglycidyl ether; bisphenol F type epoxy resins; phenolic linear phenolic epoxy resins with an average molecular weight of approximately 570 or less; and alicyclic epoxy resins such as vinyl(3,4-cyclohexene) dioxide, methyl 3,4-epoxycyclohexylcarboxylate (3,4-epoxycyclohexyl)carboxylate, di(3,4-epoxy-6-methylcyclohexylmethyl) adipic acid, and 2-(3,4-epoxycyclohexyl)5,1-spiro(3,4-epoxycyclohexyl)-1,3-dioxane. Esters; biphenyl-type epoxy resins such as 3,3',5,5'-tetramethyl-4,4'-diglycidoxybiphenyl; glycidyl ester-type epoxy resins such as diglycidyl hexahydrophthalic acid, diglycidyl 3-methylhexahydrophthalic acid, and diglycidyl hexahydroterephthalic acid; glycidylamine-type epoxy resins such as diglycidylaniline, diglycidyltoluidine, triglycidyl-p-aminophenol, tetraglycidyl-m-phenylenediamine, and tetraglycidyldi(aminomethyl)cyclohexane; and hydantoin-type epoxy resins such as 1,3-diglycidyl-5-methyl-5-ethylhydantoin; epoxy resins containing a naphthalene ring. In addition, examples include epoxy resins with a silicone backbone such as 1,3-bis(3-epoxypropoxypropyl)-1,1,3,3-tetramethyldisiloxane; diepoxide compounds such as polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, and cyclohexanediethanol diglycidyl ether; and triepoxide compounds such as trimethylolpropane triglycidyl ether and glycerol triglycidyl ether. Alternatively, solid epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, naphthalene type epoxy resin, phenol linear phenolic type epoxy resin, phenol aralkyl type epoxy resin, cresol linear phenolic type epoxy resin, biphenyl type epoxy resin, biphenyl linear phenolic type epoxy resin, biphenyl aralkyl type epoxy resin, triphenylmethane type epoxy resin, and dimercyclopentadiene type epoxy resin may be used in combination to make (B) a liquid overall. Bisphenol A type epoxy resin and bisphenol F type epoxy resin are among the more preferred epoxy resins.

[0053] As a thermosetting resin (B), phenolic resin can be used in conjunction with epoxy resin. Phenolic resin is a general term for thermosetting resins that can be cross-linked and networked using phenolic hydroxyl groups present in the compound, including prepolymer compounds before cross-linking and networking. Phenolic resin is an epoxy resin curing agent that reacts with the epoxy groups of epoxy resin, which helps to impart wettability to solder. Examples of phenolic resins include linear phenolic resins of phenol and their alkyl or allyl derivatives, linear phenolic resins of cresol, aralkyl phenol (including phenylene and biphenylene skeletons) resins of phenol, aralkyl naphthol resins, terphenylmethane resins, and dimercyclopentadiene-type phenolic resins. Among these, linear phenolic resins of cresol and aralkyl phenol are preferred from the perspective of improving wettability to solder.

[0054] As a thermosetting resin (B), phenoxy resins can also be used in combination with epoxy resins. A phenoxy resin is a polyhydroxy polyether synthesized through the direct reaction of a diphenol compound with epichlorohydrin, or through the addition polymerization reaction of the diglycidyl ether of a diphenol compound with the diphenol compound. Bisphenol A type phenoxy resins can be used as phenoxy resins and are available as commercially available products (e.g., bisphenol A type phenoxy resin 4250 (Mitsubishi Chemical), bisphenol A type phenoxy resin Fx316 (Nippon Steel & Sumitomo Metal), bisphenol A type phenoxy resin YP50 (Nippon Steel & Sumitomo Metal) etc.).

[0055] In the conductive paste for external electrodes of the present invention, when epoxy resin is included in component (B), a self-curing resin can be used as the curing mechanism of the epoxy resin, or curing agents or curing catalysts such as amines, imidazoles, acid anhydrides or onium salts can be used, or amino resins or phenolic resins can be used as curing agents for epoxy resin.

[0056] Epoxy resins cured using phenolic resins are particularly preferred. As the phenolic resin, any initial condensate of a phenolic resin commonly used as a curing agent for epoxy resins is acceptable, whether it be a methyl phenolic type or a linear phenolic type. However, to obtain excellent heat cycling resistance, phenolic resins, xylene resins, or allyl phenolic resins in which 50% or more by mass is an alkyl methyl phenolic type, an alkyl linear phenolic type, an aralkyl linear phenolic type, or an allyl phenolic resin are preferred. Aralkyl linear phenolic resins, which are phenol / terephthalic alcohol dimethyl ether condensates, are also preferred, represented by the following general formula (where n is 0 to 300):

[0057] [Chemistry 1]

[0058]

[0059] Furthermore, in the case of alkyl-methyl phenolic resins, an average molecular weight of 2000 or higher is preferred to obtain excellent printability. In these alkyl-methyl or alkyl-linear phenolic resins, the alkyl group can be an alkyl group with 1 to 18 carbon atoms, preferably an alkyl group with 2 to 10 carbon atoms such as ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, or decyl.

[0060] Among these, combinations of epoxy resin and aralkyl linear phenolic resin, methanogenic phenolic resin, xylene resin, or allyl phenolic resin are preferred from the perspective of obtaining excellent adhesion and heat resistance. When using a combination of epoxy resin and aralkyl linear phenolic resin, methanogenic phenolic resin, xylene resin, or allyl phenolic resin, the mass ratio of epoxy resin to phenolic resin is preferably in the range of 5:1 to 1:5, more preferably 4:1 to 1:2. Furthermore, from the viewpoint of heat resistance, polyimide resins, etc., are also effective.

[0061] In the conductive paste of the present invention, the content of the thermosetting resin (B) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more, relative to 100 parts by mass of the conductive particles (A). Furthermore, relative to 100 parts by mass of the conductive particles (A), it is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less. By setting the content of the thermosetting resin (B) within this range, sufficient adhesion to the copper substrate and solder layer can be achieved without compromising the conductivity originally required for the conductive paste.

[0062] (C) Rubber particles

[0063] The conductive paste of the present invention comprises rubber particles whose main chain backbone includes carbon-carbon bonds and whose average particle size is 1 μm or less. The rubber particles are a component that facilitates stress relaxation of the external electrode. Furthermore, by including rubber particles whose main chain backbone includes carbon-carbon bonds and whose average particle size is 1 μm or less in the conductive paste of the present invention, adhesion to the copper substrate can be improved. The reason for the improved adhesion is not clear, but it can be presumed that by including rubber particles with an average particle size of 1 μm or less, the rubber particles are uniformly dispersed in the conductive paste, thus improving adhesion to the copper substrate. It can also be presumed that by including carbon-carbon bonds in the main chain backbone of the (C) rubber particles, physical properties such as toughness can also be improved. However, the present invention is not limited to these presumptions. As the (C) rubber particles, rubber other than rubber satisfying the above requirements may be included to a extent that does not impair the effects of the present invention; however, it is preferable to consist only of rubber satisfying the above requirements.

[0064] The phrase "main chain backbone containing carbon-carbon bonds" means that when the molecules constituting the rubber particles are considered as a chain-like backbone, carbon-carbon bonds are present within this chain-like backbone. It should be noted that, from the viewpoint of improving adhesion to copper substrates and coating toughness, it is preferable that at least 50% of the atoms constituting this chain-like backbone are carbon atoms. Therefore, as long as the portion constituting the molecular chain through carbon atom connections is included, and preferably the proportion of carbon atoms is large, functional groups containing heteroatoms can be included in the molecular backbone, similar to urethane rubber and acrylic rubber. Furthermore, as long as it is based on a rubber with carbon-carbon bonds in its chain-like backbone, at least a portion of it can be halogenated rubber. It has been found that by including rubber particles with an average particle size of 1 μm or less and carbon-carbon bonds in the main chain in the conductive paste of the present invention, compared to conductive pastes containing silicone rubber particles whose chain-like backbone is mainly composed of silicon and oxygen bonds, not only is adhesion to copper substrates improved, but the toughness of the coating is also improved.

[0065] As rubber particles, any organic compound whose main chain backbone contains carbon-carbon bonds is acceptable. Examples include hydrocarbon-derived rubbers such as natural rubber, acrylic rubbers, and urethane rubbers, which contain functional groups with heteroatoms in their backbone. Preferably, at least one type selected from diene rubbers, (meth)acrylate rubbers, urethane rubbers, isoprene rubbers, fluorinated rubbers, and chloroprene rubbers is used. These can be used alone or in combination of two or more types.

[0066] Examples of diene-based rubbers include butadiene rubber, styrene-butadiene rubber, ethylene-propylene-diene terpolymer rubber, and copolymers of hydrocarbon-derived rubbers such as nitrile rubber with dienes. Additionally, hydrogenated diene-based rubbers obtained by hydrogenating at least a portion of the diene can also be used. It should be noted that, from the viewpoint of suppressing the viscosity increase of conductive pastes, butadiene rubber using 1,3-butadiene, and / or butadiene-styrene rubber as a copolymer of 1,3-butadiene and styrene, are preferred among diene-based rubbers, and butadiene rubber is more preferred.

[0067] Examples of (meth)acrylate-based rubbers include copolymers of (meth)acrylate and 2-chloroethyl vinyl ether, and copolymers of (meth)acrylate and acrylonitrile.

[0068] Examples of urethane-based rubbers include polyether-based urethane rubbers obtained by reacting polyether polyols such as polyethylene glycol, poly1,4-butanediol, and ethylene oxide adducts of bisphenol A with polyisocyanates, and polyester-based urethane rubbers obtained by reacting polyester polyols, which are products of the reaction between diols and diacids, with polyisocyanates.

[0069] Examples of isoprene-based rubbers include natural rubber, polyisoprene rubber, and butyl rubber (a copolymer of isobutylene and isoprene).

[0070] In addition to rubbers obtained by fluorinating at least a portion of the aforementioned hydrocarbon rubbers, examples of fluororubbers include binary copolymers of vinylidene fluoride and hexafluoropropylene, binary copolymers of vinylidene fluoride and pentafluoropropylene, binary copolymers of vinylidene fluoride and chlorotrifluoroethylene, terpolymers of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene, terpolymers of vinylidene fluoride, pentafluoropropylene, and tetrafluoroethylene, and terpolymers of vinylidene fluoride, perfluoromethyl vinyl ether, and tetrafluoroethylene.

[0071] In addition to these rubbers, hydrocarbon-derived rubbers, primarily containing polyolefins, such as ethylene-propylene rubber and styrene rubber, can also be used as rubber particles. Furthermore, these rubber particles can also undergo cross-linking treatment.

[0072] Regarding the average particle diameter of the rubber particles, from the perspective of balancing adhesive strength and coating toughness, it is preferably 1 μm or less. From the viewpoint of improving the dispersibility of the conductive paste and the toughness of the coating, the average particle diameter of the rubber particles is more preferably 500 nm or less, further preferably 400 nm or less, and particularly preferably 300 nm or less. The lower limit of the average particle diameter is not particularly limited, but it is 20 nm or more. It should be noted that in this application specification, the average particle diameter of the rubber particles is the average primary particle diameter, which is a value obtained by observation using a scanning electron microscope (SEM) and image analysis. It should be noted that the shape of the rubber particles can be spherical, plate-like, sheet-like, rod-like, or other non-spherical shapes, but spherical is preferred. If the rubber particles are spherical, the dispersibility and the softness of the coating can be improved when making the conductive paste. It should be noted that in this invention, "spherical" is not limited to a perfect sphere, but also includes shapes close to a sphere such as ellipsoids, spheres with uneven surfaces, etc. On the other hand, plate-like, sheet-like, and rod-like shapes are not spherical. The shape of rubber particles can be confirmed by observation using a scanning electron microscope (SEM).

[0073] Rubber particles can utilize core-shell type particle structures. For example, by configuring highly dispersible rubber on the surface (shell) of core particles with good physical properties such as toughness, modified rubber particles that combine the properties of both can be obtained, thus enabling the design of rubber particles that are more suitable for conductive pastes. The core-shell type particle structure can be a simple two-layer structure or multiple layers of three or more stacked layers.

[0074] When the rubber particles are core-shell type rubber particles, there are no particular restrictions on the type of rubber particles selected in each layer, the thickness ratio of each layer, the mass ratio, etc., and any type and range can be designed. However, it is preferred that the core of the rubber particles is a rubber particle whose main chain skeleton contains carbon-carbon bonds. The shell part is preferably made of a material that exhibits properties different from those of the core.

[0075] (C) When the rubber particles are core-shell type rubber particles, the core is equivalent to the aforementioned rubber particles whose main chain skeleton contains carbon-carbon bonds and whose average particle size is less than 1 μm. By making the core the aforementioned rubber particles, the coating film can be made tough while its adhesion to the substrate can be improved. In addition, by making the core the aforementioned rubber particles, the toughness of the coating film can be improved compared with conductive pastes containing silicone rubber particles.

[0076] (C) When the rubber particles are core-shell type rubber particles, the shell portion can be formed using a polymer that can copolymerize with the core portion. In this case, it becomes a structure having a core portion present inside and at least one shell portion covering a portion of its surface. As long as the average particle size of the core portion is 1 μm or less, the average particle size of the rubber particles including the shell portion can also be greater than 1 μm; however, it is preferable that the average particle size of the rubber particles, including the shell portion, is also 1 μm or less.

[0077] When the rubber particles are core-shell type rubber particles, the shell portion preferably contains a polymer with an epoxy group-containing structural unit content of 10 parts by mass or more. It should be noted that "a polymer with an epoxy group-containing structural unit content of 10 parts by mass or more" means a polymer in which the proportion of structural units derived from epoxy group-containing monomers is 10 parts by mass or more of all structural units (i.e., a polymer in which the proportion of epoxy group-containing monomers is 10 parts by mass or more when the total mass of the monomers to be used as raw materials is set to 100 parts by mass). It should be noted that the content of epoxy group-containing structural units in the polymer is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, and even more preferably 30 parts by mass or more. It should be noted that the shell portion may be composed solely of a polymer with an epoxy group-containing structural unit content of 10 parts by mass or more, or it may include this polymer and other polymers.

[0078] By including core-shell type rubber particles with a shell portion in a conductive paste, wherein the shell portion contains a polymer having an epoxy group structural unit content of 10 parts by mass or more, the toughness and adhesion of the coating film can be improved. While the reason for the improved toughness and adhesion is unclear, it is presumed that by having the polymer contained in the shell portion possess a certain amount of epoxy groups, the affinity at the interface between the epoxy resin and the shell portion is increased. However, the present invention is not limited to this presumption.

[0079] It should be noted that monomers containing epoxy groups include, for example, ether compounds such as allyl glycidyl ether; ester compounds such as glycidyl (meth)acrylate and glycidyl (meth)acrylate (especially (meth)acrylates containing epoxy groups). They can be used alone or in combination of two or more.

[0080] Regarding the mass ratio of the core to the shell, from the viewpoint of reducing the viscosity of the conductive paste and imparting toughness, the core / shell ratio (the mass ratio of the monomers forming each polymer) is preferably in the range of 50 / 50 to 99 / 1, more preferably 60 / 40 to 95 / 5, and even more preferably 70 / 30 to 95 / 5.

[0081] The content of (C) rubber particles in the conductive paste of the present invention is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, further preferably 1.0 parts by mass or more, and particularly preferably 2.0 parts by mass or more, relative to 100 parts by mass of (A) conductive particles. Furthermore, it is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and particularly preferably 5 parts by mass or less, relative to 100 parts by mass of (A) conductive particles. By setting it within the above range, not only can the resistivity value be suppressed, but the adhesion can also be improved, and the flexibility and toughness of the cured coating film can be enhanced.

[0082] Furthermore, in the conductive paste for the external electrode of the present invention, from the viewpoint of possessing sufficient conductivity, it is preferable to design the total content of (C) rubber particles and (B) thermosetting resin as the ratio relative to (A) conductive particles. Specifically, from the viewpoint of reducing the flexural modulus of the external electrode, the total amount of component (B) and component (C) relative to 100 parts by mass of conductive particles (A) is preferably 10 to 45 parts by mass. More preferably, it is 15 to 35 parts by mass, and even more preferably, it is 25 to 35 parts by mass. By setting the mass ratio of (A) to (B) + (C) within the above range, not only can the resistivity value be suppressed, but also softness and toughness can be imparted, and TI can be reduced, thereby resulting in good coating shape and coating adhesion, which is preferable.

[0083] The mass ratio of (B) thermosetting resin to (C) rubber particles ((B):(C)) is preferably 90:10 to 45:55, more preferably 85:15 to 70:30.

[0084] In the conductive paste of the present invention, imidazole derivatives such as 2-phenyl-4-methyl-5-hydroxymethylimidazolium, curing catalysts such as dicyandiamide, coupling agents, thixotropic agents, and dispersants may be added to components (A) to (C) without impairing the effects of the present invention. Alternatively, a thermoplastic resin may be used in conjunction with a thermosetting resin. Polysulfone, polyethersulfone, and maleimide resins are preferred as thermoplastic resins.

[0085] From the viewpoint of operability and coatability, the viscosity of the conductive paste of the present invention, measured using an HB type viscometer at 25°C and 10 rpm, is preferably 60 Pa·s or less, more preferably 40 Pa·s or less, and even more preferably 20 Pa·s or less. The lower limit of viscosity is not limited as long as a paste with a uniform composition and good flowability can be obtained; however, 5 Pa·s or more is preferred.

[0086] Furthermore, in the conductive paste of the present invention, an organic solvent can be used to adjust the viscosity. Examples of organic solvents include aromatic hydrocarbons such as toluene, xylene, mesitylene, and tetrahydronaphthalene; ethers such as tetrahydrofuran; ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; lactones such as 2-pyrrolidone and 1-methyl-2-pyrrolidone; ether alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and their corresponding propylene glycol derivatives; esters such as their corresponding acetates; and diesters such as methyl esters and ethyl esters of dicarboxylic acids such as malonic acid and succinic acid. The amount of organic solvent used can be arbitrarily selected according to the printing or coating paste method, for example, in the case of screen printing, it is preferable to use an amount that makes the apparent viscosity of the paste at room temperature 10 to 500 Pa·s, and more preferably to use an amount that makes the apparent viscosity 15 to 300 Pa·s.

[0087] In the paste of the present invention, known additives may be further incorporated as needed. For example, as dispersing agents, aluminum chelates such as diisopropoxy (ethyl acetoacetate) aluminum chelate; titanates such as isopropyl triisostearoyl titanate; aliphatic polycarboxylic acid esters; unsaturated fatty acid amine salts; surfactants such as monooleate dehydrated sorbitan ester; or polymeric compounds such as polyester amine salts and polyamides may be incorporated. In addition, inorganic and organic pigments, silane coupling agents, leveling agents, thixotropic agents, defoamers, etc., may also be incorporated. Furthermore, liquid rubber may be further incorporated in addition to component (C).

[0088] The flowability of conductive pastes can be evaluated using the thixotropic index (TI). From this perspective, the thixotropic index, measured at 25°C using an HB-type viscometer as the ratio of viscosity at 10 rpm to viscosity at 100 rpm, is preferably 7 or less, more preferably 5 or less, and even more preferably 3 or less. It should be noted that the lower limit of TI is not particularly limited, but it is 1 or more. By ensuring that the TI is within the above range, good coating shape and coating adhesion can be achieved.

[0089] The TI of a conductive paste is expressed by the following formula:

[0090] TI = η1 / η 10

[0091] (In the formula,

[0092] η1 is the viscosity measured using a rotational viscometer at a temperature of 25°C and a rotation speed of 10 rpm.

[0093] η 10 (This is the viscosity measured under the same conditions as η1, except that the rotation speed is 100 rpm).

[0094] If the TI (Temperature Intensity) is within the aforementioned range, the conductive paste can be smoothly discharged from the coating apparatus. Furthermore, in the manufacturing process of multilayer ceramic capacitors, there is a certain amount of time required between applying the conductive paste to the multilayer ceramic chip and curing it through processes such as sintering. Since the external electrodes are not coated in a planar manner, if the conductive paste has high fluidity, it may naturally diffuse to some extent during the period from coating to sintering. However, if the TI is within the aforementioned range, manufacturing can be carried out while maintaining the original dimensions.

[0095] It should be noted that, according to the definition of TI above, when the TI of a conductive paste is below 1, the viscosity of the conductive paste under relatively high shear stress is equal to or higher than the viscosity of the same conductive paste under relatively low shear stress. However, since the viscosity of a conductive paste varies with the measurement conditions, the behavior of a conductive paste under actual compression molding conditions sometimes differs from the behavior predicted based on the TI defined above.

[0096] The conductive paste of the present invention can be prepared by uniformly mixing the compounding components using a mixing mechanism such as a pounder, propeller mixer, kneader, roller mill, or can mill. The preparation temperature is not particularly limited; however, it can be carried out, for example, at 10–40°C.

[0097] The conductive paste of the present invention can be used to form a second conductor layer in a multilayer ceramic electronic component, having a first conductor layer connected to an internal electrode layer and a second conductor layer stacked on the first conductor layer as an external electrode. By using the conductive paste of the present invention as the second conductor layer, an external electrode consisting of multiple layers can be formed. The method of formation is not particularly limited, and known methods can be used. For example, the paste of the present invention can be printed or coated onto the first conductor layer of the external electrode of the multilayer ceramic electronic component, dried as appropriate, and then cured by heating to form the second conductor layer.

[0098] The first conductor layer connected to the internal electrode layer can be formed, for example, by coating an electrode paste, for example, with silver as the main agent and containing glass powder, onto the internal electrode lead-out surface of the laminated ceramic composite, drying it as appropriate, and then firing it. Methods known to those skilled in the art can be used as methods for printing, coating, drying, and firing the electrode paste.

[0099] The coating thickness in the printing and coating process is typically 10–200 μm, preferably 20–100 μm. The drying process is mainly carried out using organic solvents and can be performed at room temperature or by heating (e.g., at 80–160°C). The curing process is typically performed at 150–250°C. The curing temperature is preferably 150°C or higher, more preferably 180°C or higher. Furthermore, to eliminate the adverse effects of heat on the (C) rubber particles, the temperature is preferably 250°C or lower, more preferably 220°C or lower.

[0100] The curing time can vary depending on the curing temperature, but from an operational perspective, 1 to 60 minutes is preferred. For example, if the resin in the paste is an epoxy resin using phenolic resin as a curing agent, it can be cured at 150 to 250°C for 10 to 60 minutes to form the second conductor layer constituting the external electrode.

[0101] The conductive paste of the present invention exhibits flexibility upon curing and demonstrates excellent stress relaxation capability against physical forces applied to laminated ceramic electronic components. The flexibility is evaluated based on the flexural modulus. The conductive paste of the present invention is dried at 120°C for 60 minutes and then cured in air at 180°C for 30 minutes using a blower dryer. The flexural modulus at this time is preferably 3 GPa to 15 GPa, more preferably 4 GPa to 12 GPa, and even more preferably 5 GPa to 10 GPa.

[0102] A stacked ceramic electronic component having external electrodes having a first conductor layer and a second conductor layer formed using the paste of the present invention can control the capacitance drop after a bending test to less than 10%. The bending test is performed, for example, by applying pressure to the central portion at a displacement speed of 1 mm / s with two supports spaced 90 mm apart, causing the substrate to flex by 10 mm.

[0103] Furthermore, the conductive paste of the present invention exhibits high adhesion to the first conductor layer that forms the external electrode and is in contact with it. The metal typically used in the first conductor layer is copper. The conductive paste of the present invention, after drying at 120°C for 60 minutes, is then cured in air at 180°C for 30 minutes using a blower dryer. The preferred adhesion strength to the copper substrate at this time is 1.0 kN / cm. 2 The above, more preferably 1.5 kN / cm 2 The above is further optimized to be 2.0 kN / cm. 2 The above. A particularly preferred value is 3.0 kN / cm. 2 The above describes the method for determining adhesive strength. Based on the test methods in the following examples, when applying a force to release the adhesive, it is preferable that the failure occurs within the adhesive layer (cohesive failure) rather than at the interface with the adhesive layer (interfacial failure).

[0104] To further improve the bonding strength when soldering to circuit boards or other substrates, nickel plating, tin plating, or other plating treatments can be applied to the external electrodes formed in this way, as needed.

[0105] Examples of multilayer ceramic electronic components having external electrodes formed using the conductive paste of the present invention include capacitors, capacitor arrays, thermistors, varistors, inductors, and LC, CR, LR, and LCR composite components.

[0106] Example

[0107] The present invention will be further described in detail below with reference to embodiments and comparative examples. The present invention is not limited to these embodiments.

[0108] [Preparation of conductive paste]

[0109] The conductive pastes of the Examples and Comparative Examples were prepared by combining the components in Table 1 (unless otherwise specified, the numbers in the table are parts by mass).

[0110] • Conductive particles (component (A))

[0111] In the examples and comparative examples, the substances used as component (A) are as follows.

[0112] (A1) Flake-shaped silver powder (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., AGC B4) with an average particle size of 7.0 μm.

[0113] (A2) Spherical silver powder (Mitsui Metals & Minerals Co., Ltd., HP 15) with an average particle size of 2.0 μm.

[0114] Thermosetting resin (component (B))

[0115] In the examples and comparative examples, the compounds used as component (B) are shown below.

[0116] (B1) Epoxy resin (ADEKA resin EP4901E; epoxy equivalent 170g / eq) liquid bisphenol F type epoxy resin

[0117] (B2) Phenolic resin (PSM4324 manufactured by Chung Yung Chemical Industry Co., Ltd.; epoxy equivalent 105 g / eq) Linear phenolic resin

[0118] • Rubber components (component (C))

[0119] In the examples and comparative examples, the compounds used as component (C) are shown below.

[0120] (C1) Butadiene rubber particles (a core-shell particle containing butadiene rubber in the core and glycidyl methacrylate (10 parts by mass) and methyl methacrylate (90 parts by mass) in the shell, with an average primary particle size of 100-200 nm). It should be noted that a dispersion in which the core-shell rubber particles are dispersed in bisphenol A type epoxy resin is used.

[0121] (C2) Butadiene rubber particles (a core-shell particle consisting of butadiene rubber in the core and a shell composed of a polymer of glycidyl methacrylate and methyl methacrylate, with an average primary particle size of 100-200 nm). It should be noted that a dispersion in which the core-shell rubber particles are dispersed in bisphenol F type epoxy resin is used.

[0122] (C3) Acrylic rubber particles (core and shell particles containing butyl acrylate in the core and methyl methacrylate-styrene in the shell, with an average primary particle size of 100-200 nm)

[0123] (C'4) Liquid rubber (CTBN1300 manufactured by Hycar)

[0124] (C´5) Silicone rubber particles with an average particle size of 3.0 μm (Shin-Etsu Chemical Industry Co., Ltd. KMP-605M)

[0125] (C'6) Silicone rubber particles (core-shell particles consisting of a core of silicone rubber and a shell of a polymer of glycidyl methacrylate and methyl methacrylate, with an average primary particle size of 100-200 nm), it should be noted that a dispersion is used to disperse the core-shell rubber particles in bisphenol F type epoxy resin.

[0126] In addition to the above three components, the following substances are also used as optional components.

[0127] • Curing catalyst

[0128] Shikoku Chemical Co., Ltd. 2P 4MHZ PW

[0129] ADEKA EH-3842

[0130] Solvent

[0131] Ethylene glycol monophenyl ether (HISOLVE EPH, manufactured by Toho Chemical Co., Ltd.)

[0132] Diethylene glycol monoethyl ether (EC manufactured by Dashin Chemical Co., Ltd.)

[0133] In the examples and comparative examples, the properties of the conductive paste were measured as follows.

[0134] (Viscosity)

[0135] The viscosity of the freshly prepared evaluation sample was measured using an HB type viscometer (BrookField) (SC4-14 rotor) at 25°C and 10 rpm.

[0136] (Thixotropic index value TI)

[0137] Calculate the ratio of viscosity measured at 25℃ and 10 rpm using an HB type viscometer to viscosity measured at 100 rpm.

[0138] (Resistivity value)

[0139] For the conductive paste of the Examples and Comparative Examples, a zigzag pattern with a length of 71 mm, a width of 1 mm, and a thickness of 20 μm was printed on an alumina substrate with a width of 20 mm, a length of 20 mm, and a thickness of 1 mm using a 250-mesh stainless steel screen. After drying at 120°C for 60 minutes, it was cured at 180°C in the atmosphere for 30 minutes to form an external electrode. Regarding the thickness of the zigzag pattern, the values ​​at six points intersecting the pattern were measured using a Tokyo Seisin Surface Roughness Profile Shape Measuring Instrument (product name: SURFCOM 1400), and the average value was calculated. After curing, the resistivity was measured using an LCR meter using the four-terminal method.

[0140] (Adhesive strength)

[0141] 1: Substrate fabrication

[0142] On an alumina substrate with a width of 20 mm, a length of 20 mm, and a thickness of 1 mm, copper was printed onto the substrate using a 250-mesh stainless steel screen, resulting in a width of 20 mm, a length of 20 mm, and a thickness of approximately 20 μm after firing. After drying at 150°C for 10 minutes, the substrate was fired at 900°C for 60 minutes in a nitrogen atmosphere to form a fired copper substrate on the alumina substrate.

[0143] 2: Determination of bond strength

[0144] For the conductive paste of the Examples and Comparative Examples, a pattern was printed on an alumina substrate with a sintered copper substrate using a 250-mesh stainless steel screen. The pattern consisted of 5 vertical x 5 horizontal patterns, each 1.5 mm wide and 1.5 mm long, with a cured thickness of approximately 25 μm. Ten 3216-sized alumina chips were randomly placed on this pattern. After drying at 120°C for 60 minutes, the chips were cured at 180°C in atmospheric conditions for 30 minutes to form a test piece. After curing, the bond strength (shear strength) between the alumina chips and the sintered copper substrate was measured using an AIKOH ENGINEERING benchtop strength tester (model: 1605VC) at a displacement speed of 12 mm / min. The bond strength was expressed as 3.0 kN / cm. 2 Above and below 3.0 kN / cm 2 ~1.0kN / cm 2 Above and below 1.0 kN / cm 2 The evaluation is conducted at three levels. Additionally, the condition of the adhesive surface during the peeling of the alumina chip is visually assessed to determine whether the failure mode is cohesive failure or interfacial failure.

[0145] (Flexural modulus)

[0146] The conductive paste of the Example / Comparative Example was applied to a substrate, dried at 120°C for 60 minutes, and then cured at 180°C in the atmosphere for 30 minutes using a blower dryer. The paste was then peeled off from the substrate to produce three 40×10×0.13mm test pieces. A two-point support, one-point loading bending test was performed using a Shimadzu universal testing machine at a displacement speed of 1 mm / min, and the stress-strain curves were calculated.

[0147] (toughness)

[0148] The determination of whether toughness can be imparted is based on the stress-strain curve (SS curve) calculated by measuring the flexural modulus. That is, after the strain point (yield point) exceeding the calculated maximum stress is exceeded, the load is continued at a displacement rate of 1 mm / min. After 1 minute, the determination is made based on whether the three test pieces break.

[0149] The case where the load exceeded the yield point and was subsequently applied at a displacement rate of 1 mm / min for 1 minute, and none of the three test pieces fractured, was defined as "not fractured".

[0150] The case where, after exceeding the yield point and continuing loading at a displacement rate of 1 mm / min for 1 minute, one or two of the three test pieces do not fracture is defined as "partial fracture".

[0151] The case where all three test pieces fractured before reaching the yield point is defined as "fracture".

[0152] Evaluation is conducted using three levels: fractured, partially fractured, and unfractured.

[0153]

[0154] As shown in Table 1, the conductive paste of the present invention, containing specific rubber particles, possesses good flexural modulus and high toughness, conductivity as an external electrode, and high adhesion to copper. Furthermore, Comparative Example 1, which uses only liquid rubber as component (C'4), exhibits low adhesion strength to copper and increased resistance, raising concerns about its effectiveness as a conductive paste. Additionally, Comparative Examples 3 and 4, which use silicone rubber particles without carbon as the main component as component (C'5), show insufficient adhesion strength. It is also evident that, including cases without rubber particles, the cured products in these comparative examples lack toughness and cannot achieve the purpose of serving as a second conductive layer for external electrodes (Comparative Examples 1-4).

[0155] Industrial availability

[0156] The conductive paste of the present invention has the same level of conductivity as conventional conductive pastes, while also possessing the properties of imparting flexibility and toughness to external electrodes, and is a material with high adhesion to copper, thus making it suitable for electronic components such as external electrodes of multilayer ceramic capacitors.

[0157] Explanation of reference numerals in the attached figures

[0158] 1. Multilayer ceramic capacitor; 2. Ceramic dielectric; 3. Internal electrode layer; 4. External electrode layer; 5. Plating layer; 6. Solder layer; 7. Substrate; 11. First conductor layer connected to the internal electrode; 12. Second conductor layer containing resin.

Claims

1. A conductive paste comprising: A conductive particle, B thermosetting resins, and C rubber particles, The C rubber particles comprise rubber particles whose main chain backbone contains carbon-carbon bonds and whose average particle diameter is less than 1 μm.

2. The conductive paste according to claim 1, wherein, The C rubber particles comprise at least one type selected from diene rubber, (meth)acrylate rubber, urethane rubber, isoprene rubber, fluorinated rubber, and chloroprene rubber.

3. The conductive paste according to claim 1 or 2, wherein, The C rubber particles comprise core-shell type rubber particles.

4. The conductive paste according to claim 3, wherein, The core of the core-shell type rubber particle is a rubber particle whose main chain skeleton contains carbon-carbon bonds.

5. The conductive paste according to claim 3 or 4, wherein, The shell portion of the core-shell type rubber particle is a shell portion containing a polymer having an epoxy group structural unit content of 10 parts by mass or more.

6. The conductive paste according to any one of claims 1 to 5, wherein, The amount of the C rubber particles is in the range of 0.1 to 10 parts by mass relative to 100 parts by mass of component A.

7. The conductive paste according to any one of claims 1 to 6, wherein, The thermosetting resin B comprises epoxy resin, and the epoxy equivalent relative to the total mass of the thermosetting resin is less than 2000 g / eq.

8. The conductive paste according to any one of claims 1 to 7, wherein, The A comprises spherical silver particles and flake-shaped silver particles.

9. The conductive paste according to any one of claims 1 to 8, wherein, The content of component B is 3 to 25 parts by mass relative to 100 parts by mass of component A.

10. The conductive paste according to any one of claims 1 to 9, wherein, After drying at 120℃ for 60 minutes, it is cured in the atmosphere at 180℃ for 30 minutes using a blower dryer. At this time, the flexural modulus is 3GPa~15GPa.

11. The conductive paste according to any one of claims 1 to 9, wherein, After drying at 120℃ for 60 minutes, the material was cured in air at 180℃ for 30 minutes using a blower dryer. The resulting bond strength to the copper substrate was 1.0 kN / cm. 2 above.

12. The conductive paste according to any one of claims 1 to 11, wherein, The thixotropic index, measured at 25°C using an HB type viscometer, is 7 or less, representing the ratio of viscosity at 10 rpm to viscosity at 100 rpm.

13. The conductive paste according to any one of claims 1 to 12, used to form a second conductive layer of an external electrode, the external electrode having a first conductive layer connected to an internal electrode and a second conductive layer stacked on the first conductive layer.

14. A stacked ceramic electronic component having an external electrode formed using the conductive paste of claim 13.

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