Copper fine particle dispersion

Abstract

One embodiment of the present invention relates to a copper fine particle dispersion. The copper fine particle dispersion includes copper fine particles A and a dispersion medium C. The dispersion medium C content is 3-40 mass%, and the dispersion medium C includes a dispersion medium C1 that has a boiling point of 200-270°C and a dispersion medium C2 that has a boiling point greater than 270°C. The mass ratio C1 / C2 of the dispersion medium C1 with respect to the dispersion medium C2 is greater than 1. The dispersion medium C2 content in the dispersion medium C is 10-48 mass%. The copper fine particles A are preferably at least one type selected from copper nanoparticles A1 and copper microparticles A2. The copper nanoparticles A1 are preferably obtained by dispersion using a dispersion medium B. The average particle size of the copper nanoparticles A1 is preferably 105-270 nm.

Description

Copper fine particle dispersion

[0001] The present invention relates to a copper particulate dispersion and a method for producing a bonded body using the copper particulate dispersion.

[0002] Copper has excellent electrical and thermal conductivity, and is therefore widely used, for example, as a conductor wiring material, a heat transfer material, a heat exchange material, a heat dissipation material, etc. Because copper has excellent thermal conductivity, it is sometimes used as an alternative material to solder for joining objects to be joined.

[0003] In recent years, semiconductor devices known as power devices have become increasingly popular as power conversion and control devices, such as inverters. Unlike integrated circuits such as memory and microprocessors, power devices control high currents and generate a large amount of heat during operation. Therefore, solder used to mount power devices requires not only high bonding strength but also heat resistance. However, lead-free solder, which is widely used these days, has the disadvantage of low heat resistance. Therefore, various techniques have been proposed to bond objects by using copper particle dispersions instead of solder, which are applied to the objects by various coating methods and then baked. Copper contains oxidized copper atoms because its oxidation state is stable at room temperature (25°C). Therefore, to bond objects using copper particle dispersions, it is necessary to reduce the oxidized copper atoms and bake them to form a copper continuum.

[0004] For example, WO 2023 / 013034 (Patent Document 1) discloses a copper microparticle dispersion containing copper nanoparticles A dispersed in a polymer B and a dispersion medium C, wherein the polymer B comprises a structural unit derived from a monomer (b-1) having a carboxy group, and a structural unit derived from a monomer (b-2) having a polyalkylene glycol segment, and the content of the polyalkylene glycol segment in the polymer B is 55% by mass or more and 97% by mass or less, the acid value of the polymer B is 20 mg KOH / g or more and 250 mg KOH / g or less, and the dispersion medium C is (poly) alkylene glycol, (poly) alkylene glycol derivative, terpene alcohol, glycerin, and at least one selected from the group consisting of a glycerin derivative. Furthermore, International Publication No. 2021 / 060204 (Patent Document 2) discloses a copper paste for forming sintered copper pillars that bond members together, the copper paste containing metal particles and an organic dispersion medium, the metal particles including copper particles, and the organic dispersion medium containing 50 to 99 mass% of a high-boiling point solvent having a boiling point of 280°C or higher, based on the total mass of the organic dispersion medium.

[0005] The present inventors have found that the above-mentioned problems can be solved by including, in a copper particulate dispersion containing copper particulates A and a dispersion medium C, dispersion media C1 and C2 each having a specific boiling point within the dispersion medium C in specific proportions. The present invention relates to the following [1] to [3]. [1] A copper particulate dispersion containing copper particulates A and a dispersion medium C, wherein the content of the dispersion medium C is 3% by mass or more and 40% by mass or less, the dispersion medium C includes dispersion medium C1 having a boiling point of 200°C or more and 270°C or less and dispersion medium C2 having a boiling point above 270°C, the mass ratio C1 / C2 of the dispersion medium C1 to the dispersion medium C2 being greater than 1, and the content of the dispersion medium C2 in the dispersion medium C being 10% by mass or more and 48% by mass or less. [2] A method for producing a bonded body, comprising the following steps 1 to 3 in this order: Step 1: A step of applying the copper particulate dispersion according to the above item [1] onto a metal substrate. Step 2: Pre-baking the metal substrate obtained in Step 1 at a temperature of 100° C. or higher and 150° C. or lower. Step 3: Placing objects to be bonded on the copper microparticle dispersion of the metal substrate pre-baked in Step 2, and firing under pressure at a temperature of 150° C. or higher and 300° C. or lower and a pressure of 5 MPa or higher and 50 MPa or lower. [3] Use of the copper microparticle dispersion according to [1] above as a bonding material for bonding objects to be bonded together. Detailed Description of the Invention

[0006] Copper microparticle dispersions that have been proposed as solder-alternative joining materials have higher heat resistance than solder, but may experience uneven coating during application, leaving room for improvement in terms of coatability. Furthermore, conventional copper microparticle dispersions may experience defects such as cracking during firing depending on the drying state after application. The copper microparticle dispersion disclosed in Patent Document 1 has storage stability, but has issues with coatability during the formation of a bonded body. Furthermore, the copper paste disclosed in Patent Document 2 has insufficient coatability during the formation of a bonded body, and may experience cracking during firing.

[0007] The present invention relates to a copper fine particle dispersion that has excellent coatability, suppresses cracking during firing, and has excellent bonding strength, and to a method for producing a bonded body using the copper fine particle dispersion.

[0008] [Copper microparticle dispersion] The copper microparticle dispersion of the present invention is a copper microparticle dispersion containing copper microparticles A and a dispersion medium C, the content of which is 3% by mass or more and 40% by mass or less, the dispersion medium C containing a dispersion medium C1 having a boiling point of 200°C or more and 270°C or less and a dispersion medium C2 having a boiling point higher than 270°C, the mass ratio C1 / C2 of the dispersion medium C1 to the dispersion medium C2 exceeding 1, and the content of the dispersion medium C2 in the dispersion medium C being 10% by mass or more and 48% by mass or less.

[0009] According to the present invention, a copper microparticle dispersion can be obtained that exhibits excellent coatability, suppresses cracking during firing, and provides excellent bonding strength. The reason for this is unclear, but it is believed to be as follows. Typically, bonded structures such as semiconductor devices are produced by coating a substrate with a bonding material such as a copper microparticle dispersion, prebaking, placing a component such as an electronic chip on the prebaked bonding material, and then firing under pressure. When coating a copper microparticle dispersion, the copper microparticle dispersion must contain an appropriate amount of dispersion medium to achieve a viscosity suitable for coating. However, if the dispersion medium content is high, the dispersion medium cannot be sufficiently removed during prebaking, and sintering of the copper microparticles during pressure firing does not proceed. On the other hand, if the dispersion medium content is low, the amount of dispersion medium in the copper microparticle dispersion after prebaking is reduced, preventing atomic diffusion of the copper microparticles through the dispersion medium during pressure firing, thereby slowing sintering of the copper microparticles. As a result, it has been difficult for conventional copper microparticle dispersions to achieve both coatability, suppression of cracking during sintering, and bonding strength.

[0010] The copper microparticle dispersion of the present invention has a dispersion medium C content of 3% by mass or more and 40% by mass or less, thereby maintaining a viscosity appropriate for coating and improving coatability. Furthermore, the copper microparticle dispersion of the present invention has a dispersion medium C2 content of 20% by mass or more and 48% by mass or less, the dispersion medium C2 having a boiling point of greater than 270°C, thereby retaining a sufficient amount of dispersion medium to promote sintering of the copper microparticles during pressure firing, thereby suppressing cracking after firing and improving bonding strength. Furthermore, the copper microparticle dispersion of the present invention has a dispersion medium C1 having a boiling point of 200°C or more and 270°C or less, and the mass ratio C1 / C2 of the dispersion medium C1 to the dispersion medium C2 exceeds 1, thereby maintaining the viscosity of the copper microparticle dispersion within an appropriate range for coating. Furthermore, by keeping the content of the dispersion medium C1 within the above range, the dispersion medium C1 with a low boiling point is removed from the applied copper microparticle dispersion from the pre-bake process to the early stage of the pressurized firing, thereby increasing the sintering rate, suppressing cracking after firing, and improving the bonding strength.

[0011] According to the present invention, it is possible to provide a copper particulate dispersion that has excellent coatability, suppresses cracking during firing, and has excellent bonding strength, and a method for producing a bonded body using the copper particulate dispersion.

[0012] <Copper Fine Particles A> In the present invention, the copper fine particles A are preferably at least one type selected from copper nanoparticles A1 and copper microparticles A2, and more preferably comprise copper nanoparticles A1 and copper microparticles A2.

[0013] The copper content in the copper fine particles A is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and even more preferably substantially 100% by mass, from the viewpoints of improving conductivity, suppressing cracking, and improving bonding strength. Here, "substantially 100% by mass" means that unintentionally contained components may be included. Examples of unintentionally contained components include unavoidable impurities.

[0014] In the present invention, the content of copper microparticles A in the copper microparticle dispersion is, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, preferably 60% by mass or more, more preferably 68% by mass or more, even more preferably 75% by mass or more, still more preferably 85% by mass or more, still more preferably 90% by mass or more, and is preferably 97% by mass or less, more preferably 96% by mass or less, even more preferably 95% by mass or less, still more preferably 94% by mass or less, and still more preferably 93% by mass or less.

[0015] (Copper nanoparticles A1) In the present invention, the copper nanoparticles A1 are preferably copper nanoparticles A1 dispersed in a dispersant B from the viewpoints of improving coating properties, suppressing cracking, and improving bonding strength.

[0016] The average particle size of the copper nanoparticles A1 is preferably 105 nm or more, more preferably 110 nm or more, even more preferably 115 nm or more, even more preferably 120 nm or more, from the viewpoint of improving coating properties, suppressing cracking, and improving bonding strength, and is preferably 270 nm or less, more preferably 250 nm or less, even more preferably 240 nm or less, even more preferably 230 nm or less. The average particle size of the copper nanoparticles A1 is measured by the method described in the examples. The average particle size of the copper nanoparticles A1 can be adjusted by the reduction metal rate, the type and amount of the reducing agent, the type and amount of the dispersant B, and the production conditions of the copper microparticles such as the reduction temperature and reduction time.

[0017] In the present invention, the content of copper nanoparticles A1 in the copper microparticle dispersion is, from the viewpoint of improving coatability, suppressing cracking, and improving bonding strength, preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 65% ​​by mass or more, and preferably 97% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, still more preferably 80% by mass or less, and still more preferably 75% by mass or less.

[0018] [Dispersant B] In the present invention, copper nanoparticles A1 are dispersed with dispersant B, whereby the dispersibility of copper nanoparticles A1 is improved, the coatability of the copper fine particle dispersion is further improved, cracking is further suppressed, and further, the bonding strength is further improved.

[0019] From the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, the dispersant B is preferably a vinyl polymer P containing a structural unit derived from a monomer (p-1) having a carboxy group and a structural unit derived from a monomer (p-2) having a polyalkylene glycol segment. The vinyl polymer refers to a polymer obtained by polymerizing a monomer having a vinyl group by addition polymerization. Examples of the vinyl polymer P in the present invention include vinyl polymers such as acrylic resins, styrene resins, styrene-acrylic resins, and acrylic silicone resins.

[0020] <<Monomer (p-1) Having a Carboxy Group>> Examples of the monomer (p-1) having a carboxy group (hereinafter also referred to as "monomer (p-1)") include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and 2-methacryloyloxymethylsuccinic acid; and unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, and citraconic acid. The unsaturated dicarboxylic acids may be anhydrides. The monomer (p-1) may be used alone or in combination of two or more.

[0021] From the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, the monomer (p-1) is preferably at least one selected from (meth)acrylic acid and maleic acid, more preferably (meth)acrylic acid, and even more preferably methacrylic acid. In this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. Hereinafter, "(meth)acrylic acid" has the same meaning.

[0022] <Monomer (p-2) Having a Polyalkylene Glycol Segment> Examples of the monomer (p-2) having a polyalkylene glycol segment (hereinafter also referred to as "monomer (p-2)") include polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, and phenoxy polyalkylene glycol (meth)acrylate. The monomer (p-2) may be used alone or in combination of two or more. In this specification, "(meth)acrylate" refers to at least one selected from acrylate and methacrylate. The "(meth)acrylate" below has the same meaning.

[0023] From the viewpoints of improving the coatability, suppressing cracking, and improving the bonding strength, the monomer (p-2) is preferably at least one selected from polyalkylene glycol (meth)acrylates and alkoxy polyalkylene glycol (meth)acrylates, more preferably alkoxy polyalkylene glycol (meth)acrylates, and even more preferably alkoxy polyalkylene glycol methacrylates.

[0024] The number of carbon atoms in the alkoxy group of the alkoxy polyalkylene glycol (meth)acrylate is preferably 1 or more and 18 or less, more preferably 1 or more and 14 or less, even more preferably 1 or more and 12 or less, still more preferably 1 or more and 4 or less, still more preferably 1 or more and 3 or less, and still more preferably 1 or more and 2 or less, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength.

[0025] Examples of alkoxypolyalkylene glycol (meth)acrylates include methoxypolyalkylene glycol (meth)acrylate, ethoxypolyalkylene glycol (meth)acrylate, propoxypolyalkylene glycol (meth)acrylate, butoxypolyalkylene glycol (meth)acrylate, octoxypolyalkylene glycol (meth)acrylate, lauroxypolyalkylene glycol (meth)acrylate, etc. Among these, from the viewpoint of availability, the alkoxypolyalkylene glycol (meth)acrylate is preferably methoxypolyalkylene glycol (meth)acrylate, more preferably methoxypolyalkylene glycol methacrylate.

[0026] The polyalkylene glycol segment of monomer (p-2) preferably contains units derived from alkylene oxide having 2 to 4 carbon atoms, from the viewpoints of improving coatability, suppressing cracking, and improving bond strength. Examples of alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, etc., and is preferably at least one selected from ethylene oxide and propylene oxide, more preferably ethylene oxide. The number of alkylene oxide-derived units in the polyalkylene glycol segment is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, from the viewpoints of improving coatability, suppressing cracking, and improving bond strength, and is preferably 100 or less, more preferably 70 or less, even more preferably 50 or less, even more preferably 40 or less, and even more preferably 35 or less. The polyalkylene glycol segment may be a copolymer containing units derived from ethylene oxide and units derived from propylene oxide, from the viewpoints of improving coatability, suppressing cracking, and improving bond strength. The copolymer containing units derived from ethylene oxide and units derived from propylene oxide may be any of a block copolymer, a random copolymer, and an alternating copolymer.

[0027] Specific examples of commercially available monomer (p-2) include NK Ester AM-90G, AM-130G, AM-230G, AMP-20GY, M-20G, M-40G, M-90G, and M-230G, manufactured by Shin-Nakamura Chemical Co., Ltd.; and Blenmar PE-90, PE-200, PE-350, PME-100, and PME-230G, manufactured by NOF Corporation. Examples of such polyether esters include ME-200, PME-400, PME-1000, PME-4000, PP-500, PP-500D, PP-800, PP-1000, PP-2000D, AP-150, AP-400, AP-550, 50PEP-300, 50POEP-800B, 43PAPE-600B, and PLE-1300.

[0028] <Hydrophobic Monomer (p-3)> From the viewpoints of improving coatability, suppressing cracking, and improving bond strength, the vinyl polymer P preferably further contains a structural unit derived from a hydrophobic monomer (p-3) (hereinafter also referred to as "monomer (p-3)"). As used herein, "hydrophobic monomer" refers to a monomer that dissolves in an amount of less than 10 g when dissolved in 100 g of ion-exchanged water at 25°C until saturated. From the viewpoints of improving coatability, suppressing cracking, and improving bond strength, the amount of monomer (p-3) dissolved is preferably 5 g or less, more preferably 1 g or less. Monomer (p-3) is preferably at least one selected from aromatic group-containing monomers and (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol.

[0029] From the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, the aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group having from 6 to 22 carbon atoms, which may have a substituent containing a heteroatom, and more preferably at least one selected from a styrene-based monomer and an aromatic group-containing (meth)acrylate. The molecular weight of the aromatic group-containing monomer is preferably less than 500. Examples of styrene-based monomers include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), and divinylbenzene. Examples of aromatic group-containing (meth)acrylates include phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0030] From the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, the (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol preferably has a hydrocarbon group derived from an aliphatic alcohol having from 1 to 22 carbon atoms, more preferably has a hydrocarbon group derived from an aliphatic alcohol having from 1 to 12 carbon atoms, even more preferably has a hydrocarbon group derived from an aliphatic alcohol having from 1 to 8 carbon atoms, and even more preferably has a hydrocarbon group derived from an aliphatic alcohol having from 1 to 4 carbon atoms, and examples thereof include (meth)acrylates having a linear alkyl group, (meth)acrylates having a branched alkyl group, and (meth)acrylates having an alicyclic alkyl group. Examples of (meth)acrylates having a linear alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. Examples of (meth)acrylates having a branched alkyl group include isopropyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isopentyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, isododecyl (meth)acrylate, isostearyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of (meth)acrylates having an alicyclic alkyl group include cyclohexyl (meth)acrylate. Monomer (p-3) may be used alone or in combination of two or more.

[0031] From the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, the monomer (p-3) is preferably at least one selected from an aromatic group-containing monomer and a (meth)acrylate having a linear alkyl group, more preferably at least one selected from a styrene-based monomer and a (meth)acrylate having a linear alkyl group having from 1 to 4 carbon atoms, even more preferably at least one selected from styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate, still more preferably at least one selected from styrene and methyl (meth)acrylate, still more preferably at least one selected from methyl (meth)acrylate, and still more preferably methyl methacrylate.

[0032] The total content of monomer (p-1) and monomer (p-2) in the raw material monomers used in the production of the vinyl polymer P, or the total content of the structural units derived from monomer (p-1) and the structural units derived from monomer (p-2) in all the structural units of the vinyl polymer P, is, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 78% by mass or more, still more preferably 80% by mass or more, and is preferably 100% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less, and still more preferably 85% by mass or less.

[0033] The content of monomer (p-1) in the raw material monomers used in the production of the vinyl polymer P, or the content of structural units derived from monomer (p-1) in all structural units of the vinyl polymer P, is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, still more preferably 12% by mass or more, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, and is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and still more preferably 18% by mass or less.

[0034] The content of monomer (p-2) in the raw material monomers used in the production of the vinyl polymer P, or the content of structural units derived from monomer (p-2) in all structural units of the vinyl polymer P, is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, still more preferably 65% ​​by mass or more, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, and is preferably 97% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less, and still more preferably 70% by mass or less.

[0035] When the vinyl polymer P further contains a structural unit derived from the monomer (p-3), the content of the monomer (p-3) in the raw material monomers used in the production of the vinyl polymer P, or the content of the structural unit derived from the monomer (p-3) in all structural units of the vinyl polymer P, is, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 22% by mass or less, and still more preferably 20% by mass or less.

[0036] From the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, the content of polyalkylene glycol segments in the vinyl polymer P is preferably 55% by mass or more, more preferably 56% by mass or more, even more preferably 58% by mass or more, still more preferably 60% by mass or more, and is preferably 97% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less, and still more preferably 70% by mass or less.

[0037] From the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, the number average molecular weight Mn of the vinyl polymer P is preferably 4,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, and is preferably 50,000 or less, more preferably 30,000 or less, even more preferably 10,000 or less. The number average molecular weight Mn of the vinyl polymer P is measured by the method described in the Examples.

[0038] From the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, the acid value of the vinyl polymer P is preferably 20 mgKOH / g or more, more preferably 40 mgKOH / g or more, even more preferably 60 mgKOH / g or more, still more preferably 80 mgKOH / g or more, and is preferably 250 mgKOH / g or less, more preferably 200 mgKOH / g or less, even more preferably 150 mgKOH / g or less, and still more preferably 120 mgKOH / g or less. The acid value of the vinyl polymer P is measured by the method described in the Examples.

[0039] In the present invention, from the viewpoints of improving coating properties, suppressing cracking, and improving bonding strength, the content of dispersant B in the copper microparticle dispersion is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more, still more preferably 0.7% by mass or more, still more preferably 0.9% by mass or more, and is preferably 10% by mass or less, more preferably 8.0% by mass or less, still more preferably 5.0% by mass or less, still more preferably 3.0% by mass or less, still more preferably 2.0% by mass or less, still more preferably 1.5% by mass or less, and still more preferably 1.2% by mass or less.

[0040] In the present invention, the mass ratio of the content of dispersant B to the total content of copper nanoparticles A1 and dispersant B in the copper microparticle dispersion [dispersant B / (copper nanoparticles A1 + dispersant B)] (hereinafter also referred to as "dispersant B mass ratio") is preferably 0.005 or more, more preferably 0.008 or more, even more preferably 0.010 or more, from the viewpoint of improving coatability, suppressing cracking, and improving bonding strength. It is preferably 0.025 or less, more preferably 0.022 or less, even more preferably 0.020 or less, and even more preferably 0.018 or less. The dispersant B mass ratio is calculated from the content of copper nanoparticles A1 and the content of dispersant B in the copper microparticle dispersion measured by the method described in the examples using a differential thermal / thermogravimetric simultaneous analyzer (TG / DTA).

[0041] [Production of Copper Nanoparticles A1] Copper nanoparticles A1 can be obtained by mixing a copper raw material compound, a reducing agent, and a dispersant B, reducing the copper raw material compound in this mixture with the reducing agent to form a dispersion of copper nanoparticles A1 containing a dispersion medium B, and drying this dispersion. In the production of copper nanoparticles A1, a solvent for dispersing the copper raw material compound and the reducing agent, a complexing agent, etc. may be mixed as needed. In the production of copper nanoparticles A1, the reducing agent may be added simultaneously with other raw materials, or may be added dropwise to a mixture containing other raw materials.

[0042] The copper source compound is not particularly limited as long as it is a compound containing copper. Examples of copper source compounds include copper sulfate, copper nitrate, cupric oxide, cuprous oxide, copper formate, copper acetate, and copper oxalate. Among these, copper sulfate is preferred as the copper source compound from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength. The copper source compounds may be used alone or in combination of two or more.

[0043] The reducing agent is not particularly limited as long as it is a compound capable of reducing the copper raw material compound. Examples of the reducing agent include hydrazine compounds, boron compounds, and inorganic acid salts. Examples of hydrazine compounds include hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine hydrate (hydrazine monohydrate). Examples of boron compounds include sodium borohydride. Examples of inorganic acid salts include sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, and sodium hypophosphite. Among these, from the viewpoint of productivity, the reducing agent is preferably a hydrazine compound, more preferably at least one selected from the group consisting of hydrazine and hydrazine hydrate, and even more preferably hydrazine hydrate (hydrazine monohydrate). The reducing agents may be used alone or in combination of two or more.

[0044] Examples of solvents for dispersing the copper source compound and the reducing agent include water, methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol. Among these, water is preferred as the solvent from the viewpoints of availability and economy. The solvents may be used alone or in combination of two or more.

[0045] The temperature of the reduction reaction is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, even more preferably 20 ° C. or higher, and even more preferably 30 ° C. or higher from the viewpoint of reducing and uniformly dispersing the copper nanoparticles A1. From the viewpoint of stably producing the copper nanoparticles A1, the temperature is preferably 100 ° C. or lower, more preferably 80 ° C. or lower, even more preferably 60 ° C. or lower, and even more preferably 50 ° C. or lower. The reduction reaction may be carried out in an air atmosphere or an inert gas atmosphere such as nitrogen gas.

[0046] In the production of copper microparticle dispersions, the dispersion of copper nanoparticles A1 may be purified before drying in order to remove impurities such as unreacted reducing agent and excess dispersant B that does not contribute to the dispersion of copper nanoparticles A1. The method for purifying the dispersion of copper nanoparticles A1 is not particularly limited, and examples include membrane treatments such as dialysis and ultrafiltration; and centrifugation. Among these, membrane treatments are preferred, and dialysis is more preferred, in order to efficiently remove impurities. Regenerated cellulose is preferred as the material for the dialysis membrane used in dialysis. The molecular weight cutoff of the dialysis membrane is preferably 1,000 or more, more preferably 5,000 or more, and even more preferably 10,000 or more, in order to efficiently remove impurities, and is preferably 100,000 or less, more preferably 70,000 or less.

[0047] (Copper Microparticles A2) In the present invention, the copper microparticles A preferably contain copper microparticles A2 from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength.

[0048] From the viewpoints of improving coating properties, suppressing cracking, and improving bonding strength, the average particle size of the copper microparticles A2 is preferably more than 0.27 μm, more preferably 1 μm or more, even more preferably 1.5 μm or more, still more preferably 2 μm or more, still more preferably 2.5 μm or more, and is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 6 μm or less, and still more preferably 4 μm or less. The average particle size of the copper microparticles A2 is measured by the method described in the Examples.

[0049] In the present invention, the content of copper microparticles A2 in the copper microparticle dispersion is, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 12% by mass or more, still more preferably 15% by mass or more, even more preferably 18% by mass or more, still more preferably 20% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and still more preferably 25% by mass or less.

[0050] In the present invention, the mass ratio of the content of copper nanoparticles A1 to the total content of copper nanoparticles A1 and copper microparticles A2 in the copper microparticle dispersion [copper nanoparticles A1 / (copper nanoparticles A1+copper microparticles A2)] is, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, preferably 0.3 or more, more preferably 0.4 or more, even more preferably 0.5 or more, still more preferably 0.6 or more, and is preferably 1.0 or less, more preferably 0.9 or less, even more preferably 0.85 or less, and still more preferably 0.8 or less.

[0051] In the present invention, the total content of copper nanoparticles A1 and copper microparticles A2 in the copper microparticle dispersion is, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 85% by mass or more, and preferably 95% by mass or less, more preferably 94% by mass or less, still more preferably 93% by mass or less, and still more preferably 92% by mass or less.

[0052] <Dispersion medium C> The copper fine particle dispersion of the present invention has a dispersion medium C content of 3% by mass or more and 40% by mass or less, the dispersion medium C comprising dispersion medium C1 having a boiling point of 200° C. or more and 270° C. or less and dispersion medium C2 having a boiling point above 270° C., the mass ratio C1 / C2 of dispersion medium C1 to dispersion medium C2 being greater than 1, and the content of dispersion medium C2 in dispersion medium C being 20% ​​by mass or more and 48% by mass or less. In this specification, the boiling points of dispersion mediums C1 and C2 refer to boiling points at normal pressure (1 atmosphere).

[0053] In the present invention, the content of dispersion medium C in the copper microparticle dispersion is 3% by mass or more, preferably 4% by mass or more, more preferably 4.5% by mass or more, even more preferably 5% by mass or more, and even more preferably 5.5% by mass or more, from the viewpoints of improving coating properties, suppressing cracking, and improving bonding strength, and is 40% by mass or less, preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0054] In the present invention, the content of dispersion medium C1 in dispersion medium C is, from the viewpoint of improving coatability, suppressing cracking, and improving bonding strength, preferably 52% by mass or more, more preferably 54% by mass or more, even more preferably 55% by mass or more, still more preferably 56% by mass or more, still more preferably 57% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, still more preferably 65% ​​by mass or less, still more preferably 62% by mass or less, and still more preferably 60% by mass or less.

[0055] In the present invention, the content of dispersion medium C2 in dispersion medium C is 10% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 35% by mass or more, still more preferably 38% by mass or more, still more preferably 40% by mass or more, and 48% by mass or less, preferably 46% by mass or less, more preferably 45% by mass or less, even more preferably 44% by mass or less, and still more preferably 43% by mass or less. In the present invention, the mass ratio C1 / C2 of dispersion medium C1 to dispersion medium C2 in the copper microparticle dispersion is more than 1, preferably 1.1 or more, more preferably 1.2 or more, even more preferably 1.3 or more, and preferably 10.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less, from the viewpoints of improving coatability, suppressing cracking, and improving bond strength.

[0056] (Dispersion medium C1) In the present invention, the dispersion medium C1 is preferably at least one selected from (poly)alkylene glycols, (poly)alkylene glycol derivatives, and terpene alcohols, each having a boiling point of 200°C or higher and 270°C or lower, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength.

[0057] As used herein, the term "(poly)alkylene glycol" refers to at least one selected from alkylene glycols and polyalkylene glycols. Examples of (poly)alkylene glycols having a boiling point of 200°C or higher and 270°C or lower include diethylene glycol (boiling point: 244°C), dipropylene glycol (boiling point: 232°C), and 2-ethyl-1,3-hexanediol (boiling point: 244°C).

[0058] As used herein, the term "(poly)alkylene glycol derivative" refers to at least one selected from alkylene glycol derivatives and polyalkylene glycol derivatives. Examples of (poly)alkylene glycol derivatives having a boiling point of 200°C or higher and 270°C or lower include compounds in which the terminal hydroxy groups of the (poly)alkylene glycol are etherified or esterified. Examples of the (poly)alkylene glycol compound in which the hydroxy groups at both terminals are etherified or esterified include diethylene glycol dibutyl ether (boiling point: 254°C), triethylene glycol dimethyl ether (boiling point: 216°C), diethylene glycol monoethyl ether acetate (boiling point: 217°C), and diethylene glycol monobutyl ether acetate (boiling point: 247°C). Examples of the polyalkylene glycol compound in which the hydroxy group at one terminal is etherified or esterified include diethylene glycol monoethyl ether (boiling point: 202°C) and diethylene glycol monobutyl ether (boiling point: 231°C).

[0059] Examples of terpene alcohols having a boiling point of 200° C. or higher and 270° C. or lower include α-terpineol (boiling point: 219° C.), geraniol (boiling point: 229° C.), and citronellol (boiling point: 225° C.).

[0060] Among these, from the viewpoints of improving coating properties, suppressing cracking, and improving bonding strength, the dispersion medium C1 is more preferably a (poly)alkylene glycol having a boiling point of 200°C or more and 270°C or less, even more preferably at least one selected from diethylene glycol and dipropylene glycol, and even more preferably diethylene glycol and dipropylene glycol.

[0061] (Dispersion medium C2) In the present invention, from the viewpoint of improving the coatability, suppressing cracking, and improving the bonding strength, the dispersion medium C2 is preferably at least one selected from (poly)alkylene glycols, glycerin (boiling point: 290°C), and glycerin derivatives, each having a boiling point of more than 270°C.

[0062] Examples of (poly)alkylene glycols having a boiling point of more than 270°C include triethylene glycol (boiling point: 287°C), tetraethylene glycol (boiling point: 327°C), tripropylene glycol (boiling point: 273°C), tetrapropylene glycol (boiling point: 300°C or higher), polyethylene glycol (number average molecular weight preferably 100 or more and 1000 or less, more preferably 150 or more and 600 or less, and even more preferably 180 or more and 500 or less), and polypropylene glycol (number average molecular weight preferably 150 or more and 1000 or less, more preferably 180 or more and 600 or less, and even more preferably 200 or more and 500 or less).

[0063] Glycerin derivatives having a temperature exceeding 270°C are not particularly limited as long as they contain a structure derived from glycerin, and examples thereof include ether derivatives of glycerin, ester derivatives of glycerin, polyglycerin, and alkylene oxide adducts of glycerin (e.g., ethylene oxide adducts and propylene oxide adducts). Examples of polyglycerin include diglycerin and triglycerin, and commercially available polyglycerin includes Polyglycerin #310, Polyglycerin #500, and Polyglycerin #750 manufactured by Sakamoto Pharmaceutical Co., Ltd. Examples of ether derivatives of glycerin include 3-(2-ethylhexyloxy)-1,2-propanediol (boiling point: 325°C). Examples of ester derivatives of glycerin include glyceryl tributyrate (boiling point: 305°C).

[0064] Among these, from the viewpoints of improving coating properties, suppressing cracking, and improving bonding strength, the dispersion medium C2 is more preferably a (poly)alkylene glycol having a temperature of above 270°C, even more preferably at least one selected from tetraethylene glycol and polyethylene glycol (number average molecular weight of preferably 100 or more and 1000 or less, more preferably 150 or more and 600 or less, even more preferably 180 or more and 500 or less), and even more preferably at least one selected from tetraethylene glycol and polyethylene glycol (number average molecular weight of 180 or more and 500 or less).

[0065] The copper microparticle dispersion of the present invention may contain various additives as components other than the above-described components, provided that the effects of the present invention are not impaired. Examples of such additives include metal particles other than copper microparticles A, dispersion aids, sintering accelerators such as glass frit, antioxidants, viscosity modifiers, pH adjusters, buffers, antifoaming agents, leveling agents, and volatilization inhibitors. Examples of metal particles other than copper microparticles A include metal particles of zinc, nickel, silver, gold, palladium, and platinum. Examples of dispersion aids include, from the viewpoint of improving the dispersibility of copper microparticles and reducing the surface tension of the dispersion medium C and suppressing cracking, preferably 2,4,7,9-tetramethyl-5-decyne-4,7-diol and ethylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol. The content of additives in the copper microparticle dispersion of the present invention is preferably 1% by mass or less.

[0066] In the present invention, the mass ratio (C / A) of the content of dispersion medium C to the content of copper fine particles A in the copper particle dispersion is, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, preferably 0.03 or more, more preferably 0.04 or more, even more preferably 0.05 or more, and still more preferably 0.06 or more, and is preferably 0.70 or less, more preferably 0.67 or less, even more preferably 0.55 or less, still more preferably 0.50 or less, still more preferably 0.30 or less, still more preferably 0.20 or less, still more preferably 0.15 or less, and still more preferably 0.10 or less.

[0067] <Method for producing copper particle dispersion> The copper particle dispersion of the present invention is obtained by mixing the above-mentioned copper particle A and dispersion medium C of the present invention. The copper particle dispersion of the present invention can be produced by a method of adding and mixing previously prepared copper particle A and dispersion medium C, and optionally various additives; a method of mixing a copper raw compound, a reducing agent, and dispersant B, and optionally a solvent for dispersing the copper raw compound and the reducing agent, reducing the copper raw compound to obtain a dispersion of copper nanoparticles A1, and then adding and mixing dispersion medium C, and optionally copper microparticles A2 and various additives, etc. Among these, from the viewpoints of improving coatability, suppressing cracking, and improving bonding strength, a method of adding and mixing previously prepared copper particle A and dispersion medium C, and optionally various additives, is preferred. As the mixing method, known methods can be used. From the viewpoint of further dispersing the copper particle A in the dispersion medium C, it is preferable to pre-mix the copper particle A and dispersion medium C using an agate mortar or the like, and then further mix them using a stirring device such as a rotation / revolution stirring device.

[0068] <Applications> The copper microparticle dispersion of the present invention has excellent coatability, suppresses cracking during firing, and has excellent bonding strength, and therefore can be used to form conductive members for various electronic and electrical devices. The copper microparticle dispersion of the present invention can be used to form conductive members as a substitute for bonding agents such as solder. The copper microparticle dispersion of the present invention can also be used to form conductive members constituting antennas such as RFID (radio frequency identifier) ​​tags; capacitors such as MLCCs (multilayer ceramic capacitors); electronic paper; image display devices such as liquid crystal displays and organic EL displays; organic EL elements; organic transistors; wiring boards such as printed wiring boards and flexible wiring boards; organic solar cells; sensors such as flexible sensors, and the like.

[0069] [Method for manufacturing a bonded body] The method for manufacturing a bonded body of the present invention comprises the following steps 1 to 3 in this order: Step 1: A step of applying the above-mentioned copper fine particle dispersion of the present invention onto a metal substrate. Step 2: A step of pre-baking the metal substrate obtained in step 1 at a temperature of 100°C or higher and 150°C or lower. Step 3: A step of placing bodies to be bonded on the copper fine particle dispersion on the metal substrate pre-baked in step 2, and performing pressure firing at a temperature of 150°C or higher and 300°C or lower and a pressure of 5 MPa or higher and 50 MPa or lower.

[0070] (Step 1) Step 1 is a step of applying the copper particle dispersion of the present invention onto a metal substrate.

[0071] Examples of metal substrates include gold substrates, gold-plated substrates, silver substrates, silver-plated metal substrates, copper substrates, palladium substrates, palladium-plated metal substrates, platinum substrates, platinum-plated metal substrates, aluminum substrates, nickel substrates, nickel-plated metal substrates, tin substrates, and tin-plated metal substrates.

[0072] The copper microparticle dispersion can be applied by any known coating method, including, for example, various coating methods such as slot die coating, dip coating, spray coating, spin coating, doctor blading, knife edge coating, and bar coating; and various patterning printing methods such as stencil printing, screen printing, flexographic printing, gravure printing, offset printing, dispenser printing, and inkjet printing. Among these, stencil printing is preferred from the viewpoint of improving coatability. The amount of copper microparticle dispersion applied to the metal member can be appropriately adjusted depending on the size and type of the metal substrate.

[0073] (Step 2) This is a step of pre-baking the metal substrate obtained in step 1 at a temperature of 100° C. or higher and 150° C. or lower. By performing pre-baking in step 2, a portion of the dispersion medium C (particularly dispersion medium C1) can be appropriately removed from the applied copper microparticle dispersion, while the dispersion medium C (particularly dispersion medium C2) necessary for promoting sintering of the copper microparticles in the pressure firing in step 3 can remain, thereby suppressing cracking at the bonded portion of the resulting bonded body and improving the bonding strength.

[0074] The pre-bake temperature in step 2 is, from the viewpoint of suppressing cracking and improving bonding strength, 100°C or higher, preferably 105°C or higher, more preferably 110°C or higher, even more preferably 115°C or higher, and is 150°C or lower, preferably 140°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower.

[0075] The pre-baking time in step 2 is preferably 1 minute or longer, more preferably 3 minutes or longer, even more preferably 5 minutes or longer, from the viewpoint of suppressing cracking and improving bonding strength, and is preferably 60 minutes or shorter, more preferably 30 minutes or shorter, and even more preferably 20 minutes or shorter.

[0076] The atmosphere in step 2 may be an air atmosphere (atmospheric air), an inert gas atmosphere such as nitrogen gas, or a reducing gas atmosphere such as hydrogen gas, but from the viewpoint of productivity, an air atmosphere is preferred.

[0077] (Step 3) Step 3 is a step of placing the bonded body on the copper fine particle dispersion on the metal substrate prebaked in step 2, and firing the body under pressure at a temperature of 150°C to 300°C and a pressure of 5 MPa to 50 MPa.

[0078] Examples of the object to be bonded include a metal substrate, an electrically insulating substrate, a chip component, a semiconductor chip, etc. Examples of the metal substrate include the same as the metal substrate in step 1 above. Examples of the chip component include a capacitor, a resistor, etc. Examples of the semiconductor chip include a silicon chip, a memory, a diode, a transistor, an IC, a CPU, etc.

[0079] The temperature of the pressure firing treatment in step 3 is 150°C or higher, preferably 160°C or higher, more preferably 170°C or higher, and even more preferably 180°C or higher, from the viewpoint of improving the bonding strength, and is preferably 300°C or lower from the viewpoint of preventing damage to surrounding members.

[0080] The pressure of the pressurized firing treatment in step 3 is 5 MPa or more, preferably 10 MPa or more, more preferably 12 MPa or more, and even more preferably 15 MPa or more, from the viewpoint of suppressing cracking and improving bonding strength, and is 50 MPa or less, preferably 40 MPa or less, more preferably 30 MPa or less, and even more preferably 25 MPa or less, from the viewpoint of preventing damage to surrounding components.

[0081] The processing time of the pressure firing treatment in step 3 is preferably 30 seconds or more, more preferably 60 seconds or more, and even more preferably 120 seconds or more, from the viewpoint of suppressing cracking and improving bonding strength, and is preferably 300 seconds or less, more preferably 240 seconds or less, and even more preferably 180 seconds or less, from the viewpoint of productivity.

[0082] The atmosphere in the heating step may be an air atmosphere (atmospheric air), an inert gas atmosphere such as nitrogen gas, or a reducing gas atmosphere such as hydrogen gas. From the viewpoints of inhibiting copper oxidation and safety, however, an inert gas atmosphere is preferred, and a nitrogen gas atmosphere is more preferred.

[0083] The present application discloses the following invention as still another aspect.

[0084] <1> A copper microparticle dispersion comprising copper microparticles A and a dispersion medium C, wherein the content of the dispersion medium C is 3% by mass or more and 40% by mass or less, the dispersion medium C comprises a dispersion medium C1 having a boiling point of 200°C or more and 270°C or less and a dispersion medium C2 having a boiling point above 270°C, the mass ratio C1 / C2 of the dispersion medium C1 to the dispersion medium C2 being greater than 1, and the content of the dispersion medium C2 in the dispersion medium C being 10% by mass or more and 48% by mass or less. <2> The copper microparticle dispersion according to <1> above, wherein the copper microparticles A are at least one selected from copper nanoparticles A1 and copper microparticles A2. <3> The copper microparticle dispersion according to <1> or <2>, wherein the content of copper microparticles A in the copper microparticle dispersion is preferably 60% by mass or more, more preferably 68% by mass or more, even more preferably 75% by mass or more, still more preferably 85% by mass or more, still more preferably 90% by mass or more, and preferably 97% by mass or less, more preferably 96% by mass or less, even more preferably 95% by mass or less, still more preferably 94% by mass or less, and still more preferably 93% by mass or less. <4> The copper microparticle dispersion according to <2>, wherein the copper nanoparticles A1 are copper nanoparticles A1 dispersed in dispersant B. <5> The copper microparticle dispersion according to <2> or <4>, wherein the average particle size of the copper nanoparticles A1 is preferably 105 nm or more, more preferably 110 nm or more, even more preferably 115 nm or more, even more preferably 120 nm or more, and preferably 270 nm or less, more preferably 250 nm or less, even more preferably 240 nm or less, and even more preferably 230 nm or less. <6> The copper microparticle dispersion according to any one of <2>, <4> and <5>, wherein the content of copper nanoparticles A1 in the copper microparticle dispersion is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 65% ​​by mass or more, and preferably 97% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, still more preferably 80% by mass or less, and still more preferably 75% by mass or less.<7> The copper microparticle dispersion according to <4>, wherein the dispersant B is a vinyl polymer P containing a structural unit derived from a monomer (p-1) having a carboxy group and a structural unit derived from a monomer (p-2) having a polyalkylene glycol segment. <8> The copper microparticle dispersion according to <7>, wherein the monomer (p-1) having a carboxy group is one or more monomers selected from unsaturated monocarboxylic acids and unsaturated dicarboxylic acids, the unsaturated monocarboxylic acid is one or more monomers selected from (meth)acrylic acid, crotonic acid, and 2-methacryloyloxymethylsuccinic acid, and the unsaturated dicarboxylic acid is one or more monomers selected from maleic acid, itaconic acid, fumaric acid, and citraconic acid. <9> The copper microparticle dispersion according to <7>, wherein the monomer (p-2) having a polyalkylene glycol segment is one or more monomers selected from the group consisting of polyalkylene glycol (meth)acrylate, alkoxypolyalkylene glycol (meth)acrylate, and phenoxypolyalkylene glycol (meth)acrylate. <10> The copper microparticle dispersion according to any one of <7> to <9>, wherein Dispersant B further contains a structural unit derived from a hydrophobic monomer (p-3). <11> The copper fine particle dispersion according to any one of the above <7> to <10>, wherein the total content of monomer (p-1) and monomer (p-2) in the raw material monomers used in the production of the vinyl polymer P, or the total content of structural units derived from monomer (p-1) and structural units derived from monomer (p-2) in all structural units of the vinyl polymer P, is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 78% by mass or more, still more preferably 80% by mass or more, and is preferably 100% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less, and still more preferably 85% by mass or less.<12> The copper fine particle dispersion according to any one of the above items <7> to <11>, wherein the content of the monomer (p-1) in the raw material monomers used in the production of the vinyl polymer P, or the content of structural units derived from the monomer (p-1) in all structural units of the vinyl polymer P, is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, still more preferably 12% by mass or more, and is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and still more preferably 18% by mass or less. <13> The copper fine particle dispersion according to any one of the above <7> to <12>, wherein the content of the monomer (p-2) in the raw material monomers used in the production of the vinyl polymer P, or the content of structural units derived from the monomer (p-2) in all structural units of the vinyl polymer P, is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, still more preferably 65% ​​by mass or more, and is preferably 97% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less, and still more preferably 70% by mass or less. <14> The copper microparticle dispersion according to <10>, wherein the content of monomer (p-3) in the raw material monomers used to produce the vinyl polymer P, or the content of structural units derived from monomer (p-3) in all structural units of the vinyl polymer P, is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 22% by mass or less, and still more preferably 20% by mass or less. <15> The copper microparticle dispersion according to <7> or <9>, wherein the content of polyalkylene glycol segments in the vinyl polymer P is preferably 55% by mass or more, more preferably 56% by mass or more, even more preferably 58% by mass or more, still more preferably 60% by mass or more, and preferably 97% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less, and still more preferably 70% by mass or less.<16> The copper microparticle dispersion according to any one of <7> and <11> to <15>, wherein the vinyl polymer P has a number-average molecular weight Mn of preferably 4,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, and even more preferably 10,000 or less. <17> The copper microparticle dispersion according to any one of <7> and <11> to <16>, wherein the vinyl polymer P has an acid value of preferably 20 mgKOH / g or more, more preferably 40 mgKOH / g or more, even more preferably 60 mgKOH / g or more, still more preferably 80 mgKOH / g or more, and preferably 250 mgKOH / g or less, more preferably 200 mgKOH / g or less, even more preferably 150 mgKOH / g or less, and still more preferably 120 mgKOH / g or less. <18> The copper fine particle dispersion according to any one of <4> and <7> to <17> above, wherein the content of dispersant B in the copper fine particle dispersion is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more, still more preferably 0.7% by mass or more, still more preferably 0.9% by mass or more, and is preferably 10% by mass or less, more preferably 8.0% by mass or less, even more preferably 5.0% by mass or less, still more preferably 3.0% by mass or less, still more preferably 2.0% by mass or less, still more preferably 1.5% by mass or less, and still more preferably 1.2% by mass or less. <19> The copper fine particles according to any one of <4> and <7> to <18>, wherein the mass ratio of the content of dispersant B to the total content of copper nanoparticles A1 and dispersant B in the copper fine particle dispersion [dispersant B / (copper nanoparticles A1+dispersant B)] is preferably 0.005 or more, more preferably 0.008 or more, even more preferably 0.010 or more, and preferably 0.025 or less, more preferably 0.022 or less, even more preferably 0.020 or less, and even more preferably 0.018 or less.<20> The copper microparticle dispersion according to <2>, wherein the copper microparticles A2 have an average particle size of preferably more than 0.27 μm, more preferably 1 μm or more, even more preferably 1.5 μm or more, still more preferably 2 μm or more, still more preferably 2.5 μm or more, and preferably 10 μm or less, more preferably 8 μm or less, even more preferably 6 μm or less, and still more preferably 4 μm or less. <21> The copper microparticle dispersion according to <2> or <20>, wherein the content of the copper microparticles A2 in the copper microparticle dispersion is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 12% by mass or more, still more preferably 15% by mass or more, still more preferably 18% by mass or more, still more preferably 20% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and still more preferably 25% by mass or less. <22> The copper microparticle dispersion according to any one of <2>, <20>, and <21>, wherein the mass ratio of the content of copper nanoparticles A1 to the total content of copper nanoparticles A1 and copper microparticles A2 in the copper microparticle dispersion [copper nanoparticles A1 / (copper nanoparticles A1+copper microparticles A2)] is preferably 0.3 or more, more preferably 0.4 or more, even more preferably 0.5 or more, still more preferably 0.6 or more, and is preferably 1.0 or less, more preferably 0.9 or less, even more preferably 0.85 or less, and still more preferably 0.8 or less. <23> The copper microparticle dispersion according to any one of <2>, <20>, <21>, and <22>, wherein the total content of the copper nanoparticles A1 and the copper microparticles A2 in the copper microparticle dispersion is preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 85% by mass or more, and is preferably 95% by mass or less, more preferably 94% by mass or less, even more preferably 93% by mass or less, and still more preferably 92% by mass or less. <24> The copper microparticle dispersion according to <1>, wherein the dispersion medium C1 is at least one selected from the group consisting of a (poly)alkylene glycol, a (poly)alkylene glycol derivative, and a terpene alcohol, each having a boiling point of 200°C or more and 270°C or less.<25> The copper microparticle dispersion according to <1>, wherein the dispersion medium C2 is at least one selected from the group consisting of (poly)alkylene glycol, glycerin, and a glycerin derivative, and has a boiling point of greater than 270° C. <26> The copper microparticle dispersion according to <1>, wherein the content of the dispersion medium C in the copper microparticle dispersion is 3% by mass or more, preferably 4% by mass or more, more preferably 4.5% by mass or more, even more preferably 5% by mass or more, still more preferably 5.5% by mass or more, and is 40% by mass or less, preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, still more preferably 15% by mass or less, and still more preferably 10% by mass or less. <27> The copper microparticle dispersion according to <1> or <24>, wherein the content of dispersion medium C1 in dispersion medium C is preferably 52% by mass or more, more preferably 54% by mass or more, even more preferably 55% by mass or more, still more preferably 56% by mass or more, still more preferably 57% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 65% ​​by mass or less, still more preferably 62% by mass or less, and still more preferably 60% by mass or less. <28> The copper microparticle dispersion according to <1> or <25>, wherein the content of dispersion medium C2 in dispersion medium C is 10% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 35% by mass or more, still more preferably 38% by mass or more, still more preferably 40% by mass or more, and 48% by mass or less, preferably 46% by mass or less, more preferably 45% by mass or less, even more preferably 44% by mass or less, and still more preferably 43% by mass or less. <29> The copper fine particle dispersion according to <1>, wherein the mass ratio C1 / C2 of the dispersion medium C1 to the dispersion medium C2 in the copper fine particle dispersion exceeds 1, preferably 1.1 or more, more preferably 1.2 or more, even more preferably 1.3 or more, and is preferably 10.0 or less, more preferably 4.0 or less, even more preferably 3.0 or less.<30> The copper microparticle dispersion according to <1>, wherein the mass ratio (C / A) of the content of the dispersion medium C to the content of the copper microparticles A is preferably 0.03 or more, more preferably 0.04 or more, even more preferably 0.05 or more, still more preferably 0.06 or more, and is preferably 0.70 or less, more preferably 0.67 or less, even more preferably 0.55 or less, still more preferably 0.50 or less, still more preferably 0.30 or less, still more preferably 0.20 or less, still more preferably 0.15 or less, and still more preferably 0.10 or less. <31> A method for producing a bonded body, comprising the following steps 1 to 3 in this order: Step 1: applying the copper microparticle dispersion according to any one of <1> to <30> onto a metal substrate. Step 2: pre-baking the metal substrate obtained in Step 1 at a temperature of 100°C or more and 150°C or less. Step 3: A step of placing the objects to be bonded on the copper fine particle dispersion on the metal substrate prebaked in Step 2, and performing pressure firing under conditions of a temperature of 150° C. or higher and 300° C. or lower and a pressure of 5 MPa or higher and 50 MPa or lower. <32> The method for producing a bonded body according to <31> above, wherein the prebaking temperature in Step 2 is 100° C. or higher, preferably 105° C. or higher, more preferably 110° C. or higher, even more preferably 115° C. or higher, and 150° C. or lower, preferably 140° C. or lower, more preferably 130° C. or lower, and still more preferably 125° C. or lower. <33> The method for producing a bonded body according to <31> or <32> above, wherein the prebaking time in Step 2 is preferably 1 minute or longer, more preferably 3 minutes or longer, even more preferably 5 minutes or longer, and preferably 60 minutes or shorter, more preferably 30 minutes or shorter, and still more preferably 20 minutes or shorter. <34> The method for producing a joined body according to <31>, wherein the temperature of the pressure firing treatment in step 3 is 150°C or higher, preferably 160°C or higher, more preferably 170°C or higher, even more preferably 180°C or higher, and preferably 300°C or lower.<35> The method for producing a bonded body according to <31> or <34>, wherein the pressure in the pressure firing treatment in step 3 is 5 MPa or more, preferably 10 MPa or more, more preferably 12 MPa or more, even more preferably 15 MPa or more, and 50 MPa or less, preferably 40 MPa or less, more preferably 30 MPa or less, and even more preferably 25 MPa or less. <36> The method for producing a bonded body according to any one of <31>, <34>, and <35>, wherein the treatment time for the pressure firing treatment in step 3 is preferably 30 seconds or more, more preferably 60 seconds or more, even more preferably 120 seconds or more, and preferably 300 seconds or less, more preferably 240 seconds or less, and even more preferably 180 seconds or less. <37> Use of the copper fine particle dispersion according to any one of <1> to <30> as a bonding material for bonding objects to be bonded together.

[0085] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. In the following production examples, examples, and comparative examples, "parts" and "%" refer to "parts by mass" and "% by mass" unless otherwise specified. Various physical properties were measured or calculated by the following methods.

[0086] <Number-average molecular weight Mn of vinyl polymer P> This was determined by gel permeation chromatography under the following measurement conditions: The measurement sample was prepared by mixing 0.1 g of polymer with 10 mL of eluent in a glass vial, stirring the mixture with a magnetic stirrer at 25°C for 10 hours, and filtering the mixture through a syringe filter (DISMIC-13HP PTFE 0.2 μm, manufactured by Advantec Toyo Kaisha, Ltd.) to obtain a filtrate. (Measurement conditions) GPC apparatus: "HLC-8320GPC" manufactured by Tosoh Corporation Column: "TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guard column Super AW-H" manufactured by Tosoh Corporation Eluent: N,N-dimethylformamide dissolved with phosphoric acid and lithium bromide to concentrations of 60 mmol / L and 50 mmol / L, respectively Flow rate: 0.5 mL / min Standard substance: Monodisperse polystyrene kit manufactured by Tosoh Corporation "PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)"

[0087] <Acid Value of Vinyl Polymer P> The acid value of Polymer B was measured in accordance with JIS K0070-1992 (potentiometric titration method), except that the measurement solvent was changed from the ethanol and ether mixed solvent specified in JIS K0070 to an acetone and toluene mixed solvent (acetone:toluene=4:6 (volume ratio)).

[0088] <Calculation of the content of polyalkylene glycol segments in vinyl polymer P> The content of polyalkylene glycol segments in vinyl polymer P was calculated by multiplying the composition (parts by mass) of each monomer in vinyl polymer P by the ratio of polyalkylene glycol segments in each monomer.

[0089] <Average particle size of copper nanoparticles A1 and copper microparticles A2> Scanning electron microscope (SEM) images of copper nanoparticles A1 and copper microparticles A2 were taken using a scanning electron microscope (Hitachi High-Tech Corporation, field emission scanning electron microscope: S-4800). The magnification was determined according to the particle size of the particles, and images were taken in the range of 5,000 to 150,000 times. The SEM images were analyzed using image analysis software ImageJ (National Institutes of Health), and the particle sizes of 100 or more particles per sample were determined. The arithmetic average value was used as the average particle size of copper nanoparticles A1 and copper microparticles A2.

[0090] <Dispersant B mass ratio [Dispersant B / (copper nanoparticles A1 + dispersant B)]> Using a differential thermal thermogravimetric simultaneous analyzer (TG / DTA) (Hitachi High-Tech Science Corporation, trade name: STA7200RV), 10 mg of sample (dried powder of copper nanoparticles A1 containing dispersant B) was weighed into an aluminum pan cell, and heated from 35 ° C. to 550 ° C. at a heating rate of 10 ° C. / min under a nitrogen flow of 50 mL / min, and the mass loss was measured. The mass loss from 35 ° C. to 550 ° C. was the mass of polymer B, and the remaining mass at 550 ° C. was the mass of copper nanoparticles A1. The dispersant B mass ratio [Dispersant B / (copper nanoparticles A1 + dispersant B)] was calculated using the following formula. Dispersant B mass ratio = (mass loss from 35 ° C. to 550 ° C.) / (mass loss from 35 ° C. to 550 ° C. + remaining mass at 550 ° C.)

[0091] [Production of vinyl polymer P] Production Example 1 20.0 g of ethanol (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in a 1000 mL four-necked round-bottom flask equipped with a thermometer, two 100 mL dropping funnels with nitrogen bypasses, and a reflux apparatus, and the internal temperature of the flask was heated to 80°C in an oil bath, followed by bubbling with nitrogen for 10 minutes. Next, 15.3 g of methacrylic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., special reagent grade), 17.2 g of methyl methacrylate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., special reagent grade), 67.5 g of methoxypolyethylene glycol (EO 23 mol) methacrylate (NOF Corporation, "PME-1000", polyalkylene glycol segment ratio: 93.8%), 1.0 g of 3-mercaptopropionic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., special reagent grade), and 28.7 g of ethanol were mixed and dissolved in a polybeaker and placed in the dropping funnel (1). Separately, 1.3 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., "V-65", polymerization initiator) was dissolved in 51.3 g of ethanol in a polybeaker and placed in the dropping funnel (2). Next, the mixtures in the dropping funnels (1) and (2) were simultaneously added dropwise to the flask over 90 minutes. The internal temperature of the flask was then raised to 90°C, and stirring was continued for another hour to terminate the reaction. The resin solution was freeze-dried using a freeze dryer (Tokyo Rikakikai Co., Ltd., Model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., Model: DRC-1000) under drying conditions (freezing at -25°C for 1 hour, reduced pressure at -10°C for 9 hours, reduced pressure at 25°C for 5 hours, vacuum degree 5 Pa) to obtain bone-dried vinyl polymer P-1 (methacrylic acid / methyl methacrylate / methoxypolyethylene glycol (EO 23 mol) methacrylate polymer, acid value: 100 mg KOH / g, Mn: 8,000). The physical properties of the obtained vinyl polymer P-1 are shown in Table 1.

[0092]

[0093] Details of each monomer in Table 1 are as follows: (Monomer (p-1)) MAA: methacrylic acid (Monomer (p-2)) PEG (23) MA: methoxypolyethylene glycol (EO 23 moles) methacrylate (ratio of polyalkylene glycol segment: 93.8%) (Monomer (p-3)) MMA: methyl methacrylate

[0094] [Synthesis of dried powder of copper nanoparticles A1] Synthesis Example 1 In a 2 L beaker, 88.4 g of copper sulfate pentahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., special grade reagent) as a copper raw material compound, 0.7 g of the vinyl polymer P-1 obtained in Production Example 1 in an absolute dry state as dispersant B, and 1000 g of ion-exchanged water were added, and the mixture was stirred at 40 ° C. using a magnetic stirrer until it became visually transparent to obtain a mixed solution. Next, 17.8 g of hydrazine monohydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., special grade reagent) placed in a 50 mL dropping funnel was added dropwise to the mixed solution at 25 ° C. over 60 minutes. Thereafter, the reaction solution was stirred for 5 hours while controlling the temperature at 40 ° C. in an oil bath, and then air-cooled to obtain a reddish-brown dispersion containing dispersed copper nanoparticles. The entire amount of the obtained dispersion was placed in a dialysis tube (manufactured by REPLIGEN, trade name: Spectra / Por 6, dialysis membrane: regenerated cellulose, molecular weight cutoff (MWCO) = 50K), and the top and bottom of the tube were sealed with closures. This tube was immersed in 5 L of ion-exchanged water in a 5 L glass beaker, and the water temperature was maintained at 20 to 25 ° C and stirred for 1 hour. Thereafter, the process of replacing the entire amount of ion-exchanged water every hour was repeated. Sampling was performed before replacing the ion-exchanged water, and dialysis was terminated when the conductivity of the copper nanoparticle dispersion became 7 mS / m or less, thereby obtaining a copper nanoparticle dispersion. The conductivity was measured by diluting with ion-exchanged water to adjust the copper concentration to 1%. The purified copper nanoparticle dispersion was freeze-dried using a freeze dryer (manufactured by Tokyo Rikakikai Co., Ltd., model: DRC-1000) equipped with a dry chamber (manufactured by Tokyo Rikakikai Co., Ltd., model: FDU-2110), to obtain 21.3 g of dry powder containing vinyl polymer P-1 and copper nanoparticles A1-1 as dispersant B. Freeze-drying was performed by freezing at -25 ° C. for 1 hour, then drying under reduced pressure at -10 ° C. for 9 hours at 5 Pa, and then further drying under reduced pressure at 25 ° C. for 5 hours at 5 Pa. The obtained copper nanoparticles A1-1 had an average particle size of 160 nm and a dispersant B mass ratio of 0.014. The physical properties of the obtained dried powder are shown in Table 2.

[0095]

[0096] Example 1 <Production of copper microparticle dispersion> 3.7 parts by mass of dipropylene glycol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., first-class reagent) as dispersion medium C1, 2.8 parts by mass of polyethylene glycol 200 (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., first-class reagent, number average molecular weight: 200) as dispersion medium C2, 70 parts by mass of dry powder containing vinyl polymer P-1 and copper nanoparticles A1-1 obtained in Synthesis Example 1 as copper nanoparticles A1 and dispersant B, 23 parts by mass of MA-C03K (Mitsui Mining & Smelting Co., Ltd., particle size 3.4 μm) as copper microparticles A2, and 0.5 parts by mass of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (manufactured by Tokyo Chemical Industry Co., Ltd., DL-, meso-mixture) as other additives were added to an agate mortar and kneaded until the dry powder was no longer visible to the naked eye, and the resulting mixture was transferred to a plastic bottle. The sealed plastic bottle was stirred for 2000 min using a planetary vacuum mixer (Thinky Corporation, Planetary Vacuum Mixer ARV-310). －１ The mixture was stirred at 2000 rpm for 5 minutes to obtain a copper fine particle dispersion.

[0097] <Production of Bonded Assembly> A bonded assembly was produced using the obtained copper microparticle dispersion according to the following method. (Step 1) First, a stainless steel metal mask (thickness: 150 μm) having three rows of 6 mm x 6 mm square openings was placed on a 30 mm x 30 mm copper plate (total thickness: 1 mm), and the copper microparticle dispersion was applied to the copper plate by stencil printing using a metal squeegee. (Step 2) Then, the copper plate was prebaked at 120°C for 10 minutes on a Shamal hot plate (HHP-441, manufactured by AS ONE Corporation) in the atmosphere. (Step 3) Then, a 5 mm x 5 mm silicon chip (thickness: 400 μm) on which titanium, nickel, and gold had been sputtered in this order was prepared, and the silicon chip was placed on the applied copper microparticle dispersion so that the gold was in contact with the copper microparticle dispersion. This resulted in a laminate comprising a copper plate, a copper microparticle dispersion, and a silicon chip stacked in this order. The resulting laminate was fired by the following method to obtain a bonded assembly. First, the laminate was placed in a pressure firing machine (HTM-1000, manufactured by Meisho Kiko Co., Ltd.), and nitrogen was flowed into the furnace at 500 mL / min to replace the air in the furnace with nitrogen. Then, the temperature of the heating heads was raised to 200°C over 10 minutes while pressurizing the laminate at 20 MPa using the upper and lower heating heads. After the temperature increase, the laminate was sintered by holding at 200°C for 150 seconds to obtain a bonded body. After sintering, the heating heads were water-cooled at -60°C / min, and the bonded body was taken out into air at 100°C or below.

[0098] Examples 2 to 6 and Comparative Examples 1 to 4 The same procedures as in Example 1 were carried out except that the composition of the copper particulate dispersion was changed to the composition shown in Table 3, to obtain copper particulate dispersions and joined bodies of Examples 2 to 6 and Comparative Examples 1 to 4, respectively.

[0099] Details of the raw materials (each raw material in Table 3) used in producing the copper particulate dispersions of the Examples and Comparative Examples are as follows. (Copper microparticles A2) MA-C03K (Mitsui Mining & Smelting Co., Ltd., particle size 3.4 μm) (Dispersion medium C1) DPG: dipropylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent, boiling point: 232°C) DEG: diethylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent, boiling point: 244°C) (Dispersion medium C2) TEG: tetraethylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent, 327°C) PEG200: polyethylene glycol 200 (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent, number average molecular weight: 200, boiling point: 270°C or higher) (Other additives) TMDD: 2,4,7,9-tetramethyl-5-decyne-4,7-diol (Tokyo Chemical Industry Co., Ltd., DL-, meso-mixture)

[0100] [Evaluation of Copper Particle Dispersion] <Coatability> A stainless steel metal mask (thickness: 150 μm) having three rows of 6 mm × 6 mm square openings was placed on a 30 mm × 30 mm copper plate (total thickness: 1 mm), and the copper particle dispersion was applied to the copper plate by stencil printing using a metal squeegee. The state of the copper particle dispersion after application was visually confirmed and evaluated according to the following evaluation criteria. (Evaluation criteria) A: The copper particle dispersion applied in the three rows was not in contact with each other and was uniformly applied. B: The copper particle dispersion applied in the three rows was in contact with each other or was not uniformly applied.

[0101] <Cracks> Cracks at the bonded interface of the bonded bodies of the examples and comparative examples were evaluated according to the following procedure. The bonded interface was observed from the copper plate side of the bonded body using an ultrasonic flaw detector (Hitachi Power Solutions Co., Ltd., model: FS100III) equipped with a 50 MHz frequency probe. The probe was adjusted to the conditions under which the reflected wave from the bonded interface was strongest (highest peak), and measurements were performed under the following measurement conditions. The obtained images were visually inspected and evaluated according to the following evaluation criteria. (Measurement conditions) - Material sound velocity = Cu: 4700 mm / s - Gain = 28 dB (Evaluation criteria) A: No cracks were observed. B: Cracks were observed.

[0102] <Bonding Strength> The bonding strength of the bonded bodies of the Examples and Comparative Examples was measured according to the following procedure. Using a universal bond tester (Prospector, manufactured by Nordson Advanced Technology Co., Ltd.), the silicon chip of the bonded body was pressed horizontally at a test speed of 5 mm / min and a shear height of 50 μm to measure the die shear strength of the bonded body. Three bonded bodies were tested, and the average value of the values ​​measured for the three bonded bodies was taken as the bonding strength of the bonded body.

[0103]

[0104] As can be seen from Table 3, the copper microparticle dispersions of Examples 1 to 6 were superior in coatability, suppressed cracking during firing, and had superior bonding strength compared to the copper microparticle dispersions of Comparative Examples 1 to 4.

[0105] According to the present invention, it is possible to provide a copper particulate dispersion that has excellent coatability, suppresses cracking during firing, and has excellent bonding strength, and a method for producing a bonded body using the copper particulate dispersion.

Claims

A copper fine particle dispersion containing copper fine particles A and a dispersion medium C, the content of the dispersion medium C is 3% by mass or more and 40% by mass or less, The dispersion medium C includes a dispersion medium C1 having a boiling point of 200°C or higher and 270°C or lower, and a dispersion medium C2 having a boiling point of higher than 270°C, the mass ratio C1 / C2 of the dispersion medium C1 to the dispersion medium C2 exceeds 1; A copper fine particle dispersion, wherein the content of the dispersion medium C2 in the dispersion medium C is 10% by mass or more and 48% by mass or less. 　 The copper microparticle dispersion according to claim 1, wherein the copper microparticles A are at least one selected from copper nanoparticles A1 and copper microparticles A2. 　 The copper fine particle dispersion according to claim 2, wherein the copper nanoparticles A1 are copper nanoparticles A1 dispersed in a dispersant B. 　 The copper microparticle dispersion according to claim 2 or 3, wherein the copper nanoparticles A1 have an average particle size of 105 nm or more and 270 nm or less. 　 The copper microparticle dispersion according to any one of claims 2 to 4, wherein the content of copper nanoparticles A1 in the copper microparticle dispersion is 40% by mass or more and 97% by mass or less. 　 The copper fine particle dispersion according to claim 3, or any one of claims 4 and 5 dependent on claim 3, wherein dispersant B is a vinyl polymer P containing a structural unit derived from a monomer (p-1) having a carboxy group and a structural unit derived from a monomer (p-2) having a polyalkylene glycol segment.

7. The copper fine particle dispersion according to claim 6, wherein the vinyl polymer P has a number average molecular weight Mn of 4,000 or more and 50,000 or less.

8. The copper fine particle dispersion according to claim 6, wherein the vinyl polymer P has an acid value of 20 mgKOH / g or more and 250 mgKOH / g or less.

3. The copper microparticle dispersion according to claim 3, wherein the mass ratio of the content of dispersant B to the total content of copper nanoparticles A1 and dispersant B in the copper microparticle dispersion [dispersant B / (copper nanoparticles A1+dispersant B)] is 0.005 or more and 0.025 or less.

4. The copper microparticle dispersion according to claim 3, or any one of claims 4 to 8 dependent on claim 3. 　 The copper microparticle dispersion according to claim 2, wherein the copper microparticles A2 have an average particle size of more than 0.27 μm and not more than 10 μm. 　 The copper microparticle dispersion according to any one of claims 1 to 10, wherein the dispersion medium C1 is at least one selected from the group consisting of (poly)alkylene glycols, (poly)alkylene glycol derivatives, and terpene alcohols, each having a boiling point of 200°C or higher and 270°C or lower.

12. The copper microparticle dispersion according to claim 1, wherein the dispersion medium C2 is at least one selected from the group consisting of (poly)alkylene glycols, glycerin, and glycerin derivatives, each having a boiling point of more than 270°C.

13. The copper microparticle dispersion according to claim 1, wherein the mass ratio (C / A) of the content of the dispersion medium C to the content of the copper microparticles A is 0.03 or more and 0.70 or less. 　 A method for producing a bonded body, comprising the following steps 1 to 3 in this order: 　　 Step 1: A step of applying the copper fine particle dispersion according to any one of claims 1 to 13 onto a metal substrate. 　　 Step 2: A step of pre-baking the metal substrate obtained in step 1 at a temperature of 100°C or higher and 150°C or lower. 　　 Step 3: A step of placing the object to be bonded on the copper fine particle dispersion on the metal substrate prebaked in step 2, and firing the object under pressure at a temperature of 150°C to 300°C and a pressure of 5 MPa to 50 MPa. 　 Use of the copper fine particle dispersion according to any one of claims 1 to 13 as a bonding material for bonding objects to be bonded together.

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