Composite microparticles

Abstract

One embodiment of the present invention pertains to composite microparticles in which at least a portion of the surfaces of copper microparticles is covered by a dispersant. The composite microparticles have an average particle diameter D50 of 50-350 nm. In a number-based particle diameter histogram of the composite microparticles, the particle diameter D10 at a cumulative frequency of 10% and the particle diameter D90 at a cumulative frequency of 90% satisfy the condition D90 / D10≤4.0. The dispersant is a vinyl-based polymer that has a carboxyl group and includes a structure represented by formula (1). In formula (1), R1 is a hydrogen atom or a methyl group, and R2 is an organic group including a cyclic structure or an organic group including a chain structure that has a straight chain having at least three carbon atoms.

Description

composite fine particles

[0001] The present invention relates to composite microparticles, a method for producing composite microparticles, a dispersion of composite microparticles, and a copper bonding layer and wiring pattern, etc.

[0002] Copper has excellent electrical and thermal conductivity, and is therefore widely used as a conductive wiring material, heat transfer material, heat exchange material, and heat dissipation material. Because of its excellent thermal conductivity, copper is sometimes used as a substitute for solder when joining objects.

[0003] In recent years, semiconductor devices called power devices have become widely used as power conversion and control devices such as inverters. Unlike integrated circuits such as memory and microprocessors, power devices are designed to control high currents, resulting in high heat generation during operation, or so-called operating temperature. In particular, with the advent of wide-bandgap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN), it is possible to control even higher currents, but operating temperatures exceeding 200°C are also anticipated. Therefore, the solder used to mount power devices requires not only 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 technologies have been proposed that use a metal particle dispersion, which contains dispersed metal particles, instead of solder, and apply this to the target object using various coating methods, then sinter it to join the objects to be joined. The metal species used in the metal particle dispersion for mounting are mainly silver or copper. On the other hand, when joining parts using a metal particle dispersion, pressure and heat are applied, but if done at high pressures of 20 MPa or higher and high temperatures of 350°C or higher, there is a risk of damaging the semiconductor chip of the power device. Therefore, dispersions using metal nanoparticles with high surface energy, so-called large specific surface area, are often used so that joining can be done at low pressures of 20 MPa or lower and low temperatures of 350°C or lower. Among these, silver bonding layers formed by silver nanoparticle dispersions, when exposed to high temperatures of 200°C or higher, repeatedly undergo bonding and expansion of vacancies in the bonding layer, leading to vacancy coarsening and ultimately fracture. In contrast, copper bonding layers formed by copper particle dispersions show little bonding and expansion of vacancies even when exposed to high temperatures of 200°C or higher, and have high thermal stability, making them promising as next-generation bonding materials.

[0004] Patent Document 1 (International Publication No. 2023 / 013034) discloses a copper nanoparticle dispersion containing copper nanoparticles A dispersed in polymer B having a specific monomer composition and a specific acid value, and a specific dispersion medium C, and states that a bonded body with improved bonding strength can be obtained using this copper nanoparticle dispersion even after storage for a certain period of time. Patent Document 2 (Japanese Patent Application Publication No. 2022-169512) discloses a sintered powder containing copper nanoparticles for die attachment, wherein the particles are at least partially coated with a predetermined type and amount of capping agent, and the sintered powder exhibits a D10 of 100 nm or more and a D90 of 2000 nm or less, and states that this sintered powder exhibits advantageous sintering properties while being less susceptible to oxidation than conventional copper-containing sintered powders. Patent Document 3 (Japanese Patent Application Publication No. 2012-126942) discloses spherical copper fine powder obtained by a disproportionation reaction, characterized in that the average particle size of the copper fine powder measured by a laser diffraction particle size distribution analyzer is 0.25 μm or less, and the powder has only a single peak in particle size, and is particularly effective as powder for use in internal electrodes of multilayer ceramics.

[0005] The present inventors have found that composite microparticles having a specific average particle diameter D50, satisfying the relationship D90 / D10 ≤ 4.0 between the particle diameter D10 at a cumulative frequency of 10% and the particle diameter D90 at a cumulative frequency of 90% in a particle diameter histogram based on particle count, and comprising copper microparticles and a specific dispersant coating at least a portion of their surface, can solve the above problems. That is, the present invention relates to the following [1] to [8]. [1] Composite microparticles in which at least a portion of the surface of copper microparticles is coated with a dispersant, wherein the average particle diameter D50 of the composite microparticles is 50 nm or more and 350 nm or less, satisfying the relationship D90 / D10 ≤ 4.0 between the particle diameter D10 at a cumulative frequency of 10% and the particle diameter D90 at a cumulative frequency of 90% in a particle diameter histogram based on particle count, and the dispersant is a vinyl polymer having a carboxyl group and a structure represented by the following formula (1). In the above formula (1), R 1 R is a hydrogen atom or a methyl group.2 [2] A method for producing composite fine particles in which at least a portion of the surface of copper fine particles is coated with a dispersant, comprising the step of dropping a reducing agent into a mixed solution containing a copper raw material compound, a dispersant and a solvent with an SP value of 8 or more and 18 or less, wherein the dropping rate of the reducing agent per 1 mol of copper in the copper raw material compound is 0.01 mol / min or more. In the above formula (1), R 1 R is a hydrogen atom or a methyl group. 2 [1] is an organic group containing a cyclic structure or an organic group containing a chain structure having a linear chain with 3 or more carbon atoms, and n is a number between 1 and 1000. [3] A composite microparticle dispersion containing the composite microparticles described in [1]. [4] A copper bonding layer which is a sintered body of the composite microparticles described in [1]. [5] A wiring pattern which is a sintered body of the composite microparticles described in [1]. [6] A bonded body in which metal members are joined together via a copper bonding layer, wherein the copper bonding layer is a sintered body of the composite microparticles described in [1]. [7] A method for manufacturing a bonded body in which metal members are joined together via a copper bonding layer, comprising: applying the composite microparticle dispersion described in [3] to one metal member; placing the other metal member on the composite microparticle dispersion applied to the one metal substrate; and pressurizing and firing them. [8] Use of the composite microparticle dispersion described in [3] as a bonding material for joining metal members together. Detailed description of the invention

[0006] While copper bonding materials containing copper nanoparticles have higher heat resistance than solder, there is still room for improvement when used in power devices operating at temperatures exceeding 200°C. Specifically, even when using copper bonding materials containing copper nanoparticles with excellent low-temperature sinterability, cracks may occur in the copper bonding layer during or after sintering, or the layer may rupture due to thermal shrinkage caused by temperature changes after sintering. Such cracks or ruptures reduce heat dissipation in the copper bonding layer, hindering the stable operation of the power device. Furthermore, copper wiring formed using copper bonding materials containing copper nanoparticles may not fully function as wiring.

[0007] The present invention aims to provide composite microparticles that can be sintered at low temperatures and that can suppress the occurrence of cracks and fractures due to sintering, a method for producing composite microparticles, a dispersion of composite microparticles, a copper bonding layer and wiring pattern which are sintered bodies of the composite microparticles, a bonding body which includes a sintered body of composite microparticles as a copper bonding layer, and a method for producing the bonding body.

[0008] [Composite Fine Particles] The composite fine particles of the present invention are composite fine particles comprising copper fine particles and a dispersant that coats at least a portion of the surface of the copper fine particles, wherein the average particle diameter D50 of the composite fine particles is 50 nm or more and 350 nm or less, and in the particle diameter histogram of the composite fine particles based on the number of particles, the particle diameter D10 when the cumulative frequency is 10% and the particle diameter D90 when the cumulative frequency is 90% satisfy the relationship D90 / D10 ≤ 4.0, and the dispersant is a vinyl polymer having a carboxyl group and containing a structure represented by the following formula (1). In the above formula (1), R 1 R is a hydrogen atom or a methyl group. 2 n is an organic group containing a cyclic structure or an organic group containing a chain structure having three or more carbon atoms in a straight chain, and n is a number between 1 and 1000.

[0009] The composite microparticles of the present invention can be sintered at low temperatures, and the occurrence of cracks and fractures due to sintering can be suppressed. The reason for this is not entirely clear, but it is thought to be as follows. The composite microparticles of the present invention have an average particle diameter D50 of 50 nm or more and 350 nm or less, and at least a portion of the surface of the copper microparticles is coated with a dispersant that is a vinyl polymer containing a predetermined structure, and the particle diameters D10 and D90 in the particle diameter histogram based on the number of composite microparticles satisfy the relationship D90 / D10 ≤ 4.0. Therefore, the composite microparticles of the present invention are particles with relatively small particle diameters, and are dispersed in the dispersion medium by the dispersant that coats at least a portion of the surface of the copper microparticles, resulting in uniform dispersion of particles and suppression of aggregation. In addition, since the particle diameter values ​​of the individual composite microparticles are close, their surface energy values ​​are also similar, and it is thought that sintering proceeds uniformly. As a result, the resulting copper bonding layer has a uniform and strong structure, and it is thought that the occurrence of cracks and fractures due to sintering can be significantly suppressed. On the other hand, if the particle size histogram based on the number of composite fine particles does not satisfy the relationship D90 / D10 ≤ 4.0, the variation in particle size becomes large, which may cause an unevenness in the degree of sintering, resulting in an ununiform sintered body that cannot be obtained, and making it easier for cracks and fractures to occur in the areas where distortion occurs. Furthermore, composite fine particles that satisfy the above characteristics can be suitably manufactured by a wet chemical reduction method using a solvent with an SP value of 8 to 18, and by dropping a reducing agent into the solvent at a predetermined dropping rate.

[0010] According to the present invention, it is possible to provide composite fine particles that can be sintered at low temperatures and that can suppress the occurrence of cracks and fractures due to sintering, a method for producing composite fine particles, a dispersion of composite fine particles, a copper bonding layer and wiring pattern which are sintered bodies of the composite fine particles, a bonded body including a sintered body of composite fine particles as a copper bonding layer, and a method for producing the bonded body.

[0011] In this specification, "low-temperature sintering" means sintering at a temperature of 300°C or lower. The copper fine particles are granular copper components derived from the copper raw material compound used in the method for producing composite fine particles, which will be described in detail later, and are produced by the reduction of the copper raw material compound. The copper component preferably consists only of copper, but may contain some unavoidable impurities. The copper content in the copper component 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. "Substantially 100% by mass" means that it may contain components that are unintentionally included (unavoidable impurities).

[0012] The average particle size D50 of the composite fine particles (primary particles) of the present invention is 50 nm to 350 nm, from the viewpoint of improving sinterability at low temperatures and suppressing the occurrence of cracks and fractures due to sintering. The average particle size D50 of these composite fine particles is preferably 60 nm or more, more preferably 65 nm or more, from the viewpoint of providing good oxidation resistance and suppressing shrinkage during sintering, and from the viewpoint of improving the density of the sintered body, suppressing the occurrence of cracks and fractures, and improving sinterability at low temperatures, it is preferably 300 nm or less, more preferably 250 nm or less, even more preferably 210 nm or less, and even more preferably 175 nm or less. The average particle size D50 of the composite fine particles is the particle size D50 when the cumulative frequency is 50% in the particle size histogram based on the number of particles shown below. Specifically, it is measured by the method described in the examples. The average particle size D50 of the composite microparticles can be adjusted by the copper raw material compound used in the production of the composite microparticles, the type and amount of reducing agent, the type and amount of dispersant, the type and amount of solvent, and the temperature and time of the reduction reaction (the duration for which the temperature of the reduction reaction is maintained), as described later.

[0013] In the composite fine particles of the present invention, the ratio [D90 / D10] of the particle size D90 at a cumulative frequency of 90% to the particle size D10 at a cumulative frequency of 10% in a particle size histogram based on the number of particles satisfies the relationship D90 / D10 ≤ 4.0. The ratio [D90 / D10] is an index that shows the spread of the particle size distribution, and the smaller the value, the narrower the particle size distribution and the more uniform the particle size is. From the viewpoint of uniformly advancing sintering to improve the density of the sintered body and suppressing the occurrence of cracks and fractures, this ratio [D90 / D10] is 4.0 or less, preferably 3.5 or less, more preferably 3.1 or less. Furthermore, from the viewpoint of high close-packing properties of the composite fine particles, improving the density of the sintered body, suppressing the occurrence of cracks and fractures, and ease of manufacturing the composite fine particles, it is preferably 1.5 or more, more preferably 1.8 or more, even more preferably 2.1 or more, and even more preferably 2.3 or more. This ratio [D90 / D10] is calculated for composite microparticles by determining the particle size D10 when the cumulative frequency is 10% and the particle size D90 when the cumulative frequency is 90% from a particle size histogram based on the particle size of each particle measured from scanning electron microscope (SEM) images of the composite microparticles. The ratio [D90 / D10] is then determined from the calculated D10 and D90. Specifically, it is measured by the method described in the examples. This ratio [D90 / D10] can be adjusted by the copper raw material compound used in the production of the composite microparticles described later, the type and amount of reducing agent, the type and amount of dispersant, the type and amount of solvent, and the temperature and reduction time of the reduction reaction (the duration of maintenance of the reduction reaction temperature), etc., as well as other conditions for the production of the composite microparticles.

[0014] Here, the particle size D10 of the composite fine particles (primary particles) is preferably 20 nm or more, more preferably 30 nm or more, and even more preferably 40 nm or more, from the viewpoint of improving oxidation resistance and suppressing shrinkage during sintering, thereby suppressing the occurrence of cracks and fractures. Furthermore, from the viewpoint of improving the density of the sintered body and suppressing the occurrence of cracks and fractures, it is preferably 105 nm or less, more preferably 100 nm or less, even more preferably 95 nm or less, and even more preferably 90 nm or less.

[0015] <Dispersant> The composite microparticles of the present invention are preferably used as a composite microparticle dispersion for forming a conjugate by being dispersed in a dispersion medium as described below. Therefore, from the viewpoint of improving the dispersibility of the composite microparticles, suppressing uneven distribution due to aggregation of the composite microparticles when obtaining a sintered body, and allowing sintering to proceed uniformly, the composite microparticles include copper microparticles and a dispersant that coats at least a part of the surface of the copper microparticles.

[0016] As the dispersant, a vinyl polymer having a carboxy group is used from the viewpoint of improving the dispersion stability of the composite microparticles, improving the denseness of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures. The vinyl polymer refers to a polymer obtained by polymerizing a monomer having a vinyl group by addition polymerization, and examples thereof include acrylic resins, styrene resins, styrene-acrylic resins, and acrylic silicone resins. As the vinyl polymer used in the present invention, a vinyl polymer having a carboxy group and including a structure represented by the following formula (1) is used. In the above formula (1), R 1 is a hydrogen atom or a methyl group, R 2 is an organic group including a cyclic structure or an organic group including a chain structure having a straight chain with 3 or more carbon atoms, n is a number of 1 or more and 1000 or less, preferably 2 or more and 500 or less.

[0017] In this vinyl polymer, R 1 is a hydrogen atom or a methyl group, and preferably a methyl group from the viewpoint of improving its stability.

[0018] In this vinyl polymer, R 2The organic group containing the cyclic structure represented by may be any organic group containing one or more structures selected from the group consisting of aromatic ring structures and alicyclic structures. In the alicyclic structure, all bonds may be saturated bonds, or some may be unsaturated bonds. Furthermore, heteroatoms may be included in the cyclic structure. Examples of aromatic ring structures of this cyclic structure include benzene, naphthalene, anthracene, and phenanthrene. From the viewpoint of further demonstrating the effects of the present invention, the number of ring-forming carbon atoms in the aromatic ring is preferably 5 to 10. Specifically, the aromatic ring structure is preferably benzene. Furthermore, examples of alicyclic structures in this cyclic structure include monocyclic structures such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, cyclododecane, cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclodecene, and cyclododecene, as well as polycyclic structures such as norbornane, adamantane, norbornene, and adamantene. From the viewpoint of further demonstrating the effects of the present invention, the number of ring-forming carbon atoms in the alicyclic structure is preferably 5 to 10. Specifically, the alicyclic structure is preferably cyclohexane.

[0019] In this vinyl polymer, R 2 An organic group containing a chain structure represented by (excluding the organic group containing the cyclic structure) is any organic group containing a chain structure having a straight chain with three or more carbon atoms, and the chain structure may contain heteroatoms. This chain structure may be either a straight chain or a branched chain, and preferably contains an alkylene oxide structure.

[0020] This vinyl polymer R 2The number of carbon atoms constituting the linear structure of the organic group containing the chain structure represented by is preferably 5 or more, more preferably 15 or more, even more preferably 25 or more, even more preferably 35 or more, and even more preferably 45 or more, from the viewpoint of improving the dispersion stability of the composite fine particles and suppressing the occurrence of cracks and fractures due to sintering, and is preferably 200 or less, more preferably 150 or less, even more preferably 100 or less, and even more preferably 60 or less, from the viewpoint of improving the sinterability of the composite fine particles and suppressing the occurrence of cracks and fractures due to sintering.

[0021] This vinyl polymer R 2 The linear structure of an organic group containing a chain structure represented by includes, for example, an alkylene structure or an alkylene oxide structure. When, for example, an alkylene structure (meth)acrylate is used as a monomer as a raw material for the production of vinyl polymers, R 2 is, -COO-R 3 - (Here, R 3 This is a linear or branched alkylene group having two or more carbon atoms. ) and the number of carbon atoms constituting the chain structure is at least three. Furthermore, when using an ethylene oxide structure (meth)acrylate as a monomer, R 2 is -COO-(CH2-CH2-O) n The structure is represented by -, and the number of carbon atoms constituting the chain structure is at least 3 when n=1, and at least 5 when n=2. Here, n represents the repeating unit and is a number of 1 or more, preferably 2 or more, more preferably 3 or more, even more preferably 15 or more, even more preferably 20 or more, and 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.

[0022] This vinyl polymer R 2The total atomic weight of the atoms constituting the organic group represented by is preferably 50 or more, more preferably 100 or more, still more preferably 500 or more, and even more preferably 800 or more from the viewpoint of improving the dispersibility of the composite fine particles and suppressing the occurrence of cracks and fractures due to sintering. And, from the viewpoint of improving the sinterability of the composite fine particles and suppressing the occurrence of cracks and fractures due to sintering, it is preferably 5000 or less, more preferably 3500 or less, and still more preferably 2000 or less.

[0023] This vinyl polymer is preferably a polymer of a monomer having a carboxy group and a monomer represented by the following formula (2). In the above formula (2), R 1 and R 2 are the same organic group as that in formula (1).

[0024] Among these, the dispersant is preferably a vinyl polymer 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 (poly) alkylene glycol segment from the viewpoint of improving the dispersion stability of the composite fine particles, improving the denseness of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures. The vinyl polymer may be any of a random copolymer, a block copolymer, and an alternating copolymer. Here, "having a (poly) alkylene glycol segment" means that the monomer (p-2) has an alkylene glycol segment or a polyalkylene glycol segment.

[0025] [Monomer (p-1) having a carboxy group] As the monomer (p-1), unsaturated monocarboxylic acids such as (meth) acrylic acid, crotonic acid, 2-methacryloyloxymethyl succinic acid; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, citraconic acid, etc. are preferably mentioned. Note that the unsaturated dicarboxylic acid may be an anhydride. The monomer (p-1) may be used alone or in combination of two or more. From the viewpoints of improving the dispersion stability of the composite fine particles, improving the denseness of the sintered body formed by sintering, suppressing the occurrence of cracks and breakage, and availability and economy, the monomer (p-1) is preferably at least one selected from the group consisting of (meth) acrylic acid and maleic acid, more preferably (meth) acrylic acid, and still more preferably methacrylic acid. In this specification, "(meth) acrylic acid" means at least one selected from the group consisting of acrylic acid and methacrylic acid.

[0026] [Monomer (p-2) having a (poly) alkylene glycol segment] Examples of the monomer (p-2) include alkylene glycol (meth) acrylate, polyalkylene glycol (meth) acrylate, alkoxypolyalkylene glycol (meth) acrylate, phenoxypolyalkylene glycol (meth) acrylate, and the like. The monomer (p-2) may be used alone or in combination of two or more. In this specification, "(meth) acrylate" means at least one selected from the group consisting of acrylate and methacrylate.

[0027] From the viewpoint of improving the dispersion stability of the composite fine particles, improving the density of the sintered body, and suppressing the occurrence of cracks and fractures, the monomer (p-2) is preferably one or more selected from the group consisting of alkylene glycol (meth)acrylate, polyalkylene glycol (meth)acrylate, and alkoxy polyalkylene glycol (meth)acrylate, more preferably one or more selected from the group consisting of alkylene glycol (meth)acrylate and alkoxy polyalkylene glycol (meth)acrylate, and even more preferably alkoxy polyalkylene glycol (meth)acrylate. From the viewpoint of the same as above, the number of carbon atoms in the alkoxy polyalkylene glycol (meth)acrylate is preferably 18 or less, more preferably 12 or less, even more preferably 4 or less, and even more preferably 1. Examples of the alkylene glycol (meth)acrylate include hydroxypropyl (meth)acrylate. Examples of preferred alkoxy polyalkylene glycol (meth)acrylates include methoxypolyalkylene glycol (meth)acrylate, ethoxypolyalkylene glycol (meth)acrylate, propoxypolyalkylene glycol (meth)acrylate, butoxypolyalkylene glycol (meth)acrylate, octoxypolyalkylene glycol (meth)acrylate, and lauroxypolyalkylene glycol (meth)acrylate. Among these, methoxypolyalkylene glycol (meth)acrylate is more preferred, and methoxypolyalkylene glycol methacrylate is even more preferred.

[0028] The (poly)alkylene glycol segment of monomer (p-2) preferably contains units derived from alkylene oxide having 2 to 4 carbon atoms, from the viewpoint of improving the dispersion stability of composite fine particles, improving the density of the sintered body formed by sintering, suppressing the occurrence of cracks and fractures, as well as from the viewpoint of availability and economy. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, and the like, preferably one or more selected from the group consisting of ethylene oxide and propylene oxide, and more preferably ethylene oxide. The number of alkylene oxide-derived units in the (poly)alkylene glycol segment is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, even more preferably 15 or more, even more preferably 20 or more, and 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, from the viewpoint of improving the dispersion stability of composite fine particles, improving the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures. The (poly)alkylene glycol segment may be a copolymer containing units derived from ethylene oxide and units derived from propylene oxide, from the viewpoint of improving the dispersion stability of composite fine particles, improving the density of the sintered body formed by sintering, suppressing the occurrence of cracks and fractures, as well as from the viewpoint of availability and economy. The copolymer containing units derived from ethylene oxide and units derived from propylene oxide may be a random copolymer, a block copolymer, or an alternating copolymer.

[0029] The monomer (p-2) is preferably one or more selected from hydroxypropyl (meth)acrylate, polyethylene glycol (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate, more preferably one or more selected from hydroxypropyl (meth)acrylate and methoxypolyethylene glycol (meth)acrylate, even more preferably one or more selected from hydroxypropyl (meth)acrylate and methoxypolyethylene glycol (meth)acrylate, even more preferably one or more selected from hydroxypropyl methacrylate and methoxypolyethylene glycol methacrylate, and even more preferably methoxypolyethylene glycol methacrylate. The number of repeating oxyethylene groups in methoxypolyethylene glycol methacrylate is preferably 2 or more, more preferably 3 or more, even more preferably 15 or more, even more preferably 20 or more, and 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.

[0030] Specific examples of commercially available monomers (p-2) include NK ester AM-90G, AM-130G, AM-230G, AMP-20GY, M-20G, M-40G, M-90G, M-230G, etc., manufactured by Shin Nakamura Chemical Industry Co., Ltd.; and Bremmer PE-90, PE-200, PE-350, PME-100, P, etc., manufactured by NOF Corporation. Examples 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, PLE-1300, and others.

[0031] [Hydrophobic monomer (p-3)] The vinyl polymer may further contain constituent units derived from hydrophobic monomer (p-3) from the viewpoint of improving the density of the sintered body formed by sintering and suppressing the occurrence of cracks and fractures. In this specification, "hydrophobic monomer" means that when the monomer is dissolved in 100 g of ion-exchanged water at 25°C until saturated, the amount dissolved is less than 10 g. The amount of monomer (p-3) dissolved is preferably 5 g or less, more preferably 1 g or less, from the viewpoint of improving the density of the sintered body formed by sintering and suppressing the occurrence of cracks and fractures. The monomer (p-3) is preferably one or more selected from the group consisting of aromatic group-containing monomers and (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols.

[0032] Examples of aromatic group-containing monomers include styrene monomers and aromatic group-containing (meth)acrylates. The molecular weight of the aromatic group-containing monomer is preferably less than 500. Examples of styrene 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.

[0033] Examples of (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols include (meth)acrylates having linear alkyl groups, (meth)acrylates having branched alkyl groups, and (meth)acrylates having alicyclic alkyl groups. Examples of (meth)acrylates having linear alkyl groups 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 branched alkyl groups 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. As for (meth)acrylates having alicyclic alkyl groups, cyclohexyl (meth)acrylate is a preferred example.

[0034] The vinyl polymer preferably contains, from the viewpoint of improving the dispersion stability of composite fine particles, improving the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures, one or more constituent units selected from (meth)acrylic acid and maleic acid as monomer (p-1), and constituent units derived from hydroxypropyl (meth)acrylate, polyethylene glycol (meth)acrylate and methoxypolyethylene glycol (meth)acrylate as monomer (p-2), more preferably a constituent unit derived from (meth)acrylic acid as monomer (p-1), and constituent units derived from hydroxypropyl (meth)acrylate and methoxypolyethylene glycol (meth)acrylate as monomer (p-2).

[0035] The content of monomer (p-1) in the raw material monomer during the production of vinyl polymers, or the content of monomer (p-1)-derived constituent units in the total constituent units of the vinyl polymer, is preferably 3% by mass or more, more preferably 5% by mass or more, and preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, from the viewpoint of improving the dispersion stability of composite fine particles, improving the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures. Furthermore, the content of monomer (p-2) in the raw material monomer during the production of vinyl polymers, or the content of monomer (p-2)-derived constituent units in the total constituent units of the vinyl polymer, is preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, and preferably 97% by mass or less, and even more preferably 95% by mass or less, from the viewpoint of improving the dispersion stability of composite fine particles, improving the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures.

[0036] In the present invention, the total content of monomer (p-1) and monomer (p-2) in the raw material monomer during the production of vinyl polymers, or the total content of constituent units derived from monomer (p-1) and monomer (p-2) in all constituent units of the vinyl polymer, is preferably 90% by mass or more, more preferably 97% by mass or more, and even more preferably substantially 100% by mass, from the viewpoint of improving the dispersion stability of composite fine particles, improving the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures. Here, "substantially 100% by mass" means that it may include components that are included unintentionally. Examples of components that are included unintentionally include monomers other than monomer (p-1) and monomer (p-2) contained in the raw material monomer (p-1) and monomer (p-2), so-called impurities.

[0037] The weight-average molecular weight Mw of the vinyl polymer is preferably 3,000 or more, more preferably 6,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 17,000 or less, and even more preferably 10,000 or less, from the viewpoint of improving the dispersion stability of the composite fine particles, improving the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures. The weight-average molecular weight Mw is measured by the method described in the examples.

[0038] The acid value of the vinyl polymer is preferably 10 mg KOH / g or more, more preferably 20 mg KOH / g or more, even more preferably 30 mg KOH / g or more, and even more preferably 40 mg KOH / g or more, and preferably 250 mg KOH / g or less, more preferably 230 mg KOH / g or less, and even more preferably 210 mg KOH / g or less, from the viewpoint of improving the dispersion stability of the composite fine particles, improving the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures. The acid value of the vinyl polymer can be measured by the method described in the examples, but it can also be calculated from the mass ratio of the constituent monomers.

[0039] In the composite microparticles of the present invention, the ratio of the mass of the dispersant to the total mass of the copper microparticles and the dispersant [dispersant / (copper microparticles + dispersant)] (hereinafter also referred to as the "dispersant mass ratio") is preferably 0.001 or higher, more preferably 0.003 or higher, even more preferably 0.005 or higher, even more preferably 0.009 or higher, and preferably 0.020 or lower, more preferably 0.018 or lower, even more preferably 0.016 or lower, and even more preferably 0.014 or lower. The dispersant mass ratio is calculated from the content of composite microparticles and the content of dispersant in the composite microparticle dispersion using a differential thermogravimetric / dry thermometer (TG / DTA). Specifically, it is measured by the method described in the examples.

[0040] [Method for Manufacturing Composite Fine Microparticles] The present invention provides a method for manufacturing composite fine microparticles, which includes a composite fine microparticle manufacturing step in which a copper raw material compound is reduced by a wet chemical reduction method to produce the composite fine microparticles. For example, this method involves mixing a copper raw material compound, a reducing agent, and a solvent, and then reducing the copper raw material compound with the reducing agent. Here, it is preferable to mix the copper raw material compound, a dispersant, a solvent, and a reducing agent to obtain a dispersion of composite fine microparticles containing copper fine microparticles and a dispersant that disperses the copper fine microparticles in the solvent, and then dry the dispersion of composite fine microparticles by freeze-drying or the like. In the dried composite fine microparticle powder obtained in this way, part or all of the surface of the copper fine microparticles is coated with the dispersant.

[0041] Furthermore, in one embodiment, the method for producing composite fine particles of the present invention is a method for producing composite fine particles comprising copper fine particles and a dispersant that coats at least a part of the surface thereof, comprising the step of dropping a reducing agent onto a mixed solution containing a copper raw material compound, a dispersant, and a solvent with an SP value of 8 or more and 18 or less, wherein the dispersant is a vinyl polymer having a carboxyl group and a structure represented by the following formula (1), and the dropping rate of the reducing agent per 1 mol of copper in the copper raw material compound is 0.01 mol / min or more.

[0042] In the above formula (1), R 1 R is a hydrogen atom or a methyl group. 2 The group is an organic group containing a cyclic structure or an organic group containing a chain structure having three or more carbon atoms in a straight chain, and n is a number between 1 and 1000. Preferred vinyl polymers are as described above. In one embodiment, the method for producing composite fine particles of the present invention preferably includes maintaining a mixture containing a copper raw material compound, a dispersant, and a solvent with an SP value of 8 to 18 at a predetermined temperature below the boiling point of the solvent for at least one minute in order to reduce the copper raw material compound.

[0043] The temperature of the reduction reaction in the composite fine particle manufacturing process, in other words, the temperature for reducing the copper raw material compound in the mixture of the copper raw material compound, reducing agent, dispersant, and solvent, more specifically, the temperature of the reaction solution containing the mixture of the copper raw material compound, dispersant, and solvent and the reducing agent dropped into the mixture (the predetermined temperature), is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 30°C or higher, even more preferably 50°C or higher, and even more preferably 60°C or higher, from the viewpoint of increasing the specific surface area of ​​the composite fine particles and making the particle size distribution uniform. Furthermore, from the viewpoint of suppressing the generation of bubbles and making the particle size distribution uniform, it is preferably carried out in a range of less than the boiling point of the solvent, more preferably 2.5°C or less below the boiling point of the solvent, and even more preferably 5°C or less below the boiling point of the solvent. In other words, the predetermined temperature is preferably less than the boiling point of the solvent, more preferably 2.5°C or more below the boiling point of the solvent, and even more preferably 5°C or more below the boiling point of the solvent. The upper limit of the reduction reaction temperature varies depending on the solvent used, but from the viewpoint of suppressing foam generation and ensuring a uniform particle size distribution, it is preferably 75°C or lower, more preferably 73°C or lower. The reduction of the copper raw material compound may be carried out in an air atmosphere or in an inert gas atmosphere such as nitrogen gas. From the viewpoint of suppressing foam generation and ensuring a uniform particle size distribution, the maintenance time for the reduction reaction temperature is preferably 1 minute or more, more preferably 30 minutes or more, and even more preferably 1 hour or more, and from the viewpoint of productivity, it is preferably 30 hours or less, more preferably 20 hours or less, and even more preferably 10 hours or less.

[0044] There are no particular restrictions on the copper raw material compound as long as it is a compound containing copper. Examples of copper raw material compounds include copper sulfate, copper nitrate, cupric oxide, cuprous oxide, copper formate, copper acetate, and copper oxalate. Among these, the copper raw material compound is preferably one or more selected from copper oxides such as cupric oxide and cuprous oxide, and more preferably cupric acid value, from the viewpoint of improving the density of the sintered body formed by sintering and suppressing the occurrence of cracks and fractures. The copper raw material compound can be used alone or as a mixture of two or more.

[0045] There are no particular restrictions on the reducing agent as long as it is a compound that can reduce the copper raw material compound. Examples of reducing agents include hydrazine compounds, boron compounds, and inorganic salts. Examples of hydrazine compounds include hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrated hydrazine (hydrazine monohydrate). Examples of boron compounds include sodium borohydride. Examples of inorganic 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 and uniform particle size distribution, the reducing agent is preferably one or more selected from the group consisting of hydrazine compounds, more preferably hydrazine and hydrated hydrazine (hydrazine monohydrate), and even more preferably hydrated hydrazine (hydrazine monohydrate). The reducing agent may be used alone or in combination of two or more.

[0046] In the aforementioned composite microparticle manufacturing process, a solvent that leaves minimal foam during manufacturing is preferred for dispersing the copper raw material compound and the reducing agent, because if foam remains, the particles will aggregate starting from that point. This is because, from the viewpoint of achieving a uniform particle size distribution, a solvent that leaves minimal foam during manufacturing is preferable.

[0047] The solubility parameter (SP value) of the solvent is preferably 18 or less, more preferably 16 or less, even more preferably 14 or less, and even more preferably 13 or less, from the viewpoint of reducing foam persistence and ensuring a uniform particle size distribution, and preferably 8 or more, more preferably 10 or more, and even more preferably 12 or more, from the viewpoint of uniformly dispersing the reducing agent and ensuring a uniform particle size distribution. Here, the SP value is a value calculated by the Fedors method (see "Polym.Eng.Sci.14(2)152, (1974)"). Note that even if the upper and lower limits of the numerical range in the present invention fall slightly outside the numerical range specified by the present invention, they are included in the equivalent range of the present invention as long as they have the same effects as those within the numerical range.

[0048] Examples of solvents include methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol. Among these, ethanol is preferred as the solvent from the viewpoint of reducing foam persistence, ensuring a uniform particle size distribution, and from the viewpoint of availability and cost-effectiveness. The solvent may be used alone or in combination of two or more types.

[0049] When adding the reducing agent dropwise to the copper raw material compound and solvent, the amount of reducing agent added (dropping rate) is preferably 0.01 mol / min or more per 1 mol of copper in the copper raw material compound, from the viewpoint of making the primary particle size of the composite fine particles uniform and improving the density of the sintered body formed by sintering, thereby suppressing the occurrence of cracks and fractures. More preferably, this amount of reducing agent (dropping rate) is 0.02 mol / min or more, even more preferably 0.05 mol / min or more, and even more preferably 0.10 mol / min or more. Furthermore, from the viewpoint of stably producing composite fine particles, it is preferably 2.00 mol / min or less, more preferably 1.50 mol / min or less, even more preferably 1.00 mol / min or less, even more preferably 0.80 mol / min or less, even more preferably 0.50 mol / min or less, and even more preferably 0.40 mol / min or less.

[0050] In the production of composite microparticles, from the viewpoint of removing impurities such as unreacted reducing agents and excess dispersants that do not contribute to the dispersion of copper microparticles, the dispersion of composite microparticles may be purified after obtaining it, before freeze-drying. There are no particular limitations on the method of purifying the composite microparticles, and methods such as decantation, dialysis, membrane treatment such as ultrafiltration, and centrifugation of the dispersion of composite microparticles can be used. Among these, centrifugation is preferred from the viewpoint of efficiently removing impurities.

[0051] [Composite Microparticle Dispersion] The composite microparticle dispersion of the present invention is a composite microparticle dispersion containing the composite microparticles of the present invention and a dispersion medium. The composite microparticles are as described above, and their description is omitted. <Dispersion Medium> The dispersion medium used here may be any solvent capable of dispersing the composite microparticles, preferably one or more organic solvents selected from the group consisting of hydrocarbons, alcohols, ethers, and esters. One organic solvent may be used alone, or two or more may be used in combination. Furthermore, from the viewpoint of improving the density of the sintered body formed by sintering and suppressing the occurrence of cracks and fractures, the organic solvent is more preferably one or more selected from the group consisting of alcohols, ethers, and esters, and even more preferably one or more selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, (poly)alkylene glycol derivatives, glycerin, and glycerin derivatives.

[0052] Examples of aliphatic monohydric alcohols include allyl alcohol, n-heptanol, n-octanol, 2-ethylhexyl alcohol, n-nonanol, n-decanol, lauryl alcohol, myristyl alcohol, cetyl alcohol, hexadecenol, stearyl alcohol, oleyl alcohol, and terpene alcohols.

[0053] (Poly)alkylene glycol is one or more selected from the group consisting of alkylene glycols and polyalkylene glycols. Examples of alkylene glycols include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, etc. Examples of polyalkylene glycols include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (number average molecular weight preferably 100 to 1000, more preferably 150 to 600, and even more preferably 180 to 500), dipropylene glycol, tripropylene glycol, polypropylene glycol (number average molecular weight preferably 150 to 1000, more preferably 180 to 600, and even more preferably 200 to 500), polytetramethylene glycol, etc.

[0054] Examples of (poly)alkylene glycol derivatives include compounds in which the terminal hydroxyl groups of the (poly)alkylene glycol are etherified or esterified. Specifically, one or more selected from the group consisting of (poly)alkylene glycol alkyl ethers and (poly)alkylene glycol monoalkyl ether acetates are included. A (poly)alkylene glycol alkyl ether is one or more selected from the group consisting of alkylene glycol alkyl ethers and polyalkylene glycol alkyl ethers. Examples of (poly)alkylene glycol alkyl ethers include (poly)alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether. A (poly)alkylene glycol monoalkyl ether acetate is one or more selected from the group consisting of alkylene glycol monoalkyl ether acetate and polyalkylene glycol monoalkyl ether acetate. Examples of (poly)alkylene glycol monoalkyl ether acetates include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

[0055] There are no particular restrictions on glycerin derivatives as long as they are solvents containing a structure derived from glycerin. Examples include glycerin ether derivatives, glycerin ester derivatives, polyglycerin, and glycerin alkylene oxide adducts (e.g., ethylene oxide adducts and propylene oxide adducts). Examples of polyglycerin include diglycerin and triglycerin. Examples of commercially available polyglycerin include polyglycerin #310, polyglycerin #500, and polyglycerin #750 manufactured by Sakamoto Pharmaceutical Co., Ltd. Examples of glycerin ether derivatives include 3-(2-ethylhexyloxy)-1,2-propanediol (boiling point: 325°C, molecular weight 204). Examples of glycerin ester derivatives include glyceryl tributyrate (boiling point: 305°C, molecular weight 302).

[0056] Among these, the dispersion medium is preferably one or more selected from the group consisting of (poly)alkylene glycol and (poly)alkylene glycol alkyl ether, more preferably (poly)alkylene glycol, even more preferably one or more selected from dipropylene glycol and polyethylene glycol, even more preferably one or more selected from dipropylene glycol and polyethylene glycol with a number average molecular weight of 200, and even more preferably a combination of dipropylene glycol and polyethylene glycol with a number average molecular weight of 200.

[0057] <Copper Microparticles> The composite fine particle dispersion of the present invention may further contain copper microparticles from the viewpoint of improving the density of the sintered body formed by sintering and suppressing the occurrence of cracks and fractures. The copper content in the copper microparticles 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 viewpoint of improving the density of the sintered body formed by sintering and suppressing the occurrence of cracks and fractures. Here, "substantially 100% by mass" means that it may include components that are included unintentionally. Examples of components that are included unintentionally include unavoidable impurities.

[0058] The average particle size of the copper microparticles is preferably greater than 0.35 μm, more preferably 0.5 μm or more, even more preferably 0.6 μm or more, and even more preferably 0.7 μm or more, and preferably 10 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, and even more preferably 6 μm or less, from the viewpoint of improving the density of the sintered body formed by sintering and suppressing the occurrence of cracks and fractures. The average particle size of the copper microparticles is measured by the same method as the average particle size (particle size D50) of the composite fine particles described in the examples.

[0059] <Content of each component in the dispersion> The composite microparticle dispersion of the present invention can be used to manufacture a bonded body by sintering. When the composite microparticle dispersion of the present invention is used to manufacture a bonded body, the content of composite microparticles is preferably 35% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and preferably 95% by mass or less, and more preferably 93% by mass or less, from the viewpoint of improving the dispersibility of composite microparticles in the dispersion, improving the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures. The content of the dispersant in the dispersion is preferably 0.001 or more, more preferably 0.003 or more, even more preferably 0.005 or more, even more preferably 0.009 or more, and preferably 0.020 or less, more preferably 0.018 or less, even more preferably 0.016 or less, and even more preferably 0.014 or less, from the viewpoint of improving the dispersibility of the composite fine particles in the dispersion, the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures, expressed as the mass ratio of the dispersant to the composite fine particles (dispersant / composite fine particles), is preferably 0.001 or more, more preferably 0.003 or more, even more preferably 0.005 or more, even more preferably 0.009 or more, and preferably 0.020 or less, more preferably 0.018 or less, even more preferably 0.016 or less, and even more preferably 0.014 or less. The content of the dispersion medium in the dispersion is preferably 4% by mass or more, more preferably 6% by mass or more, even more preferably 7% by mass or more, and preferably 60% by mass or less, more preferably 25% by mass or less, and even more preferably 15% by mass or less, from the viewpoint of improving the dispersibility of the composite fine particles in the dispersion, the density of the sintered body formed by sintering, and suppressing the occurrence of cracks and fractures. Furthermore, if the dispersion contains copper microparticles, from a similar viewpoint, the content of composite fine particles in the dispersion is preferably 30% by mass or more and 95% by mass or less, the content of the dispersant is preferably 0.1% by mass or more and 10% by mass or less, the content of the dispersion medium is preferably 4% by mass or more and 60% by mass or less, and the content of copper microparticles is preferably 0% by mass or more and 65% by mass or less.Furthermore, if the dispersion contains copper microparticles, from a similar viewpoint, the content of composite fine particles in the dispersion is preferably 30% by mass or more and 95% by mass or less, the content of the dispersant is preferably 0.001 to 0.020 when expressed as the mass ratio (dispersant / composite fine particles), the content of the dispersion medium is preferably 4% by mass or more and 60% by mass or less, and the content of copper microparticles is preferably 0% by mass or more and 65% by mass or less.

[0060] The dispersion may contain various additives as components other than those mentioned above, to the extent that they do not impair the effects of the present invention. Examples of such additives include metal particles other than composite fine particles and copper microparticles, sintering accelerators such as glass frit, antioxidants, viscosity modifiers, pH adjusters, buffers, defoamers, leveling agents, and volatilization inhibitors. Examples of metal particles other than composite fine particles and copper microparticles include metal particles such as zinc, nickel, silver, gold, palladium, and platinum. The content of the additives in the dispersion is preferably 1% by mass or less.

[0061] <Method for producing a composite microparticle dispersion> The composite microparticle dispersion according to the present invention can be obtained by adding and mixing a dispersion medium and, if necessary, various additives to composite microparticles. Known methods can be used for mixing, and from the viewpoint of better dispersing the composite microparticles in the dispersion medium, it is preferable to pre-mix the composite microparticles and the dispersion medium using an agate mortar and pestle, and then further mix the resulting mixture using a stirring device such as a rotating and revolving stirring device.

[0062] The composite microparticle dispersion of the present invention obtained in this way can be sintered at low temperatures, has good density in the sintered body formed by sintering, and can suppress the occurrence of cracks and fractures in the sintered body, so it can be used to form conductive members of various electronic and electrical devices. Examples of such conductive members include conductive members that were conventionally formed using conductive bonding agents such as solder. Furthermore, the composite microparticle dispersion of the present invention is preferably used to form conductive members that constitute 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 circuit boards and flexible circuit boards; organic solar cells; and sensors such as flexible sensors. Among these, the composite microparticle dispersion of the present invention is preferably used for joining multiple metal members together or for manufacturing wiring patterns.

[0063] [Wiring Pattern] The wiring pattern of the present invention is a sintered body obtained by heat-treating the composite fine particle dispersion of the present invention described above. In other words, the wiring pattern of the present invention is a sintered body of the composite fine particles of the present invention. Because the composite fine particle dispersion of the present invention has the above-described characteristics, it has excellent low-temperature sinterability, and therefore the wiring pattern of the present invention can be formed at a low temperature of 250°C or less. As a result, the wiring pattern of the present invention can reduce damage to semiconductor chips and the like. Because the wiring pattern of the present invention has the above-described characteristics, it is preferably used in wiring boards such as printed circuit boards and flexible circuit boards, which have low high-temperature resistance of the substrate.

[0064] [Copper Bonding Layer] The copper bonding layer of the present invention is a sintered body obtained by heat-treating the composite fine particle dispersion of the present invention described above. In other words, the copper bonding layer of the present invention is a sintered body of the composite fine particles of the present invention. Since the composite fine particle dispersion used here has the above-described characteristics, sintering proceeds uniformly, and a dense copper bonding layer can be formed. Therefore, crack generation in the copper bonding layer due to sintering is suppressed, and a copper bonding layer with high thermal stability can be formed. Since the copper bonding layer of the present invention has the above characteristics, it is preferably used for bonding members to be bonded that constitute a device with a high operating temperature.

[0065] [Jointed Body and Method for Manufacturing the Same] The composite fine particle dispersion of the present invention is interposed between a plurality of metal members, and these are then fired at low pressure and low temperature to produce a jointed body in which the plurality of metal members are joined via a copper bonding layer. That is, the jointed body obtained here has a metal member-copper bonding layer-metal member structure in which the plurality of metal members are joined to each other by the copper bonding layer obtained when the composite fine particle dispersion of the present invention is fired. The metal members are examples of members to be joined. Furthermore, the jointed body of the present invention is a jointed body that includes a plurality of metal members and a copper bonding layer that is placed between adjacent metal members and joins the adjacent metal members, wherein the copper bonding layer is a sintered body of the composite fine particles of the present invention. In one embodiment of the present invention, the method for manufacturing a jointed body includes the following steps 1 to 2 in this order. Step 1: A step of applying the composite fine particle dispersion of the present invention to one main surface of one of the metal members. Step 2: A step in which one metal member is placed on a composite fine particle dispersion applied to one metal member to form a laminate, and the laminate is fired while being pressed in the thickness direction.

[0066] Examples of metal members joined by the copper bonding layer include metal substrates or metal substrates such as 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; and metal parts such as electrodes of electrical insulating substrates. The multiple metal members used in the present invention may be of the same type or different types. Among these, the metal members preferably include at least one selected from 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, tin-plated metal substrates, and metal parts of electrical insulating substrates. The joining of metal members in this invention includes joining chip components such as capacitors and resistors to a circuit board; joining semiconductor chips such as memory, diodes, transistors, ICs, and CPUs to a lead frame or circuit board; and joining high-heat-generating semiconductor chips to a cooling plate.

[0067] In forming the wiring pattern and the copper bonding layer, methods for applying the composite fine particle dispersion to the metal member include various coating methods such as slot die coating, dip coating, spray coating, spin coating, doctor bladeding, 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. The amount of the composite fine particle dispersion applied to the metal member can be appropriately adjusted according to the size and type of the metal member to be bonded.

[0068] In forming the wiring pattern, the heating temperature (firing temperature) for forming the copper sintered body is preferably 150°C or higher, more preferably 160°C or higher, and even more preferably 180°C or higher, from the viewpoint of improving the density of the sintered body and suppressing the occurrence of cracks and fractures, and preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 230°C or lower, from the viewpoint of reducing damage to the semiconductor chip.

[0069] In forming the wiring pattern, the heating time (firing time) for forming the copper sintered body can be appropriately adjusted by the heating temperature and pressurizing pressure. However, from the viewpoint of improving the density of the sintered body and suppressing the occurrence of cracks and fractures, it is preferably 600 seconds or more, more preferably 900 seconds or more, and even more preferably 1200 seconds or more. Furthermore, from the viewpoint of reducing damage to the substrate and semiconductor chip, it is preferably 5400 seconds or less, more preferably 4500 seconds or less, and even more preferably 3600 seconds or less.

[0070] In forming the copper bonding layer, the heating temperature (firing temperature) for forming the bonded body is preferably 200°C or higher, more preferably 230°C or higher, even more preferably 250°C or higher, and even more preferably 280°C or higher, from the viewpoint of strengthening the bond between the composite fine particles and the member to be bonded, such as a metal member. From the viewpoint of reducing damage to the semiconductor chip, it is preferably 350°C or lower, more preferably 330°C or lower, and even more preferably 310°C or lower.

[0071] In forming the copper bonding layer, the pressurizing pressure for forming the bonded body is preferably 5 MPa or more, more preferably 7 MPa or more, and even more preferably 10 MPa or more, from the viewpoint of improving the density of the sintered body and suppressing the occurrence of cracks and fractures, and preferably 30 MPa or less, more preferably 25 MPa or less, and even more preferably 22 MPa or less, from the viewpoint of reducing damage to the semiconductor chip.

[0072] In forming the copper bonding layer, the heating time for forming the bonded body can be appropriately adjusted according to the heating temperature (firing temperature) and the pressure during pressurization. However, from the viewpoint of improving the density of the sintered body formed by sintering and suppressing the occurrence of cracks and fractures, the heating time is preferably 150 seconds or more, more preferably 200 seconds or more, and even more preferably 250 seconds or more. Furthermore, from the viewpoint of reducing damage to the semiconductor chip, the heating time is preferably 3600 seconds or less, more preferably 1800 seconds or less, even more preferably 1200 seconds or less, even more preferably 600 seconds or less, and even more preferably 400 seconds or less.

[0073] The atmosphere in which the low-temperature firing is carried out may be an air atmosphere, an inert gas atmosphere such as nitrogen gas, or a reducing gas atmosphere such as hydrogen gas, but a nitrogen gas atmosphere is more preferable from the viewpoint of suppressing copper oxidation and ensuring safety.

[0074] This application further discloses the following inventions.

[0075] <1> Composite microparticles in which at least a portion of the surface of copper microparticles is coated with a dispersant, wherein the average particle size D50 of the composite microparticles is 50 nm or more and 350 nm or less, in a particle size histogram based on the number of composite microparticles, the particle size D10 when the cumulative frequency is 10% and the particle size D90 when the cumulative frequency is 90% satisfy the relationship D90 / D10 ≤ 4.0, and the dispersant is a vinyl polymer having a carboxyl group and containing a structure represented by the following formula (1). In the above formula (1), R 1 R is a hydrogen atom or a methyl group. 2<1> The composite fine particles according to <1>, wherein the particle size histogram based on the number of composite fine particles has a particle size of 50%, the particle size D50 when the cumulative frequency is 50%, is 50 nm or more, preferably 60 nm or more, more preferably 65 nm or more, and preferably 300 nm or less, more preferably 250 nm or less, even more preferably 210 nm or less, and even more preferably 175 nm or less. <3> The composite fine particles according to <1> or <2>, wherein the D90 / D10 is 4.0 or less, preferably 3.5 or less, more preferably 3.1 or less, and preferably 1.5 or more, more preferably 1.8 or more, even more preferably 2.1 or more, and even more preferably 2.3 or more. <4> The composite fine particles according to any one of <1> to <3>, wherein the particle size D10 of the composite fine particles is 20 nm or more, more preferably 30 nm or more, even more preferably 40 nm or more, and preferably 105 nm or less, more preferably 100 nm or less, even more preferably 95 nm or less, and even more preferably 90 nm or less. <5> The R of the vinyl polymer 2 The composite fine particles according to any one of <1> to <4>, wherein the sum of the atomic weights of the constituent atoms is preferably 5000 or less, more preferably 3500 or less, even more preferably 2000 or less, and preferably 50 or more, more preferably 100 or more, even more preferably 500 or more, and even more preferably 800 or more. <6> The composite fine particles according to any one of <1> to <5>, wherein the vinyl polymer is a polymer of a monomer having a carboxyl group and a monomer represented by the following formula (2). In the above formula (2), R 1 and R 2 is the same organic group as in formula (1) above. <7> The R of the vinyl polymer 2The composite microparticle according to any one of <1> to <6>, wherein the microparticle has an organic group containing an alkylene oxide structure or a cyclic structure, the organic group containing the cyclic structure is an organic group containing one or more structures selected from the group consisting of aromatic ring structures and alicyclic structures, the aromatic ring structure is benzene, naphthalene, anthracene, or phenanthrene, the alicyclic structure is a monocyclic or polycyclic structure, the monocyclic structure is cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, cyclododecane, cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclodecene, or cyclododecene, and the polycyclic structure is norbornane, adamantane, norbornene, or adamantene. <8> The composite fine particles according to any one of <1> to <7>, wherein the acid value of the vinyl polymer is preferably 10 mg KOH / g or more, more preferably 20 mg KOH / g or more, even more preferably 30 mg KOH / g or more, and even more preferably 40 mg KOH / g or more, and preferably 250 mg KOH / g or less, more preferably 230 mg KOH / g or less, and even more preferably 210 mg KOH / g or less. <9> The composite fine particles according to any one of <1> to <8>, wherein the vinyl polymer comprises a constituent unit derived from a monomer (p-1) having a carboxyl group and a constituent unit derived from a monomer (p-2) having a (poly)alkylene glycol segment. <10> The composite fine particles according to <9>, wherein the monomer (p-1) is preferably one or more selected from the group consisting of (meth)acrylic acid and maleic acid, more preferably (meth)acrylic acid, and even more preferably methacrylic acid. <11> The composite fine particles according to <9> or <10>, wherein the monomer (p-2) is one or more selected from alkylene glycol (meth)acrylate, polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, and phenoxy polyalkylene glycol (meth)acrylate.<12> The composite fine particles according to any one of <9> to <11>, wherein the vinyl polymer further contains a constituent unit derived from a hydrophobic monomer (p-3). <13> The composite fine particles according to any one of <9> to <12>, wherein the content of the constituent unit derived from the monomer (p-2) having the (poly)alkylene glycol segment in the vinyl polymer is preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, and preferably 97% by mass or less, and more preferably 95% by mass or less. <14> The composite fine particles according to any one of <9> to <13>, wherein the weight-average molecular weight of the vinyl polymer is preferably 3,000 or more, more preferably 6,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 17,000 or less, and even more preferably 10,000 or less. <15> The composite fine particles according to any one of <1> to <14>, wherein the particle size D10 of the composite fine particles is 20 nm or more, more preferably 30 nm or more, even more preferably 40 nm or more, and preferably 105 nm or less, more preferably 100 nm or less, even more preferably 95 nm or less, and even more preferably 90 nm or less. <16> A method for producing composite fine particles in which at least a part of the surface of copper fine particles is coated with a dispersant, comprising dropping a reducing agent onto a mixed solution containing a copper raw material compound, a dispersant, and a solvent with an SP value of 8 or more and 18 or less, wherein the dispersant is a vinyl polymer having a carboxyl group and containing a structure represented by the following formula (1), and the dropping rate of the reducing agent per 1 mol of copper in the copper raw material compound is 0.01 mol / min or more. In the above formula (1), R 1 R is a hydrogen atom or a methyl group. 2 R is an organic group containing a cyclic structure or an organic group containing a chain structure having three or more carbon atoms, and n is a number between 1 and 1000. <17> The R of the vinyl polymer 2A method for producing composite fine particles according to <16>, wherein the sum of the atomic weights of the constituent atoms is preferably 50 or more, more preferably 100 or more, even more preferably 500 or more, and even more preferably 800 or more, and preferably 5000 or less, more preferably 3500 or less, and even more preferably 2000 or less. <18> A method for producing composite fine particles according to <16> or <17>, wherein the vinyl polymer is a polymer of a monomer having a carboxyl group and a monomer represented by the following formula (2). In the above formula (2), R 1 and R 2 is the same organic group as in formula (1) above. <19> The R of the vinyl polymer 2A method for producing composite fine particles according to any one of <16> to <18>, wherein the organic group comprises an alkylene oxide structure or a cyclic structure, the organic group comprising a cyclic structure comprises one or more structures selected from the group consisting of aromatic ring structures and alicyclic structures, the aromatic ring structure is benzene, naphthalene, anthracene, or phenanthrene, the alicyclic structure is monocyclic or polycyclic, the monocyclic structure is cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, cyclododecane, cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclodecene, or cyclododecene, and the polycyclic structure is norbornane, adamantane, norbornene, or adamantene. <20> The method for producing composite fine particles according to any one of <16> to <19>, wherein the solvent is one or more selected from methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol. <21> The method for producing composite fine particles according to any one of <16> to <20>, wherein the dropping rate of the reducing agent is preferably 0.01 mol / min or more, more preferably 0.02 mol / min or more, even more preferably 0.05 mol / min or more, even more preferably 0.10 mol / min or more, and preferably 2.00 mol / min or less, more preferably 1.50 mol / min or less, even more preferably 1.00 mol / min or less, even more preferably 0.80 mol / min or less, even more preferably 0.50 mol / min or less, and even more preferably 0.40 mol / min or less. <22> A method for producing composite fine particles according to any one of <16> to <21>, wherein the copper raw material compound is cupric oxide and the reducing agent is a hydrazine compound.<23> The method for producing composite fine particles according to any one of <16> to <22>, wherein the reaction temperature of the reaction solution containing the mixture and the reducing agent dropped into the mixture is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 30°C or higher, even more preferably 50°C or higher, more preferably 60°C or higher, and 75°C or lower, more preferably 73°C or lower. <24> The method for producing composite fine particles according to any one of <16> to <23>, wherein the step comprises maintaining the mixture at a predetermined temperature below the boiling point of the solvent for the reduction of the copper raw material compound, the maintenance time of the temperature being 1 minute or more, more preferably 30 minutes or more, even more preferably 1 hour or more, and preferably 30 hours or less, more preferably 20 hours or less, even more preferably 10 hours or less. <25> A composite fine particle dispersion comprising the composite fine particles according to any one of <1> to <15>. <26> The composite microparticle dispersion according to <25>, wherein the composite microparticle dispersion comprises the composite microparticles and a dispersion medium, the dispersion medium being one or more organic solvents selected from the group consisting of hydrocarbons, alcohols, ethers, and esters. <27> The composite microparticle dispersion according to <25> or <26>, further comprising copper microparticles. <28> The composite microparticle dispersion according to <27>, wherein the average particle diameter of the copper microparticles is preferably greater than 0.35 μm, more preferably 0.5 μm or more, even more preferably 0.6 μm or more, even more preferably 0.7 μm or more, and preferably 10 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, and even more preferably 6 μm or less. <29> The composite microparticle dispersion according to any one of <25> to <28>, wherein the content of the composite microparticles in the composite microparticle dispersion is preferably 35% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and preferably 95% by mass or less, more preferably 93% by mass or less.<30> The composite microparticle dispersion according to any one of <25> to <29>, wherein the content of the dispersant in the composite microparticle dispersion is preferably 0.001 or more, more preferably 0.003 or more, even more preferably 0.005 or more, even more preferably 0.009 or more, and preferably 0.020 or less, more preferably 0.018 or less, even more preferably 0.016 or less, and even more preferably 0.014 or less. <31> The composite microparticle dispersion according to <26>, wherein the content of the dispersion medium in the composite microparticle dispersion is preferably 4% by mass or more, more preferably 6% by mass or more, even more preferably 7% by mass or more, and preferably 60% by mass or less, more preferably 25% by mass or less, even more preferably 15% by mass or less. <32> A copper bonding layer which is a sintered body of composite microparticles according to any one of <1> to <15>. <33> A wiring pattern which is a sintered body of composite fine particles as described in any of <1> to <15> above. <34> A joint in which metal members are joined together via a copper bonding layer, wherein the copper bonding layer is a sintered body of composite fine particles as described in any of <1> to <15> above. <35> A method for manufacturing a joint in which metal members are joined together via a copper bonding layer, comprising: applying a composite fine particle dispersion as described in any of <25> to <31> above to one metal member; placing the other metal member on the composite fine particle dispersion applied to the one metal substrate; and pressurizing and firing the joint. <36> Use of a composite fine particle dispersion as described in any of <25> to <31> above as a bonding material for joining metal members together.

[0076] The present invention will be described in more detail below with reference to examples and comparative examples. However, the scope of the present invention is not limited to these examples. In the following manufacturing examples, examples, and comparative examples, "parts" and "%" refer to "parts by mass" and "mass%" unless otherwise specified. Various physical properties were measured or calculated by the following methods.

[0077] [Measurement of weight-average molecular weight Mw of the dispersant] The weight-average molecular weight Mw of the dispersant was determined by gel permeation chromatography. The sample prepared for measurement was a glass vial containing 0.1 g of dispersant mixed with 10 mL of eluent, stirred with a magnetic stirrer at 25°C for 10 hours, and filtered through a syringe filter (DISMIC-13HP PTFE 0.2 μm, manufactured by Advantec Toyo Co., Ltd.). The measurement conditions are shown below. GPC apparatus: Tosoh Corporation "HLC-8320GPC" Columns: Tosoh Corporation "TSKgel Super AWM-H, TSKgel Super AW3000, TSKgel guardcolumn Super AW-H" Eluent: Solution prepared by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively Flow rate: 0.5 mL / min Standards: Monodisperse polystyrene kits 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)"

[0078] [Measurement of Acid Value of Dispersant] The acid value of the dispersant was measured in accordance with JIS K0070-1992 (potentiometric titration method). However, the measurement solvent was changed from the ethanol and ether mixed solvent specified in JIS K 0070 to an acetone and toluene mixed solvent (acetone:toluene = 4:6 (volume ratio)).

[0079] [Calculation of the ratio of the mass of the dispersant to the total mass of copper nanoparticles and dispersant [dispersant / (copper nanoparticles + dispersant)]] Using a differential thermogravimetric analyzer (TG / DTA) (manufactured by Hitachi High-Tech Science Corporation, product name: STA7200RV), 10 mg of the sample (dried powder of composite nanoparticles) was weighed into an aluminum pancell 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 taken as the mass of the dispersant, and the remaining mass at 550°C was taken as the mass of copper nanoparticles (granular copper components) not coated with the dispersant. The mass ratio [dispersant / (copper nanoparticles + dispersant)] was calculated using the following formula: Mass ratio [dispersant / (copper nanoparticles + dispersant)] = (mass loss from 35°C to 550°C) / (mass loss from 35°C to 550°C + remaining mass at 550°C)

[0080] [Calculation of D10, D50, D90 and ratio [D90 / D10] of composite microparticles] Scanning electron microscope (SEM) images of composite microparticles were taken using a scanning electron microscope (Hitachi High-Tech Corporation, field emission scanning electron microscope, product name: S-4800). The magnification was determined according to the particle size, and images were taken in the range of 5,000x to 150,000x. The SEM images were analyzed using the image analysis software ImageJ (National Institutes of Health, USA), and the particle size was determined for 1,000 particles per sample. From the particle size histogram based on the determined particle sizes, the particle size D10 when the cumulative frequency is 10%, the particle size D50 (average particle size D50) when the cumulative frequency is 50%, and the particle size D90 when the cumulative frequency is 90% were calculated. Furthermore, the ratio [D90 / D10] was calculated from the calculated D90 and D10.

[0081] [Preparation of Dispersant] Preparation Example 1 (Preparation of Vinyl Polymer P1) 20.0 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) was placed in a 1000 mL four-necked round-bottom flask equipped with a thermometer, two 100 mL dropping funnels with nitrogen bypass, and a reflux apparatus. The internal temperature of the flask was heated to 80°C in an oil bath, and then nitrogen bubbling was performed for 10 minutes. Separately, 32.5 g of methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) as monomer (p-1), 67.5 g of methoxypolyethylene glycol (EO 4 mol) methacrylate (manufactured by NOF Corporation, "PME-200") as monomer (p-2), 3.0 g of mercaptopropanediol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) as a chain transfer agent, and 28.7 g of ethanol were dissolved in a polybeaker and placed in dropping funnel (A). In addition, 51.3 g of ethanol and 1.3 g of 2,2'-azobis(isobutyrate)dimethyl (V-601, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., polymerization initiator) were dissolved in a poly beaker and placed in dropping funnel (B). Then, the respective mixtures in dropping funnel (A) and dropping funnel (B) were simultaneously added to the contents of the four-necked round-bottom flask over 90 minutes while stirring. After that, the internal temperature of the four-necked round-bottom flask was raised to 90°C, and stirring was continued for another hour to complete the reaction. After the reaction was complete, the resulting polymer solution was freeze-dried using a freeze-dryer (FDU-2110, manufactured by Tokyo Rikakikai Co., Ltd., model: DRC-1000) equipped with a dry chamber, 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; pressure level 5 Pa) to obtain vinyl polymer P1. The monomer composition and physical properties are shown in Table 1.

[0082] Preparation Examples 2-7 (Preparation of Vinyl Polymers P2-P7) Vinyl polymers P2-P7 were obtained by performing the same procedure as in Production Example 1, except that the types and amounts of monomer (p-1), monomer (p-2), and chain transfer agent were changed to those shown in Table 1. Weight-average molecular weight, acid value, R 2 Table 1 shows the sum of the atomic weights of the constituent atoms.

[0083]

[0084] • MAA: Methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) • PEG(4)MA: Methoxypolyethylene glycol (EO 4 mol) methacrylate (manufactured by NOF Corporation, "PME-200") • PEG(9)MA: Methoxypolyethylene glycol (EO 9 mol) methacrylate (manufactured by NOF Corporation, "PME-400") • PEG(23)MA: Methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by NOF Corporation, "PME-1000") • HPMA: Hydroxypropyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0085] [Production of Composite Microparticles] Example 1 (Production of Composite Microparticle 1) 50.0 g of cupric oxide (manufactured by Nisshin Chemco Co., Ltd., N-120) as a copper raw material compound, 2.0 g of vinyl polymer P1, and 500 g of ethanol (95) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., first-grade reagent) were added to a 2 L beaker and stirred for 90 minutes to obtain a mixture. During stirring, the temperature of the mixture was controlled to 70°C using an oil bath. Next, 63.0 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special-grade reagent) in a 100 mL dropping funnel was added dropwise to the mixture at 25°C over 13 minutes. After that, the reaction solution containing the mixture and the hydrazine monohydrate (reducing agent) added dropwise was stirred for 1 hour while controlling the temperature to 70°C using an oil bath, and then air-cooled to obtain a reddish-brown dispersion containing composite microparticles. The entire amount of the obtained dispersion was placed in a Hitachi Koki Co., Ltd. 500PA centrifugal sedimentation tube bottle using a Hitachi Koki Co., Ltd. refrigerated centrifuge "himacCR22G" and rotor (R12A, radius 15.1 cm), and centrifugal acceleration of 675 G was applied at 3000 rpm for 15 minutes. 300 g of ethanol (95) (Fujifilm Wako Pure Chemical Industries, Ltd., first-grade reagent) was added to the precipitate separated by centrifugation, and the mixture was stirred for 15 minutes to redisperse. The entire amount of the redispersed solution was again centrifuged under the same conditions, and the precipitate was separated. This operation was repeated twice. The purified precipitate of composite microparticles 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) to obtain 136.5 g of composite microparticles. The drying conditions involved freezing at -25°C for 1 hour, followed by vacuum drying at -10°C for 9 hours at 5 Pa, and then further vacuum drying at 25°C for 5 hours at 5 Pa to obtain the dried powder of composite fine particles 1.

[0086] Examples 2-6, 9 (Production of composite fine particles 2-6, 9) Composite fine particles 2-6, 9 were obtained by the same procedure as in Example 1, except that vinyl polymer P1 was changed to vinyl polymers P2-P7 shown in Tables 2 and 3.

[0087] Example 7 (Production of composite microparticles 7) Composite microparticles 7 were obtained in the same manner as in Example 1, except that vinyl polymer P1 was replaced with vinyl polymer P5 and 63.0 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) was added dropwise to the mixture over 60 minutes.

[0088] Example 8 (Production of composite microparticles 8) Composite microparticles 8 were obtained in the same manner as in Example 1, except that vinyl polymer P1 was replaced with vinyl polymer P5 and 63.0 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) was added dropwise to the mixture over 6 minutes.

[0089] Comparative Example 1 (Production of Composite Fine Particles C1) 88.4 g of copper sulfate pentahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 0.7 g of vinyl polymer P7, and 1000 g of deionized water were added to a 2 L beaker as a copper raw material compound. The mixture was stirred at 40°C using a magnetic stirrer until it became visibly clear 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 over 60 minutes at 25°C. Subsequently, the reaction solution containing the mixed solution and the hydrazine monohydrate (reducing agent) added dropwise was stirred for 5 hours while controlling the temperature to 40°C using an oil bath, and then air-cooled to obtain a reddish-brown dispersion containing composite fine particles. The entire volume of the obtained dispersion was placed into a dialysis tube (REPLIGEN, product name: Spectra / Pore 6, dialysis membrane: regenerated cellulose, molecular weight cutoff (MWCO) = 50K), and the top and bottom of the tube were sealed with a closeer. This tube was immersed in 5 L of deionized water in a 5 L glass beaker, and a dialysis treatment was performed by stirring for 1 hour while maintaining the water temperature at 20-25°C. This dialysis treatment was repeated, with the entire volume of deionized water being replaced after each 1 hour of stirring. A sample was taken before replacing the deionized water, and the dialysis treatment was terminated when the conductivity of the dispersion of composite microparticles fell to 7 mS / m or less, to obtain the dispersion of composite microparticles. Conductivity was measured by diluting the sampled solution with deionized water to adjust the copper concentration to 1%. The precipitate of the purified composite microparticles was freeze-dried using a freeze-dryer (FDU-2110, manufactured by Tokyo Rikakikai Co., Ltd., model: DRC-1000) equipped with a dry chamber, yielding 20.8 g of composite microparticles C1. The drying conditions were: freezing at -25°C for 1 hour, then drying under reduced pressure at -10°C for 9 hours at 5 Pa, and finally drying under reduced pressure at 25°C for 5 hours at 5 Pa to obtain a dried powder of composite microparticles C1.

[0090] Comparative Example 2 (Production of Composite Fine Particles C2) Except that vinyl polymer P1 was replaced with vinyl polymer P5 and 63.0 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) was added dropwise to the mixture over 600 minutes, a dried powder of composite fine particles C2 was obtained in the same manner as in Example 1.

[0091] Comparative Example 3 (Production of Composite Fine Particles C3) A dried powder of composite fine particles C3 was obtained in the same manner as in Example 1, except that the vinyl polymer P1 was replaced with polyacrylic acid.

[0092] Comparative Example 4 (Production of Composite Fine Particles C4) A dried powder of composite fine particles C4 was obtained in the same manner as in Example 1, except that vinyl polymer P1 was replaced with vinyl polymer P5 and ethanol was replaced with deionized water.

[0093] The manufacturing conditions for Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Tables 2 and 3. Here, the dropping rate of the reducing agent is the amount of reducing agent dropped per 1 mol of copper in the copper raw material compound. The cumulative frequency particle sizes D10, D50, D90 and ratio [D90 / D10] and mass ratio [dispersant / (copper fine particles + dispersant)] of the obtained composite fine particles 1 to 9 and C1 to C4 are also summarized in Tables 2 and 3.

[0094] [Production of Composite Microparticle Dispersion] 5.0 parts by mass of polyethylene glycol 200, 5.0 parts by mass of dipropylene glycol, and 90 parts by mass of the dried powder of each composite microparticle obtained in the above examples and comparative examples were added to an agate mortar and kneaded until the dried powder was no longer visible, and the resulting mixture was transferred to a plastic bottle. The sealed plastic bottle was stirred for 2000 mins using a rotation-and-revolution type stirring device (Sinky Co., Ltd., Planetary Vacuum Mixer ARV-310). -1 The mixture was stirred at 2000 revolutions per minute for 5 minutes. Then, it was passed three times through a three-roll mill (manufactured by AIMEX Co., Ltd., BV 100) with the roll gap adjusted to 0.2 mm to obtain composite microparticle dispersions 1 to 9 and C1 to C4 containing the composite microparticles obtained in the above examples and comparative examples.

[0095] [Manufacturing and Evaluation of Sintered Bodies] Using the obtained composite microparticle dispersions 1-9 and C1-C4, sintered bodies 1-9 and C1-C4 were manufactured according to the following method. A stainless steel metal mask (thickness: 50 μm) with a 7.6 mm x 7.6 mm square opening was placed on a glass slide, and the composite microparticle dispersion was applied to the glass slide by stencil printing using a metal squeegee. Then, the glass slide coated with the composite microparticle dispersion was placed on a hot plate heated to 200°C, a two-port separable cover was placed over it, and nitrogen was circulated through one of the ports to start firing. After firing for 1 hour, the coating (sintered body) was observed with a digital microscope (Keyence, VHX-8000) to check for the presence or absence of cracks. Cracks were observed throughout the entire coating (sintered body), and the number of cracks in the sintered body was measured.

[0096] [Manufacturing and Evaluation of Joints] Using the obtained composite microparticle dispersions 1-9 and C1-C4, joints 1-9 and C1-C4 having copper bonding layers were manufactured according to the following method. A stainless steel metal mask (thickness: 50 μm) with a 7.6 mm x 7.6 mm square opening was placed on a solid copper plate, and the composite microparticle dispersion was applied to the solid copper plate by stencil printing using a metal squeegee. Then, the solid copper plate coated with the composite microparticle dispersion was heated at 120°C for 10 minutes, and then 5 mm x 5 mm Si chips were placed on the coated composite microparticle dispersion, and these were fired at 300°C for 5 minutes while being pressurized at 20 MPa. The joints containing the copper bonding layer, which is a sintered body of composite microparticles contained in the composite microparticle dispersion, were observed using SAT (ultrasonic testing) to check for the presence or absence of cracks. Cracks were observed throughout the copper bonding layer, and the number of cracks in the joint was measured.

[0097] Tables 2 and 3 show details of the composite fine particles obtained in Examples 1 to 9 and Comparative Examples 1 to 4, the number of cracks in the sintered body, and the number of cracks in the bonded body.

[0098]

[0099]

[0100] - Cupric oxide (manufactured by Nisshin Chemco Co., Ltd., N-120) - Copper(II) sulfate pentahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) - Hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) - Ethanol (95) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., first grade reagent): (boiling point 78°C, SP value 12.7, viscosity 1.1 mPa·s) - Ion-exchanged water (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purified water): (boiling point 100°C, SP value 23.4, viscosity 1.0 mPa·s)

[0101] Tables 2 and 3 show that the composite microparticles of Examples 1 to 9 suppress the occurrence of cracks in the sintered bodies and joined bodies obtained by sintering, compared to the composite microparticles of Comparative Examples 1 to 4. In other words, the composite microparticles of the present invention can be used to obtain sintered bodies and joined bodies with good heat resistance. This is thought to be because the composite microparticles have a specific average particle diameter D50, satisfy the relationship D90 / D10 ≤ 4.0, and the copper microparticles are coated with a specific dispersant, which suppresses aggregation of the composite microparticles and ensures good dispersion. Furthermore, because the particle diameter and surface energy of each composite microparticle are similar, sintering proceeds uniformly.

[0102] According to the present invention, it is possible to provide composite microparticles and composite microparticle dispersions that enable low-pressure, low-temperature sintering, form a dense sintered body, and suppress the occurrence of cracks and fractures in the resulting sintered body. Furthermore, it is possible to provide a wiring pattern that is a sintered body of the composite microparticles, and a bonded body having a copper bonding layer.

Claims

1. Composite microparticles in which at least a portion of the surface of copper microparticles is coated with a dispersant, wherein the average particle size D50 of the composite microparticles is 50 nm or more and 350 nm or less, in a particle size histogram based on the number of composite microparticles, the particle size D10 at a cumulative frequency of 10% and the particle size D90 at a cumulative frequency of 90% satisfy the relationship D90 / D10 ≤ 4.0, and the dispersant is a vinyl polymer having a carboxyl group and containing a structure represented by the following formula (1). In the above formula (1), R 1 R is a hydrogen atom or a methyl group. 2 is an organic group containing a cyclic structure or an organic group containing a chain structure having three or more carbon atoms in a straight chain, and n is a number between 1 and 1000.

2. The R of the vinyl polymer 2 The composite fine particles according to claim 1, wherein the sum of the atomic weights of the constituent atoms is 5000 or less.

3. The composite fine particles according to claim 1 or 2, wherein the vinyl polymer is a polymer of a monomer having a carboxyl group and a monomer represented by the following formula (2). In the above formula (2), R 1 and R 2 This is the same organic group as the one in formula (1) above.

4. The R of the vinyl polymer 2 The composite fine particles according to any one of claims 1 to 3, wherein the composite fine particles have an organic group containing an alkylene oxide structure or a cyclic structure.

5. The composite fine particles according to any one of claims 1 to 4, wherein the acid value of the vinyl polymer is 10 mg KOH / g or more and 250 mg KOH / g or less.

6. The composite fine particles according to any one of claims 1 to 5, wherein the vinyl polymer comprises a constituent unit derived from a monomer (p-1) having a carboxyl group and a constituent unit derived from a monomer (p-2) having a (poly)alkylene glycol segment.

7. The composite fine particles according to claim 6, wherein the content of constituent units derived from the monomer (p-2) having the (poly)alkylene glycol segment in the vinyl polymer is 55% by mass or more and 97% by mass or less.

8. The composite fine particles according to any one of claims 1 to 7, wherein the weight-average molecular weight of the vinyl polymer is 3,000 or more and 50,000 or less.

9. The composite fine particles according to any one of claims 1 to 8, wherein the particle size D10 of the composite fine particles is 105 nm or less.

10. A method for producing composite fine particles in which at least a portion of the surface of copper fine particles is coated with a dispersant, comprising the step of dropping a reducing agent into a mixed solution containing a copper raw material compound, a dispersant, and a solvent with an SP value of 8 or more and 18 or less, wherein the dispersant is a vinyl polymer having a carboxyl group and a structure represented by the following formula (1), and the dropping rate of the reducing agent per 1 mol of copper in the copper raw material compound is 0.01 mol / min or more. In the above formula (1), R 1 R is a hydrogen atom or a methyl group. 2 is an organic group containing a cyclic structure or an organic group containing a chain structure having three or more carbon atoms in a straight chain, and n is a number between 1 and 1000.

11. The sum of the atomic weights of the atoms constituting the R of the vinyl polymer is 5000 or less, and the method for producing composite fine particles according to claim 10. 2 ​ 12. The method for producing composite fine particles according to claim 10 or 11, wherein the vinyl polymer is a polymer of a monomer having a carboxyl group and a monomer represented by the following formula (2). In the above formula (2), R 1 and R 2 This is the same organic group as the one in formula (1) above.

13. The R of the vinyl polymer 2 A method for producing composite fine particles according to any one of claims 10 to 12, wherein the composite fine particles have an organic group containing an alkylene oxide structure or a cyclic structure.

14. A method for producing composite fine particles according to any one of claims 10 to 13, wherein the solvent is one or more selected from methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol.

15. A method for producing composite fine particles according to any one of claims 10 to 14, wherein the dropping rate of the reducing agent is 2.00 mol / min or less.

16. A method for producing composite fine particles according to any one of claims 10 to 15, wherein the copper raw material compound is cupric oxide and the reducing agent is a hydrazine-based compound.

17. A method for producing composite fine particles according to any one of claims 10 to 16, wherein the reaction temperature of the reaction solution containing the mixed solution and the reducing agent dropped into the mixed solution is 5°C or higher and 75°C or lower.

18. A composite particle dispersion comprising composite particles according to any one of claims 1 to 9.

19. A copper bonding layer which is a sintered body of composite fine particles according to any one of claims 1 to 9.

20. A wiring pattern which is a sintered body of composite fine particles according to any one of claims 1 to 9.

21. A bonded body in which metal members are joined together via a copper bonding layer, wherein the copper bonding layer is a sintered body of composite fine particles as described in any one of claims 1 to 9.

22. A method for manufacturing a bonded body in which metal members are joined together via a copper bonding layer, comprising: applying the composite fine particle dispersion described in claim 18 to one metal member; and placing the other metal member on the composite fine particle dispersion applied to the one metal substrate, and then pressurizing and firing them.

23. Use of the composite fine particle dispersion according to claim 18 as a bonding material for joining metal members together.

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