Copper microparticles

Abstract

One embodiment of the present invention pertains to copper microparticles that have a tap density of 2.8 g / cm3 or more and a specific surface area of 1-5 m2 / g, and in which, in a number-based particle diameter histogram, 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≤3.7.<sp / > Another embodiment of the present invention also pertains to a copper microparticle dispersion containing the copper microparticles. Another embodiment of the present invention also pertains to a copper microparticle production method including maintaining a mixture, which contains a copper raw material compound, a reducing agent, a dispersant agent, and a solvent having an SP value of 8-18, at a prescribed temperature lower than the boiling point of the solvent for at least 1 minute in order to reduce the copper raw material compound.

Description

copper fine particles

[0001] This invention relates to copper nanoparticles, copper nanoparticle dispersions, and methods for producing copper nanoparticles.

[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 300°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 300°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 (Japanese Patent Publication No. 2022-187936) states that the compacted bulk density (so-called tap density) is 1.30 g / cm³. 3 ~2.96 g / cm³ 3 Disclosed is a low-temperature sinterable copper powder in which the 50% particle size D50, at which the cumulative frequency in the volume-based particle size histogram of copper particles reaches 50%, and the crystallite size D, determined using Scherrer's formula from the diffraction peak of the Cu(111) plane in the X-ray diffraction profile obtained by powder X-ray diffraction for the copper powder, satisfy D / D50 ≥ 0.060.

[0005] The inventors have found that copper nanoparticles having a specific tap density and a specific specific surface area, and satisfying the relationship D90 / D10 ≤ 3.7 in a particle size histogram based on particle count, where the particle size D10 at a cumulative frequency of 10% and the particle size D90 at a cumulative frequency of 90% are D90 / D10 ≤ 3.7, can solve the above problem. That is, the present invention relates to the following [1] to [6]. [1] Tap density is 2.8 g / cm³ 3 In summary, the specific surface area is 1 m². 2 / g or more 5m 2 [1] Copper nanoparticles having a particle size of 10% or less per gram, and in a particle size histogram based on the number of particles, 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 ≤ 3.7. [2] A dispersion of copper nanoparticles containing the copper nanoparticles described in [1]. [3] A method for producing copper nanoparticles, comprising maintaining a mixture containing a copper raw material compound, a reducing agent, a dispersant, and a solvent with an SP value of 8 or more and 18 or less at a predetermined temperature below the boiling point of the solvent for 1 minute or more in order to reduce the copper raw material compound. [4] 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 copper nanoparticles described in [1]. [5] A method for producing a bonded body in which metal members are joined together via a copper bonding layer, comprising: applying the dispersion of copper nanoparticles described in [2] to one metal member; placing the other metal member on the composite nanoparticle dispersion applied to the metal substrate; and pressurizing and firing them. [6] Use of the copper fine particle dispersion described in [2] above as a bonding material for joining metal members together. Detailed description of the invention

[0006] Although copper bonding materials containing copper nanoparticles have higher heat resistance than solder, there is still room for improvement when it comes to their use in power devices where the operating temperature exceeds 200°C. In other words, while copper particles with excellent low-temperature sinterability can be sintered even under low-pressure and low-temperature conditions, simply sintering them to bond them does not allow for the formation of a dense bonding layer, resulting in insufficient heat resistance in practical applications and making it difficult to use them in the mounting of power devices. The copper particles described in Patent Document 1, when used as a copper nanoparticle dispersion for copper bonding, are considered to have insufficient heat resistance as they cannot form a dense copper bonding layer even under pressurized and heated conditions of 20 MPa and 300°C.

[0007] The present invention aims to provide copper nanoparticles that can be sintered at low pressure and low temperature, that can form a dense copper bonding layer even by low pressure and low temperature sintering, and that have good heat resistance to the resulting copper bonding layer, a copper nanoparticle dispersion containing the copper nanoparticles, and a method for producing the copper nanoparticles.

[0008] [Copper nanoparticles] The copper nanoparticles of the present invention have a tap density of 2.8 g / cm³. 3 In summary, the specific surface area is 1 m². 2 / g or more 5m 2 For particles less than or equal to / g, and in a particle size histogram based on particle count, 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 ≤ 3.7.

[0009] The copper nanoparticles of the present invention can be sintered at low pressure and low temperature, and a dense copper bonding layer can be formed even by low pressure and low temperature sintering. Furthermore, the heat resistance of the resulting copper bonding layer can be improved, that is, the porosity of the copper bonding layer and the peeling rate of the copper bonding layer after temperature cycling can be reduced. The reason for this is not entirely clear, but it is thought to be as follows: The copper nanoparticles of the present invention have a high tap density and a large specific surface area, and the particle diameter D10 and particle diameter D90 in the particle diameter histogram based on the number of particles satisfy the relationship D90 / D10 ≤ 3.7. Therefore, in addition to the copper nanoparticles being densely packed (stuck) during low-pressure, low-temperature sintering, the particle diameters of the individual copper particles are similar, so their surface energies are also similar, and it is thought that sintering proceeds uniformly. As a result, the resulting copper bonding layer has a dense yet uniform and strong structure, and peeling is less likely to occur even after temperature cycling, making it possible to obtain a bonded body with high heat resistance. On the other hand, if the tap density is low and the particle size histogram based on the number of particles does not satisfy the relationship D90 / D10 ≤ 3.7, the variation in particle size becomes large, making it impossible to densely pack multiple copper particles before sintering. Furthermore, because the individual particle sizes vary, the surface energy of these copper nanoparticles differs, resulting in variations in the sintering state, and thus a dense and uniform sintered body cannot be obtained. Copper nanoparticles that satisfy the above characteristics can be suitably produced by a wet chemical reduction method using a solvent with an SP value of 8 to 18, and by maintaining the temperature of the solvent below its boiling point.

[0010] According to the present invention, it is possible to provide copper nanoparticles that can be sintered at low pressure and low temperature, that can form a dense copper bonding layer even by low pressure and low temperature sintering, and that have good heat resistance as a result, a method for producing the copper nanoparticles, a copper nanoparticle dispersion containing the copper nanoparticles, use of the copper nanoparticle dispersion as a bonding material, a bonded body formed using the copper nanoparticle dispersion, and a method for producing the bonded body.

[0011] In this specification, "low-pressure low-temperature sintering" means pressurized sintering at a pressure of 20 MPa or less and a temperature of 300°C or less.

[0012] The tap density of the copper microparticles of the present invention is 2.8 g / cm 3 or more, preferably 2.9 g / cm 3 or more, more preferably 3.3 g / cm 3 or more, still more preferably 3.8 g / cm 3 or more, even more preferably 4.3 g / cm 3 or more, even more preferably 4.6 g / cm 3 or more, even more preferably 4.7 g / cm 3 or more, and from the viewpoint of preventing complication of the dispersion step due to a decrease in the permeability of the solvent into the copper microparticles, preferably 7.0 g / cm 3 or less, more preferably 6.5 g / cm 3 or less, still more preferably 6.0 g / cm 3 or less. In the present specification, the "tap density" is a density obtained by a method of measuring the density of copper microparticles obtained by tapping a container under defined conditions, and is measured in accordance with JIS Z2512:2012. Specifically, it is measured by the method described in the examples. The tap density of the copper microparticles can be adjusted by the manufacturing conditions of the copper microparticles such as the type and amount of the copper raw material compound, the type and amount of the reducing agent, the type and amount of the dispersant, the type and amount of the solvent, and the temperature and reduction time (the duration of maintaining the temperature of the reduction reaction) of the reduction reaction, which will be described later.

[0013] The specific surface area of the copper microparticles of the present invention is 1 m 2 / g or more and 5 m 2 / g or less from the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after the temperature cycle, preferably 1.5 m 2 / g or more, more preferably 2.0 m 2 / g or more, even more preferably 2.2 m 2 / g or more, even more preferably 2.4 m 2 / g or more, even more preferably 2.5 m 2 / g or more, and from the same viewpoint and the viewpoint of suppressing oxidation of the copper microparticles, preferably 4.5 m 2 / g or less, more preferably 4.0 m 2 / g or less, more preferably 3.5m 2 It is less than or equal to / g. In this specification, the specific surface area of ​​copper nanoparticles is determined by measuring the amount of physically adsorbed gas based on the Brunauer, Emmett and Teller method (BET method), and is measured in accordance with JIS Z8830:2013. Specifically, it is measured by the method described in the examples. The specific surface area of ​​copper nanoparticles can be adjusted by the copper raw material compound used, the type and amount of reducing agent, the type and amount of dispersant, the type and amount of solvent, and the manufacturing conditions of the copper nanoparticles, such as the temperature and reduction time of the reduction reaction (the duration of maintenance of the reduction reaction temperature), which will be described later.

[0014] In the present invention, the copper fine particles satisfy the relationship D90 / D10 ≤ 3.7 in the particle size histogram based on the number of particles, where the ratio of particle size D90 at a cumulative frequency of 90% to particle size D10 at a cumulative frequency of 10% [D90 / D10] is D90 / D10 ≤ 3.7. D90 / D10 is an index indicating the spread of the particle size distribution; a smaller value means a narrower particle size distribution and more uniform particle size. From the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, this ratio [D90 / D10] is 3.7 or less, preferably 3.4 or less, more preferably 3.3 or less, even more preferably 3.1 or less, and even more preferably 2.5 or less. From the viewpoint of ease of manufacture, it is preferably 1.5 or more, more preferably 1.8 or more, and even more preferably 2.1 or more. This ratio [D90 / D10] is calculated for copper nanoparticles 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 copper nanoparticles. 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 depending on the copper raw material compound used, the type and amount of reducing agent, the type and amount of dispersant, the type and amount of solvent, and the manufacturing conditions of the copper nanoparticles, such as the temperature and reduction time of the reduction reaction (the duration of maintenance of the reduction reaction temperature), which will be described later.

[0015] The average particle size of the copper nanoparticles of the present invention is preferably 50 nm or more, more preferably 60 nm or more, even more preferably 100 nm or more, even more preferably 120 nm or more, and even more preferably 160 nm or more, from the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. Similarly, from the viewpoint of improving sinterability at low pressure and low temperature, it is preferably 300 nm or less, more preferably 250 nm or less, even more preferably 210 nm or less, even more preferably 200 nm or less, and even more preferably 170 nm or less. The average particle size of the copper nanoparticles is the particle size D50 when the cumulative frequency is 50% in the particle size histogram based on the number of particles, and is hereinafter simply referred to as "particle size D50". Specifically, it is measured by the method described in the examples. The average particle size of the copper nanoparticles can be adjusted by the copper raw material compound used, the type and amount of reducing agent, the type and amount of dispersant, the type and amount of solvent, and the manufacturing conditions of the copper nanoparticles, such as the temperature and reduction time of the reduction reaction (the duration of maintenance of the temperature of the reduction reaction), which will be described later.

[0016] <Dispersant> The copper nanoparticles of the present invention are preferably used as a copper nanoparticle dispersion for forming a bonded body by dispersing them in a dispersion medium, as described later. Therefore, from the viewpoint of improving the dispersibility of the copper nanoparticle dispersion, suppressing uneven distribution due to aggregation of copper nanoparticles when obtaining a bonded body, and improving the density and heat resistance of the copper bonded layer formed by sintering, the copper nanoparticles of the present invention are preferably copper nanoparticles whose surface is coated with a dispersant. As for the dispersant, from the viewpoint of improving the dispersion stability of the copper nanoparticles and reducing the porosity of the copper bonded layer formed by sintering and the peeling rate of the copper bonded layer after temperature cycling, one or more types selected from the group consisting of low molecular weight dispersants having carboxyl groups as adsorbent groups and polymer dispersants containing hydrophilic groups are preferred.

[0017] Examples of the low molecular weight dispersant having a carboxy group include, for example, aliphatic carboxylic acids having 1 to 24 carbon atoms, monocarboxylic acids having 2 to 24 carbon atoms and having at least one functional group or bond selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond, and tartaric acid or citric acid having a plurality of carboxy groups. Preferably, from the viewpoints of compatibility with a hydrophilic solvent that easily reduces the oxide film of copper fine particles that inhibits sintering and improvement of the dispersibility of copper fine particles, it is a monocarboxylic acid having 2 to 24 carbon atoms and having at least one functional group or bond selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond, or tartaric acid or citric acid having a plurality of carboxy groups. More preferably, it is a monocarboxylic acid having 5 to 12 carbon atoms and having at least one functional group or bond selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond. The molecular weight of the low molecular weight dispersant is preferably 100 or more, more preferably 120 or more, and preferably 1,000 or less, more preferably 500 or less, still more preferably 300 or less, and even more preferably 230 or less. Specifically, as the low molecular weight dispersant having a carboxy group, from the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after the temperature cycle, it is preferably at least one selected from the group consisting of 5-oxohexanoic acid, citric acid, and tartaric acid, and more preferably 5-oxohexanoic acid.

[0018] From the viewpoint of improving the dispersion stability of copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after the temperature cycle, the polymer dispersant containing a hydrophilic group is preferably a vinyl polymer containing a structural unit derived from a monomer (b-1) having a carboxy group and a structural unit derived from a monomer (b-2) having a polyalkylene glycol segment. The vinyl polymer may be any of a random copolymer, a block copolymer, and an alternating copolymer.

[0019] [Carboxylic acid-containing monomer (b-1)] Examples of monomer (b-1) include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and 2-methacryloyloxymethyl succinic acid; and unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, and citraconic acid. The unsaturated dicarboxylic acid may also be an anhydride. Monomer (b-1) may be used alone or in combination of two or more. From the viewpoint of improving the dispersion stability of copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, monomer (b-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. In this specification, "(meth)acrylic acid" means one or more selected from acrylic acid and methacrylic acid.

[0020] [Monomer (b-2) having a polyalkylene glycol segment] Examples of monomer (b-2) include polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, phenoxy polyalkylene glycol (meth)acrylate, etc. Monomer (b-2) may be used alone or in combination of two or more. In this specification, "(meth)acrylate" means one or more selected from the group consisting of acrylate and methacrylate.

[0021] The monomer (b-2) is preferably at least one selected from the group consisting of polyalkylene glycol (meth)acrylate and alkoxypolyalkylene glycol (meth)acrylate from the viewpoint of improving the dispersion stability of copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. More preferably, it is alkoxypolyalkylene glycol (meth)acrylate. From the viewpoints of the same as above and availability and economy, the carbon number of the alkoxy group of the alkoxypolyalkylene glycol (meth)acrylate is preferably 18 or less, more preferably 12 or less, still more preferably 4 or less, and even more preferably 1. Examples of the alkoxypolyalkylene glycol (meth)acrylate 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 them, methoxypolyalkylene glycol (meth)acrylate is more preferable, and methoxypolyalkylene glycol methacrylate is still more preferable.

[0022] The monomer (b-2) polyalkylene glycol segment preferably contains units derived from alkylene oxide having 2 to 4 carbon atoms, from the viewpoint of improving the dispersion stability of copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, as well as from the viewpoint of availability and economy. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, and 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 polyalkylene glycol segment is preferably 2 or more, more preferably 3 or more, even more preferably 4 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 25 or less, from the viewpoint of improving the dispersion stability of copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. The polyalkylene 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 copper fine particles, reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, 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. The monomer (b-2) is preferably methoxypolyethylene glycol methacrylate, from the viewpoint of improving the dispersion stability of copper fine particles, reducing the porosity of the copper bonding layer and the peeling rate of the copper bonding layer after temperature cycling, as well as from the viewpoint of availability and economy.The number of repeating oxyethylene groups in methoxypolyethylene glycol methacrylate 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 25 or less, from the viewpoint of improving the dispersion stability of copper fine particles, improving the density of the sintered body formed by sintering, and reducing the porosity of the copper bonding layer and the peeling rate of the copper bonding layer after temperature cycling.

[0023] Specific examples of commercially available monomers (b-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.

[0024] [Hydrophobic monomer (b-3)] The vinyl polymer may further contain constituent units derived from hydrophobic monomer (b-3) from the viewpoint of reducing the porosity of the copper bond layer formed by sintering and the peeling rate of the copper bond layer after temperature cycling. 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 (b-3) dissolved is preferably 5 g or less, more preferably 1 g or less, from the viewpoint of reducing the porosity of the sintering and the peeling rate of the copper bond layer after temperature cycling. The monomer (b-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.

[0025] The aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group with 6 to 22 carbon atoms, which may have substituents containing heteroatoms, from the viewpoint of reducing the porosity of the copper bond layer formed by sintering and the peeling rate of the copper bond layer after temperature cycling. More preferably, it is one or more selected from the group consisting of 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. From the viewpoint of reducing the porosity of the copper bond layer formed by sintering and the peeling rate of the copper bond layer after temperature cycling, as well as from the viewpoint of availability and economy, styrene and α-methylstyrene are more preferred, and styrene is even more preferred. As aromatic group-containing (meth)acrylates, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc. are preferred, with benzyl (meth)acrylate being more preferred, from the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, as well as from the viewpoint of availability and economic efficiency.

[0026] (Meth)acrylates having hydrocarbon groups derived from aliphatic alcohols are preferably (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols with 22 or fewer carbon atoms, more preferably (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols with 12 or fewer carbon atoms, even more preferably (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols with 8 or fewer carbon atoms, and even more preferably (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols with 4 or fewer carbon atoms, from the viewpoint of reducing the porosity of the copper bond layer formed by sintering and the peeling rate of the copper bond layer after temperature cycling. Examples of preferred (meth)acrylates having a linear alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. Among these, methyl (meth)acrylate is more preferred from the viewpoint of reducing the porosity of the copper bonded layer formed by sintering and the peeling rate of the copper bonded layer after temperature cycling, as well as from the viewpoint of availability and economic efficiency. Examples of preferred (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. Examples of preferred (meth)acrylates having alicyclic alkyl groups include cyclohexyl (meth)acrylate.The (meth)acrylate having hydrocarbon groups derived from aliphatic alcohols is preferably a (meth)acrylate having a linear alkyl group having 22 or fewer carbon atoms, more preferably a (meth)acrylate having a linear alkyl group having 12 or fewer carbon atoms, even more preferably a (meth)acrylate having a linear alkyl group having 8 or fewer carbon atoms, and even more preferably a (meth)acrylate having a linear alkyl group having 4 or fewer carbon atoms, from the viewpoint of reducing the porosity of the copper bond layer formed by sintering and the peeling rate of the copper bond layer after temperature cycling. Monomer (b-3) may be used alone or in combination of two or more types.

[0027] From the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, monomer (b-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, more preferably one or more selected from the group consisting of styrene monomers and (meth)acrylates having a linear alkyl group having 1 to 4 carbon atoms, even more preferably one or more selected from the group consisting of styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate, even more preferably one or more selected from the group consisting of styrene, α-methylstyrene, and methyl (meth)acrylate, and even more preferably one or more selected from the group consisting of styrene and methyl (meth)acrylate.

[0028] From the viewpoint of improving the dispersion stability of copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, the vinyl polymer preferably contains, as monomer (b-1), one or more constituent units selected from the group consisting of (meth)acrylic acid and maleic acid, and as monomer (b-2), a constituent unit derived from alkoxypolyalkylene glycol (meth)acrylate, more preferably, as monomer (b-1), a constituent unit derived from (meth)acrylic acid, and as monomer (b-2), a constituent unit derived from methoxypolyethylene glycol (meth)acrylate.

[0029] The content of monomer (b-1) in the raw material monomer during the production of vinyl polymers, or the content of monomer (b-1)-derived constituent units in all constituent units of the vinyl polymer, is preferably 3% by mass or more, more preferably 5% by mass or more, and preferably 35% by mass or less, more preferably 25% by mass or less, and even more preferably 18% by mass or less, from the viewpoint of improving the dispersion stability of copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. Furthermore, the content of monomer (b-2) in the raw material monomer during the production of vinyl polymers, or the content of monomer (b-2)-derived constituent units in all 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 copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling.

[0030] Furthermore, when the vinyl polymer contains constituent units derived from monomer (b-1), monomer (b-2), and monomer (b-3), the content of monomer (b-1) in the raw material monomer during the production of the vinyl polymer, or the content of constituent units derived from monomer (b-1) in the total constituent units of the vinyl polymer, is preferably 3% by mass or more, more preferably 9% by mass or more, even more preferably 13% by mass or more, and preferably 35% by mass or less, more preferably 25% by mass or less, and even more preferably 18% by mass or less. Furthermore, when the vinyl polymer contains constituent units derived from monomer (b-1), monomer (b-2), and monomer (b-3), the content of monomer (b-2) in the raw material monomer during the production of the vinyl polymer, or the content of constituent units derived from monomer (b-2) 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 92% by mass or less, more preferably 85% by mass or less, even more preferably 75% by mass or less, and even more preferably 70% by mass or less. Furthermore, when the vinyl polymer contains constituent units derived from monomer (b-1), monomer (b-2), and monomer (b-3), the content of monomer (b-3) in the raw material monomer during the production of the vinyl polymer, or the content of constituent units derived from monomer (b-3) in the total constituent units of the vinyl polymer, is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 8% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 18% by mass or less.

[0031] Furthermore, when the vinyl polymer consists only of constituent units derived from monomer (b-1) and monomer (b-2), the content of monomer (b-1) in the raw material monomer during the production of the vinyl polymer, or the content of constituent units derived from monomer (b-1) 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 35% by mass or less, more preferably 30% by mass or less, even more preferably 15% by mass or less, and even more preferably 10% by mass or less. Also, when the vinyl polymer consists only of constituent units derived from monomer (b-1) and monomer (b-2), the content of monomer (b-2) in the raw material monomer during the production of the vinyl polymer, or the content of constituent units derived from monomer (b-2) in the total constituent units of the vinyl polymer, is preferably 65% ​​by mass or more, more preferably 70% by mass or more, even more preferably 85% by mass or more, even more preferably 90% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less.

[0032] In the present invention, the total content of monomer (b-1) and monomer (b-2) in the raw material monomer during the production of the vinyl polymer, or the total content of constituent units derived from monomer (b-1) and monomer (b-2) in the total constituent units of the vinyl polymer, is preferably 58% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 97% by mass or more, and even more preferably substantially 100% by mass, from the viewpoint of improving the dispersion stability of copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. 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 (b-1) and monomer (b-2) contained in the raw material monomer (b-1) and monomer (b-2), so-called impurities.

[0033] The number-average molecular weight Mn of the vinyl polymer is preferably 4,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 15,000 or less, and even more preferably 10,000 or less, from the viewpoint of improving the dispersion stability of copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling.

[0034] The acid value of the vinyl polymer is preferably 20 mg KOH / g or more, more preferably 25 mg KOH / g or more, even more preferably 30 mg KOH / g or more, even more preferably 35 mg KOH / g or more, even more preferably 40 mg KOH / g or more, and preferably 250 mg KOH / g or less, more preferably 200 mg KOH / g or less, even more preferably 150 mg KOH / g or less, even more preferably 110 mg KOH / g or less, even more preferably 80 mg KOH / g or less, and even more preferably 60 mg KOH / g or less. 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.

[0035] When the copper fine particles of the present invention are composite fine particles in which at least a portion of the surface of a granular copper component is coated with a dispersant, in other words, composite fine particles comprising a granular copper component and a dispersant coating at least a portion of its surface, the ratio of the mass of the dispersant to the total mass of the copper component and the dispersant (dispersant / dispersant + copper component) (hereinafter also referred to as the "dispersant mass ratio") is preferably 0.003 or higher, more preferably 0.005 or higher, even more preferably 0.007 or higher, even more preferably 0.009 or higher, and preferably 0.070 or lower, more preferably 0.050 or lower, even more preferably 0.040 or lower, even more preferably 0.035 or lower, and even more preferably 0.028 or lower, from the viewpoint of improving the dispersion stability of the copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. Furthermore, the mass ratio of the dispersant is calculated from the content of copper nanoparticles and the content of the dispersant in the copper nanoparticle dispersion using a differential thermogravimetric / thermogravimetric analysis (TG / DTA) device.

[0036] As described above, the copper fine particles of the present invention are required to have good dispersibility in organic solvents. From the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, the degree of dispersion of the copper fine particles is preferably 15 μm or less, more preferably 9.5 μm or less, even more preferably 8.5 μm or less, even more preferably 6.0 μm or less, and even more preferably 5.0 μm or less.

[0037] [Method for Producing Copper Microparticles] The present invention provides a method for producing copper microparticles, which includes a copper microparticle production step in which a copper raw material compound is reduced by a wet chemical reduction method to produce the copper 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, the reducing agent, and the solvent to obtain a dispersion of copper microparticles, and then dry the dispersion of copper microparticles by freeze-drying or the like. It is preferable to add a dispersant at the same time as the reduction, and in the dried powder of copper microparticles (composite microparticles) obtained at this time, part or all of the surface of the granular copper components is coated with the dispersant.

[0038] The temperature of the reduction reaction in the copper nanoparticle 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 reaction 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, is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 20°C or higher, even more preferably 30°C or higher, and even more preferably 45°C or higher, from the viewpoint of increasing the specific surface area of ​​the copper nanoparticles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. Furthermore, from the viewpoint of suppressing the generation of bubbles and ensuring a uniform particle size distribution, it is preferably below the boiling point of the solvent, more preferably -2.5°C or lower from the boiling point of the solvent, and even more preferably -5°C or lower from the boiling point of the solvent. The upper limit of the reduction reaction temperature varies depending on the type of solvent used, but from the viewpoint of suppressing the generation of bubbles and ensuring a uniform particle size distribution, it is preferably 75°C or lower, more preferably 72°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 the generation of bubbles and ensuring a uniform particle size distribution, the maintenance time for the temperature of the reduction reaction is preferably 1 minute or more, more preferably 30 minutes or more, and even more preferably 1 hour or more. 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.

[0039] 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. The copper raw material compound can be used individually or in a mixture of two or more. From the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, 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 oxide.

[0040] 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. The reducing agent may be used alone or in combination of two or more. As a reducing agent, a hydrazine compound is preferred, more preferably hydrated hydrazine (hydrazine monohydrate), from the viewpoint of reducing the porosity of the copper bond layer formed by sintering and the peeling rate of the copper bond layer after temperature cycling.

[0041] In the copper nanoparticle manufacturing process described above, a solvent that leaves little foam during manufacturing is preferred as the solvent 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 little foam during manufacturing is preferred.

[0042] The solubility parameter (SP value) of the solvent is preferably 18 or less, more preferably 16 or less, even more preferably 14 or less, even more preferably 13 or less, and even more preferably 12 or less, from the viewpoint of reducing the persistence of bubbles, and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. From the viewpoint of uniformly dispersing the reducing agent, and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, the SP value is preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, and even more preferably 11 or more. That is, in one embodiment, the method for producing copper fine particles of the present invention includes maintaining a mixture containing a copper raw material compound, a reducing agent, a dispersant, and a solvent with an SP value of 8 or more and 18 or less at a predetermined temperature below the boiling point of the solvent for 1 minute or more for the reduction of the copper raw material compound. The SP value of the solvent is preferably 9 or more and 13 or less. Here, the SP value is a value calculated by the Fedors method (see "Polym.Eng.Sci. 14(2)152, (1974)"). Note that the upper and lower limits of the numerical range in the present invention are included in the equivalence range of the present invention even if they fall slightly outside the numerical range specified by the present invention, as long as they have the same effects as those within the numerical range. The boiling point of the solvent is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher, from the viewpoint of reducing the persistence of bubbles and making the particle size distribution uniform, and from the same viewpoint, preferably less than 100°C, more preferably less than 95°C, and even more preferably 90°C or lower. The predetermined temperature is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 20°C or higher, even more preferably 30°C or higher, and even more preferably 45°C or higher, from the viewpoint of increasing the specific surface area of ​​the copper fine particles and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. Furthermore, from the viewpoint of suppressing the generation of bubbles and making the particle size distribution uniform, the temperature is preferably below the boiling point of the solvent, more preferably 2.5°C or higher below the boiling point of the solvent, and even more preferably 5°C or higher below the boiling point of the solvent.

[0043] From the viewpoint of reducing the persistence of bubbles in the copper fine particle manufacturing process, and from the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, the viscosity of the solvent at 20°C is preferably 10 mPa·s or less, more preferably 5 mPa·s or less, and even more preferably 3 mPa·s or less. Furthermore, from the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, it is preferably 0.30 mPa·s or more, more preferably 0.70 mPa·s or more, even more preferably 1.50 mPa·s or more, and even more preferably 2.0 mPa·s or more.

[0044] Furthermore, the molecular weight of the solvent is preferably 20 or more, more preferably 30 or more, and even more preferably 40 or more, from the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. Similarly, from the same viewpoint, it is preferably 500 or less, more preferably 400 or less, even more preferably 300 or less, even more preferably 200 or less, even more preferably 100 or less, and even more preferably 80 or less.

[0045] Examples of solvents include methanol, ethanol, 2-propanol, 2-butanone, butanol, hexanol, cyclohexanol, and acetone. From the viewpoint of reducing the porosity of the copper bonded layer formed by sintering and the peeling rate of the copper bonded layer after temperature cycling, one or more selected from the group consisting of ethanol, 2-propanol, and 2-butanone is preferred, one or more selected from the group consisting of ethanol and 2-propanol is preferred, and 2-propanol is even more preferred.

[0046] In the production of copper nanoparticle dispersions, the dispersion may be purified before freeze-drying from the viewpoint of removing impurities such as unreacted reducing agents and excess dispersants that do not contribute to the dispersion of copper nanoparticles. There are no particular limitations on the method of purifying the dispersion containing copper nanoparticles, and examples include membrane treatment such as decantation, dialysis, and ultrafiltration; and centrifugal separation. Among these, decantation and centrifugal separation are preferred from the viewpoint of improving yield. As the material of the dialysis membrane used for dialysis, regenerated cellulose is preferred. From the viewpoint of efficiently removing impurities, the molecular weight cutoff of the dialysis membrane is preferably 1,000 or more, more preferably 5,000 or more, even more preferably 10,000 or more, and preferably 100,000 or less, and more preferably 70,000 or less.

[0047] [Copper Microparticle Dispersion] The copper microparticle dispersion of the present invention is a copper microparticle dispersion containing the copper microparticles of the present invention and a dispersion medium. The copper microparticles are as described above, and their description is omitted. <Dispersion Medium> The dispersion medium used here can be any solvent capable of dispersing the copper microparticles, and 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 reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, 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.

[0048] 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. Among these, terpene alcohols are preferred as aliphatic monohydric alcohols from the viewpoint of reducing the porosity of the copper bond layer formed by sintering and the peeling rate of the copper bond layer after temperature cycling. Examples of terpene alcohols include monoterpene alcohols such as α-terpineol, linalool, geraniol, citronellol, and dihydroterpineol.

[0049] (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.

[0050] 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.

[0051] 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).

[0052] 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 polyethylene glycol, and even more preferably tetraethylene glycol, from the viewpoint of improving the dispersion stability of copper nanoparticles in the copper nanoparticle dispersion and reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling.

[0053] <Copper Microparticles> The copper microparticle dispersion of the present invention may further contain copper microparticles from the viewpoint of reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. 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 reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. 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.

[0054] 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 reducing the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling. The average particle size of the copper microparticles is measured by the same method as the average particle size (particle size D50) of the copper fine particles described in the examples.

[0055] When the copper fine particle dispersion of the present invention contains copper microparticles, the ratio of the content of copper fine particles to the total content of copper fine particles and copper microparticles in the copper fine particle dispersion [copper fine particles / (copper fine particles + copper microparticles)] is preferably 0.3 or more, more preferably 0.4 or more, even more preferably 0.5 or more, and preferably less than 1.0, more preferably 0.9 or less, even more preferably 0.8 or less, and even more preferably 0.75 or less.

[0056] <Content of each component in the dispersion> The copper fine particle dispersion of the present invention can be used to manufacture a bonded body by sintering. When the copper fine particle dispersion of the present invention is used to manufacture a bonded body, the content of copper fine particles in the copper fine particle 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 97% by mass or less, and more preferably 95% by mass or less, from the viewpoint of reducing the dispersibility of copper fine particles in the dispersion, the porosity of the copper bonded layer formed by sintering, and the peeling rate of the copper bonded layer after temperature cycling. From the viewpoint of reducing the dispersibility of copper nanoparticles in the dispersion, the porosity of the copper bonding layer formed by sintering, and the peeling rate of the copper bonding layer after temperature cycling, the content of the dispersant in the copper nanoparticle dispersion of the present invention, expressed as the mass ratio of the dispersant to the copper nanoparticles in the dispersion (dispersant / copper nanoparticles), is preferably 0.003 or more, more preferably 0.005 or more, even more preferably 0.007 or more, even more preferably 0.009 or more, and preferably 0.070 or less, more preferably 0.050 or less, even more preferably 0.040 or less, even more preferably 0.035 or less, and even more preferably 0.028 or less. From the viewpoint of reducing the dispersibility of copper nanoparticles in the dispersion, the porosity of the copper bonding layer formed by sintering, and the peeling rate of the copper bonding layer after temperature cycling, the content of the dispersion medium in the copper nanoparticle dispersion of the present invention is preferably 2.5% by mass or more, more preferably 3.5% by mass or more, even more preferably 4.5% by mass or more, and preferably 40% by mass or less, more preferably 25% by mass or less, and even more preferably 15% by mass or less.Furthermore, if the copper fine particle dispersion of the present invention contains copper microparticles, from a similar viewpoint, the content of copper fine particles 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 more than 0% by mass and 65% by mass or less. Furthermore, if the copper fine particle dispersion of the present invention contains copper microparticles, from a similar viewpoint, the content of copper fine particles is preferably 30% by mass or more and 95% by mass or less, the content of the dispersant is preferably 0.003 to 0.070 when expressed as the above mass ratio (dispersant / copper 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 more than 0% by mass and 65% by mass or less.

[0057] 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 copper 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 copper 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.

[0058] <Method for Producing Copper Microparticle Dispersion> The copper microparticle dispersion according to the present invention can be obtained by a known method, such as by adding and mixing a dispersion medium and, if necessary, various additives to pre-prepared copper microparticles (composite microparticles). As for the mixing method, a known method can be used, and from the viewpoint of better dispersing the copper microparticles in the dispersion medium, it is preferable to pre-mix the copper 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 rotation-and-revolution stirring device.

[0059] <Applications of the Composite Microparticle Dispersion> The copper microparticle dispersion of the present invention obtained in this way can be sintered at low pressure and low temperature, and the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling are good, 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 copper microparticle dispersion of the present invention is preferably used for joining multiple metal members together.

[0060] [Jointed Body and Method for Manufacturing the Same] The copper fine particle dispersion of the present invention can be interposed between a plurality of metal members, and then joined together by low-pressure, low-temperature firing to manufacture a jointed body. That is, the jointed body obtained here is a jointed body having a metal member-copper bonding layer-metal member structure, in which a plurality of metal members are joined by a copper bonding layer formed by sintering the copper fine particle dispersion of the present invention. 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 to join the adjacent metal members together, wherein the copper bonding layer is a sintered body of copper fine particles of the present invention. In one embodiment of the present invention, the method for manufacturing a jointed body comprises the following steps 1 to 2 in this order. Step 1: A step of applying the above-described copper fine particle dispersion of the present invention to one main surface of one of the metal members. Step 2: A step of placing the other metal member on the copper fine particle dispersion applied to the metal substrate to form a laminate, and firing the laminate while applying pressure in the thickness direction.

[0061] In the present invention, 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 an electrically insulating substrate. 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 one or more selected from the group consisting of 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 an electrically insulating substrate. Examples of joining metal components in this invention include 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.

[0062] Methods for applying the copper nanoparticle dispersion to a metal component 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 copper nanoparticle dispersion applied to the metal component can be appropriately adjusted according to the size and type of the metal component to be joined.

[0063] The heating temperature (firing temperature) in the low-pressure low-temperature firing described above is preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 240°C or higher, from the viewpoint of reducing the porosity of the copper bonding layer obtained by sintering and the peeling rate of the copper bonding layer after temperature cycling, and from the viewpoint of reducing damage to the semiconductor chip, it is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 270°C or lower.

[0064] The low-pressure low-temperature firing described above can be carried out under either no pressure or pressure, but from the viewpoint of bonding strength and conductivity, it is preferable to perform it under pressure. The pressure in the low-pressure low-temperature firing is preferably 2 MPa or more, more preferably 5 MPa or more, even more preferably 6 MPa or more, and even more preferably 8 MPa or more, from the viewpoint of reducing the porosity of the copper bonded layer obtained by sintering and the peeling rate of the copper bonded layer after temperature cycling, and from the viewpoint of reducing damage to the semiconductor chip, it is preferably 50 MPa or less, more preferably 40 MPa or less, even more preferably 30 MPa or less, even more preferably 20 MPa or less, and even more preferably 15 MPa or less.

[0065] The heating time in the low-pressure low-temperature firing described above can be appropriately adjusted by the heating temperature and pressure, but from the viewpoint of reducing the porosity of the copper bonding layer obtained by sintering and the peeling rate of the copper bonding layer after temperature cycling, it 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, it 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.

[0066] The atmosphere during the low-pressure, low-temperature firing may be an air atmosphere, an inert gas atmosphere such as nitrogen gas, or a reducing gas atmosphere such as hydrogen gas. However, from the viewpoint of suppressing copper oxidation and ensuring safety, a nitrogen gas atmosphere is more preferable.

[0067] In the bonded body obtained in this way, the copper bonding layer is obtained as a dense structure, and from the viewpoint of reducing the porosity of the copper bonding layer obtained by sintering and the peeling rate of the copper bonding layer after temperature cycling, the porosity of the copper bonding layer is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, even more preferably 7% or less, and even more preferably 6% or less.

[0068] The present invention further discloses the following inventions.

[0069] <1> Tap density is 2.8 g / cm³ 3 In summary, the specific surface area is 1 m².2 / g or more 5m 2<1> The copper nanoparticles are less than or equal to / g, and in a particle size histogram based on the number of particles, 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 ≤ 3.7. <2> The copper nanoparticles according to <1>, wherein 90 parts by mass of copper nanoparticles are dispersed in 10 parts by mass of tetraethylene glycol as the dispersion medium, and the degree of dispersion of the copper nanoparticle dispersion measured in accordance with JIS K 5600-2-5:1999 is preferably 15 μm or less, more preferably 9.5 μm or less, even more preferably 8.5 μm or less, even more preferably 6.0 μm or less, and even more preferably 5.0 μm or less. <3> The copper nanoparticles according to <1> or <2>, wherein the copper nanoparticles are composite nanoparticles in which at least a part of the surface of the granular copper component is coated with a dispersant having a carboxyl group. <4> The copper nanoparticles according to <3>, wherein the dispersant is a monocarboxylic acid having 5 to 12 carbon atoms and having one or more functional groups or bonds selected from the group consisting of a hydroxyl group, a ketonic carbonyl group, and an ether bond. <5> The copper nanoparticles according to <4>, wherein the molecular weight of the dispersant is preferably 100 or more, more preferably 120 or more, and preferably 1,000 or less, more preferably 500 or less, even more preferably 300 or less, and even more preferably 230 or less. <6> The copper nanoparticles according to <3>, wherein the dispersant is a vinyl polymer containing a constituent unit derived from a monomer (b-1) having a carboxyl group and a constituent unit of a monomer (b-2) having a polyalkylene glycol segment. <7> The copper nanoparticles according to <6>, wherein the monomer (b-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. <8> The copper nanoparticles according to <6> or <7> above, wherein the monomer (b-2) is one or more selected from the group consisting of polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, and phenoxy polyalkylene glycol (meth)acrylate.<9> The copper fine particles according to any one of <6> to <8>, wherein the dispersant further contains a constituent unit derived from a hydrophobic monomer (b-3), and the hydrophobic monomer (b-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. <10> The copper fine particles according to any one of <6> to <9>, wherein the number average molecular weight Mn of the vinyl polymer is preferably 4,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 15,000 or less, and even more preferably 10,000 or less. <11> The copper fine particles according to any one of <6> to <10>, wherein the acid value of the vinyl polymer is preferably 20 mg KOH / g or more, more preferably 25 mg KOH / g or more, even more preferably 30 mg KOH / g or more, even more preferably 35 mg KOH / g or more, even more preferably 40 mg KOH / g or more, and preferably 250 mg KOH / g or less, more preferably 200 mg KOH / g or less, even more preferably 150 mg KOH / g or less, even more preferably 110 mg KOH / g or less, even more preferably 80 mg KOH / g or less, and even more preferably 60 mg KOH / g or less. <12> The copper fine particles according to any one of <1> to <11>, wherein the average particle size of the copper fine particles is preferably 50 nm or more, more preferably 60 nm or more, even more preferably 100 nm or more, even more preferably 120 nm or more, even more preferably 160 nm or more, and preferably 300 nm or less, more preferably 250 nm or less, even more preferably 210 nm or less, even more preferably 200 nm or less, and even more preferably 170 nm or less. <13> The tap density of the copper fine particles is 2.8 g / cm. 3 The above is preferable, preferably 2.9 g / cm³. 3 More preferably, 3.3 g / cm³ 3 More preferably, 3.8 g / cm³ 3 More preferably 4.3 g / cm³ 3More preferably 4.6 g / cm³ 3 More preferably 4.7 g / cm³ 3 The above applies, and preferably 7.0 g / cm³. 3 More preferably, 6.5 g / cm³ 3 More preferably, 6.0 g / cm³ 3 The copper fine particles described in any of <1> to <12> above, which are as follows: <14> The specific surface area of ​​the copper fine particles is 1 m 2 The amount is 1.5 m or more, preferably 1.5 m 2 / g or more, more preferably 2.0m 2 / g or more, more preferably 2.2m 2 / g or more, more preferably 2.4m 2 / g or more, more preferably 2.5m 2 It is 1 / g or more, and 5m 2 It is less than or equal to / g, preferably 4.5m 2 / g or less, more preferably 4.0m 2 / g or less, more preferably 3.5m 2Copper fine particles according to any one of <1> to <13> above, wherein the amount is less than or equal to / g. <15> Copper fine particles according to any one of <1> to <14> above, wherein the ratio of the particle size D90 to the particle size D10 [D90 / D10] is 3.7 or less, preferably 3.4 or less, more preferably 3.3 or less, even more preferably 3.1 or less, even more preferably 2.5 or less, and preferably 1.5 or more, more preferably 1.8 or more, and even more preferably 2.1 or more. <16> The copper fine particles according to <3>, wherein the ratio of the mass of the dispersant to the total mass of the granular copper component and the dispersant (dispersant / dispersant + copper component) is preferably 0.003 or more, more preferably 0.005 or more, even more preferably 0.007 or more, even more preferably 0.009 or more, and preferably 0.070 or less, more preferably 0.050 or less, even more preferably 0.040 or less, even more preferably 0.035 or less, and even more preferably 0.028 or less. <17> A copper fine particle dispersion comprising the copper fine particles according to any one of <1> to <16>. <18> The copper fine particle dispersion according to <17>, wherein the copper fine particle dispersion comprises a dispersion medium, and the dispersion medium comprises one or more selected from the group consisting of aliphatic monohydric alcohol, (poly)alkylene glycol, (poly)alkylene glycol derivative, glycerin, and glycerin derivative. <19> The copper fine particle dispersion according to <17> or <18>, further comprising copper microparticles. <20> The copper fine particle dispersion according to <19>, 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.<21> The copper nanoparticle dispersion according to <19> or <20>, wherein the ratio of the content of copper nanoparticles to the total content of copper nanoparticles and copper microparticles in the copper nanoparticle dispersion [copper nanoparticles / (copper nanoparticles + copper microparticles)] is preferably 0.3 or more, more preferably 0.4 or more, even more preferably 0.5 or more, and preferably less than 1.0, more preferably 0.9 or less, even more preferably 0.8 or less, and even more preferably 0.75 or less. <22> A method for producing copper nanoparticles, comprising maintaining a mixture containing a copper raw material compound, a reducing agent, a dispersant and a solvent at a predetermined temperature below the boiling point of the solvent for 1 minute or more for the reduction of the copper raw material compound, wherein the SP value of the solvent is preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, even more preferably 11 or more, and preferably 18 or less, more preferably 16 or less, even more preferably 14 or less, even more preferably 13 or less, and even more preferably 12 or less. <23> The method for producing copper nanoparticles according to <22>, wherein the predetermined temperature is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 20°C or higher, even more preferably 30°C or higher, even more preferably 45°C or higher, and preferably a temperature below the boiling point of the solvent, more preferably a temperature 2.5°C or higher below the boiling point of the solvent, and even more preferably a temperature 5°C or higher below the boiling point of the solvent. <24> The method for producing copper nanoparticles according to <22> or <23>, wherein the molecular weight of the solvent is preferably 20 or higher, more preferably 30 or higher, even more preferably 40 or higher, and preferably 500 or less, more preferably 400 or less, even more preferably 300 or less, even more preferably 200 or less, even more preferably 100 or less, and even more preferably 80 or less. <25> The method for producing copper nanoparticles according to any one of <22> to <24>, wherein the copper raw material compound is a copper oxide. <26> The method for producing copper nanoparticles according to any one of <22> to <25>, wherein the copper raw material compound is cupric oxide. <27> The method for producing copper nanoparticles according to any one of <22> to <26>, wherein the dispersant is one or more selected from the group consisting of low molecular weight dispersants having carboxyl groups and polymer dispersants containing hydrophilic groups.<28> A joined body in which metal members are joined together via a copper bonding layer, wherein the copper bonding layer is a sintered body of copper fine particles as described in any of <1> to <16> above. <29> A method for manufacturing a joined body in which metal members are joined together via a copper bonding layer, comprising: applying a copper fine particle dispersion as described in any of <17> to <21> above to one metal member; and placing the other metal member on the composite fine particle dispersion applied to the metal substrate, and pressurizing and firing the two. <30> The method for manufacturing a joined body according to <29> above, wherein the firing temperature during pressurizing and firing is preferably 200°C or higher, more preferably 220°C or higher, even more preferably 240°C or higher, and preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 270°C or lower. <31> The method for manufacturing a joined body according to <29> or <30>, wherein the pressure during pressurization and firing is preferably 2 MPa or more, more preferably 5 MPa or more, even more preferably 6 MPa or more, even more preferably 8 MPa or more, and preferably 50 MPa or less, more preferably 40 MPa or less, even more preferably 30 MPa or less, even more preferably 20 MPa or less, and even more preferably 15 MPa or less. <32> The method for manufacturing a joined body according to any one of <29> to <31>, wherein the heating time during pressurization and firing is preferably 150 seconds or more, more preferably 200 seconds or more, even more preferably 250 seconds or more, and 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. <33> Use of the copper fine particle dispersion according to any one of <17> to <21> as a joining material for joining metal members together.

[0070] 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.

[0071] [Measurement of Number-Average Molecular Weight (Mn) of Dispersant] The number-average molecular weight (Mn) of the dispersant was determined by gel permeation chromatography. The sample prepared for measurement was obtained by mixing 0.1 g of dispersant with 10 mL of eluent in a glass vial, stirring with a magnetic stirrer at 25°C for 10 hours, and filtering 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: N,N-dimethylformamide in which phosphoric acid and lithium bromide are dissolved 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)"

[0072] [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)).

[0073] [Calculation of D10, D50, D90 and ratio [D90 / D10] of copper nanoparticles] Scanning electron microscope (SEM) images of copper nanoparticles 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 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.

[0074] [Evaluation of Specific Surface Area of ​​Copper Microparticles] The specific surface area of ​​the obtained copper microparticles was measured in accordance with JIS Z8830:2013. Specifically, 2 g of copper microparticles were weighed out and placed in a sample cell, and after firing at 90°C for 60 min, the specific surface area was measured at multiple points using nitrogen gas at relative pressures of 0.1, 0.2, 0.3, 0.4, and 0.5.

[0075] [Evaluation of Tap Density of Copper Fine Particles] The tap density of the obtained copper fine particles was measured in accordance with JIS Z2512:2012. Specifically, a guide was attached to a 10cc cup of Hosokawa Micron Corporation's Powder Tester PT-X, the powder was placed inside, and the cup was tapped 1000 times. After that, the guide was removed, the portion exceeding the 10cc volume was leveled off, and the weight of the powder in the container was measured to determine the tap density.

[0076] <Dispersant Mass Ratio> Using a differential thermogravimetric / thermogravimetric analysis system (TG / DTA) (manufactured by Hitachi High-Tech Science Corporation, product name: STA7200RV), 10 mg of the sample (dried copper nanoparticle powder) 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 the copper component. The dispersant mass ratio was calculated using the following formula: Dispersant Mass Ratio = (Mass loss from 35°C to 550°C [mg]) / (Mass loss from 35°C to 550°C [mg] + Remaining mass at 550°C [mg])

[0077] [Evaluation of the degree of dispersion of copper nanoparticle dispersions] Tetraethylene glycol was used as the dispersion medium, and 90 parts by mass of copper nanoparticles were dispersed in 10 parts by mass of the dispersion medium. The degree of dispersion of the copper nanoparticle dispersions was evaluated in accordance with JIS K5600-2-5:1999.

[0078] [Preparation of Dispersant] (Production Example 1: Preparation of Dispersant B-1) 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. Next, 15.3 g of methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 7.2 g of methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 10 g of styrene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 67.5 g of methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by NOF Corporation, "PME-1000"), 2.0 g of 3-mercaptopropionic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), and 28.7 g of ethanol were dissolved in a poly beaker and placed in a dropping funnel (1). Separately, 51.3 g of ethanol and 1.3 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "V-65", polymerization initiator) were dissolved in a poly beaker and placed in a dropping funnel (2). Next, the mixtures in dropping funnel (1) and dropping funnel (2) were simultaneously added to the flask over 90 minutes each. After that, the internal temperature of the flask was raised to 90°C, and stirring was continued for another hour to complete the reaction. The obtained resin solution was freeze-dried using a freeze-dryer (Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: DRC-1000) under drying conditions (freezing at -25°C for 1 hour, reduced pressure at -10°C for 9 hours, reduced pressure at 25°C for 5 hours. Reduced pressure degree: 5 Pa) to obtain an oven-dried dispersant B-1 (methacrylic acid / methyl methacrylate / styrene / methoxypolyethylene glycol (EO 23 mol) methacrylate polymer, acid value: 100 mg KOH / g, Mn: 8,300). The monomer composition is shown in Table 1.

[0079] (Production Example 2: Preparation of Dispersant B-2) Dispersant B-2 was obtained by the same production method as in Production Example 1, except that the monomer composition shown in Table 1 was changed.

[0080]

[0081] • 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(23)MA: Methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by NOF Corporation, "PME-1000") • MMA: Methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) • St: Styrene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent)

[0082] For the dispersant B-3, 5-oxohexanoic acid (Tokyo Chemical Industries, Ltd., purity (test method): >98.0% (GC) (T)) was prepared.

[0083] [Production of Copper Microparticles] (Example 1: Production of Copper Microparticles A-1) 8.14 g of cupric oxide (N-120, manufactured by Nisshin Chemco Co., Ltd.) as the copper raw material compound, 0.20 g of dispersant B-1, and 81.40 g of ethanol (95) (first-grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 300 mL beaker and stirred for 15 minutes. During stirring, the temperature of the reaction solution was controlled to 70°C using an oil bath. Next, 10.26 g of hydrazine monohydrate (special-grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), placed in a 50 mL dropping funnel, was added dropwise to the mixture over 20 minutes at 25°C. After that, the reaction solution 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 copper microparticles. The entire amount of the obtained dispersion was placed in a Hitachi Koki Co., Ltd. 500PA bottle with 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, and the mixture was held in this state for 30 minutes. 60 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 three times. The precipitate of the purified copper nanoparticles was freeze-dried using a freeze-dryer (FDU-2110, Tokyo Rikakikai Co., Ltd., model: FRC-1000) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: FRC-1000) to obtain 6.3 g of copper nanoparticles A-1. The drying conditions involved 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 dried copper fine particles A-1.

[0084] (Examples 2-8, Comparative Examples 1-5) As shown in Tables 2 and 3, copper nanoparticles were produced in the same manner as in Example 1, except that the heating temperature, synthesis time, type and amount of copper raw material compound, type and amount of dispersant, and type and amount of solvent were changed, to obtain copper nanoparticles A-2 to A-8 and copper nanoparticles CA-1 to CA-5. The tap density, specific surface area, and cumulative frequency particle diameters D10, D50, D90, and ratio [D90 / D10] of the obtained copper nanoparticles are summarized in Tables 4 and 5.

[0085]

[0086]

[0087] - Cupric oxide (manufactured by Nisshin Chemco Co., Ltd., N-120) - Cuprous oxide (manufactured by Nisshin Chemco Co., Ltd., NC-301) - 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) - 2-Propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent): (boiling point 82°C, SP value 11.5, viscosity 2.4 mPa·s) - 2-Butanone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent): (boiling point 80°C, SP value 9.3, viscosity 0.4 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)

[0088] [Preparation of copper nanoparticle dispersion and manufacture of bonded material] (Example 9) 10 parts by mass of tetraethylene glycol and 90 parts by mass of copper nanoparticles A-1 obtained in Example 1 were added to an agate mortar and kneaded until no dry powder was visible to the naked eye, 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 gap between the rolls adjusted to 0.2 mm to obtain copper fine particle dispersion 1.

[0089] A bonded body was manufactured using the obtained copper nanoparticle dispersion 1 according to the following method. First, a stainless steel metal mask (thickness: 50 μm) having three rows of 6 mm x 6 mm square openings was placed on a 30 mm x 30 mm copper plate (total thickness: 1 mm), and the copper nanoparticle dispersion 1 was applied to three locations on the copper plate by stencil printing using a metal squeegee. Then, the copper plate coated with the copper nanoparticle dispersion 1 was dried in the atmosphere on a Shamal hot plate (manufactured by AS ONE Corporation, model: HHP-441) at 110°C for 10 minutes. After that, three silicon chips (thickness: 400 μm) of 5 mm x 5 mm were prepared, each sputtered with titanium, nickel, and gold in that order, and these silicon chips were placed on the copper nanoparticle dispersion 1 so that the gold side of each silicon chip was in contact with the applied copper nanoparticle dispersion 1. This resulted in a laminated body in which the copper plate, copper nanoparticle dispersion 1, and silicon chips were stacked in this order. The obtained laminate was sintered using the following method to obtain jointed body 1. First, the laminate was placed in a pressure sintering machine (manufactured by Meisho Kiko Co., Ltd., model: HTM-1000), and nitrogen was flowed into the furnace at a rate of 500 mL / min to replace the air in the furnace with nitrogen. Then, the laminate was pressurized at 10 MPa using the upper and lower heating heads, and the temperature of the heating heads was raised to 260°C over 3 minutes. After raising the temperature, the sintering process was performed by holding the temperature at 260°C for 300 seconds to obtain the jointed body. After sintering, the heating heads were water-cooled at -60°C / min, and jointed body 1 was removed into the air at a temperature of 100°C or lower.

[0090] [Examples 10-16, Comparative Examples 6-10] Copper nanoparticle dispersions 2-8 and composites 2-8 of Examples 10-16, and copper nanoparticle dispersions C1-C5 and composites C1-C5 of Comparative Examples 6-10 were obtained in the same manner as in Example 9, except that copper nanoparticle A-1 was replaced with the copper nanoparticles shown in Tables 4-5. The composites obtained in Examples 9-16 and Comparative Examples 6-10 were evaluated as follows. The evaluation results are shown in Tables 4-5. The degree of dispersion of the copper nanoparticle dispersions obtained in Examples 9-16 and Comparative Examples 6-10 is also shown in Tables 4-5.

[0091] <Evaluation> [Porosity of the copper bonding layer in the bonded body] Cross-sectional milling was performed on the obtained bonded body using a cooled cross-section polisher (JEOL Ltd., model: IB-19520CCP). The cross-section of the copper bonding layer obtained by cross-sectional milling was observed with a scanning electron microscope (Hitachi High-Tech Corporation, model: S-4800) and SEM images were taken. Images were taken at a magnification of 5000x. The SEM images were converted to two-tone images of black and white by binarization using the image analysis software ImageJ (National Institutes of Health, USA), and the porosity was calculated using the following formula: Porosity (%) = Pore area (number of black pixels) / Total area of ​​the copper bonding layer {Copper bonding area (number of white pixels) + Pore area (number of black pixels)} × 100

[0092] [Delamination rate of copper bonded layer after temperature cycling] The obtained bonded body was placed in a small thermal shock device (manufactured by ESPEC Corporation, model: TSE-12-A), and a temperature cycle was performed 1000 times, holding it at -55°C and 200°C in air for 15 minutes each. After that, the bonded interface of the bonded body was observed from the copper substrate side using an ultrasonic flaw detection device (Hitachi Power Solutions Co., Ltd., model: FS100III) equipped with a 50 MHz frequency probe. The position and angle of the probe were finely adjusted so that the reflection peak at the bonded interface was highest, and measurements were taken with a material sound velocity = Cu: 4700 mm / s and Gain = 28 dB. A reflection intensity of 60% or more was considered "delamination," and a reflection intensity of less than 60% was considered "bonded." The data was analyzed by binarizing the areas with a reflectance of 60% or more and areas with a reflectance of less than 60%. The area of ​​the bond interface that was "delaminating" (the area with a reflectance of 60% or more) was calculated using software, and the delamination rate was determined. A lower delamination rate indicates higher bond strength.

[0093] The evaluation results of the copper nanoparticle dispersions and composites obtained in Examples 9 to 16 and Comparative Examples 6 to 10 are shown in Tables 4 and 5.

[0094]

[0095]

[0096] Tables 4 and 5 show that the copper nanoparticles of Examples 1 to 8, compared to the copper nanoparticles of Comparative Examples 1 to 5, have a lower porosity in the copper bonding layer obtained by sintering and an extremely low peeling rate in the copper bonding layer after temperature cycling. In other words, the copper nanoparticles of the present invention can be used to obtain a bonded body with good density and heat resistance. This is thought to be because the high tap density, large specific surface area, and small D90 / D10 of 3.7 or less allow the copper nanoparticles to pack tightly during low-pressure, low-temperature sintering, and because the particle size and surface energy of each copper nanoparticle are similar, sintering proceeds uniformly.

[0097] According to the present invention, it is possible to provide copper fine particles and copper fine particle dispersions that enable low-pressure, low-temperature sintering, allow for the formation of a dense copper bonding layer even by low-pressure, low-temperature sintering, and have good heat resistance for the resulting copper bonding layer. Furthermore, it is possible to provide bonded bodies and wiring patterns using the copper fine particle dispersion.

Claims

1. Tap density is 2.8 g / cm³ 3 In summary, the specific surface area is 1 m². 2 / g or more 5m 2 Copper nanoparticles with a particle size of less than or equal to / g, and in a particle size histogram based on particle count, 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 ≤ 3.

7.

2. The copper fine particles according to claim 1, wherein tetraethylene glycol is used as the dispersion medium, and 90 parts by mass of copper fine particles are dispersed in 10 parts by mass of the dispersion medium, and the degree of dispersion of the copper fine particle dispersion, measured in accordance with JIS K 5600-2-5:1999, is 15 μm or less.

3. The copper fine particles according to claim 1 or 2, wherein the copper fine particles are composite fine particles in which at least a portion of the surface of a granular copper component is coated with a dispersant having a carboxyl group.

4. The copper nanoparticles according to claim 3, wherein the dispersant is a monocarboxylic acid having 5 to 12 carbon atoms and having one or more functional groups or bonds selected from the group consisting of a hydroxyl group, a ketonic carbonyl group, and an ether bond.

5. The copper fine particles according to claim 3, wherein the dispersant is a vinyl polymer comprising a constituent unit derived from a monomer (b-1) having a carboxyl group and a constituent unit of a monomer (b-2) having a polyalkylene glycol segment.

6. The copper fine particles according to any one of claims 1 to 5, wherein the average particle size of the copper fine particles is 50 nm or more and 300 nm or less.

7. The tap density of the copper nanoparticles is 7.0 g / cm³. 3 The copper fine particles according to any one of claims 1 to 6, which are as follows:

8. The copper fine particles according to claim 3, wherein the ratio of the mass of the dispersant to the total mass of the granular copper component and the dispersant (dispersant / dispersant + copper component) is 0.003 or more and 0.070 or less.

9. A dispersion of copper fine particles comprising copper fine particles according to any one of claims 1 to 8.

10. The copper fine particle dispersion according to claim 9, wherein the copper fine particle dispersion comprises a dispersion medium, and the dispersion medium comprises one or more selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, (poly)alkylene glycol derivatives, glycerin, and glycerin derivatives.

11. A method for producing copper nanoparticles, comprising maintaining a mixture containing a copper raw material compound, a reducing agent, 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 one minute or more in order to reduce the copper raw material compound.

12. The method for producing copper fine particles according to claim 11, wherein the SP value of the solvent is 9 or more and 13 or less.

13. The method for producing copper fine particles according to claim 11 or 12, wherein the predetermined temperature is 5°C or higher.

14. A method for producing copper fine particles according to any one of claims 11 to 13, wherein the molecular weight of the solvent is 20 or more and 500 or less.

15. The method for producing copper fine particles according to any one of claims 11 to 14, wherein the copper raw material compound is a copper oxide.

16. The method for producing copper fine particles according to any one of claims 11 to 15, wherein the copper raw material compound is cupric oxide.

17. The method for producing copper nanoparticles according to any one of claims 11 to 16, wherein the reducing agent is a hydrazine compound.

18. The method for producing copper nanoparticles according to any one of claims 11 to 17, wherein the dispersant is one or more selected from the group consisting of low molecular weight dispersants having carboxyl groups and polymer dispersants containing hydrophilic groups.

19. 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 copper fine particles as described in any one of claims 1 to 8.

20. A method for manufacturing a bonded body in which metal members are joined together via a copper bonding layer, comprising: applying the copper fine particle dispersion described in claim 9 or 10 to one metal member; and placing the other metal member on the composite fine particle dispersion applied to the metal substrate, and then pressurizing and firing the bonded body.

21. Use of the copper fine particle dispersion according to claim 9 or 10 as a bonding material for joining metal members together.

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