Copper microparticles

Abstract

The present invention provides 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. [Solution] [1] Tap density is 2.8 gcm 3 Above, the specific surface area is 1 m². 2 / g or more 5m 2 [2] Copper nanoparticles having a density of 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. [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.

Description

[Technical Field]

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

[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. As a result, various technologies have been proposed that use a metal particle dispersion, which contains dispersed metal particles, as a substitute for solder. This dispersion is then applied to the target object using various coating methods, sintered, and used 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 metal particle dispersions, 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 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. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-187936 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Although copper bonding materials containing copper nanoparticles form copper bonding layers with 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. 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. [Means for solving the problem]

[0007] The inventors have found that copper nanoparticles having a specific tap density and specific specific surface area, and satisfying the relationship D90 / D10 ≤ 3.7 in a particle size histogram based on particle size, 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. In other words, the present invention relates to the following [1] to [6]. [1] Tap density is 2.8 g / cm³ 3 That's all. Specific surface area is 1 m 2 / g or more 5m 2 / g or less, and Copper nanoparticles 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% satisfy the relationship D90 / D10 ≤ 3.7. [2] A dispersion of copper fine particles containing the copper fine particles described in [1] above. [3]A method for producing copper fine particles, comprising maintaining a mixture containing a copper raw material compound, a reducing agent, a dispersant, and a solvent having 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. [4]A joined body in which metal members are joined via a copper joining layer, wherein the copper joining layer is a sintered body of the copper fine particles described in [1] above. [5]A method for producing a joined body in which metal members are joined via a copper joining layer, applying the copper fine particle dispersion described in [2] above to one of the metal members, placing the other metal member on the composite fine particle dispersion applied to the metal substrate, and pressurizing and firing these. [6]Use of the copper fine particle dispersion described in [2] above as a joining material for joining metal members. [Advantages of the Invention]

[0008] According to the present invention, it is possible to provide copper fine particles capable of low-pressure and low-temperature sintering, forming a dense copper joining layer even by low-pressure and low-temperature sintering, and having good heat resistance of the obtained copper joining layer, a method for producing the copper fine particles, a copper fine particle dispersion containing the copper fine particles, use of the copper fine particle dispersion as a joining material, a joined body formed using the copper fine particle dispersion, and a method for producing the joined body. [Embodiments for Carrying Out the Invention]

[0009] [Copper Fine Particles] The copper fine particles of the present invention have a tap density of 2.8 g / cm 3 or more, a specific surface area of 1 m 2 / g or more and 5 m 2 / g or less, and in a particle size histogram based on the number of particles, the particle size D10 when the cumulative frequency is 10% and the particle size D90 when the cumulative frequency is 90% satisfy the relationship D90 / D10 ≦ 3.7.

[0010] The copper microparticles of the present invention can be sintered at low pressure and low temperature. A dense copper bonding layer can be formed even by low-pressure and low-temperature sintering, and the heat resistance of the obtained copper bonding layer can be made good. 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 is not clear, but it is considered as follows. The copper microparticles of the present invention have a high tap density, a large specific surface area, and the particle diameter D10 and the particle diameter D90 in the particle diameter histogram based on the number satisfy the relationship of D90 / D10 ≦ 3.7. Therefore, in addition to the dense filling (clogging) of the copper microparticles during low-pressure and low-temperature sintering, since the particle diameters of the individual copper particles are close, their surface energies are also similarly close, and it is considered that sintering proceeds uniformly. As a result, the obtained copper bonding layer has a dense, uniform, and strong structure, and it is considered that a bonded body having high heat resistance can be obtained because peeling hardly occurs even when subjected to temperature cycling. On the other hand, if the tap density is low and the relationship of D90 / D10 ≦ 3.7 is not satisfied in the particle diameter histogram based on the number, the variation in particle diameter becomes large. Therefore, before sintering, a plurality of copper particles cannot be densely filled, and furthermore, since the individual particle diameters vary, the surface energies of the copper microparticles are different, so the sintering state also varies, and a dense and uniform sintered body cannot be obtained. Moreover, the copper microparticles satisfying the above characteristics can be preferably produced by a wet chemical reduction method using a solvent having an SP value of 8 or more and 18 or less and maintaining the temperature of the solvent at a temperature below the boiling point of the solvent.

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

[0012] 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 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 / cm3 More preferably, 4.3 g / cm³ 3 More preferably, 4.6 g / cm³ 3 More preferably, 4.7 g / cm³ 3 Therefore, and from the viewpoint of preventing the dispersion process from becoming complicated due to reduced solvent permeability to copper fine particles, a concentration of 7.0 g / cm³ is preferred. 3 More preferably, 6.5 g / cm³ 3 More preferably, 6.0 g / cm³ 3 The following applies: In this specification, "tap density" refers to the density obtained by measuring the density of copper fine particles obtained by tapping a container under specified conditions, and is measured in accordance with JIS Z2512:2012. Specifically, it is measured by the method described in the examples. Furthermore, the tap density 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 for which the temperature of the reduction reaction is maintained), as described later.

[0013] The specific surface area of ​​the copper fine particles of the present invention is set to 1 m² 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. 2 / g or more 5m 2 It is less than or equal to / g, preferably 1.5m 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 from a similar viewpoint and from the viewpoint of suppressing oxidation of copper fine particles, it is preferably 4.5m 2 / g or less, more preferably 4.0m 2 / g or less, more preferably 3.5m 2 It is less than / 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 ​​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 time of the reduction reaction (the duration for which the temperature of the reduction reaction is maintained), as described later.

[0014] In the present invention, the copper nanoparticles 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 that indicates the spread of the particle size distribution; a smaller value means that the particle size distribution is narrower and the particles are more uniform in size. 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, and 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 for which the temperature of the reduction reaction is maintained), as described later.

[0015] The average particle size of the copper fine particles 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 copper nanoparticles is the particle size D50 at which 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 for which the temperature of the reduction reaction is maintained), as described later.

[0016] <Dispersant> The copper nanoparticles of the present invention are suitably used as a copper nanoparticle dispersion for forming a bonded body when dispersed in a dispersion medium, as described later. Therefore, from the viewpoint of improving the dispersibility of the copper nanoparticle dispersion, suppressing the uneven distribution due to aggregation of copper nanoparticles when obtaining the 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 a dispersant, 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, one or more dispersants 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 low molecular weight dispersants having carboxyl groups include, for example, one or more selected from the group consisting of aliphatic carboxylic acids having 1 to 24 carbon atoms, monocarboxylic acids having 2 to 24 carbon atoms and having one or more functional groups or bonds selected from the group consisting of hydroxyl groups, ketotic carbonyl groups, and ether bonds, and tartaric acid or citric acid having multiple carboxyl groups. More preferably, from the viewpoint of compatibility with hydrophilic solvents that readily reduce the oxide film of copper fine particles that inhibit sintering and improving the dispersibility of copper fine particles, the dispersant is a monocarboxylic acid having 2 to 24 carbon atoms and having one or more functional groups or bonds selected from the group consisting of hydroxyl groups, ketotic carbonyl groups, and ether bonds, or tartaric acid or citric acid having multiple carboxyl groups, and even more preferably, a monocarboxylic acid having 5 to 12 carbon atoms and having one or more functional groups or bonds selected from the group consisting of hydroxyl groups, ketotic carbonyl groups, and ether bonds. 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, even more preferably 300 or less, and even more preferably 230 or less. Specifically, the low molecular weight dispersant having a carboxyl group is preferably one or more selected from the group consisting of 5-oxohexanoic acid, citric acid, and tartaric acid, and more preferably 5-oxohexanoic acid, 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.

[0018] The polymer dispersant containing hydrophilic groups is preferably a vinyl polymer containing constituent units derived from a monomer (b-1) having a carboxyl group and a monomer (b-2) having a polyalkylene glycol segment, 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 may be a random copolymer, a block copolymer, or an alternating copolymer.

[0019] [Monomers containing a carboxyl group (b-1)] Preferred monomers (b-1) include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and 2-methacryloyloxymethylsuccinic acid; and unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, and citraconic acid. The unsaturated dicarboxylic acid may also be an anhydride. Monomer (b-1) may be used alone or in combination of two or more types. 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] [Monomers having polyalkylene glycol segments (b-2)] Examples of monomer (b-2) include polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, and phenoxy polyalkylene glycol (meth)acrylate. Monomer (b-2) may be used individually or in combination of two or more types. In this specification, "(meth)acrylate" means one or more selected from the group consisting of acrylates and methacrylates.

[0021] 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-2) is preferably one or more selected from the group consisting of polyalkylene glycol (meth)acrylate and alkoxy polyalkylene glycol (meth)acrylate, and more preferably alkoxy polyalkylene glycol (meth)acrylate. From the viewpoint of the same viewpoint as above, as well as availability and economics, the number of carbon atoms in the alkoxy polyalkylene glycol (meth)acrylate is preferably 18 or less, more preferably 12 or less, even more preferably 4 or less, and even more preferably 1. Examples of preferred alkoxy polyalkylene glycol (meth)acrylates include methoxypolyalkylene glycol (meth)acrylate, ethoxypolyalkylene glycol (meth)acrylate, propoxypolyalkylene glycol (meth)acrylate, butoxypolyalkylene glycol (meth)acrylate, octoxypolyalkylene glycol (meth)acrylate, and lauroxypolyalkylene glycol (meth)acrylate. Among these, methoxypolyalkylene glycol (meth)acrylate is more preferred, and methoxypolyalkylene glycol methacrylate is even more preferred.

[0022] The monomer (b-2) polyalkylene glycol segment preferably contains units derived from an alkylene oxide having 2 to 4 carbon atoms, 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. 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 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. 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 of 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.

[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, and PLE-1300.

[0024] [Hydrophobic monomer (b-3)] The vinyl polymer may further contain constituent units derived from hydrophobic monomers (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 a monomer in which the amount dissolved when dissolved in 100 g of deionized water at 25°C until saturated 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 formed by 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 preferred styrene monomers include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), and divinylbenzene. However, 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 economic efficiency, 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 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 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. Furthermore, (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols include (meth)acrylates having linear alkyl groups, (meth)acrylates having branched alkyl groups, and (meth)acrylates having alicyclic alkyl groups. Examples of 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. As an example of a (meth)acrylate having an alicyclic alkyl group, cyclohexyl (meth)acrylate is preferred. (Meth)acrylates having hydrocarbon groups derived from aliphatic alcohols are preferably (meth)acrylates having a linear alkyl group with 22 or fewer carbon atoms, more preferably (meth)acrylates having a linear alkyl group with 12 or fewer carbon atoms, even more preferably (meth)acrylates having a linear alkyl group with 8 or fewer carbon atoms, and even more preferably (meth)acrylates having a linear alkyl group 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. Monomer (b-3) may be used individually 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 linear alkyl groups with 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] The vinyl polymer preferably contains, 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, one or more constituent units selected from the group consisting of (meth)acrylic acid and maleic acid as monomer (b-1), and a constituent unit derived from alkoxy polyalkylene glycol (meth)acrylate as monomer (b-2), more preferably a constituent unit derived from (meth)acrylic acid as monomer (b-1) and a constituent unit derived from methoxypolyethylene glycol (meth)acrylate as monomer (b-2).

[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 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 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, 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. Furthermore, 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, from the same viewpoint as above.

[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, 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 acid value of vinyl polymers 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 nanoparticles of the present invention are composite nanoparticles in which at least a portion of the surface of a granular copper component is coated with a dispersant, in other words, when the copper nanoparticles of the present invention are composite nanoparticles containing a granular copper component and a dispersant that coats 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 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. Furthermore, the granular copper components are particles derived from the copper raw material compound used in the manufacturing method of composite microparticles, which will be described in detail later, and are produced when the copper raw material compound is reduced. 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 device (TG / DTA).

[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 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 nanoparticles] The present invention relates to a method for producing copper nanoparticles, which includes a copper nanoparticle production step in which a copper raw material compound is reduced by a wet chemical reduction method to produce the copper nanoparticles. 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 nanoparticles, and then dry the dispersion of copper nanoparticles 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 nanoparticles (composite nanoparticles) 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. The duration for maintaining 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 suppressing the generation of bubbles and ensuring a uniform particle size distribution, and from the viewpoint of productivity, 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 contains 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 compounds can be used individually or in combination 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 copper raw material compounds. Examples of reducing agents include hydrazine compounds, boron compounds, and inorganic salts. Examples of hydrazine compounds include hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine monohydrate. Examples of boron compounds include sodium borohydride. Examples of inorganic acid salts include sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, and sodium hypophosphite. The reducing agent may be used individually or in combination of two or more types. As a reducing agent, a hydrazine-based compound is preferred, more preferably a 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. In other words, in one embodiment, the method for producing copper nanoparticles 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 to 18 at a predetermined temperature below the boiling point of the solvent for at least one minute in order to reduce the copper raw material compound. The SP value of the solvent is preferably 9 to 13. 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 this invention are included in the equivalent range of this invention, even if they fall slightly outside the numerical range specified by this invention, as long as they have the same effects and advantages as those within the numerical range specified by this invention. 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 ensuring a uniform particle size distribution. Similarly, it is 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 nanoparticle 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, the viscosity of the solvent 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 bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling, one or more selected from the group consisting of ethanol, 2-propanol, and 2-butanone are preferred, one or more selected from the group consisting of ethanol and 2-propanol are 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 centrifugation. Among these, decantation and centrifugation 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 fine particle dispersion] The copper nanoparticle dispersion of the present invention is a copper nanoparticle dispersion containing the copper nanoparticles and dispersion medium of the present invention. The copper nanoparticles 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 fine particles, and preferably one or more organic solvents selected from the group consisting of hydrocarbons, alcohols, ethers, and esters. The organic solvent may be used alone or in combination of two or more. 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, and neopentyl glycol. 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), and polytetramethylene glycol.

[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. The (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 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. (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 fine particle 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, "effectively 100% by mass" means that it may include components that are present unintentionally. Examples of unintentionally present components 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, 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 copper microparticles is measured by the same method as the average particle size (particle size D50) of 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 nanoparticle dispersion of the present invention can be used to manufacture a bonded body by sintering. When the copper nanoparticle dispersion of the present invention is used to manufacture a bonded body, the content of copper nanoparticles in the copper nanoparticle 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 nanoparticles 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. The content of the dispersant in the copper fine particle dispersion of the present invention is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, even more preferably 0.9% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of reducing the dispersibility of copper fine particles 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. 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 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. The content of the dispersion medium in the copper fine particle 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, from the viewpoint of reducing the dispersibility of copper fine particles 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. Furthermore, if the copper fine particle dispersion of the present invention contains copper microparticles, from a similar viewpoint, the copper fine particle content is preferably 30% by mass or more and 95% by mass or less, the dispersant content is preferably 0.1% by mass or more and 10% by mass or less, the dispersion medium content is preferably 4% by mass or more and 60% by mass or less, and the copper microparticle content 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 copper fine particle content is preferably 30% by mass or more and 95% by mass or less, the dispersant content is preferably 0.003 to 0.070 when expressed as the above mass ratio (dispersant / copper fine particles), the dispersion medium content is preferably 4% by mass or more and 60% by mass or less, and the copper microparticle content 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 additive in the dispersion is preferably 1% by mass or less.

[0058] <Method for producing copper nanoparticle dispersions> The copper nanoparticle 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 nanoparticles (composite nanoparticles). As for the mixing method, known methods can be used, but from the viewpoint of better dispersing the copper fine particles in the dispersion medium, it is preferable to pre-mix the copper fine particles and the dispersion medium using an agate mortar or the like, and then further mix the resulting mixture using a stirring device such as a rotation-and-revolution stirring device.

[0059] <Applications of composite particulate dispersions> The copper nanoparticle dispersion of the present invention obtained in this way can be sintered at low pressure and low temperature, and since the porosity of the copper bonding layer formed by sintering and the peeling rate of the copper bonding layer after temperature cycling are good, 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 nanoparticle 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 nanoparticle 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 multiple metal members and then fired at low pressure and low temperature to join the multiple metal members and produce a joined body. That is, the joined body obtained here has a metal member-copper joining layer-metal member structure in which multiple metal members are joined by a copper joining layer obtained by sintering the copper fine particle dispersion of the present invention. Furthermore, the joint of the present invention is a joint comprising a plurality of metal members and a copper bonding layer disposed between adjacent metal members to bond 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, the present invention relates to a method for manufacturing a joined body, and in one embodiment, the method for manufacturing the joined body includes the following steps 1 to 2 in this order. Step 1: A step of applying the copper fine particle dispersion of the present invention described above to one main surface of one of the metal members. Step 2: A process in which the other metal component is placed on the copper fine particle dispersion applied to the metal substrate to form a laminate, and the laminate is fired while being pressed 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 component preferably includes 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 the metal portion of an electrically insulating substrate. Examples of joining metal members 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 fine particle 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 the copper fine particle dispersion applied to the metal member can be appropriately adjusted according to the size and type of the metal member 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 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 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. [Examples]

[0068] 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. Furthermore, in the following manufacturing examples, embodiments, and comparative examples, "parts" and "%" refer to "parts by mass" and "% by mass" respectively, unless otherwise specified. Various physical properties were measured or calculated using the following methods.

[0069] [Measurement of the number-average molecular weight (Mn) of dispersants] The number-average molecular weight (Mn) of the dispersant was determined by gel permeation chromatography. The sample prepared for measurement consisted of 0.1 g of dispersant mixed with 10 mL of eluent in a glass vial, stirred with a magnetic stirrer at 25°C for 10 hours, and filtered through a syringe filter (DISMIC-13HP PTFE 0.2 μm, Advantec Toyo Co., Ltd.). The measurement conditions are shown below. GPC device: Tosoh Corporation "HLC-8320GPC" Columns: Tosoh Corporation products "TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn Super AW-H" Eluent: A solution prepared by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively. Flow rate: 0.5mL / min Standard material: Monodisperse polystyrene kit manufactured by Tosoh Corporation: "PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)"

[0070] [Measurement of the acid value of dispersants] 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 mixture specified in JIS K 0070 to an acetone and toluene mixture (acetone:toluene = 4:6 (volume ratio)).

[0071] [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 at a cumulative frequency of 10%, D50 at a cumulative frequency of 50%, and D90 at a cumulative frequency of 90% were calculated. Furthermore, the ratio [D90 / D10] was calculated from the calculated D90 and D10.

[0072] [Evaluation of the specific surface area of ​​copper nanoparticles] The specific surface area of ​​the obtained copper nanoparticles was measured in accordance with JIS Z8830:2013. Specifically, 2 g of copper nanoparticles were weighed out, placed in a sample cell, and fired at 90°C for 60 mins. Then, multi-point measurements were taken using nitrogen gas at relative pressures of 0.1, 0.2, 0.3, 0.4, and 0.5.

[0073] [Evaluation of tap density of copper nanoparticles] The tap density of the obtained copper nanoparticles 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 10cc was leveled off, and the weight of the powder in the container was measured to determine the tap density.

[0074] <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, and 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] + Residual mass at 550°C [mg])

[0075] [Evaluation of the dispersion degree of copper nanoparticle dispersions] Tetraethylene glycol was used as the dispersion medium, and 90 parts by mass of copper fine particles were dispersed in 10 parts by mass of the dispersion medium. The degree of dispersion of the copper fine particle dispersion was evaluated in accordance with JIS K5600-2-5:1999.

[0076] [Preparation of dispersant] (Manufacturing Example 1: Preparation of Dispersant B-1) A 1000 mL four-necked round-bottom flask equipped with a thermometer, two 100 mL dropping funnels with nitrogen bypasses, and a reflux apparatus was filled with 20.0 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent). The flask was then heated to 80°C in an oil bath, and nitrogen bubbling was performed for 10 minutes. Next, 15.3g of methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 7.2g of methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 10g of styrene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 67.5g of methoxypolyethylene glycol (EO23 mol) methacrylate (manufactured by NOF Corporation, "PME-1000"), 2.0g of 3-mercaptopropionic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), and 28.7g of ethanol were dissolved in a poly beaker and placed in a dropping funnel (1). Separately, 51.3g of ethanol and 1.3g 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.

[0077] (Manufacturing Example 2: Preparation of Dispersant B-2) Dispersant B-2 was obtained by the same manufacturing method as in Manufacturing Example 1, except that the monomer composition was changed as shown in Table 1.

[0078] [Table 1]

[0079] • MAA: Methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) • PEG(4)MA: Methoxypolyethylene glycol (EO4 mol) methacrylate (manufactured by NOF Corporation, "PME-200") • PEG(23)MA: Methoxypolyethylene glycol (EO23 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)

[0080] For the dispersant B-3, 5-oxohexanoic acid (Tokyo Chemical Industries, Ltd., purity (test method): >98.0% (GC)(T)) was prepared.

[0081] [Manufacturing of copper nanoparticles] (Example 1: Production of copper nanoparticles A-1) In a 300 mL beaker, 8.14 g of cupric oxide (N-120, manufactured by Nisshin Chemco Co., Ltd.) as the copper starting 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 and the mixture was 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 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), placed in a 50 mL dropping funnel, was added dropwise to the mixture over 20 minutes at 25°C. The reaction solution was then stirred for 1 hour while controlling the temperature to 70°C in an oil bath, and then air-cooled to obtain a reddish-brown dispersion containing copper fine particles. The entire amount of the obtained dispersion was placed in a Hitachi Koki Co., Ltd. refrigerated centrifuge "himacCR22G" and rotor (R12A, radius 15.1 cm) into a Hitachi Koki Co., Ltd. 500PA centrifuge tube bottle and subjected to a centrifugal acceleration of 675 G at 3000 rpm for 30 minutes. The precipitate was separated by centrifugation, and 60 g of ethanol (95) (Fujifilm Wako Pure Chemical Industries, Ltd., first-grade reagent) was added. The mixture was stirred for 15 minutes to redisperse the precipitate. The entire redispersed liquid was again centrifuged under the same conditions, and the precipitate was separated. This procedure was repeated three times. The precipitate of purified copper nanoparticles was freeze-dried using a freeze-dryer (FDU-2110, manufactured by Tokyo Rikakikai Co., Ltd.) equipped with a dry chamber (DRC-1000, manufactured by Tokyo Rikakikai Co., Ltd.) to obtain 6.3 g of copper nanoparticle A-1. The drying conditions were: freezing at -25°C for 1 hour, drying under reduced pressure at -10°C for 9 hours at 5 Pa, and then drying under reduced pressure at 25°C for 5 hours at 5 Pa to obtain dried copper nanoparticle A-1 powder.

[0082] (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, yielding 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 sizes D10, D50, D90, and ratio [D90 / D10] of the obtained copper nanoparticles are summarized in Tables 4 and 5.

[0083] [Table 2]

[0084] [Table 3]

[0085] • 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℃, SP value 23.4, viscosity 1.0 mPa·s)

[0086] [Preparation of copper nanoparticle dispersions and manufacture of bonded materials] (Example 9) Ten parts by mass of tetraethylene glycol and 90 parts by mass of copper fine particles 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 then stirred for 2000 min 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 through a three-roll mill (manufactured by AIMEX Co., Ltd., BV 100) with the roll gap adjusted to 0.2 mm three times to obtain copper fine particle dispersion 1.

[0087] Using the obtained copper nanoparticle dispersion 1, a bonded body was manufactured according to the following method. First, a stainless steel metal mask (thickness: 50 μm) with 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 copper fine particle dispersion 1 was applied to three locations on the copper plate by stencil printing using a metal squeegee. Subsequently, the copper plate coated with copper nanoparticle dispersion 1 was dried in air at 110°C for 10 minutes on a Shamal hot plate (manufactured by AS ONE Corporation, model: HHP-441). Subsequently, three silicon chips measuring 5 mm x 5 mm (thickness: 400 μm) were prepared, each sputtered with titanium, nickel, and gold in that order. These silicon chips were then placed on the copper nanoparticle dispersion 1 so that the gold side of each chip was in contact with the coated copper nanoparticle dispersion 1. This resulted in a laminate in which a copper plate, copper nanoparticle dispersion 1, and silicon chips were stacked in that 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 inside 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 below 100°C.

[0088] [Examples 10-16, Comparative Examples 6-10] Except for replacing copper nanoparticle A-1 with the copper nanoparticles shown in Tables 4-5, copper nanoparticle dispersions 2-8 and bonded bodies 2-8 of Examples 10-16, and copper nanoparticle dispersions C1-C5 and bonded bodies C1-C5 of Comparative Examples 6-10 were obtained using the same method as in Example 9. The following evaluations were performed using the composites obtained in Examples 9-16 and Comparative Examples 6-10. The evaluation results are shown in Tables 4-5. The dispersion of the copper fine particle dispersions obtained in Examples 9-16 and Comparative Examples 6-10 is also shown in Tables 4-5.

[0089] <Rating> [Porosity of the copper bonding layer in the bonded structure] The resulting bonded structure was subjected to cross-sectional milling using a cooled cross-section polisher (JEOL Ltd., model: IB-19520CCP). The cross-section of the copper bonded 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 binarized using the image analysis software ImageJ (National Institutes of Health, USA) to convert the grayscale to black and white, and the porosity was calculated using the following formula. Porosity (%) = Pore area (number of black pixels) / Total area of ​​copper bonding layer {Copper bonding area (number of white pixels) + Pore area (number of black pixels)} × 100

[0090] [Delamination rate of copper bonding layer after temperature cycling] The resulting bonded material was placed in a small thermal shock device (ESPEC Corporation, model: TSE-12-A) and subjected to 1000 temperature cycles, holding it at -55°C and 200°C in air for 15 minutes each. Subsequently, the bonded interface was observed from the copper substrate side of the bonded material using an ultrasonic flaw detection device (Hitachi Power Solutions Co., Ltd., model: FS100III) equipped with a 50MHz frequency probe. The position and angle of the probe were finely adjusted to maximize the reflection peak at the bonded interface, and measurements were taken with a material sound velocity of Cu: 4700 mm / s and a gain of 28 dB. A reflection intensity of 60% or more was considered "delamination," and a reflection intensity of less than 60% was considered "bonded." The areas with a reflection intensity of 60% or more and areas with a reflection intensity of less than 60% were binarized and analyzed. The area of ​​the bonded interface that was "delamination" (area of ​​areas with a reflection intensity of 60% or more) was calculated using software, and the delamination rate was determined. The lower the delamination rate, the higher the bond strength.

[0091] The evaluation results of the copper nanoparticle dispersions and composites obtained in Examples 9-16 and Comparative Examples 6-10 are shown in Tables 4 and 5.

[0092] [Table 4]

[0093] [Table 5]

[0094] 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 copper nanoparticles have a high tap density, a large specific surface area, and a small D90 / D10 of 3.7 or less, which not only causes the copper nanoparticles to pack tightly during low-pressure, low-temperature sintering, but also because the particle size and surface energy of each copper nanoparticle are similar, allowing for uniform sintering. [Industrial applicability]

[0095] 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 That's all. Specific surface area is 1 m 2 / g or more 5m 2 / g or less, and Copper nanoparticles 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% 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 nanoparticles according to claim 1, wherein the copper nanoparticles are composite nanoparticles in which at least a portion of the surface of granular copper components 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 nanoparticles according to claim 1, wherein the average particle size of the copper nanoparticles 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 claim 1, 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 copper nanoparticle dispersion comprising copper nanoparticles according to any one of claims 1 to 8.

10. The copper fine particle dispersion comprises a dispersion medium, The copper fine particle dispersion according to claim 9, wherein 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. A 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, wherein the predetermined temperature is 5°C or higher.

14. The method for producing copper fine particles according to claim 11, 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 claim 11, wherein the copper raw material compound is a copper oxide.

16. The method for producing copper fine particles according to claim 11, wherein the copper raw material compound is cupric oxide.

17. The method for producing copper nanoparticles according to claim 11, wherein the reducing agent is a hydrazine-based compound.

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

19. It is a joint in which metal members are joined together via a copper bonding layer. A bonded body wherein the copper bonding layer is a sintered body of copper fine particles according to any one of claims 1 to 8.

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

21. The copper fine particle dispersion described in claim 9 is used as a bonding material for joining metal members together.

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