Copper sintered body

Abstract

The present invention relates to a copper sintered body having a low elastic modulus and a method for producing the copper sintered body. Provided are: [1] a copper sintered body having a tensile modulus of 35 GPa or less; [2] a method for producing a copper sintered body that includes a step in which a dispersion D comprising copper nanoparticles A and a polymer B is fired at a firing temperature of 240-300°C while applying a pressure of 0.1-40 MPa, the polymer B being a polymer comprising a constituent unit derived from a monomer (b-1) having a carboxy group and a constituent unit derived from a monomer (b-2) having a poly(alkylene glycol) segment; [3] a copper sintered body obtained by the production method [2]; [4] a joined body comprising a first member, a second member, and the copper sintered body [1] or [3] joining the first member and the second member; and [5] a method for producing a joined body comprising a first member, a second member, and a copper sintered body joining the first member and the second member, the method comprising a step in which a dispersion D comprising copper nanoparticles A and a polymer B is provided so as to be interposed between the first member and the second member, and a step in which the dispersion D is fired at a firing temperature of 240-300°C while applying a pressure of 0.1-40 MPa.

Description

Sintered copper

[0001] The present invention relates to a copper sintered body and a method for producing the same.

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

[0003] In recent years, semiconductor devices known as power devices have become increasingly popular for power conversion and control devices such as inverters. Unlike integrated circuits such as memory and microprocessors, power devices are designed to control high currents and generate a large amount of heat during operation. Therefore, the solder used to mount power devices requires not only high bonding strength but also heat resistance. However, lead-free solder, which is widely used these days, has the disadvantage of low heat resistance. Therefore, various techniques have been proposed to bond objects by using metal particle dispersions instead of solder, which are applied to the objects by various coating methods and then fired. The metal species of the metal particle dispersions used for mounting are mainly silver or copper. On the other hand, when silver sintered bodies formed with silver particle dispersions are exposed to high temperatures above 200°C, voids in the bonding layer repeatedly coalesce and expand, causing the voids to coarsen and ultimately break. In contrast, copper bonding layers formed with copper particle dispersions do not coalesce or expand even when exposed to high temperatures above 200°C, and due to their high thermal stability, they are expected to be next-generation bonding materials.

[0004] Non-Patent Document 1 describes that a power cycle test was conducted on a highly elastic copper sintered body of 74 GPa formed between semiconductor chips using a copper particle sintered body, in which a current was applied to the semiconductor element and heating and cooling were repeated, and the result was that the copper sintered body exhibited a cycle life that could withstand a greater number of power cycles than a silver bonding material.

[0005] (Non-patent Document 1) H. Nakako, M. Natori, D. Ishikawa, T. Tanaka and Y. Ejiri, “Copper Sintering Pastes for Die Bonding,” PCIM Europe digital days 2021; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Online, 2021, pp.1-6.

[0006] The present invention relates to the following items [1] to [5]. [1] A copper sintered body having a tensile modulus of elasticity of 35 GPa or less. [2] A method for producing a copper sintered body, comprising the following step 1: Step 1: A step of baking a dispersion D of copper nanoparticles A and a polymer B described below at a baking temperature of 240°C or higher and 300°C or lower while applying a pressure of 0.1 MPa or higher and 40 MPa or lower, where polymer B is a polymer containing a structural unit derived from a monomer (b-1) having a carboxy group and a structural unit derived from a monomer (b-2) having a polyalkylene glycol segment. [3] A copper sintered body obtained by the production method described in [2]. [4] A bonded body comprising a first member, a second member, and the copper sintered body described in [1] or [3] that bonds the first member and the second member. [5] A method for producing a bonded body comprising a first member, a second member, and a copper sintered body that bonds the first member and the second member, comprising the following steps 0-1 and 1. Step 0-1: A step of applying a dispersion D containing copper nanoparticles A and the following polymer B between the first member and the second member. Step 1: A step of baking the dispersion D at a baking temperature of 240°C or more and 300°C or less while applying a pressure of 0.1 MPa or more and 40 MPa or less. Detailed Description of the Invention

[0007] Although copper sintered bodies formed with copper bonding materials have higher heat resistance than solder, there is still room for improvement in terms of the stress they exert on the bonded objects. Generally, semiconductor elements and substrates bonded with copper sintered bodies experience large stresses at their interfaces due to temperature cycles due to the difference in the linear expansion coefficients of each material. In this case, if the copper sintered body has a high elastic modulus, it is difficult for it to deform in response to strain, resulting in greater stress on the bonded components, the semiconductor chip and substrate. Silicon, which is used in semiconductor chips, is particularly susceptible to chip cracking due to the large difference in linear expansion coefficient between it and copper, making it difficult to use it for mounting power devices.

[0008] The copper sintered body described in Non-Patent Document 1 experienced chip cracking after a power cycle test. This is thought to be due to the fact that it was joined to a copper sintered body with a high elastic modulus of 74 GPa. Therefore, further improvement by lowering the elastic modulus of the copper sintered body is required.

[0009] TECHNICAL FIELD The present invention relates to a copper sintered body having a low elastic modulus and a method for manufacturing the same.

[0010] [Copper sintered body] The copper sintered body of the present invention has a tensile modulus of elasticity of 35 GPa or less. Because the copper sintered body of the present invention has a low tensile modulus of elasticity, even when a rigorous thermal test is carried out in a state where a semiconductor chip and a substrate are bonded, no chip cracking occurs, and there is little breakage of the sintered body or peeling between the semiconductor chip and the substrate. This copper sintered body has excellent physical properties.

[0011] In this specification, "tensile modulus" refers to a value determined from the slope of the region of a stress-strain curve where the stress and strain are proportional to each other. "Tensile modulus" is also called "Young's modulus." "Stress-strain curve" refers to a plot of the stress generated when a tensile test is performed using a thermomechanical analyzer (TMA) versus the strain obtained by dividing the initial tensile length by the deformed length. The tensile modulus can be measured, for example, according to the method described in the Examples below.

[0012] A "copper sintered body" is a structure made of copper and having a pore structure (porous structure). It can usually be formed by firing a dispersion such as a paste containing copper particles.

[0013] The copper sintered body of the present invention has a tensile modulus of elasticity of 35 GPa or less, and from the viewpoint of reducing the tensile modulus and thereby preventing chip cracking during temperature cycling, the tensile modulus is preferably 30 GPa or less, more preferably 25 GPa or less.

[0014] The tensile strength of the copper sintered body of the present invention is preferably 100 GPa or more, more preferably 120 GPa or more, even more preferably 140 GPa or more, even more preferably 160 GPa or more, and even more preferably 180 GPa or more, from the viewpoint of reducing the peeling rate after temperature cycling. "Tensile strength" is a value determined from the maximum stress value of the stress-strain curve obtained in a tensile test. Tensile strength can be measured, for example, according to the method described in the Examples below.

[0015] Furthermore, the porosity of the copper sintered body of the present invention is preferably 1% or more, more preferably 3% or more, and even more preferably 5% or more from the viewpoint of preventing chip cracking during temperature cycling due to a decrease in elastic modulus, and is preferably 25% or less, more preferably 20% or less, even more preferably 15% or less, and even more preferably 10% or less from the viewpoint of improving tensile strength and thereby reducing the peeling rate after temperature cycling. "Porosity" refers to the percentage (%) of pores relative to the total volume of the copper sintered body. The porosity can be measured, for example, according to the method described in the Examples below. Specifically, it can be determined by calculating the ratio of the area of ​​pores to the area of ​​the entire cross section in a scanning electron microscope (SEM) image of the cross section of the copper sintered body.

[0016] [Jointed body] The copper sintered body of the present invention can be used to join multiple members, for example, metal members. A joined body is obtained by joining multiple members. The present invention also provides a joined body. A specific embodiment of the joined body of the present invention includes a joined body comprising a first member, a second member, and the copper sintered body of the present invention that joins the first member and the second member. More specifically, the joined body is a semiconductor device, and includes a semiconductor device comprising a first member, a second member, and the copper sintered body of the present invention that joins the first member and the second member.

[0017] Examples of the metal members to be bonded include metal-based 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 the same type of metal member or different types of metal members. Among these, the metal member preferably includes at least one selected from gold substrates, gold-plated substrates, silver substrates, silver-plated metal substrates, copper substrates, palladium substrates, palladium-plated metal substrates, platinum substrates, platinum-plated metal substrates, aluminum substrates, nickel substrates, nickel-plated metal substrates, tin substrates, tin-plated metal substrates, and metal parts of an electrically insulating substrate.

[0018] The copper sintered body of the present invention can be used for bonding in various semiconductor devices, for example, bonding chip components such as capacitors and resistors to circuit boards; bonding semiconductor chips such as memories, diodes, transistors, ICs, and CPUs to lead frames or circuit boards; and bonding high-heat-generating semiconductor chips to cooling plates. That is, a bonded body in which multiple members are bonded using the copper sintered body of the present invention is preferably a semiconductor device. One preferred embodiment of the bonded body of the present invention is a bonded body comprising a semiconductor chip, a substrate, and the copper sintered body of the present invention bonding the semiconductor chip and the substrate. Such a bonded body is preferably a semiconductor device, more preferably a power device.

[0019] The semiconductor chip preferably includes a silicon semiconductor chip, a silicon carbide semiconductor chip, a gallium nitride semiconductor chip, a gallium oxide semiconductor chip, a diamond semiconductor chip, etc. The substrate preferably includes a copper substrate.

[0020] The copper sintered body of the present invention can be produced by the method for producing a copper sintered body described in detail below. The copper sintered body of the present invention is preferably a copper sintered body obtained by the method described in the section "Method for producing a copper sintered body" below.

[0021] [Method for producing a copper sintered body] The method for producing a copper sintered body of the present invention includes the following step 1. Step 1: A step of baking a dispersion D containing copper nanoparticles A and the following polymer B at a baking temperature of 240°C or higher and 300°C or lower while applying a pressure of 0.1 MPa or higher and 40 MPa or lower Polymer B: A polymer containing a constituent unit derived from a monomer (b-1) having a carboxy group and a constituent unit derived from a monomer (b-2) having a polyalkylene glycol segment

[0022] According to the method for producing a copper sintered body of the present invention, a bonded body can be obtained that has a predetermined low tensile modulus, exhibits a small peel rate even after temperature cycling, and suppresses cracking of the semiconductor chip. The reasons for this are unclear, but some are thought to be as follows. Since the copper nanoparticles A contained in the dispersion D according to the production method of the present invention have high dispersibility, they are uniformly distributed throughout the dispersion, and sintering proceeds uniformly. As a result, the resulting sintered body is dense, yet voids are uniformly present within the structure, resulting in a copper sintered body with a low modulus of elasticity. Furthermore, by heating at a predetermined temperature, pressure, or firing time, the degree of density is adjusted, and the voids are not reduced too much, which is thought to suppress an increase in the modulus of elasticity.

[0023] <<Copper Nanoparticles A>> Dispersion D to be fired by the method for producing a copper sintered body according to the present invention contains copper nanoparticles A. The copper content in copper nanoparticles A is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and even more preferably substantially 100% by mass, from the viewpoint of improving conductivity, low-temperature sinterability, and low-temperature bondability. Here, "substantially 100% by mass" means that unintentionally contained components may be included. Examples of unintentionally contained components include unavoidable impurities.

[0024] The average particle size of the copper nanoparticles A is preferably 50 nm or more, more preferably 75 nm or more, even more preferably 100 nm or more, and even more preferably 125 nm or more from the viewpoint of suppressing oxidation of the copper nanoparticles. From the viewpoint of improving sinterability to improve tensile strength and thereby reducing the peeling rate after temperature cycling, it is preferably 400 nm or less, more preferably 375 nm or less, even more preferably 350 nm or less, and even more preferably 320 nm or less. The average particle size of the copper nanoparticles A is measured by the method described in the Examples. The average particle size of the copper nanoparticles A can be adjusted by the production conditions of the copper nanoparticles A, such as the reduction metal rate, the type and amount of polymer B, and the reduction temperature.

[0025] The content of copper nanoparticles A in dispersion D used in the present invention is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and even more preferably 35% by mass or more, from the viewpoint of improving sinterability and thereby improving tensile strength, and is preferably 95% by mass or less, more preferably 93% by mass or less, even more preferably 91% by mass or less, and even more preferably 90% by mass or less, from the viewpoint of improving the dispersion stability of the copper microparticle dispersion, which suppresses shrinkage of the bonding layer after sintering and thereby reduces the peeling rate after temperature cycling.

[0026] <<Copper Microparticles A'>> The dispersion D used in the present invention may further contain copper microparticles A' from the viewpoint of improving electrical conductivity, low-temperature sinterability, and low-temperature bondability. The copper content in the copper microparticles A' is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and even more preferably substantially 100% by mass from the viewpoint of improving electrical conductivity, low-temperature sinterability, and low-temperature bondability. Here, "substantially 100% by mass" means that unintentionally contained components may be included. Examples of unintentionally contained components include unavoidable impurities.

[0027] The average particle size of the copper microparticles A' is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.5 μm or more, and even more preferably 2.0 μm or more, from the viewpoint of suppressing shrinkage of the bonding layer after sintering and thereby reducing the peeling rate after temperature cycling, and is preferably 6 μm or less, more preferably 5 μm or less, and even more preferably 4 μm or less, from the viewpoint of improving the tensile strength by improving the surface energy and sinterability, thereby reducing the peeling rate after temperature cycling. The average particle size of the copper microparticles A' is measured by the method described in the Examples.

[0028] The content of copper microparticles A' in dispersion D used in the present invention is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more, from the viewpoint of suppressing shrinkage of the bonding layer after sintering and thereby reducing the peeling rate after temperature cycling, and is preferably 70% by mass or less, more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, even more preferably 55% by mass or less, and even more preferably 50% by mass or less, from the viewpoint of suppressing deterioration of sinterability due to a decrease in surface energy and maintaining tensile strength.

[0029] The mass ratio of the content of copper nanoparticles A to the total content of copper nanoparticles A and copper microparticles A' in dispersion D used in the present invention [copper nanoparticles A / (copper nanoparticles A+copper microparticles A')] is preferably 0.3 or more, more preferably 0.4 or more, even more preferably 0.5 or more, and even more preferably 0.6 or more, from the viewpoint of improving electrical conductivity, storage stability of the copper microparticle dispersion, low-temperature sinterability, and low-temperature bondability. From the viewpoint of improving electrical conductivity, low-temperature sinterability, and low-temperature bondability, it is preferably 1.0 or less, more preferably 0.9 or less, even more preferably 0.8 or less, and even more preferably 0.75 or less.

[0030] <<Polymer B>> Dispersion D used in the present invention contains polymer B from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving low-temperature sinterability and low-temperature bondability. Preferably, dispersion D contains copper nanoparticles A coated with polymer B. Polymer B contains a constituent unit derived from a monomer (b-1) having a carboxy group and a constituent unit derived from a monomer (b-2) having a polyalkylene glycol segment from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving low-temperature sinterability and low-temperature bondability.

[0031] <Monomer (b-1) Having a Carboxy Group> Examples of the monomer (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 be an anhydride. Monomer (b-1) may be used alone or in combination of two or more. From the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving low-temperature sintering and low-temperature bonding, monomer (b-1) is preferably at least one selected from (meth)acrylic acid and maleic acid, more preferably (meth)acrylic acid, and even more preferably methacrylic acid. In this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. The same applies to "(meth)acrylic acid" below.

[0032] <Monomer (b-2) Having a Polyalkylene Glycol Segment> Examples of the monomer (b-2) include polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, and phenoxy polyalkylene glycol (meth)acrylate. The monomer (b-2) may be used alone or in combination of two or more. In this specification, "(meth)acrylate" refers to at least one selected from acrylate and methacrylate. The "(meth)acrylate" used below has the same meaning.

[0033] Monomer (b-2) is preferably at least one selected from polyalkylene glycol (meth)acrylate and alkoxy polyalkylene glycol (meth)acrylate, more preferably alkoxy polyalkylene glycol (meth)acrylate, from the viewpoint of improving the dispersibility of copper nanoparticles A in dispersion D and improving low-temperature sintering and low-temperature bonding. From the same viewpoint as above, the number of carbon atoms in the alkoxy group of the alkoxy polyalkylene glycol (meth)acrylate is preferably 1 or more and 18 or less, more preferably 1 or more and 14 or less, and even more preferably 1 or more and 12 or less. Examples of the alkoxy polyalkylene glycol (meth)acrylate include methoxy polyalkylene glycol (meth)acrylate, ethoxy polyalkylene glycol (meth)acrylate, propoxy polyalkylene glycol (meth)acrylate, butoxy polyalkylene glycol (meth)acrylate, octoxy polyalkylene glycol (meth)acrylate, lauroxy polyalkylene glycol (meth)acrylate, and the like.

[0034] The polyalkylene glycol segment of monomer (b-2) preferably contains units derived from alkylene oxide having 2 to 4 carbon atoms from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving low-temperature sinterability and low-temperature bondability. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, etc., and are preferably one or more selected from ethylene oxide and propylene oxide, more preferably ethylene oxide. The number of alkylene oxide-derived units in the polyalkylene glycol segment is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving low-temperature sinterability and low-temperature bondability, and is preferably 100 or less, more preferably 70 or less, even more preferably 50 or less, even more preferably 40 or less, and even more preferably 35 or less. The polyalkylene glycol segment may be a copolymer containing ethylene oxide-derived units and propylene oxide-derived units from the viewpoint of improving the dispersion stability of the copper microparticle dispersion and improving low-temperature sinterability and low-temperature bondability. The copolymer containing units derived from ethylene oxide and units derived from propylene oxide may be any of a block copolymer, a random copolymer, and an alternating copolymer.

[0035] Specific examples of commercially available monomer (b-2) include NK Ester AM-90G, AM-130G, AM-230G, AMP-20GY, M-20G, M-40G, M-90G, and M-230G, manufactured by Shin-Nakamura Chemical Co., Ltd.; and Blenmar PE-90, PE-200, PE-350, PME-100, and PME-230G, manufactured by NOF Corporation. Examples of such polyether esters include ME-200, PME-400, PME-1000, PME-4000, PP-500, PP-500D, PP-800, PP-1000, PP-2000D, AP-150, AP-400, AP-550, 50PEP-300, 50POEP-800B, 43PAPE-600B, and PLE-1300.

[0036] <Hydrophobic Monomer (b-3)> From the viewpoint of improving low-temperature sinterability and low-temperature bondability, polymer B may further contain a structural unit derived from hydrophobic monomer (b-3). As used herein, the term "hydrophobic monomer" refers to a monomer that dissolves in an amount of less than 10 g when dissolved in 100 g of ion-exchanged water at 25°C until saturated. From the viewpoint of improving low-temperature sinterability and low-temperature bondability, the amount of monomer (b-3) dissolved is preferably 5 g or less, more preferably 1 g or less. Monomer (b-3) is preferably at least one selected from aromatic group-containing monomers and (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol.

[0037] From the viewpoint of improving low-temperature sinterability and low-temperature bondability, the aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group of 6 to 22 carbon atoms, which may have a substituent containing a heteroatom, and more preferably one or more selected from styrene-based monomers and aromatic group-containing (meth)acrylates. The molecular weight of the aromatic group-containing monomer is preferably less than 500. Examples of styrene-based monomers include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), and divinylbenzene. From the viewpoint of improving low-temperature sinterability and low-temperature bondability, styrene and α-methylstyrene are preferred. From the viewpoint of improving low-temperature sinterability and low-temperature bondability, the aromatic group-containing (meth)acrylate is preferably phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc., and more preferably benzyl (meth)acrylate.

[0038] From the viewpoint of improving low-temperature sinterability and low-temperature bondability, the (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol preferably has a hydrocarbon group derived from an aliphatic alcohol having from 1 to 22 carbon atoms, more preferably has a hydrocarbon group derived from an aliphatic alcohol having from 1 to 12 carbon atoms, even more preferably has a hydrocarbon group derived from an aliphatic alcohol having from 1 to 8 carbon atoms, and even more preferably has a hydrocarbon group derived from an aliphatic alcohol having from 1 to 4 carbon atoms. Examples of the (meth)acrylate having a linear alkyl group include (meth)acrylates having a branched alkyl group and (meth)acrylates having an alicyclic alkyl group. Examples of the (meth)acrylate having a linear alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. Examples of (meth)acrylates having a branched alkyl group include isopropyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isopentyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, isododecyl (meth)acrylate, isostearyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of (meth)acrylates having an alicyclic alkyl group include cyclohexyl (meth)acrylate. Monomer (b-3) may be used alone or in combination of two or more.

[0039] From the viewpoint of improving low-temperature sinterability and low-temperature bondability, the monomer (b-3) is preferably at least one selected from an aromatic group-containing monomer and a (meth)acrylate having a linear alkyl group, more preferably at least one selected from a styrene-based monomer and a (meth)acrylate having a linear alkyl group having from 1 to 4 carbon atoms, even more preferably at least one selected from styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate, even more preferably at least one selected from styrene, α-methylstyrene, and methyl (meth)acrylate, and even more preferably at least one selected from styrene and methyl (meth)acrylate.

[0040] Polymer B is, from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving low-temperature sintering and low-temperature bonding, a vinyl polymer containing a structural unit derived from at least one selected from (meth)acrylic acid and maleic acid as monomer (b-1), and a structural unit derived from alkoxy polyalkylene glycol (meth)acrylate as monomer (b-2) is more preferred. The vinyl polymer containing a structural unit derived from at least one selected from (meth)acrylic acid and maleic acid as monomer (b-1), and a structural unit derived from alkoxy polyalkylene glycol (meth)acrylate as monomer (b-2) may be a block copolymer, a random copolymer, or an alternating copolymer.

[0041] The content of the vinyl polymer containing a structural unit derived from monomer (b-1) and a structural unit derived from monomer (b-2) in polymer B is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably substantially 100% by mass, from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving low-temperature sintering and low-temperature bonding. Here, "substantially 100% by mass" means that unintentionally contained components may be included. Examples of unintentionally contained components include polymers B other than the vinyl polymers contained in polymer B.

[0042] During the production of polymer B, the total content of monomer (b-1) and monomer (b-2) in the raw material monomers or the total content of the structural units derived from monomer (b-1) and monomer (b-2) in polymer B is, from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D, improving low-temperature sintering properties and low-temperature bonding properties, preferably 72% by mass or more, more preferably 88% by mass or more, even more preferably 91% by mass or more, even more preferably 97% by mass or more, and even more preferably substantially 100% by mass. Here, "substantially 100% by mass" means that unintentionally contained components may be included. Examples of unintentionally contained components include monomers other than monomer (b-1) and monomer (b-2) contained in the raw material monomer (b-1) and monomer (b-2).

[0043] During the production of polymer B, the content of monomer (b-1) in the raw material monomer or the content of the structural unit derived from monomer (b-1) in polymer B is preferably 3% by mass or more, more preferably 5% by mass or more, from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving low-temperature sinterability and low-temperature bondability, and is preferably 35% by mass or less, more preferably 25% by mass or more, even more preferably 18% by mass or less, and even more preferably 10% by mass or less.

[0044] During the production of polymer B, the content of monomer (b-2) in the raw material monomers or the content of structural units derived from monomer (b-2) in polymer B is, from the viewpoint of improving the dispersion stability of the copper microparticle dispersion and improving low-temperature sintering properties and low-temperature bonding properties, preferably 55% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 84% 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.

[0045] The content of the polyalkylene glycol segment in polymer B is preferably 55% by mass or more and 97% by mass or less, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 84% by mass or more, from the viewpoint of improving low-temperature sintering properties and low-temperature bonding properties, and is more preferably 94% by mass or less, and even more preferably 92% by mass or less, from the viewpoint of improving the dispersion stability of the copper microparticle dispersion and improving the storage stability of the copper microparticle dispersion.

[0046] The number average molecular weight Mn of polymer B is preferably 4,000 or more, more preferably 6,000 or more, and even more preferably 7,000 or more from the viewpoint of improving the dispersion stability of the copper microparticle dispersion and improving the storage stability of the copper microparticle dispersion, and is 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 and low-temperature bonding property of the copper microparticle dispersion. The number average molecular weight Mn is measured by the method described in the Examples.

[0047] The acid value of polymer B is preferably 20 mg KOH / g or more and 250 mg KOH / g or less, and from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving the storage stability of dispersion D, 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, and even more preferably 40 mg KOH / g or more, and from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving the storage stability of dispersion D, more preferably 230 mg KOH / g or less, more preferably 220 mg KOH / g or less, and even more preferably 215 mg KOH / g or less. The acid value of polymer B can be measured by the method described in the examples. It can also be calculated from the mass ratio of the constituent monomers.

[0048] The content of polymer B in dispersion D used in the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and even more preferably 0.4% by mass or more, from the viewpoint of improving the dispersion stability of copper nanoparticles A in dispersion D and improving the storage stability of dispersion D, and is preferably 10% by mass or less, more preferably 9% by mass or less, even more preferably 8% by mass or less, and even more preferably 7% by mass or less, from the viewpoint of improving low-temperature sinterability and low-temperature bondability.

[0049] The mass ratio of the content of polymer B to the total content of copper nanoparticles A and polymer B in the dispersion D used in the present invention [polymer B / (copper nanoparticles A + polymer B)] (hereinafter also referred to as "polymer mass ratio") is preferably 0.0055 or more, more preferably 0.0058 or more, and even more preferably 0.0060 or more from the viewpoint of improving the dispersion stability of copper nanoparticles A in the dispersion D and improving the storage stability of the dispersion D. From the viewpoint of improving low-temperature sintering and low-temperature bonding, it is preferably 0.025 or less, more preferably 0.022 or less, more preferably 0.020 or less, and even more preferably 0.018 or less. The polymer mass ratio is calculated from the content of copper nanoparticles A and the content of polymer B in the dispersion D measured by the method described in the examples using a differential thermal thermogravimetry analyzer (TG / DTA).

[0050] <<Dispersion Medium C>> The dispersion D used in the present invention preferably further contains a dispersion medium C. The dispersion medium C is a medium for dispersing the copper nanoparticles A and, if necessary, the copper microparticles A' in the dispersion D. Preferred examples of the dispersion medium C include one or more organic solvents selected from the group consisting of hydrocarbons, alcohols, ethers, and esters. One organic solvent may be used alone, or two or more organic solvents may be used in combination. More preferred examples of the organic solvent include one or more organic solvents selected from the group consisting of alcohols, ethers, and esters, and even more preferred examples of the organic solvent include one or more organic solvents selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, and (poly)alkylene glycol derivatives.

[0051] 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. Preferred examples of terpene alcohols include monoterpene alcohols such as α-terpineol, linalool, geraniol, citronellol, and dihydroterpineol.

[0052] The (poly)alkylene glycol is at least one 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.

[0053] Examples of (poly)alkylene glycol derivatives include compounds in which the terminal hydroxy groups of the (poly)alkylene glycols are etherified or esterified. Specific examples include one or more compounds selected from the group consisting of (poly)alkylene glycol alkyl ethers and (poly)alkylene glycol monoalkyl ether acetates. The (poly)alkylene glycol alkyl ether is one or more compounds selected from the group consisting of alkylene glycol alkyl ethers and polyalkylene glycol alkyl ethers. Examples of (poly)alkylene glycol alkyl ethers include (poly)alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol butyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether. The (poly)alkylene glycol monoalkyl ether acetate is one or more compounds selected from the group consisting of alkylene glycol monoalkyl ether acetates and polyalkylene glycol monoalkyl ether acetates. Examples of the (poly)alkylene glycol monoalkyl ether acetate 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.

[0054] Among these, from the viewpoint of improving the dispersion stability of the copper nanoparticles A in the dispersion D and improving the bonding strength, the dispersion medium C preferably contains one or more compounds selected from the group consisting of hydroxy group-containing compounds having at least one hydroxy group in the molecule (hereinafter also referred to as "hydroxy group-containing compounds") and ester group-containing compounds having at least one ester group in the molecule (hereinafter also referred to as "ester group-containing compounds"), and more preferably contains a hydroxy group-containing compound.

[0055] The hydroxy group-containing compound is preferably at least one selected from the group consisting of (poly)alkylene glycols and (poly)alkylene glycol alkyl ethers, more preferably (poly)alkylene glycols. The ester group-containing compound is preferably a (poly)alkylene glycol monoalkyl ether acetate.

[0056] The content of dispersion medium C in dispersion D used in the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 5% by mass or more, from the viewpoint of improving the sinterability and tensile strength by improving the dispersibility of copper nanoparticles A and / or copper microparticles A ' in dispersion D. From the viewpoint of improving the sinterability and tensile strength of dispersion D, it is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less. The mass ratio of the content of dispersion medium C to the content of copper nanoparticles A in dispersion D [dispersion medium C / copper nanoparticles A] is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, from the viewpoint of improving the sinterability and tensile strength of dispersion D, and from the viewpoint of suppressing shrinkage during sintering of dispersion D, it is preferably 1.0 or less, more preferably 0.5 or less, even more preferably 0.2 or less.

[0057] <<Dispersion D>> In Dispersion D used in the present invention, from the viewpoint of improving the dispersibility of copper nanoparticles A in Dispersion D and the low-temperature sinterability and low-temperature bondability of Dispersion D, the content of copper nanoparticles A is preferably from 30% to 95% by mass, the content of polymer B is preferably from 0.1% to 10% by mass, the content of dispersion medium C is preferably from 4% to 60% by mass, and the content of copper microparticles A′ is preferably from 0% to 65% by mass.

[0058] Dispersion D may contain various additives as components other than the above components, as long as the effects of the present invention are not impaired. Examples of such additives include metal particles other than copper nanoparticles A and copper microparticles A', sintering accelerators such as glass frit, antioxidants, viscosity adjusters, pH adjusters, buffers, antifoaming agents, leveling agents, and volatilization inhibitors. Examples of metal particles other than copper nanoparticles A and copper microparticles include metal particles such as zinc, nickel, silver, gold, palladium, and platinum. The content of additives in Dispersion D is preferably 1% by mass or less.

[0059] <<Method for producing dispersion D>> Dispersion D used in the present invention can be obtained by, for example, a method of adding and mixing polymer B and dispersion medium C, and if necessary, copper microparticles A' and various additives, to copper nanoparticles A prepared in advance by a known method; a method of mixing a copper raw material compound, a reducing agent, and polymer B as a dispersant, and if necessary, a solvent for dispersing the copper raw material compound and the reducing agent, and then reducing the copper raw material compound to obtain a dispersion of copper nanoparticles A, and then adding and mixing dispersion medium C and, if necessary, copper microparticles and various additives. Among these, from the viewpoint of improving the low-temperature sinterability, low-temperature bondability, and dispersion stability of the copper nanoparticles A in dispersion D, a method of obtaining a dried powder of copper nanoparticles A containing polymer B in advance (hereinafter also referred to as "copper nanoparticle dry powder"), and then adding and mixing dispersion medium C and, if necessary, copper microparticles A' and various additives, etc. is preferred. The copper nanoparticle dry powder can be obtained by mixing a copper source compound, a reducing agent, and a polymer B, reducing the copper source compound with the reducing agent to obtain a dispersion of copper nanoparticles A dispersed in the polymer B, and then drying the dispersion of copper nanoparticles A by freeze-drying or the like. In the copper nanoparticle dry powder, preferably, part or all of the surface of the copper nanoparticles A is coated with the polymer B.

[0060] The copper source compound is not particularly limited as long as it is a compound containing copper. Examples of the copper source compound include copper sulfate, copper nitrate, cupric oxide, cuprous oxide, copper formate, copper acetate, copper oxalate, etc. The copper source compounds can be used alone or in combination of two or more.

[0061] The reducing agent is not particularly limited as long as it is a compound capable of reducing the copper raw material compound. Examples of the reducing agent include hydrazine compounds such as hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine hydrate; boron compounds such as sodium borohydride; and inorganic acid salts such as sodium sulfite, sodium hydrogen sulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, and sodium hypophosphite. The reducing agents may be used alone or in combination of two or more.

[0062] Examples of the solvent for dispersing the copper source compound and the reducing agent include water, methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol.

[0063] The temperature of the reduction reaction is preferably 20 ° C. or higher, more preferably 40 ° C. or higher, and even more preferably 60 ° C. or higher, from the viewpoint of reducing and uniformly dispersing the particle size of the copper nanoparticles A, and is preferably 100 ° C. or lower, more preferably 90 ° C. or lower, and even more preferably 80 ° C. or lower. The reduction reaction may be carried out in an air atmosphere or an inert gas atmosphere such as nitrogen gas.

[0064] In the production of copper nanoparticle dispersions, the dispersion of copper nanoparticles A may be purified before freeze-drying in order to remove impurities such as unreacted reducing agent and excess polymer B that does not contribute to the dispersion of copper nanoparticles A. The method for purifying the dispersion containing copper nanoparticles A is not particularly limited, and includes membrane treatments such as decantation, dialysis, and ultrafiltration; and centrifugation. Among these, decantation and centrifugation are preferred in terms of improving yield. Regenerated cellulose is preferred as the material for the dialysis membrane used in dialysis. 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, and even more preferably 10,000 or more, and is preferably 100,000 or less, more preferably 70,000 or less.

[0065] Dispersion D can be obtained by further adding the various additives described above as necessary and performing a filtration treatment using a filter or the like.

[0066] <<Firing Step>> The method for producing a copper sintered body of the present invention includes a step of firing the above-mentioned dispersion D at a firing temperature of 240° C. or more and 300° C. or less while applying a pressure of 0.1 MPa or more and 40 MPa or less.

[0067] The firing temperature, which is the heating temperature in the firing step, is 240°C or higher, preferably 250°C or higher, from the viewpoint of improving sinterability to improve tensile strength and thereby reducing the peeling rate after temperature cycling. It is also 300°C or lower, preferably 290°C or lower, and more preferably 275°C or lower, from the viewpoint of avoiding damage to components such as semiconductor chips when bonding them. The firing temperature can be, for example, 200°C or higher and 300°C or lower. It is also preferable to set it to 150°C or higher. The firing step is performed while applying a pressure of 0.1 MPa or higher and 40 MPa or lower. The applied pressure is 0.1 MPa or higher, preferably 2 MPa or higher, more preferably 4 MPa or higher, from the viewpoint of improving sinterability to improve tensile strength and thereby reducing the peeling rate after temperature cycling. It is also 40 MPa or lower, preferably 30 MPa or lower, more preferably 20 MPa or lower, and even more preferably 15 MPa, from the viewpoint of preventing chip cracking during temperature cycling due to a decrease in elastic modulus. The firing time can be appropriately adjusted depending on the heating temperature and the applied pressure. From the viewpoint of improving the sinterability to improve the tensile strength and thereby reducing the peeling rate after temperature cycling, it is preferably 150 seconds or more, more preferably 200 seconds or more, even more preferably 250 seconds or more, and still more preferably 300 seconds or more, and from the viewpoint of preventing chip cracking during temperature cycling due to a decrease in elastic modulus, it is preferably 3600 seconds or less, more preferably 1800 seconds or less, even more preferably 1200 seconds or less, and still more preferably 600 seconds or less.

[0068] The atmosphere in the firing step may be any of an air atmosphere, an inert gas atmosphere such as nitrogen gas, and a reducing gas atmosphere such as hydrogen gas, and from the viewpoints of inhibiting copper oxidation and safety, a nitrogen gas atmosphere is preferred.

[0069] The firing performed while applying the pressure can be performed by, for example, the HP (hot press) method, the HIP (hot isostatic pressing) method, the atmospheric pressure method, or the like. Preferably, the firing is performed by the HP method. Specifically, for example, it can be performed using a pressure firing machine (pressure sintering machine). Another simple method is to place a weight capable of applying the pressure on the material and use an oven or the like to perform the firing.

[0070] <<Application Step>> The method for producing a copper sintered body of the present invention preferably further includes the following Step 0 before Step 1. Step 0: Step of applying Dispersion D to a member The member to which Dispersion D is applied is preferably a metal member, such as a metal-based substrate or metal substrate such as a gold substrate, a gold-plated substrate, a silver substrate, a silver-plated metal substrate, a copper substrate, a palladium substrate, a palladium-plated metal substrate, a platinum substrate, a platinum-plated metal substrate, an aluminum substrate, a nickel substrate, a nickel-plated metal substrate, a tin substrate, or a tin-plated metal substrate; or a metal portion such as an electrode of an electrically insulating substrate. Among these, preferred examples of the metal member include a gold substrate, a gold-plated substrate, a silver substrate, a silver-plated metal substrate, a copper substrate, a palladium substrate, a palladium-plated metal substrate, a platinum substrate, a platinum-plated metal substrate, an aluminum substrate, a nickel substrate, a nickel-plated metal substrate, a tin substrate, or a tin-plated metal substrate, and a metal portion of an electrically insulating substrate. Examples of methods for applying Dispersion D to a member include various application methods such as slot die coating, dip coating, spray coating, spin coating, doctor blading, knife edge coating, and bar coating, and various patterning printing methods such as stencil printing, screen printing, flexographic printing, gravure printing, offset printing, dispenser printing, and inkjet printing. The amount of Dispersion D to be applied to a member such as a metal member can be adjusted appropriately depending on the size and type of the member to be joined, such as a metal member.

[0071] The step 0 is preferably the following step 0-1. Step 0-1: A step of applying the dispersion D between a first member and a second member so that the dispersion D is interposed between the first member and the second member. The first member and the second member may be the same type of member or different types of members. In this case, the obtained copper sintered body bonds the first member and the second member.

[0072] Thus, a copper sintered body is produced. The produced copper sintered body preferably has the physical properties described in the above section [Copper sintered body].

[0073] [Method for manufacturing a bonded body] The method for manufacturing a bonded body of the present invention is a method for manufacturing a bonded body including a first member, a second member, and a copper sintered body that bonds the first member and the second member, and includes the following steps 0-1 and 1. Step 0-1: A step of applying a dispersion D containing copper nanoparticles A and a polymer B described below between the first member and the second member. Step 1: A step of firing the dispersion D at a firing temperature of 240° C. or higher and 300° C. or lower while applying a pressure of 0.1 MPa or higher and 40 MPa or lower.

[0074] The conjugate to be produced and its preferred embodiments are described in the above [Conjugate] section.

[0075] Dispersion D is the one described in the above section [Method for producing sintered copper body].

[0076] The means for applying copper dispersion D between the first member and the second member is not particularly limited. Examples of the method include various application methods such as slot die coating, dip coating, spray coating, spin coating, doctor blading, knife edge coating, and bar coating; and various patterning printing methods such as stencil printing, screen printing, flexographic printing, gravure printing, offset printing, dispenser printing, and inkjet printing. The amount of dispersion D applied to the first member and / or the second member can be adjusted appropriately depending on the size and type of the first member and the second member to be joined.

[0077] The step of firing Dispersion D at a firing temperature of 240° C. or higher and 300° C. or lower while applying a pressure of 0.1 MPa or higher and 40 MPa or lower and a preferred embodiment thereof are described in the above section [Method for producing a copper sintered body].

[0078] The bonded body to be manufactured is preferably a semiconductor. In this case, the first member and the second member are preferably a semiconductor chip and a substrate. The semiconductor chip is preferably a silicon semiconductor chip, a silicon carbide semiconductor chip, a gallium nitride semiconductor chip, a gallium oxide semiconductor chip, or a diamond semiconductor chip. The substrate is preferably a copper substrate.

[0079] The copper sintered body constituting the bonded body thus produced preferably has the physical properties described in the above section [Copper sintered body].

[0080] The present invention further discloses the following <1> to <80>. <1> A copper sintered body having a tensile modulus of 35 GPa or less, preferably 30 GPa or less, and more preferably 25 GPa or less. <2> A copper sintered body according to <1>, having a tensile strength of preferably 100 MPa or more, more preferably 120 GPa or more, even more preferably 140 GPa or more, even more preferably 160 GPa or more, and even more preferably 180 GPa or more. <3> A copper sintered body according to <1> or <2>, having a porosity of preferably 1% or more, more preferably 3% or more, even more preferably 5% or more, and preferably 25% or less, more preferably 20% or less, even more preferably 15% or less, and even more preferably 10% or less. <4> A method for producing a copper sintered body, comprising the following step 1: Step 1: A step of baking a dispersion D containing copper nanoparticles A and the following polymer B at a baking temperature of 240°C or higher and 300°C or lower while applying a pressure of 0.1 MPa or higher and 40 MPa or lower. Polymer B: A polymer containing a structural unit derived from a monomer (b-1) having a carboxy group and a structural unit derived from a monomer (b-2) having a polyalkylene glycol segment. <5> The method for producing a copper sintered body according to <4>, in which the copper content in the copper nanoparticles A is preferably 95% by mass or higher, more preferably 98% by mass or higher, even more preferably 99% by mass or higher, and even more preferably substantially 100% by mass. <6> The method for producing a copper sintered body according to <4>, further comprising the following step 0 before step 1. Step 0: A step of applying the dispersion D to a member. <7> The method for producing a copper sintered body according to <4> or <5>, in which step 0 is a step of applying the dispersion D between a first member and a second member so that the dispersion D is interposed between the first member and the second member. <8> The average particle size of the copper nanoparticles A is preferably 50 nm or more, more preferably 75 nm or more, even more preferably 100 nm or more, still more preferably 125 nm or more, and preferably 400 nm or less, more preferably 375 nm or less, still more preferably 350 nm or less, still more preferably 320 nm or less. The method for producing a copper sintered body according to any one of <4> to <6>.<9> The method for producing a copper sintered body according to any one of <4> to <8>, wherein the content of copper nanoparticles A in dispersion D is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, and preferably 95% by mass or less, more preferably 93% by mass or less, even more preferably 91% by mass or less, and even more preferably 90% by mass or less. <10> The method for producing a copper sintered body according to any one of <4> to <9>, wherein dispersion D further contains copper microparticles A', and the copper content in the copper microparticles A' is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and even more preferably substantially 100% by mass. <11> The method for producing a copper sintered body according to <10>, wherein the average particle size of the copper microparticles A' is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.5 μm or more, even more preferably 2.0 μm or more, and preferably 6 μm or less, more preferably 5 μm or less, even more preferably 4 μm or less. <12> The method for producing a copper sintered body according to <10> or <11>, wherein the content of the copper microparticles A' in the dispersion D is preferably 10 mass% or more, more preferably 15 mass% or more, even more preferably 20 mass% or more, even more preferably 25 mass% or more, and preferably 70 mass% or less, more preferably 65 mass% or less, even more preferably 60 mass% or less, even more preferably 55 mass% or less, even more preferably 50 mass% or less. <13> The method for producing a copper sintered body according to any one of <10> to <12>, wherein the mass ratio of the content of copper nanoparticles A to the total content of copper nanoparticles A and copper microparticles A′ in dispersion D [copper nanoparticles A / (copper nanoparticles A+copper microparticles A′)] is preferably 0.3 or more, more preferably 0.4 or more, even more preferably 0.5 or more, still more preferably 0.6 or more, and is preferably 1.0 or less, more preferably 0.9 or less, even more preferably 0.8 or less, still more preferably 0.75 or less.<14> The method for producing a copper sintered body according to any one of <4> to <13>, wherein the monomer (b-1) is one or more selected from the group consisting of 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. <15> The method for producing a copper sintered body according to any one of <4> to <14>, wherein the monomer (b-2) is one or more selected from the group consisting of polyalkylene glycol (meth)acrylates, alkoxypolyalkylene glycol (meth)acrylates, and phenoxypolyalkylene glycol (meth)acrylates. <16> The method for producing a copper sintered body according to <15>, wherein the monomer (b-2) is preferably at least one selected from the group consisting of polyalkylene glycol (meth)acrylates and alkoxy polyalkylene glycol (meth)acrylates, more preferably alkoxy polyalkylene glycol (meth)acrylates, and the number of carbon atoms in the alkoxy group of the alkoxy polyalkylene glycol (meth)acrylate is preferably 1 or more and 18 or less, more preferably 1 or more and 14 or less, and even more preferably 1 or more and 12 or less. <17> The method for producing a copper sintered body according to any one of <4> to <16>, wherein the polyalkylene glycol segment of the monomer (b-2) preferably contains a unit derived from an alkylene oxide having from 2 to 4 carbon atoms. <18> The method for producing a copper sintered body according to any one of <4> to <17>, wherein the number of alkylene oxide-derived units in the polyalkylene glycol segment of the monomer (b-2) 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 35 or less. <19> The method for producing a copper sintered body according to any one of <4> to <16>, wherein the polymer B further contains a structural unit derived from a hydrophobic monomer (b-3). <20> The method for producing a copper sintered body according to <19>, wherein the monomer (b-3) is preferably at least one selected from the group consisting of an aromatic group-containing monomer and a (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol.<21> The method for producing a copper sintered body according to any one of <4> to <20>, wherein polymer B is a vinyl polymer containing, as monomer (b-1), a structural unit derived from at least one selected from the group consisting of (meth)acrylic acid and maleic acid, and as monomer (b-2), a structural unit derived from an alkoxy polyalkylene glycol (meth)acrylate. <22> The method for producing a copper sintered body according to <21>, wherein the content of the vinyl polymer containing the structural unit derived from monomer (b-1) and the structural unit derived from monomer (b-2) in polymer B is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably substantially 100% by mass. <23> The method for producing a copper sintered body according to any one of <4> to <22>, wherein the total content of monomer (b-1) and monomer (b-2) in the raw material monomers during the production of polymer B, or the total content of structural units derived from monomer (b-1) and structural units derived from monomer (b-2) in polymer B, is preferably 72% by mass or more, more preferably 88% by mass or more, even more preferably 91% by mass or more, even more preferably 97% by mass or more, and even more preferably substantially 100% by mass. <24> The method for producing a copper sintered body according to any one of <4> to <23>, wherein the content of monomer (b-1) in the raw material monomers during the production of polymer B, or the content of structural units derived from monomer (b-1) in polymer B, 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 more, even more preferably 18% by mass or less, and even more preferably 10% by mass or less. <25> The method for producing a copper sintered body according to any one of <4> to <24>, wherein the content of monomer (b-2) in the raw material monomers or the content of structural units derived from monomer (b-2) in polymer B during production of polymer B is preferably 55% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 84% 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.<26> The method for producing a copper sintered body according to any one of <4> to <25>, wherein the content of polyalkylene glycol segments in Polymer B is preferably 55% by mass or more and 97% by mass or less, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 84% by mass or more, and more preferably 94% by mass or less, even more preferably 92% by mass or less. <27> The method for producing a copper sintered body according to any one of <4> to <26>, wherein Polymer B has a number-average molecular weight Mn of preferably 4,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 15,000 or less, even more preferably 10,000 or less. <28> The method for producing a copper sintered body according to any one of <4> to <27>, wherein the acid value of Polymer B is preferably 20 mgKOH / g or more and 250 mgKOH / g or less, more preferably 25 mgKOH / g or more, even more preferably 30 mgKOH / g or more, even more preferably 35 mgKOH / g or more, even more preferably 40 mgKOH / g or more, and more preferably 230 mgKOH / g or less, even more preferably 220 mgKOH / g or less, and even more preferably 215 mgKOH / g or less. <29> The method for producing a copper sintered body according to any one of <4> to <28>, wherein the content of Polymer B in Dispersion D is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, even more preferably 0.4% by mass or more, and preferably 10% by mass or less, more preferably 9% by mass or less, even more preferably 8% by mass or less, and even more preferably 7% by mass or less. <30> The mass ratio of the content of polymer B to the total content of copper nanoparticles A and polymer B in dispersion D [polymer B / (copper nanoparticles A + polymer B)] is preferably 0.0055 or more, more preferably 0.0058 or more, even more preferably 0.0060 or more, and preferably 0.025 or less, more preferably 0.022 or less, even more preferably 0.020 or less, and even more preferably 0.018 or less, the method for producing a copper sintered body according to any one of <4> to <29>.<31> The method for producing a copper sintered body according to any one of <4> to <30>, wherein Dispersion D further contains Dispersion Medium C. <32> The method for producing a copper sintered body according to <31>, wherein Dispersion Medium C is one or more organic solvents selected from the group consisting of hydrocarbons, alcohols, ethers, and esters. <33> The method for producing a copper sintered body according to <31> or <32>, wherein the content of Dispersion Medium C in Dispersion D is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 5% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. <34> The method for producing a copper sintered body according to any one of <31> to <33>, wherein the mass ratio of the content of Dispersion Medium C to the content of Copper Nanoparticles A in Dispersion D [Dispersion Medium C / Copper Nanoparticles A] is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, and preferably 1.0 or less, more preferably 0.5 or less, and even more preferably 0.2 or less. <35> The method for producing a copper sintered body according to <4>, wherein in Dispersion D, the content of copper nanoparticles A is preferably 30% by mass or more and 95% by mass or less, the content of polymer B is preferably 0.1% by mass or more and 10% by mass or less, the content of dispersion medium C is preferably 4% by mass or more and 60% by mass or less, and the content of copper microparticles A' is preferably 0% by mass or more and 65% by mass or less. <36> The method for producing a copper sintered body according to any one of <4> to <35>, wherein the heating temperature in the firing step is preferably 150°C or more, more preferably 200°C or more, even more preferably 240°C or more, and still more preferably 250°C or more. <37> The method for producing a copper sintered body according to any one of <4> to <36>, wherein the pressure applied in the firing step is preferably 2 MPa or more, more preferably 4 MPa or more, and preferably 30 MPa or less, more preferably 20 MPa or less, and even more preferably 15 MPa or less. <38> The method for producing a copper sintered body according to any one of <4> to <37>, wherein the firing time is preferably 150 seconds or more, more preferably 200 seconds or more, even more preferably 250 seconds or more, even more preferably 300 seconds or more, and preferably 3600 seconds or less, more preferably 1800 seconds or less, even more preferably 1200 seconds or less, even more preferably 600 seconds or less.<39> A copper sintered body obtained by the manufacturing method according to any one of <4> to <38>. <40> A bonded body comprising a first member, a second member, and the copper sintered body according to any one of <1> to <3> and <39> that bonds the first member and the second member. <41> The bonded body according to <40>, in which the first member is preferably a semiconductor chip selected from a silicon semiconductor chip, a silicon carbide semiconductor chip, a gallium nitride semiconductor chip, a gallium oxide semiconductor chip, and a diamond semiconductor chip. <42> The bonded body according to <40> or <41>, in which the second member is preferably a copper substrate. <43> The bonded body according to any one of <40> to <42>, which is preferably a semiconductor device, more preferably a power device. <44> A method for manufacturing a bonded body comprising a first member, a second member, and a copper sintered body that bonds the first member and the second member, the method comprising the following steps 0-1 and 1: Step 0-1: a step of applying a dispersion D containing copper nanoparticles A and the following polymer B between the first member and the second member, and Step 1: a step of firing the dispersion D at a firing temperature of 240°C or higher and 300°C or lower while applying a pressure of 0.1 MPa or higher and 40 MPa or lower. <45> The method for producing a bonded body according to <44>, wherein the first member is preferably a semiconductor chip selected from a silicon semiconductor chip, a silicon carbide semiconductor chip, a gallium nitride semiconductor chip, a gallium oxide semiconductor chip, and a diamond semiconductor chip. <46> The method for producing a bonded body according to <44> or <45>, wherein the second member is preferably a copper substrate. <47> The method for producing a bonded body according to any one of <44> to <46>, wherein the bonded body is preferably a semiconductor device, more preferably a power device. <48> The method for producing a bonded body according to any one of <44> to <47>, wherein the bonded body is a semiconductor device, the first member is a semiconductor chip selected from a silicon semiconductor chip, a silicon carbide semiconductor chip, a gallium nitride semiconductor chip, a gallium oxide semiconductor chip, and a diamond semiconductor chip, and the second member is a copper substrate.<49> The method for producing a joined body according to any one of <44> to <48>, wherein the copper content in the copper nanoparticles A is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and even more preferably substantially 100% by mass. <50> The method for producing a joined body according to any one of <44> to <49>, wherein the average particle size of the copper nanoparticles A is preferably 50 nm or more, more preferably 75 nm or more, even more preferably 100 nm or more, and even more preferably 125 nm or more, and preferably 400 nm or less, more preferably 375 nm or less, even more preferably 350 nm or less, and even more preferably 320 nm or less. <51> The method for producing a conjugated body according to any one of <44> to <50>, wherein the content of copper nanoparticles A in dispersion D is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, and preferably 95% by mass or less, more preferably 93% by mass or less, even more preferably 91% by mass or less, and even more preferably 90% by mass or less. <52> The method for producing a conjugated body according to any one of <44> to <51>, wherein dispersion D further contains copper microparticles A', and the copper content in the copper microparticles A' is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and even more preferably substantially 100% by mass. <53> The method for producing a bonded body according to <52>, wherein the copper microparticles A' have an average particle size of preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.5 μm or more, even more preferably 2.0 μm or more, and preferably 6 μm or less, more preferably 5 μm or less, and even more preferably 4 μm or less. <54> The method for producing a bonded body according to any one of <52> to <53>, wherein the content of the copper microparticles A' in the dispersion D is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, and preferably 70% by mass or less, more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, even more preferably 55% by mass or less, and even more preferably 50% by mass or less.<55> The method for producing a conjugated body according to any one of <51> to <54>, wherein the mass ratio of the content of copper nanoparticles A to the total content of copper nanoparticles A and copper microparticles A' in dispersion D [copper nanoparticles A / (copper nanoparticles A+copper microparticles A')] is preferably 0.3 or more, more preferably 0.4 or more, even more preferably 0.5 or more, even more preferably 0.6 or more, and preferably 1.0 or less, more preferably 0.9 or less, even more preferably 0.8 or less, even more preferably 0.75 or less. <56> The method for producing a conjugated body according to any one of <44> to <51>, wherein the monomer (b-1) is one or more selected from the group consisting of 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. <57> The method for producing a joined body according to any one of <44> to <56>, wherein the monomer (b-2) is one or more selected from the group consisting of polyalkylene glycol (meth)acrylates, alkoxy polyalkylene glycol (meth)acrylates, and phenoxy polyalkylene glycol (meth)acrylates. <58> The method for producing a joined body according to <57>, wherein the monomer (b-2) is preferably at least one selected from the group consisting of polyalkylene glycol (meth)acrylates and alkoxy polyalkylene glycol (meth)acrylates, more preferably an alkoxy polyalkylene glycol (meth)acrylate, and the number of carbon atoms in the alkoxy group of the alkoxy polyalkylene glycol (meth)acrylate is preferably 1 or more and 18 or less, more preferably 1 or more and 14 or less, and even more preferably 1 or more and 12 or less. <59> The method for producing a joined body according to any one of <44> to <58>, wherein the polyalkylene glycol segment of the monomer (b-2) preferably contains a unit derived from an alkylene oxide having from 2 to 4 carbon atoms.<60> The method for producing a conjugated body according to any one of <44> to <59>, wherein the number of alkylene oxide-derived units in the polyalkylene glycol segment of the monomer (b-2) 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 35 or less. <61> The method for producing a conjugated body according to any one of <44> to <60>, wherein the polymer B further contains a structural unit derived from a hydrophobic monomer (b-3). <62> The method for producing a conjugated body according to <61>, wherein the monomer (b-3) is preferably at least one selected from the group consisting of an aromatic group-containing monomer and a (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol. <63> The method for producing a joined body according to any one of <44> to <62>, wherein polymer B is a vinyl polymer containing, as monomer (b-1), a structural unit derived from at least one selected from the group consisting of (meth)acrylic acid and maleic acid, and as monomer (b-2), a structural unit derived from an alkoxypolyalkylene glycol (meth)acrylate. <64> The method for producing a joined body according to <63>, wherein the content of the vinyl polymer containing the structural unit derived from monomer (b-1) and the structural unit derived from monomer (b-2) in polymer B is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably substantially 100% by mass. <65> The method for producing a joined body according to any one of <44> to <64>, wherein the total content of monomer (b-1) and monomer (b-2) in the raw material monomers, or the total content of structural units derived from monomer (b-1) and structural units derived from monomer (b-2) in polymer B during production is preferably 72% by mass or more, more preferably 88% by mass or more, even more preferably 91% by mass or more, even more preferably 97% by mass or more, and still more preferably substantially 100% by mass.<66> The method for producing a joined body according to any one of <44> to <65>, wherein, during the production of Polymer B, the content of monomer (b-1) in the raw material monomers or the content of structural units derived from monomer (b-1) in Polymer B 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 more, even more preferably 18% by mass or less, and even more preferably 10% by mass or less. <67> The method for producing a joined body according to any one of <44> to <66>, wherein, during the production of Polymer B, the content of monomer (b-2) in the raw material monomers or the content of structural units derived from monomer (b-2) in Polymer B is preferably 55% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 84% 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. <68> The method for producing a joined body according to any one of <44> to <67>, wherein the content of polyalkylene glycol segments in polymer B is preferably 55% by mass or more and 97% by mass or less, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 84% by mass or more, and more preferably 94% by mass or less, even more preferably 92% by mass or less. <69> The method for producing a joined body according to any one of <44> to <68>, wherein polymer B has a number-average molecular weight Mn of preferably 4,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 15,000 or less, even more preferably 10,000 or less.<70> The method for producing a joined body according to any one of <44> to <69>, wherein the acid value of Polymer B is preferably 20 mgKOH / g or more and 250 mgKOH / g or less, more preferably 25 mgKOH / g or more, even more preferably 30 mgKOH / g or more, even more preferably 35 mgKOH / g or more, even more preferably 40 mgKOH / g or more, and more preferably 230 mgKOH / g or less, even more preferably 220 mgKOH / g or less, and even more preferably 215 mgKOH / g or less. <71> The method for producing a joined body according to any one of <44> to <70>, wherein the content of Polymer B in Dispersion D is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, even more preferably 0.4% by mass or more, and preferably 10% by mass or less, more preferably 9% by mass or less, even more preferably 8% by mass or less, and even more preferably 7% by mass or less. <72> The mass ratio of the content of polymer B to the total content of copper nanoparticles A and polymer B in dispersion D [polymer B / (copper nanoparticles A+polymer B)] is preferably 0.0055 or more, more preferably 0.0058 or more, even more preferably 0.0060 or more, and is preferably 0.025 or less, more preferably 0.022 or less, even more preferably 0.020 or less, and even more preferably 0.018 or less. <73> The method for producing a conjugated body according to any one of <44> to <72>, wherein dispersion D further contains a dispersion medium C. <74> The method for producing a conjugated body according to <73>, wherein the dispersion medium C is one or more organic solvents selected from the group consisting of hydrocarbons, alcohols, ethers, and esters. <75> The method for producing a joined body according to <73> or <74>, wherein the content of the dispersion medium C in the dispersion D is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 5% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less.<76> The method for producing a joined body according to any one of <73> to <75>, wherein the mass ratio of the content of dispersion medium C to the content of copper nanoparticles A in dispersion D [dispersion medium C / copper nanoparticles A] is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, and preferably 1.0 or less, more preferably 0.5 or less, even more preferably 0.2 or less. <77> The method for producing a joined body according to <44> or <76>, wherein in dispersion D, the content of copper nanoparticles A is preferably 30% by mass or more and 95% by mass or less, the content of polymer B is preferably 0.1% by mass or more and 10% by mass or less, the content of dispersion medium C is preferably 4% by mass or more and 60% by mass or less, and the content of copper microparticles A' is preferably 0% by mass or more and 65% by mass or less. <78> A method for producing a bonded body according to any one of <44> to <77>, wherein the heating temperature in the firing step is preferably 150°C or higher, more preferably 200°C or higher, even more preferably 240°C or higher, and still more preferably 250°C or higher. <79> A method for producing a bonded body according to any one of <44> to <78>, wherein the pressure applied in the firing step is preferably 2 MPa or higher, more preferably 4 MPa or higher, and preferably 30 MPa or lower, more preferably 20 MPa or lower, and even more preferably 15 MPa or lower. <80> A method for producing a bonded body according to any one of <44> to <79>, wherein the firing time is preferably 150 seconds or longer, more preferably 200 seconds or longer, even more preferably 250 seconds or longer, even more preferably 300 seconds or longer, and preferably 3600 seconds or shorter, more preferably 1800 seconds or shorter, even more preferably 1200 seconds or shorter, and even more preferably 600 seconds or shorter.

[0081] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. In the following production examples, examples, and comparative examples, "parts" and "%" refer to "parts by mass" and "% by mass" unless otherwise specified. Various physical properties were measured or calculated by the following methods.

[0082] [Average particle size of copper nanoparticles A and copper microparticles A'] Scanning electron microscope (SEM) images of copper nanoparticles A and copper microparticles were taken using a scanning electron microscope (Hitachi High-Tech Corporation, field emission scanning electron microscope: S-4800). The magnification was determined according to the particle size of the particles, and images were taken in the range of 5000x to 150000x. The SEM images were analyzed using image analysis software ImageJ (obtained from the United States National Institutes of Health), and the particle sizes of 100 or more particles per sample were determined. The arithmetic average value was used as the average particle size of copper nanoparticles A and copper microparticles A'.

[0083] [Calculation of the mass ratio of the dispersion coated on copper in copper nanoparticles A [polymer B / (copper nanoparticles A)]] Using a differential thermal thermogravimetric simultaneous analyzer (TG / DTA) (Hitachi High-Tech Science Corporation, trade name: STA7200RV), 10 mg of the sample (dried powder of copper microparticles A coated with dispersion D) was weighed into an aluminum pan cell, and heated from 35 ° C. to 550 ° C. at a heating rate of 10 ° C. / min under a nitrogen flow of 50 mL / min, and the mass loss was measured. The mass loss from 35 ° C. to 550 ° C. was the mass of polymer B, and the remaining mass at 550 ° C. was the mass of copper nanoparticles A. The mass ratio of polymer B dispersion D coated on copper in copper nanoparticles A [polymer B / (copper nanoparticles A)] was calculated using the following formula. Mass ratio of polymer B coated on copper nano A = (mass loss from 35 ° C. to 550 ° C.) / (mass loss from 35 ° C. to 550 ° C. + remaining mass at 550 ° C.)

[0084] [Measurement of number average molecular weight Mn of polymer B] This was determined by gel permeation chromatography. The measurement sample was prepared by mixing 0.1 g of polymer with 10 mL of eluent in a glass vial, stirring with a magnetic stirrer at 25°C for 10 hours, and filtering with a syringe filter (DISMIC-13HP PTFE 0.2 μm, manufactured by Advantec Toyo Co., Ltd.). The measurement conditions are shown below. GPC apparatus: "HLC-8320GPC" manufactured by Tosoh Corporation Column: "TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guard column Super AW-H" manufactured by Tosoh Corporation Eluent: N,N-dimethylformamide dissolved with phosphoric acid and lithium bromide to concentrations of 60 mmol / L and 50 mmol / L, respectively Flow rate: 0.5 mL / min Standard substance: monodisperse polystyrene kit manufactured by Tosoh Corporation "PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)"

[0085] [Measurement of Acid Value of Polymer B] The acid value of Polymer B was measured in accordance with JIS K0070:1992 (potentiometric titration method), except that the measurement solvent was changed from the ethanol and ether mixed solvent specified in JIS K0070 to an acetone and toluene mixed solvent (acetone:toluene=4:6 (volume ratio)).

[0086] [Production of Polymer B-1] Production Example 1 20.0 g of ethanol (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) was placed in a 1000 mL four-necked round-bottom flask equipped with a thermometer, two 100 mL nitrogen bypass-equipped dropping funnels, and a reflux apparatus. The internal temperature of the flask was heated to 80°C in an oil bath, and then nitrogen bubbling was performed for 10 minutes. Next, 7.0 g of methacrylic acid (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 93.0 g of methoxypolyethylene glycol (EO 4 mol) methacrylate (NOF Corporation, "PME-200"), 1.0 g of 3-mercaptopropionic acid (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), and 28.7 g of ethanol were dissolved in a polybeaker and placed in the dropping funnel (1). Separately, 51.3 g of ethanol and 1.3 g of 2,2'-azobis(2,4-dimethylvaleronitrile) ("V-65" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., polymerization initiator) were dissolved in a polybeaker and placed in the dropping funnel (2). Next, the mixtures in the dropping funnels (1) and (2) were simultaneously added dropwise to the flask over 90 minutes. Thereafter, the internal temperature of the flask was raised to 90°C, and stirring was continued for another hour to terminate the reaction. The resin solution was freeze-dried using a freeze dryer (manufactured by Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (manufactured by Tokyo Rikakikai Co., Ltd., model: DRC-1000) under drying conditions (freezing at −25°C for 1 hour, vacuum at −10°C for 9 hours, vacuum at 25°C for 5 hours; vacuum degree 5 Pa) to obtain bone-dried polymer B-1 (methacrylic acid / methoxypolyethylene glycol (EO 4 mol) methacrylate polymer, acid value: 46 mg KOH / g, Mn: 12,100).

[0087]

[0088] MAA: methacrylic acid (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) PEG (4) MA: methoxypolyethylene glycol (EO 4 mol) methacrylate ("PME-200" manufactured by NOF Corporation)

[0089] (Synthesis of Copper Nanoparticle A Dry Powder) Synthesis Example 1 (Production of Copper Nanoparticles A-1) In a 2 L beaker, 50.0 g of copper oxide (N-120, manufactured by Nisshin Chemco Co., Ltd.) as a copper raw material compound, 1.20 g of polymer B-1, and 500 g of ethanol (95) (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent) were added and stirred for 15 minutes. During stirring, the temperature of the reaction solution was controlled at 70 ° C. using an oil bath. Next, 63.0 g of hydrazine monohydrate (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) placed in a 50 mL dropping funnel was added dropwise to the mixture at 25 ° C. over 20 minutes. Thereafter, the temperature of the reaction solution was stirred for 1 hour while controlling the temperature at 70 ° C. in an oil bath, and then air-cooled to obtain a reddish-brown dispersion containing copper nanoparticles. 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) in a centrifugal sedimentation tube 500PA bottle, and centrifuged at 3000 rpm with a centrifugal acceleration of 675 G. This state was maintained for 30 minutes. 300 g of ethanol (95) (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent) was added to the precipitate separated by centrifugation and re-dispersed by stirring for 15 minutes. The entire amount of the re-dispersion was centrifuged again under the same conditions, and the precipitate was separated. This operation was performed three times. The purified copper nanoparticle precipitate was freeze-dried using a freeze dryer (Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: DRC-1000) to obtain 36.5 g of copper nanoparticles 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 further drying under reduced pressure at 25 ° C for 5 hours at 5 Pa to obtain a dried powder of copper nanoparticles A-1. The obtained copper nanoparticles A-1 had an average particle size of 185 nm and a polymer B-1 content of 1.0 mass%. The results are shown in Table 2.

[0090]

[0091] Example 1 (Preparation of Copper Particle Dispersion) 4.0 parts by mass of diethylene glycol, 3.0 parts by mass of tetraethylene glycol, 50 parts by mass of dried powder of copper nanoparticles A-1, and 43 parts by mass of MA-C025K (Mitsui Mining & Smelting Co., Ltd., average particle size 2.4 μm) were added to an agate mortar and kneaded until the dried powder was no longer visible to the naked eye. The resulting mixture was transferred to a plastic bottle. The sealed plastic bottle was stirred for 2000 min using a rotation-revolution type stirring device (Thinky Corporation, Planetary Vacuum Mixer ARV-310). －１ The mixture was stirred at 2000 rpm for 5 minutes, and then passed three times through a three-roll mill (Imex Co., Ltd., BV 100) with a gap adjusted to 0.2 mm, to obtain copper particle dispersion 1.

[0092] (Production of Copper Sintered Body) A copper sintered body was produced using the obtained copper particle dispersion 1 according to the following method. First, a stainless steel metal mask (thickness: 50 μm) having a 17 mm × 17 mm square opening was placed on a 30 mm × 30 mm silicon wafer (total thickness: 0.4 mm), and the copper particle dispersion was applied to the silicon wafer by stencil printing using a metal squeegee. The resulting product was then dried at 110 °C for 10 minutes on a Shamal hot plate (manufactured by AS ONE Corporation, model: HHP-441) in the atmosphere. A 15 mm × 15 mm silicon wafer (thickness: 400 μm) was then placed on the coated copper particle dispersion. The product was then fired according to the following method. First, the copper particle dispersion sandwiched between the silicon wafers was placed in a pressure firing machine (manufactured by Meisho Kiko Co., Ltd., model: HTM-1000), and nitrogen was flowed into the furnace at 500 mL / min to replace the air in the furnace with nitrogen. The temperature of the heating heads was then raised to 260°C over 3 minutes while applying a pressure of 10 MPa to the laminate using the upper and lower heating heads, and after the temperature increase, the laminate was sintered by holding the temperature at 260°C for 300 seconds to obtain a copper sintered body. After sintering, the heating heads were water-cooled at -60°C / min, and the copper sintered body sandwiched between the silicon wafers at 100°C or below was taken out into air, and only the copper sintered body was removed from the silicon wafers.

[0093] (Production of Bonded Body) Using the obtained copper particle dispersion 1, a bonded body was produced according to the following method. First, a stainless steel metal mask (thickness: 50 μm) having three rows of 6 mm × 6 mm square openings was placed on a 30 mm × 30 mm copper plate (total thickness: 1 mm), and the copper particle dispersion was applied to the copper plate by stencil printing using a metal squeegee. The resulting material was then dried at 110°C for 10 minutes in air on a Shamal hot plate (manufactured by AS ONE Corporation, model: HHP-441). A 5 mm × 5 mm silicon chip (thickness: 400 μm) was then prepared by sputtering titanium, nickel, and gold in this order onto the silicon chip, and the silicon chip was placed on the coated copper particle dispersion so that the gold was in contact with the copper particle dispersion. This resulted in a laminate comprising a copper plate, a copper particle dispersion, and a silicon chip stacked in this order. The resulting laminate was fired by the following method to obtain a bonded body. First, the laminate was placed in a pressure firing machine (manufactured by Meisho Kiko Co., Ltd., model: HTM-1000), and nitrogen was flowed into the furnace at 500 mL / min to replace the air in the furnace with nitrogen. Then, the temperature of the heating heads was raised to 260°C over 3 minutes while pressurizing the laminate at 10 MPa using the upper and lower heating heads. After the temperature increase, the laminate was sintered by holding at 260°C for 300 seconds to obtain a bonded body. After sintering, the heating heads were water-cooled at a cooling rate of -60°C / min, and the bonded body was taken out into air at 100°C or below.

[0094] Example 2 and Comparative Example 1 The same procedures as in Example 1 were carried out except that the pressure firing conditions shown in Table 3 were changed, to obtain copper sintered bodies and joined bodies of Example 2 and Comparative Example 1, respectively.

[0095]

[0096] The copper sintered bodies and joined bodies obtained in Examples 1 and 2 and Comparative Example 1 were evaluated as follows.

[0097] <Evaluation> [Measurement of Tensile Modulus and Tensile Strength of Copper Sintered Body] The tensile modulus and tensile strength of the copper sintered body were measured according to the following procedure. The thickness of the copper sintered body was measured using a digital micrometer. The copper sintered body was cut at a width of 1 mm in the center to obtain a 15 mm x 1 mm copper sintered body. The copper sintered body was placed in a tensile fixture with a gauge length of 5 mm in a thermomechanical analyzer (Hitachi High-Tech Science Corporation, Model: TMA7100), and the thickness of the copper sintered body was then entered into the program. A heating and cooling furnace was set up to enclose the copper sintered body, and a tensile test was performed at 25°C and a tensile rate of 1 N / min up to the tensile test limit of the thermomechanical analyzer, 6.82 N. The obtained results were converted into stress-strain curves using the software accompanying the thermomechanical analyzer. The tensile modulus of the copper sintered body was calculated using an approximate equation based on the slope of the strain range of 0.25% to 0.50%. The tensile strength (MPa) was defined as the maximum stress value of the stress-strain curve.

[0098] [Porosity of Copper Sintered Body] The copper sintered body was subjected to cross-sectional milling using a cooled cross-section polisher (manufactured by JEOL Ltd., model: IB-19520CCP). The cross-section of the copper sintered body obtained by cross-sectional milling was observed with a scanning electron microscope (manufactured by Hitachi High-Tech Corporation, model: S-4800), and SEM images were taken. The images were taken at a magnification of 5000x. Using image analysis software ImageJ (obtained from the National Institutes of Health, USA), the SEM image was converted into a binary image that expresses shading in two tones of black and white by binarization, and the porosity was calculated using the following formula: Porosity (%) = Area of ​​pores (number of black pixels) / Total area of ​​copper sintered body {Area of ​​copper sintered body (number of white pixels) + Area of ​​pores (number of black pixels)} × 100

[0099] [Debonding Rate and Chip Cracks after Temperature Cycles] A bonded body was prepared using copper particle dispersion 1 in the same manner as described above. The bonded body was placed in a small thermal shock chamber (Espec Corporation, Model: TSE-12-A) and subjected to 4,000 cycles of temperature cycles at -55°C and 200°C in air for 15 minutes each. After that, cracks in the three silicon chips were visually confirmed, and if even one was cracked, it was judged to be cracked. Next, the bonded interface was observed from the copper substrate side of the bonded body using an ultrasonic flaw detector (Hitachi Power Solutions Co., Ltd., Model: FS100III) equipped with a 50 MHz frequency probe. Fine adjustment was made to the point where the reflection peak at the bonded interface was highest, and measurements were made with a material sound velocity of Cu of 4,700 mm / s and a gain of 28 dB. The reflection intensity threshold was set to 60%, and anything above that was considered debonding. The debonding area obtained by binarization using the threshold was calculated using software to determine the debonding rate.

[0100] The results of the copper sintered bodies and joined bodies obtained in Examples 1 and 2 and Comparative Example 1 are shown in Table 4.

[0101]

[0102] From Table 4, it can be seen that the copper sintered bodies of Examples 1 and 2 had a lower elastic modulus than the copper sintered body of Comparative Example 1, and therefore no chip cracking occurred after the temperature cycles, and the peeling rate of the bond after the temperature cycles was also low.

Claims

1. A copper sintered body having a tensile modulus of elasticity of 35 GPa or less.

2. The copper sintered body according to claim 1, having a porosity of 1% or more and 25% or less.

3. The copper sintered body according to claim 1, having a tensile strength of 100 MPa or more.

4. A method for producing a copper sintered body, comprising the following step 1: baking a dispersion D containing copper nanoparticles A and the following polymer B at a baking temperature of 240°C or higher and 300°C or lower while applying a pressure of 0.1 MPa or higher and 40 MPa or lower: Polymer B: a polymer containing a constituent unit derived from a monomer (b-1) having a carboxy group and a constituent unit derived from a monomer (b-2) having a polyalkylene glycol segment.

5. The method for producing a copper sintered body according to claim 4, further comprising the following step 0 before step 1: Step 0: applying the dispersion D to a member.

6. A method for producing a copper sintered body according to claim 5, wherein step 0 is a step of applying the dispersion D between a first member and a second member so that the dispersion D is interposed between the first member and the second member.

7. The method for producing a copper sintered body according to claim 4, wherein the dispersion D further contains copper microparticles A'.

8. A method for producing a copper sintered body as described in claim 4, wherein the content of the copper nanoparticles A in the dispersion D is 20% by mass or more and 95% by mass or less.

9. The method for producing a copper sintered body according to claim 4, wherein the mass ratio of the content of polymer B to the total content of copper nanoparticles A and polymer B in dispersion D [polymer B / (copper nanoparticles A + polymer B)] is 0.0055 or more and 0.025 or less.

10. A method for producing a copper sintered body according to claim 4, wherein the dispersion D further contains a dispersion medium C, and the content of the dispersion medium C in the dispersion D is 1% by mass or more and 20% by mass or less.

11. A method for producing a copper sintered body as described in claim 10, wherein the mass ratio of the content of dispersion medium C to the content of copper nanoparticles A in dispersion D [dispersion medium C / copper nanoparticles A] is 0.01 or more and 0.05 or less.

12. The method for producing a copper sintered body according to claim 4, wherein the firing time is from 150 seconds to 3,600 seconds.

13. A copper sintered body obtained by the manufacturing method described in any one of claims 4 to 12.

14. A joined body comprising a first member, a second member, and the copper sintered body according to claim 1 or 13, which joins the first member and the second member.

15. A method for producing a bonded body including a first member, a second member, and a copper sintered body bonding the first member and the second member, the method comprising the following steps 0-1 and 1: Step 0-1: applying a dispersion D containing copper nanoparticles A and a polymer B described below between the first member and the second member, and Step 1: firing the dispersion D at a firing temperature of 240°C or higher and 300°C or lower while applying a pressure of 0.1 MPa or higher and 40 MPa or lower.

16. The method for producing a joint body according to claim 15, wherein the dispersion D further contains copper microparticles A'.

17. The method for producing a bonded body according to claim 15, wherein the content of the copper nanoparticles A in the dispersion D is 20% by mass or more and 95% by mass or less.

18. The method for producing a joined body according to claim 15, wherein the mass ratio of the content of polymer B to the total content of copper nanoparticles A and polymer B in dispersion D [polymer B / (copper nanoparticles A + polymer B)] is 0.0055 or more and 0.025 or less.

19. The method for producing a bonded body according to claim 15, wherein the dispersion D further contains a dispersion medium C, and the content of the dispersion medium C in the dispersion D is 1% by mass or more and 20% by mass or less.

20. The method for producing a bonded body according to claim 15, wherein the bonded body is a semiconductor device, the first member is a semiconductor chip selected from the group consisting of a silicon semiconductor chip, a silicon carbide semiconductor chip, a gallium nitride semiconductor chip, a gallium oxide semiconductor chip, and a diamond semiconductor chip, and the second member is a copper substrate.

21. The method for producing a joined body according to claim 16, wherein the mass ratio of the content of copper nanoparticles A to the total content of copper nanoparticles A and copper microparticles A' in dispersion D [copper nanoparticles A / (copper nanoparticles A + copper microparticles A')] is 0.3 or more and 1.0 or less.

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