Composite microparticles

Abstract

This invention relates to composite microparticles that enable the preparation of low-viscosity dispersions and achieve excellent bonding strength, and to composite microparticle dispersions containing the composite microparticles. [Solution] [1] Composite fine particles in which at least a portion of the surface of copper fine particles is coated with a coating agent, wherein the coating agent is a composite fine particle represented by the following general formula (1), and [2] A composite fine particle dispersion containing the composite fine particles described in [1]. However, in the following general formula (1), n ​​is a number between 31 and 200, and R 1 It is a structure containing a carboxyl group, R 2 This is a hydrocarbon group in which hydrogen may be substituted with a functional group. [Formula 1] JPEG2026092681000013.jpg21114

Description

[Technical Field]

[0001] The present invention relates to composite microparticles, composite microparticle dispersions containing said composite microparticles, and the like. [Background technology]

[0002] Because copper has excellent electrical and thermal conductivity, it is widely used as a material for conductive wiring, heat transfer, heat exchange, and heat dissipation, as well as a joining material for joining objects. When used as a conductive wiring material, a copper nanoparticle dispersion, in which copper nanoparticles are dispersed, is applied to the object in any shape using various coating methods and then fired to form a conductive wiring pattern. When used as a joining material, various techniques have been proposed in which a copper nanoparticle dispersion, in which copper nanoparticles are dispersed, is applied to the object using various coating methods and then fired to join the objects.

[0003] For example, Patent Document 1 discloses metal nanoparticles having the property of dispersing in a polar solvent, aggregates thereof, a dispersant for dispersing metal nanoparticles in a polar solvent, a dispersion of the metal nanoparticles, and a component formed using the same. The invention relates to metal nanoparticles having the property of dispersing in a polar solvent and having a protective agent on their surface, which is composed of an organic compound having polyalkylene oxide groups and carboxyl groups. Furthermore, Patent Document 2 discloses copper powder having an organic film that prevents the formation of an oxide film that can inhibit sintering, and exhibiting excellent low-temperature sinterability, wherein the copper powder has an average particle size of 250 nm or less, and its surface is coated with an organic substance, and satisfies all of the specific conditions (1) to (4). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-68988 [Patent Document 2] International Publication No. 2023 / 163083 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, when the metal nanoparticles described in Patent Document 1 and the copper powder described in Patent Document 2 are dispersed in a dispersion medium to form a dispersion, the viscosity of the dispersion tends to increase, posing a problem with the coating properties of the dispersion. Furthermore, when the dispersion is fired after coating, the coating agent on the particle surface is not sufficiently removed, resulting in a tendency for the bonding strength of the sintered body obtained by firing the dispersion to be bonded to the member to be bonded to be low. The present invention relates to composite microparticles that enable the preparation of low viscosity dispersions and the realization of excellent bonding strength, a method for producing the composite microparticles, a composite microparticle dispersion containing the composite microparticles, a bonded body containing a sintered body of the composite microparticle dispersion as a copper bonding layer, a method for producing the bonded body, and the use of the composite microparticle dispersion as a bonding material. [Means for solving the problem]

[0006] The present inventors have found that composite fine particles comprising copper fine particles and a coating agent having a specific structure that covers at least a portion of the surface of the copper fine particles can solve the above problem. The present invention relates to the following [1] to [5]. [1] Composite microparticles in which at least a portion of the surface of copper microparticles is coated with a coating agent, The coating agent is a composite fine particle represented by the following general formula (1). [ka] In the above general formula (1), n ​​is a number between 31 and 200, and R 1 It is a structure containing a carboxyl group, R 2 This is a hydrocarbon group in which hydrogen may be substituted with a functional group. [2] A composite particle dispersion containing the composite particle described in [1] above. [3] A method for producing composite fine particles comprising copper fine particles and a coating agent that covers at least a portion of the surface thereof, Heating a mixed solution containing a copper raw material compound, a coating agent, and a solvent until it reaches a predetermined temperature, including dropping a reducing agent into the heated mixed solution, A method for producing composite fine particles, wherein the coating agent is a polymer represented by the following general formula (1). [Chemical formula] In the above general formula (1), n is a number of 31 or more and 200 or less, and R 1 is a structure containing a carboxy group, and R 2 is a hydrocarbon group in which hydrogen may be substituted with a functional group. [4] A method for producing a joined body, which comprises performing the following steps 1 to 3 in this order. Step 1: A step of coating the composite fine particle dispersion described in [2] on a metal substrate. Step 2: A step of pre-baking the metal substrate obtained in Step 1 and coated with the composite fine particle dispersion under conditions of a temperature of 100°C or higher and 150°C or lower. Step 3: A step of placing a joining member on the composite fine particle dispersion on the metal substrate pre-baked in Step 2 and performing pressure baking under conditions of a temperature of 150°C or higher and 300°C or lower and a pressure of 5 MPa or higher and 50 MPa or lower. [5] Use of the composite fine particle dispersion described in [2] as a joining material for joining joining materials to each other. [Advantages of the Invention]

[0007] According to the present invention, it is possible to provide composite fine particles, a composite fine particle dispersion containing the composite fine particles, a joined body containing a sintered body of the composite fine particle dispersion as a copper joining layer, a method for producing the joined body, and a method for using the composite fine particle dispersion as a joining material, which enable the preparation of a dispersion having a low viscosity and also enable the realization of excellent joining strength. [Embodiments for Carrying Out the Invention]

[0008] [Composite Fine Particles] The composite microparticles of the present invention are composite microparticles containing copper microparticles and a coating agent that coats at least a part of the surface thereof, and the coating agent is a polymer represented by the following general formula (1). The copper microparticles are granular copper components derived from a copper raw material compound used in the method for producing composite microparticles, which will be described in detail later, and are produced by reducing the copper raw material compound.

[0009] [Chemical formula]

[0010] In the general formula (1), n is a number of 31 or more and 200 or less, and R 1 is a structure containing a carboxy group, and R 2 is a hydrocarbon group in which hydrogen may be substituted with a functional group. Examples of the functional group include a carboxy group, a hydroxy group, an ester group, and the like.

[0011] Since the composite microparticles of the present invention have the above characteristics, it is possible to prepare a composite microparticle dispersion having a low viscosity, and it is also possible to achieve excellent bonding strength. Although the reason is not clear, it is considered as follows. In the composite microparticles of the present invention, in the coating agent represented by the general formula (1), when n is 31 or more, aggregation of the composite microparticles can be suppressed, the dispersibility can be improved, and when dispersed in a dispersion medium to form a composite microparticle dispersion, the viscosity can be lowered. On the other hand, when n is 200 or less, the composite microparticles can approach each other appropriately during firing, so that firing can be performed efficiently, and the bonding strength of the copper bonding layer (sintered body) obtained by firing the composite microparticle dispersion is excellent. Also, in the composite microparticles of the present invention, in the coating agent represented by the general formula (1), R 1 is a structure containing a carboxy group, and R 2 is a hydrocarbon group in which hydrogen may be substituted with a functional group, so that at least R 1 acts as an adsorption point of the coating agent. That is, in the present invention, the coating agent is its R 1 portion, or R 1and R 2 The coating agent partially adsorbs onto the copper nanoparticles, while its main chain portion does not adsorb onto the copper nanoparticles, and exists on the copper nanoparticles. Therefore, the main chain portion of the coating agent can spread out from the surface of the copper nanoparticles. As a result, the dispersibility of the composite nanoparticles of the present invention is improved due to the spread of the main chain portion of the coating agent, and the viscosity of the composite nanoparticle dispersion when dispersed in a dispersion medium is reduced. On the other hand, the adsorption point of the coating agent is R 1 Part, or R 1 and R 2 Because the coating is only applied to a portion of the surface, it can be quickly removed from the surface of the copper nanoparticles in a high-temperature environment. Therefore, during firing, the coating does not hinder the approach of the copper nanoparticles to each other, allowing for efficient firing and improving the bonding strength of the copper bonding layer (sintered body) obtained by firing the composite nanoparticle dispersion.

[0012] In the composite fine particles of the present invention, the median diameter (D50) of the composite fine particles is preferably 50 nm or more, more preferably 80 nm or more, even more preferably 100 nm or more, and even more preferably 120 nm or more, from the viewpoint of stability (oxidation resistance) of the composite fine particle dispersion, and from the viewpoint of improving the bonding strength when the composite fine particle dispersion containing the composite fine particles is used as a bonding material to bond members to be bonded, the median diameter (D50) is preferably 280 nm or less, more preferably 250 nm or less, even more preferably 230 nm or less, and even more preferably 210 nm or less. The median diameter (D50) of composite microparticles is the particle diameter at which the cumulative frequency is 50%, determined from the particle size histogram based on the number of particles, and is measured by the method described in the examples. The median diameter (D50) of the composite microparticles can be adjusted by the manufacturing conditions of the composite microparticles, such as the copper raw material compound, the type and amount of reducing agent, the type and amount of coating agent, the type and amount of solvent used during manufacturing, and the temperature and time of the reduction reaction (the duration for which the temperature of the reduction reaction is maintained), as described later.

[0013] In the composite fine particles of the present invention, the content of copper fine particles in the composite fine particles is preferably 97.0% by mass or more, more preferably 97.5% by mass or more, even more preferably 98.0% by mass or more, and even more preferably 98.5% by mass or more, and preferably 99.7% by mass or less, more preferably 99.5% by mass or less, even more preferably 99.3% by mass or less, and even more preferably 99.0% by mass or less, from the viewpoint of improving bonding strength.

[0014] <Coating agent> In the composite microparticles of the present invention, the coating agent represented by the above general formula (1) coats at least a portion of the surface of the copper microparticles. Because the coating agent coats at least a portion of the surface of the copper microparticles, the composite microparticles of the present invention exhibit excellent dispersibility. Therefore, when the composite microparticles of the present invention are dispersed in a dispersion medium to form a composite microparticle dispersion, the viscosity of the dispersion can be reduced. Furthermore, since the coating agent is rapidly detached from the copper microparticles during firing of the composite microparticle dispersion, the bonding strength is excellent when the composite microparticle dispersion is used as a bonding material to join members to be joined.

[0015] In the composite fine particles of the present invention, n in the above general formula (1) in the coating agent is 31 or more, preferably 40 or more, more preferably 50 or more, even more preferably 60 or more, and even more preferably 80 or more, and from the viewpoint of obtaining a composite fine particle dispersion, reducing the viscosity of the composite fine particle dispersion, and improving bonding strength, and from the viewpoint of obtaining a composite fine particle dispersion, it is 200 or less, preferably 180 or less, more preferably 150 or less, even more preferably 120 or less, and even more preferably 100 or less.

[0016] In the composite fine particles of the present invention, the R in the coating agent of the above general formula (1) 1 It is preferable that R is one of the following general formulas (a-1) to (a-5). 1 The R is one of the following general formulas (a-1) to (a-5), 1Since it acts as an adsorption site, the coating agent can be efficiently adsorbed onto the surface of the copper nanoparticles, improving the dispersibility of the copper nanoparticles and lowering the viscosity of the composite nanoparticle dispersion. On the other hand, during firing, when the coating agent decomposes due to high temperature, R 1 Because the coating material easily detaches from the surface of the copper nanoparticles, the coating material is efficiently removed from the surface of the copper nanoparticles. As a result, the proximity of the copper nanoparticles during firing is not hindered, allowing for more efficient firing and further improving the bonding strength.

[0017] [ka]

[0018] In general formulas (a-1) to (a-5), * represents R in general formula (1). 1 The bonding sites are shown. In general formulas (a-2) to (a-5), X is either NH or O. Also, in general formula (a-5), R 3 It is either H or COOH.

[0019] In the above general formula (1), R 1 From the viewpoint of ease of manufacturing the coating agent, it is preferable that the coating agent has constituent units derived from acid anhydrides. Furthermore, by having constituent units derived from acid anhydrides, these constituent units act as adsorption sites, and the increase in adsorption sites allows the coating agent to be efficiently adsorbed onto the surface of the copper fine particles, thereby improving the dispersibility of the composite fine particles and lowering the viscosity of the composite fine particle dispersion. On the other hand, when the coating agent decomposes at high temperatures, the constituent units derived from acid anhydrides are detached from the structure of the coating agent as acid anhydride molecules, so the coating agent is efficiently removed from the surface of the copper fine particles during firing. As a result, the proximity of copper fine particles during firing is not hindered, firing can be performed more efficiently, and the bonding strength can be improved. R 1The acid anhydrides that provide the constituent units derived from acid anhydrides are preferably one or more selected from maleic anhydride, succinic anhydride, trimellitic anhydride, pyromellitic anhydride, phthalic anhydride, citraconic anhydride, cis-1,2-cyclohexanedicarboxylic anhydride, cis-4-cyclohexene-1,2-dicarboxylic anhydride, itaconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride; more preferably one or more selected from maleic anhydride, succinic anhydride, trimellitic anhydride, and pyromellitic anhydride; even more preferably one or more selected from maleic anhydride and succinic anhydride; and even more preferably maleic anhydride. Furthermore, in general formulas (a-2) to (a-5), X is preferably O from the viewpoint of ease of manufacture of the coating agent.

[0020] In the above general formula (1), R 1 When X in the above general formulas (a-2) to (a-5) is O, when the coating agent decomposes at high temperatures, the constituent units derived from the acid anhydride detach from the structure of the coating agent as acid anhydride molecules. As a result, the coating agent is efficiently removed from the surface of the copper nanoparticles during firing, which does not hinder the approach of the copper nanoparticles during firing, allowing for more efficient firing and further improving bonding strength. Also, R 1 If X in the above general formulas (a-2) to (a-5) is NH, then when placed in a high-temperature environment, R 1 Since the carboxyl group and the NH group react intramolecularly to form an imid, the adsorption site is eliminated. As a result, the coating agent is efficiently removed from the surface of the copper nanoparticles during firing. Consequently, the proximity of the copper nanoparticles during firing is not hindered, allowing for more efficient firing and improved bonding strength.

[0021] In the composite fine particles of the present invention, the R in the coating agent of the above general formula (1) 1From the viewpoint of reducing the viscosity of the composite fine particle dispersion and improving the bonding strength, is preferably any of the above general formulas (a-2) to (a-5), more preferably any of the above general formulas (a-2) to (a-5) in which X is O, even more preferably any of the above general formulas (a-3) to (a-5) in which X is O, even more preferably any of the above general formulas (a-3) to (a-5) in which X is O, even more preferably any of the above general formulas (a-3) and (a-4) in which X is O, and even more preferably general formula (a-3) in which X is O.

[0022] In the composite fine particles of the present invention, the R in the coating agent of the above general formula (1) 2 From the viewpoint of reducing the viscosity of the composite fine particle dispersion and improving bonding strength, it is preferable that it be one of the following general formulas (b-1) to (b-7).

[0023] [ka]

[0024] In general formulas (b-1) to (b-7), * represents R in general formula (1). 2 The joining points are shown. In general formula (b-3), n is a number between 12 and 22. In general formulas (b-4) to (b-7), X is either NH or O. Also, in general formula (b-7), R 3 It is either H or COOH.

[0025] In coating agents, R in the above general formula (1) 2 From the viewpoint of further improving adsorption to the surface of copper fine particles and improving the dispersibility of composite fine particles, it is preferable that the compound is one of the above general formulas (b-1) and (b-4) to (b-7). Furthermore, in the coating agent, R in the above general formula (1) 2 The adsorption point is R 1In order to increase the main chain's spread and improve the dispersibility of the composite fine particles, and to more efficiently remove the coating agent from the surface of the copper fine particles during firing, it is preferable to use one of the above general formulas (b-2) and (b-3), and more preferably the above general formula (b-2). In coating agents, R in the above general formula (1) 2 When the above general formula (b-3) is used, then in the above general formula (b-3), n is preferably 12 or more, more preferably 16 or more, and preferably 22 or less, more preferably 18 or less, from the viewpoint of the dispersibility of composite fine particles.

[0026] In the composite fine particles of the present invention, the content of the coating agent in the composite fine particles is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, even more preferably 1.0% by mass or more, and preferably 3.0% by mass or less, more preferably 2.5% by mass or less, even more preferably 2.0% by mass or less, and even more preferably 1.5% by mass or less, from the viewpoint of reducing the viscosity of the composite fine particle dispersion and improving bonding strength.

[0027] In the composite fine particles of the present invention, the mass ratio of the coating agent to the copper fine particles (coating agent / copper fine particles) is preferably 0.003 or higher, more preferably 0.005 or higher, even more preferably 0.007 or higher, even more preferably 0.010 or higher, and preferably 0.031 or lower, more preferably 0.026 or lower, even more preferably 0.020 or lower, and even more preferably 0.015 or lower, from the viewpoint of reducing the viscosity of the composite fine particle dispersion and improving the bonding strength of the sintered composite fine particle body.

[0028] (Method for manufacturing composite microparticles) Composite fine particles can be obtained by mixing and heating a copper raw material compound, a reducing agent, and a coating agent. In this mixture, the copper raw material compound is reduced by the reducing agent, and the mixture becomes a dispersion of composite fine particles containing copper fine particles and a coating agent that covers at least a portion of the surface of the copper fine particles. This dispersion is then dried. In the method for producing composite fine particles, in addition to the copper raw material compound, reducing agent, and coating agent, a solvent for dispersing the copper raw material compound and reducing agent, a complexing agent, etc., may be mixed as needed. In a method for producing composite fine particles, the reducing agent may be added simultaneously with the other raw materials, or it may be added dropwise to the mixed liquid containing the other raw materials afterwards. One method for drying the dispersion is freeze-drying. Furthermore, in one embodiment, the method for producing composite fine particles of the present invention is a method for producing composite fine particles that includes copper fine particles and a coating agent that coats at least a part of the surface thereof. Heat the mixture containing the copper raw material compound, coating agent, and solvent until it reaches a predetermined temperature. The process includes adding a reducing agent dropwise to the heated mixture. The coating agent is a polymer represented by the following general formula (1). [ka] In the above general formula (1), n ​​is a number between 31 and 200, and R 1 It is a structure containing a carboxyl group, R 2 This is a hydrocarbon group in which hydrogen may be substituted with a functional group. The preferred coating agents are as described above.

[0029] There are no particular restrictions on the copper raw material compound, as long as it contains copper. Examples of copper raw material compounds include copper sulfate, copper nitrate, cupric oxide, cuprous oxide, copper formate, copper acetate, and copper oxalate. Among these, copper oxide is preferred as the copper raw material compound from the viewpoint of manufacturing efficiency, and cupric oxide is more preferred. The copper raw material compound may be used individually or as a mixture of two or more types.

[0030] There are no particular restrictions on the reducing agent, as long as it is a compound that can reduce copper raw material compounds. Examples of reducing agents include hydrazine compounds, boron compounds, and inorganic salts. Examples of hydrazine compounds include hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine monohydrate. Examples of boron compounds include sodium borohydride. Examples of inorganic acids or their salts include sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, and sodium hypophosphite. Among these, from the viewpoint of productivity, the reducing agent is preferably a hydrazine-based compound, more preferably at least one selected from hydrazine and hydrated hydrazine (hydrazine monohydrate), and even more preferably hydrated hydrazine (hydrazine monohydrate). The reducing agent may be used individually or in combination of two or more types.

[0031] Examples of solvents for dispersing the copper raw material compound and reducing agent include water, methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol. Among these, ethanol is preferred as the solvent from the viewpoint of availability and cost-effectiveness. The solvent may be used individually or in combination of two or more types.

[0032] The temperature of the reduction reaction is the predetermined temperature mentioned above, preferably 5°C or higher, more preferably 10°C or higher, even more preferably 30°C or higher, and even more preferably 50°C or higher, from the viewpoint of making the median diameter (D50) of the composite fine particles uniform. Furthermore, from the viewpoint of stably producing composite fine particles, it is preferable to carry out the reaction in the range of 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 in an inert gas atmosphere such as nitrogen gas. Here, the temperature of the reduction reaction is the temperature required to reduce the copper raw material compound in a mixture of the copper raw material compound, reducing agent, coating agent, and solvent. More specifically, it is the reaction temperature of the reaction solution containing the mixture of the copper raw material compound, coating agent, and solvent, and the reducing agent added dropwise to the mixture. From the viewpoint of ensuring a uniform particle size distribution, the maintenance time for the temperature of the reduction reaction is preferably 1 minute or more, more preferably 30 minutes or more, and even more preferably 1 hour or more. From the viewpoint of productivity, it is preferably 30 hours or less, more preferably 20 hours or less, and even more preferably 10 hours or less.

[0033] In the production of composite microparticles, from the viewpoint of removing impurities such as unreacted reducing agents, the dispersion of composite microparticles may be purified after obtaining it, before drying or other processes. There are no particular limitations on the method for purifying a dispersion of composite microparticles, and examples include membrane treatment such as dialysis and ultrafiltration; and centrifugal separation. Among these, centrifugal separation is preferred from the viewpoint of efficiently removing impurities.

[0034] <Applications of composite microparticles> Because the composite microparticle dispersion containing the composite microparticles of the present invention has low viscosity and excellent bonding strength, the composite microparticles of the present invention can be used to form conductive members of various electronic and electrical devices. Examples of such conductive members include those conventionally formed using conductive bonding agents such as solder. Furthermore, the composite microparticles of the present invention are preferably used to form conductive members that constitute antennas such as RFID (radio frequency identifier) ​​tags; capacitors such as MLCCs (multilayer ceramic capacitors); electronic paper; image display devices such as liquid crystal displays and organic EL displays; organic EL elements; organic transistors; wiring boards such as printed circuit boards and flexible circuit boards; organic solar cells; sensors such as flexible sensors, etc.

[0035] [Composite fine particle dispersion] The composite microparticle dispersion of the present invention contains the composite microparticles of the present invention described above. The composite microparticle dispersion of the present invention is prepared using the composite microparticles of the present invention described above. Because the composite microparticle dispersion of the present invention contains the above-mentioned composite microparticles, it has low viscosity and excellent bonding strength.

[0036] The composite microparticle dispersion of the present invention preferably contains a dispersion medium, which is a solvent for dispersing the composite microparticles. That is, the composite microparticle dispersion of the present invention preferably contains the composite microparticles of the present invention and the dispersion medium described above. The dispersion medium preferably includes at least one selected from aliphatic monohydric alcohols, (poly)alkylene glycols, (poly)alkylene glycol derivatives, glycerin, and glycerin derivatives, from the viewpoint of reducing the viscosity of the composite fine particle dispersion and improving bonding strength.

[0037] Examples of aliphatic monohydric alcohols include allyl alcohol, n-heptanol, n-octanol, 2-ethylhexanol, n-nonanol, and terpene alcohols. Examples of preferred terpene alcohols include monoterpene alcohols such as α-terpineol, linalool, geraniol, and citronellol.

[0038] In this specification, "(poly)alkylene glycol" means at least one selected from alkylene glycols and polyalkylene glycols. Examples of alkylene glycols include ethylene glycol, propylene glycol, and butylene glycol (1,3-butanediol). Examples of polyalkylene glycols include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, and polytetramethylene glycol. The number-average molecular weight of polyethylene glycol is preferably 70 to 1000, more preferably 80 to 500, and even more preferably 90 to 200, from the viewpoint of reducing the viscosity of the composite fine particle dispersion and improving bonding strength. The number-average molecular weight of polypropylene glycol is preferably 100 to 1000, more preferably 110 to 600, and even more preferably 120 to 500, from the viewpoint of reducing the viscosity of the composite fine particle dispersion and improving bonding strength. Among these, from the viewpoint of reducing the viscosity of the composite fine particle dispersion and improving bonding strength, it is preferably at least one selected from diethylene glycol and dipropylene glycol.

[0039] Examples of (poly)alkylene glycol derivatives include compounds in which the terminal hydroxyl groups of the (poly)alkylene glycol are etherified or esterified. Specifically, one or more compounds selected from the group consisting of (poly)alkylene glycol alkyl ethers and (poly)alkylene glycol monoalkyl ether acetates are included.

[0040] In this specification, "(poly)alkylene glycol alkyl ether" means at least one selected from alkylene glycol alkyl ethers and polyalkylene glycol alkyl ethers. Examples of alkylene glycol alkyl ethers include ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monobutyl ether. Examples of polyalkylene glycol alkyl ethers include diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether.

[0041] In this specification, "(poly)alkylene glycol monoalkyl ether acetate" means at least one selected from alkylene glycol monoalkyl ether acetate and polyalkylene glycol monoalkyl ether acetate. Examples of alkylene glycol monoalkyl ether acetates include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate. Examples of polyalkylene glycol monoalkyl ether acetates include diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

[0042] There are no particular restrictions on glycerin derivatives as long as they are solvents containing a structure derived from glycerin. Examples include glycerin ether derivatives, glycerin ester derivatives, polyglycerins, and glycerin alkylene oxide adducts (e.g., ethylene oxide adducts and propylene oxide adducts). Preferred polyglycerins include, for example, diglycerin and triglycerin. Commercially available polyglycerins include, for example, polyglycerin #310, polyglycerin #500, and polyglycerin #750 manufactured by Sakamoto Pharmaceutical Co., Ltd. A preferred ether derivative of glycerin is, for example, 3-(2-ethylhexyloxy)-1,2-propanediol. As an ester derivative of glycerin, glyceryl tributyrate (tributyline) is a preferred example.

[0043] The dispersion medium preferably contains (poly)alkylene glycol, and more preferably contains at least one selected from diethylene glycol and dipropylene glycol, from the viewpoint of reducing the viscosity of the composite fine particle dispersion and improving the bonding strength.

[0044] The composite microparticle dispersion of the present invention may further contain copper microparticles in addition to the composite microparticles of the present invention, from the viewpoint of stability (oxidation resistance) of the composite microparticle dispersion and improvement of bonding strength. The median diameter (D50) of the copper microparticles 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 stability (oxidation resistance) of the composite microparticle dispersion, and preferably 6.0 μm or less, more preferably 5.0 μm or less, even more preferably 4.5 μm or less, and even more preferably 4.0 μm or less, from the viewpoint of improving bonding strength. The median diameter (D50) of copper microparticles is the particle diameter at which the cumulative frequency is 50%, determined from a particle size histogram based on the number of particles, and is measured by the method described in the examples.

[0045] From the viewpoint of improving bonding strength, the copper content in the copper microparticles is preferably 97.0% by mass or more, more preferably 98.0% by mass or more, even more preferably 99.0% by mass or more, even more preferably substantially 100% by mass, and even more preferably 100% by mass. Here, "effectively 100% by mass" means that it may include components that are present unintentionally. Examples of unintentionally present components include unavoidable impurities.

[0046] In the composite microparticle dispersion of the present invention, when copper microparticles are not contained, the content of the dispersion medium in the composite microparticle dispersion is preferably 2% by mass or more, more preferably 3% by mass or more, even more preferably 4% by mass or more, and even more preferably 5% by mass or more, from the viewpoint of reducing the viscosity of the composite microparticle dispersion, and preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, and even more preferably 45% by mass or less, from the viewpoint of improving bonding strength. Furthermore, in the composite microparticle dispersion of the present invention, if copper microparticles are included, the content of the dispersion medium in the composite microparticle dispersion is preferably 2% by mass or more, more preferably 3% by mass or more, even more preferably 4% by mass or more, and even more preferably 5% by mass or more, from the viewpoint of reducing the viscosity of the composite microparticle dispersion, and preferably 20% by mass or less, more preferably 18% by mass or less, even more preferably 15% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of improving bonding strength.

[0047] In the composite microparticle dispersion of the present invention, when copper microparticles are not contained, the content of composite microparticles in the composite microparticle dispersion is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and even more preferably 55% by mass or more, from the viewpoint of improving bonding strength, and from the viewpoint of reducing the viscosity of the composite microparticle dispersion, it is preferably 98% by mass or less, more preferably 97% by mass or less, even more preferably 96% by mass or less, and even more preferably 95% by mass or less. Furthermore, in the composite microparticle dispersion of the present invention, if copper microparticles are included, the content of composite microparticles in the composite microparticle dispersion is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and even more preferably 55% by mass or more, from the viewpoint of improving bonding strength, and preferably 75% by mass or less, more preferably 72% by mass or less, even more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less, from the viewpoint of reducing the viscosity of the composite microparticle dispersion.

[0048] In the composite microparticle dispersion of the present invention, if copper microparticles are included, the content of copper microparticles in the composite microparticle dispersion is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 25% by mass or more, from the viewpoint of improving bonding strength, and preferably 58% by mass or less, more preferably 52% by mass or less, even more preferably 46% by mass or less, and even more preferably 40% by mass or less, from the viewpoint of reducing the viscosity of the composite microparticle dispersion.

[0049] In the composite microparticle dispersion of the present invention, if copper microparticles are included, the total content of composite microparticles and copper microparticles in the composite microparticle dispersion is preferably 80% by mass or more, more preferably 82% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of improving bonding strength, and preferably 98% by mass or less, more preferably 97% by mass or less, even more preferably 96% by mass or less, and even more preferably 95% by mass or less, from the viewpoint of reducing the viscosity of the composite microparticle dispersion.

[0050] The composite microparticle dispersion of the present invention may contain various additives as components other than those mentioned above, to the extent that they do not impair the effects of the present invention. Examples of such additives include metal particles other than the composite microparticles and copper microparticles of the present invention, sintering accelerators such as glass frit, antioxidants, viscosity modifiers, pH adjusters, buffers, defoamers, leveling agents, volatilization inhibitors, and the like. Examples of metal particles in composite fine particles and copper microparticles include zinc, nickel, silver, gold, palladium, and platinum. The additive content in the composite fine particle dispersion is preferably 1% by mass or less.

[0051] (Manufacturing of composite microparticle dispersions) The composite microparticle dispersion of the present invention is obtained by mixing the composite microparticles and dispersion medium of the present invention described above, and optionally copper microparticles and various additives. The present invention provides a method for producing a composite microparticle dispersion, preferably by adding and mixing composite microparticles, a dispersion medium, and, if necessary, copper microparticles and various additives, from the viewpoint of reducing the viscosity of the composite microparticle dispersion and improving the bonding strength. As for the mixing method, known methods can be used, and from the viewpoint of further dispersing the composite fine particles in the dispersion medium, it is preferable to pre-mix the composite fine particles and the dispersion medium using an agate mortar or the like, and then further mix the resulting mixture using a stirring device such as a rotational stirring device.

[0052] <Applications of composite particulate dispersions> The composite microparticle dispersion of the present invention has low viscosity and excellent bonding strength, and can therefore be used to form conductive members for various electronic and electrical devices. Examples of such conductive members include those conventionally formed using conductive bonding agents such as solder. Furthermore, the composite microparticle dispersion of the present invention is preferably used to form conductive members that constitute antennas such as RFID (radio frequency identifier) ​​tags; capacitors such as MLCCs (multilayer ceramic capacitors); electronic paper; image display devices such as liquid crystal displays and organic EL displays; organic EL elements; organic transistors; wiring boards such as printed circuit boards and flexible circuit boards; organic solar cells; sensors such as flexible sensors, etc.

[0053] [Method for manufacturing a jointed body] The composite fine particle dispersion of the present invention is interposed between a plurality of members to be joined, and then these are fired at low pressure and low temperature to produce a joined body in which the plurality of metal members are joined via a copper bonding layer. That is, the joined body obtained here has a metal member-copper bonding layer-metal member structure in which the plurality of metal members are joined by a copper bonding layer formed by sintering the composite fine particle dispersion of the present invention. Furthermore, the joint of the present invention is a joint comprising a plurality of metal members and a copper bonding layer disposed between adjacent metal members to bond the adjacent metal members together, wherein the copper bonding layer is a sintered body of composite fine particles of the present invention. The metal members are examples of members to be joined. In one embodiment, the present invention relates to a method for manufacturing a joined body, and in one embodiment, the method for manufacturing the joined body comprises the following steps 1 to 3 in this order. Step 1: A step of applying the composite fine particle dispersion of the present invention described above onto a metal substrate. Step 2: A step in which the metal substrate obtained in Step 1, to which the composite fine particle dispersion has been applied, is pre-baked at a temperature of 100°C to 150°C. Step 3: The member to be bonded is placed on the composite fine particle dispersion on the metal substrate pre-baked in Step 2, and then pressure-fired under conditions of a temperature of 150°C to 300°C and a pressure of 5 MPa to 50 MPa.

[0054] (Process 1) Step 1 is the step of applying the composite fine particle dispersion of the present invention onto a metal substrate.

[0055] Examples of metal substrates include gold substrates, gold-plated substrates, silver substrates, silver-plated metal substrates, copper substrates, palladium substrates, palladium-plated metal substrates, platinum substrates, platinum-plated metal substrates, aluminum substrates, nickel substrates, nickel-plated metal substrates, tin substrates, and tin-plated metal substrates.

[0056] As for the method of applying the composite fine particle dispersion, known application methods can be used, such as various coating methods including slot die coating, dip coating, spray coating, spin coating, doctor bladeding, knife edge coating, and bar coating; and various patterning printing methods including stencil printing, screen printing, flexographic printing, gravure printing, offset printing, dispenser printing, and inkjet printing. Among these methods, stencil printing is preferred from the viewpoint of improving coating properties. The amount of composite fine particle dispersion applied to the metal component can be appropriately adjusted according to the size and type of the metal substrate.

[0057] (Process 2) This step involves pre-baking the metal substrate obtained in step 1 at a temperature of 100°C to 150°C. Step 2 involves pre-baking, which allows for the appropriate removal of a portion of the dispersion medium from the applied composite microparticle dispersion. On the other hand, in step 3, the pressure firing process allows for the retention of the dispersion medium necessary to promote the sintering of the composite microparticles. This suppresses cracking in the joint (copper joint layer) of the resulting bonded body and improves the joint strength.

[0058] The pre-bake temperature in step 2 is 100°C or higher, preferably 105°C or higher, more preferably 110°C or higher, even more preferably 115°C or higher, and 150°C or lower, preferably 140°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower, from the viewpoint of suppressing cracking and improving joint strength.

[0059] The pre-bake processing time in step 2 is preferably 1 minute or more, more preferably 3 minutes or more, even more preferably 5 minutes or more, and preferably 60 minutes or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less, from the viewpoint of suppressing cracking and improving joint strength.

[0060] The atmosphere in step 2 may be an air atmosphere (atmospheric atmosphere), an inert gas atmosphere such as nitrogen gas, or a reducing gas atmosphere such as hydrogen gas, but from the viewpoint of productivity, it is an air atmosphere.

[0061] (Step 3) Step 3 involves placing the member to be bonded onto the composite fine particle dispersion on the metal substrate pre-baked in Step 2, and then pressurizing and firing it under conditions of a temperature of 150°C to 300°C and a pressure of 5 MPa to 50 MPa.

[0062] Examples of members to be joined include metal substrates, electrically insulating substrates, chip components, and semiconductor chips. Examples of metal substrates include those similar to the metal substrate used in step 1 above. Examples of chip components include capacitors and resistors. Examples of semiconductor chips include silicon chips, memory, diodes, transistors, ICs, and CPUs.

[0063] The temperature of the pressurized firing process in step 3 is 150°C or higher, preferably 160°C or higher, more preferably 170°C or higher, and even more preferably 180°C or higher, from the viewpoint of improving bonding strength, and preferably 300°C or lower from the viewpoint of preventing damage to surrounding components.

[0064] The pressure for the pressurized firing process in step 3 is 5 MPa or more, preferably 10 MPa or more, more preferably 12 MPa or more, and even more preferably 15 MPa or more, from the viewpoint of suppressing cracking and improving joint strength, and from the viewpoint of preventing damage to surrounding members, it is 50 MPa or less, preferably 40 MPa or less, more preferably 30 MPa or less, and even more preferably 25 MPa or less.

[0065] The processing time for the pressurized firing treatment in step 3 is preferably 30 seconds or more, more preferably 60 seconds or more, and even more preferably 120 seconds or more, from the viewpoint of suppressing cracking and improving joint strength, and from the viewpoint of productivity, preferably 300 seconds or less, more preferably 240 seconds or less, and even more preferably 180 seconds or less.

[0066] The atmosphere during the heating process may be an air atmosphere (atmosphere), an inert gas atmosphere such as nitrogen gas, or a reducing gas atmosphere such as hydrogen gas. However, from the viewpoint of suppressing copper oxidation and ensuring safety, an inert gas atmosphere is preferred, and a nitrogen gas atmosphere is more preferred.

[0067] The metal substrate used in the above (Step 1) can also be called the member to be joined. Therefore, the present invention discloses, as one embodiment, the use of the composite fine particle dispersion of the present invention as a joining material for joining members to be joined together. [Examples]

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

[0069] <Median diameter (D50) of composite microparticles and copper microparticles> Scanning electron microscope (SEM) images of composite microparticles and copper microparticles were taken using a scanning electron microscope (Hitachi High-Tech Corporation, field emission scanning electron microscope, product name: S-4800). The magnification was determined according to the particle size, and images were taken in the range of 5,000x to 150,000x. The SEM images were analyzed using the image analysis software ImageJ (National Institutes of Health, USA), and the particle size was determined for 1,000 particles per sample. From the particle size histogram based on the determined particle sizes, the median diameter (D50) (particle size when the cumulative frequency is 50%) was calculated.

[0070] <Content of coating agent in composite microparticles> Using a differential thermogravimetric / thermogravimetric analysis system (TG / DTA) (manufactured by Hitachi High-Tech Science Corporation, product name: STA7200RV), 10 mg of the sample (dried powder of composite microparticles) was weighed into an aluminum pancell and heated from 35°C to 550°C at a heating rate of 10°C / min under a nitrogen flow of 50 mL / min, and the mass loss was measured. The mass loss from 35°C to 550°C was taken as the mass of the coating agent, and the remaining mass at 550°C was taken as the mass of the copper microparticles that were not coated, and the content of the coating agent in the composite microparticles was calculated using the following formula. (Content of coating agent in composite microparticles [mass %]) = (Mass loss from 35°C to 550°C [mg]) / (Mass loss from 35°C to 550°C [mg] + Remaining mass at 550°C [mg]) × 100

[0071] [Manufacturing of coating agents] Manufacturing Example 1 (Preparation of Coating Agent 1) In a 500 mL beaker, 1.2 g of maleic anhydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade), 0.02 g of p-toluenesulfonic acid monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade), and 48.8 g of polyethylene glycol monomethyl ether 4000 (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and the temperature was raised to 110°C. After raising the temperature, the mixture was reacted for 4 hours with stirring to obtain coating agent 1.

[0072] Manufacturing Example 2 (Preparation of Coating Agent 2) Coating agent 2 was obtained in the same manner as in Production Example 1, except that polyethylene glycol monomethyl ether 4000 was replaced with polyethylene glycol monomethyl ether 2000 (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0073] Comparative manufacturing example 1 (Preparation of coating agent C1) Coating agent C1 was obtained in the same manner as in Production Example 1, except that polyethylene glycol monomethyl ether 4000 was replaced with polyethylene glycol monomethyl ether 550 (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0074] Comparative manufacturing example 2 (Preparation of coating agent C2) 0.5 g of maleic anhydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade), 0.01 g of p-toluenesulfonic acid monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade), and 49.5 g of polyethylene glycol 20000 (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to a 500 mL beaker, and the temperature was raised to 110 °C. After raising the temperature, the mixture was reacted for 4 hours with stirring to obtain coating agent C2.

[0075] Comparative manufacturing example 3 (Preparation of coating agent C3) A 500 mL four-necked round-bottom flask equipped with a thermometer, two 100 mL dropping funnels with nitrogen bypasses, and a reflux apparatus was filled with 20.0 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent). The flask was then heated to 80°C in an oil bath, and nitrogen bubbling was performed for 10 minutes. Next, 10.8 g of methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 139.2 g of methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by NOF Corporation, "PME-1000"), 4.1 g of 3-mercaptopropionic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), and 49.4 g of ethanol were dissolved in a poly beaker and placed in a dropping funnel (1). Separately, 30.6 g of ethanol and 2.3 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "V-65", polymerization initiator) were dissolved in a poly beaker and placed in a dropping funnel (2). Next, the mixtures in dropping funnel (1) and dropping funnel (2) were simultaneously added to the flask over 90 minutes each. After that, the internal temperature of the flask was raised to 90°C, and stirring was continued for another hour to complete the reaction. The obtained resin solution was freeze-dried using a freeze-dryer (Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: DRC-1000) under drying conditions (freezing at -25°C for 1 hour, reduced pressure at -10°C for 9 hours, reduced pressure at 25°C for 5 hours. Reduced pressure of 5 Pa) to obtain an oven-dried coating agent C3 (methacrylic acid / methoxypolyethylene glycol (EO 23 mol) methacrylate polymer, number average molecular weight (Mn): 4600).

[0076] <<Measurement of the number-average molecular weight (Mn) of coating agent C3>> The number-average molecular weight (Mn) of the coating agent C3 was determined by gel permeation chromatography. The sample was prepared by mixing 0.1 g of the coating agent (C3) with 10 mL of eluent in a glass vial, stirring with a magnetic stirrer at 25°C for 10 hours, and filtering through a syringe filter (DISMIC-13HP PTFE 0.2 μm, Advantec Toyo Co., Ltd.). The filtrate was used. The measurement conditions are shown below. (Measurement conditions) GPC device: Tosoh Corporation "HLC-8320GPC" Columns: Tosoh Corporation products "TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn Super AW-H" Eluent: A solution prepared by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively. Flow rate: 0.5mL / min Standard material: Monodisperse polystyrene kit manufactured by Tosoh Corporation: "PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)"

[0077] Table 1 summarizes the details of the coatings obtained in each manufacturing example and comparative manufacturing example.

[0078] [Table 1]

[0079] [Manufacturing of composite microparticles] Example 1 (Preparation of composite microparticles 1) (1) In a 1L beaker, 50.0g of copper oxide (N-120, cupric oxide, manufactured by Nisshin Chemco Co., Ltd.), 4.0g of coating agent 1 obtained in Production Example 1, and 230g of ethanol (first-grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries Ltd.) were added and stirred for 15 minutes. During stirring, an oil bath was used to control the temperature of the mixture to 70°C. (2) 32.0 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), placed in a 50 mL dropping funnel, was added dropwise to the mixture from (1) over a period of 50 minutes. (3) After the operation in (2) above, the mixture was stirred in an oil bath for 1 hour while controlling the temperature to 70°C, and then air-cooled to obtain a reddish-brown dispersion containing composite fine particles. The entire amount of this dispersion was placed in a Hitachi Koki Co., Ltd. cooling centrifuge "himacCR22G" and rotor (R12A, radius 15.1 cm) and centrifuged in a Hitachi Koki Co., Ltd. 500PA bottle centrifugal sedimentation tube at 3000 rpm and centrifugal acceleration of 675 G for 15 minutes. (4) After the operation in (3) above, 300 g of ethanol was added to the precipitate separated by centrifugation, and the mixture was stirred for 15 minutes to redisperse it. Then, the centrifugation treatment was performed again under the same conditions as in (3) above. This operation was performed a total of two times. (5) The precipitate of the purified composite microparticles was freeze-dried using a freeze-dryer (Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: DRC-1000) to obtain 35.5 g of composite microparticle 1. Freeze-drying was performed by freezing at -25°C for 1 hour, then drying under reduced pressure at -10°C for 9 hours at 5 Pa, and then drying under reduced pressure at 25°C for 5 hours at 5 Pa.

[0080] Example 2 and Comparative Examples 1-3 (Preparation of composite microparticles 2 and C1-C3) Composite fine particles 2 and C1-C3 were obtained in the same manner as in Example 1, except that the coating agent 1 used in operation (1) was changed to one of the coating agents listed in Table 2.

[0081] [Evaluation of composite microparticles] <Preparation of composite microparticle dispersions> As a dispersion medium, 5.4 parts by mass of dipropylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., first-grade reagent) and 2.6 parts by mass of polyethylene glycol 200 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., first-grade reagent, number average molecular weight: 200), 61.3 parts by mass of composite fine particles obtained in each example and comparative example, and 30.7 parts by mass of MA-C03K (Mitsui Mining & Smelting Co., Ltd., median diameter (D50) 3.4 μm, copper component 100% by mass) were added to an agate mortar and kneaded until the particles were no longer visible, and the resulting mixture was transferred to a plastic bottle. The sealed plastic bottle was stirred for 2000 min using a rotation-and-revolution type stirring device (Sinky Co., Ltd., Planetary Vacuum Mixer ARV-310). -1 The mixture was stirred at 2000 revolutions per minute for 5 minutes to obtain a composite fine particle dispersion.

[0082] <Viscosity of composite microparticle dispersion at 25°C> Using an MCR302 rheometer (manufactured by Anton Paar) equipped with a CP25 cone plate, the shear rate was measured at a temperature of 25°C at 0.1 s². -1 from 1000s -1 The shear rate is increased exponentially in steps within the range of 10s. -1 The viscosity was measured and defined as the viscosity of the composite fine particle dispersion at 25°C.

[0083] <Joining strength> (Fabrication of the joint) (1) A stainless steel metal mask (thickness: 100 μm) with three rows of 6 mm x 6 mm square openings was placed on a 30 mm x 30 mm copper plate (total thickness: 1 mm), and a composite fine particle dispersion was applied to the copper plate by stencil printing using a metal squeegee. (2) Next, the copper plate coated with the composite fine particle dispersion was pre-baked at 110°C for 10 minutes on a Shamal hot plate (manufactured by AS ONE Corporation, HHP-441) under open air. (3) Next, three silicon chips measuring 5 mm x 5 mm (thickness: 300 μm) were prepared, each sputtered with titanium, nickel, and gold in that order. The copper plate and the three silicon chips were then stacked so that the gold side of each silicon chip was in contact with the coated composite fine particle dispersion. This resulted in a laminate in which the copper plate, composite fine particle dispersion, and silicon chips were stacked in that order. (4) Next, the obtained laminate was fired in the following manner to obtain a joined body. First, the laminate was set in a pressurized firing machine (HTM-1000, manufactured by Meisho Kiko Co., Ltd.), and nitrogen was flowed into the furnace at a rate of 500 mL / min to replace the air in the furnace with nitrogen. Then, the laminate was pressurized at 10 MPa by the upper and lower heating heads, and the temperature of the heating heads was raised to 240°C over 6 minutes. After the temperature was raised, the joint was obtained by holding the temperature at 240°C for 500 seconds to perform a sintering treatment. After sintering, the heating heads were cooled with water at -60°C / min, and the joint was removed into the air at a temperature of 100°C or lower. (Measurement of joint strength) A universal bond tester (Prospector, manufactured by Nordson Advanced Technologies, Inc.) was used to measure the die shear strength of the bonded structure by pressing the silicon chip of the bonded structure horizontally at a test speed of 5 mm / min with the shear tool height set to 50 μm. The die shear strength was measured for three silicon chips in the bonded structure, and the average value obtained from the measurements was taken as the bond strength of the bonded structure.

[0084] Table 2 summarizes the details of the composite microparticles obtained in each example and comparative example, as well as the measurement results of the viscosity and bonding strength of the composite microparticle dispersion.

[0085] [Table 2]

[0086] As shown in Table 2, in the coating agent represented by the above general formula (1), n ​​is a number between 31 and 200, and R 1 However, the viscosity of the composite microparticle dispersion prepared using the composite microparticles of Examples 1 and 2, which have a structure containing a carboxyl group, is low, and the bonding strength of the copper bonding layer formed using the composite microparticle dispersion is excellent. On the other hand, the composite microparticles of Comparative Example 1, in which n in the above general formula (1) is less than 31, and Comparative Example 2, in which n is greater than 200, had insufficient dispersibility, and it was not possible to obtain a composite microparticle dispersion. Furthermore, the composite microparticles of Comparative Example 3, in which n in the above general formula (1) is less than 31, showed high viscosity when used in the preparation of the composite microparticle dispersion, and also exhibited inferior bonding strength compared to the examples. [Industrial applicability]

[0087] According to the present invention, it is possible to provide composite microparticles and a composite microparticle dispersion containing said composite microparticles that enable the preparation of a low-viscosity composite microparticle dispersion and achieve excellent bonding strength.

Claims

1. A composite microparticle in which at least a portion of the surface of copper microparticles is coated with a coating agent, wherein the coating agent is represented by the following general formula (1). 【Chemistry 1】 In the above general formula (1), n ​​is a number between 31 and 200, and R 1 It is a structure containing a carboxyl group, R 2 This is a hydrocarbon group in which hydrogen may be substituted with a functional group.

2. R in the general formula (1) 1 The composite fine particles according to claim 1, wherein the fine particles are selected from the following general formulas (a-1) to (a-5). 【Chemistry 2】 In the above general formulas (a-1) to (a-5), * represents R in general formula (1). 1 The bonding site is shown as follows, where X is NH or O, and in general formula (a-5), R 3 It is either H or COOH.

3. R in the general formula (1) 2 The composite fine particles according to claim 1, wherein the composite fine particles are selected from the following general formulas (b-1) to (b-7). 【Transformation 3】 In the above general formulas (b-1) to (b-7), * represents R in general formula (1). 2 The joining points are shown as follows: In general formula (b-3), n is a number between 12 and 22, in general formulas (b-4) to (b-7), X is NH or O, and in general formula (b-7), R 3 It is either H or COOH.

4. R in the general formula (1) 1 The composite fine particles according to claim 1, wherein R has a structural unit derived from an acid anhydride.

5. The aforementioned R 1 The composite fine particles according to claim 1, having constituent units derived from one or more acid anhydrides selected from maleic anhydride, succinic anhydride, trimellitic anhydride, pyromellitic anhydride, phthalic anhydride, citraconic anhydride, cis-1,2-cyclohexanedicarboxylic anhydride, cis-4-cyclohexene-1,2-dicarboxylic anhydride, itaconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride.

6. The composite fine particles according to claim 1, wherein the content of the coating agent in the composite fine particles is 0.3% by mass or more and 3.0% by mass or less.

7. The composite fine particles according to claim 1, wherein the median diameter (D50) of the composite fine particles is 50 nm or more and 280 nm or less.

8. The composite fine particles according to claim 1, wherein the mass ratio of the coating agent to the copper fine particles (coating agent / copper fine particles) is 0.003 or more and 0.031 or less.

9. A composite particle dispersion containing composite particles according to any one of claims 1 to 8.

10. A method for producing composite fine particles comprising copper fine particles and a coating agent that covers at least a portion of the surface thereof, Heat the mixture containing the copper raw material compound, coating agent, and solvent until it reaches a predetermined temperature. The process includes adding a reducing agent dropwise to the heated mixture. A method for producing composite fine particles, wherein the coating agent is a polymer represented by the following general formula (1). 【Chemistry 4】 In the above general formula (1), n ​​is a number between 31 and 200, and R 1 It is a structure containing a carboxyl group, R 2 This is a hydrocarbon group in which hydrogen may be substituted with a functional group.

11. The method for producing composite fine particles according to claim 10, wherein the copper raw material compound is copper oxide.

12. The method for producing composite fine particles according to claim 10, wherein the copper raw material compound is cupric oxide.

13. The method for producing composite fine particles according to claim 10, wherein the reducing agent is a hydrazine-based compound.

14. A method for manufacturing a joined body, comprising performing the following steps 1 to 3 in this order. Step 1: A step of coating a metal substrate with the composite fine particle dispersion described in claim 9. Step 2: A step of pre-baking the metal substrate, which is coated with the composite fine particle dispersion obtained in Step 1, at a temperature of 100°C to 150°C. Step 3: The member to be joined is placed on the composite fine particle dispersion on the metal substrate pre-baked in Step 2, and then pressure-fired under conditions of a temperature of 150°C to 300°C and a pressure of 5 MPa to 50 MPa.

15. The composite fine particle dispersion described in claim 9 is used as a bonding material for joining materials to be joined together.

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