Copper microparticle dispersion

Abstract

The present invention relates to: a copper microparticle dispersion comprising copper nanoparticles A, a carboxylic acid B having 6 to 14 carbon atoms inclusive, a compound C represented by formula (1): RO-(CH2CH2O)n-CH2-COOH (in formula (1), R represents a hydrocarbon group having 6 to 14 carbon atoms inclusive, and n represents an average number of moles of ethyleneoxy groups added and is a numerical value of 0.5 to 20 inclusive) and a dispersion medium D, in which the dispersion medium D comprises at least one component selected from the group consisting of a (poly)alkylene glycol, a (poly)alkylene glycol derivative, terpene alcohol, glycerin and a glycerin derivative, the content of the carboxylic acid B is 0.1% by mass or more, the content of the compound C is 0.05% by mass or more, and the total content of the carboxylic acid B and the compound C is 8% by mass or less; and a method for producing an assembly, comprising a step for heating the copper microparticle dispersion while placing the copper microparticle dispersion between a plurality of metal members.

Description

Technical Field

[0001] The present invention relates to a copper fine particle dispersion and a method for manufacturing a bonded body using the copper fine particle dispersion.

Background Art

[0002] Since copper is excellent in electrical conductivity and thermal conductivity, it is widely used, for example, as a conductor wiring material, a heat transfer material, a heat exchange material, a heat dissipation material, and the like. Since copper is excellent in thermal conductivity, it may also be used as an alternative material to solder for joining an object to be joined.

[0003] In recent years, semiconductor devices called power devices have been increasingly used as power conversion and control devices such as inverters. Unlike integrated circuits such as memories and microprocessors, power devices are for controlling high currents and generate a large amount of heat during operation. Therefore, the solder used for mounting power devices is required to have heat resistance in addition to bonding strength. However, the lead-free solder widely used nowadays has the drawback of low heat resistance. Therefore, various techniques have been proposed in which a copper fine particle dispersion is used instead of solder, and this is applied to an object by various coating means and fired to join the object to be joined. Since copper is stable in an oxidized state at room temperature (25°C), it contains copper atoms in an oxidized state. Therefore, in order to join an object to be joined with a copper fine particle dispersion, it is necessary to reduce the copper atoms in the oxidized state and fire them to form a continuous body of copper.

[0004] Japanese Patent Application Laid-Open No. 2020-053404 (Patent Document 1) discloses a copper paste containing copper powder and a liquid medium for the purpose of providing a copper paste having high bonding strength with an object to be joined. The liquid medium contains polyethylene glycol. The copper particles constituting the copper powder have an average primary particle size of 0.03 μm or more and 1.0 μm or less, a fatty acid having 6 to 18 carbon atoms is applied to the surface thereof, and the crystallite size of the (111) plane is 50 nm or less. A copper paste in which the mass ratio of the copper powder in the copper paste is 50% or more and 99% or less is described. Further, Japanese Patent Application Laid-Open No. 2017-172003 (Patent Document 2) aims to provide a method for producing copper nanoparticles capable of easily obtaining monodisperse copper nanoparticles. A preparation step of dissolving a first metal salt containing copper, a complexing agent, a dispersant, and a second metal salt containing a metal with a lower ionization tendency than copper in water to prepare a reaction solution, and a precipitation step of adding a reducing agent while stirring the reaction solution to precipitate copper nanoparticles are provided. A method for producing copper nanoparticles is described, which is characterized by comprising the above steps.

Summary of the Invention

[0005] The present invention contains copper nanoparticles A, a carboxylic acid B having 6 to 14 carbon atoms, a compound C represented by the following formula (1), and a dispersion medium D. The dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative. The content of the carboxylic acid B is 0.1% by mass or more. The content of the compound C is 0.05% by mass or more. The present invention relates to a copper fine particle dispersion in which the total content of the carboxylic acid B and the compound C is 8% by mass or less. RO-(CH2CH2O) n -CH2-COOH (1) 〔In formula (1), R is a hydrocarbon group having 6 to 14 carbon atoms, n is the average number of moles of ethyleneoxy groups added, and is a number from 0.5 to 20.〕

Embodiments for Carrying Out the Invention

[0006] Copper fine particle dispersions that have been proposed as solder alternative joining materials so far have higher heat resistance than solder, but still have room for improvement in terms of the joining strength with the object to be joined. In addition, in some cases, depending on the storage period of the conventional copper fine particle dispersion, poor joining strength of the obtained joined body may occur. Such a copper fine particle dispersion with poor storage stability is difficult to use for mounting power devices. The copper paste in which copper fine particles treated with hydrophobic lauric acid were dispersed with hydrophilic polyethylene glycol as described in Patent Document 1 showed poor bonding strength of the obtained bonded body when the bonded body was produced after one month of storage. This is presumably due to poor dispersion of the copper paste. In addition, in the aqueous dispersion of copper nanoparticles described in Patent Document 2, since polyvinylpyrrolidone and polyvinyl alcohol that protected the copper fine particles were insufficiently removed during firing, poor bonding strength was observed in the obtained bonded body. Therefore, further improvement in the storage stability and bondability of the copper fine particle dispersion is required. The present invention relates to a copper fine particle dispersion capable of obtaining a bonded body with improved bonding strength even after storage for a certain period, and a method for producing a bonded body using the copper fine particle dispersion.

[0007] The present inventors have found that copper nanoparticles A, carboxylic acid B having 6 to 14 carbon atoms, compound C represented by RO-(CH2CH2O) n -CH2-COOH, and a copper fine particle dispersion containing a dispersion medium D containing at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative, wherein the content of carboxylic acid B, the content of compound C, and the total content of carboxylic acid B and compound C are each within a predetermined range, thereby improving the dispersion stability, storage stability, and sinterability at low temperature of the copper fine particle dispersion, and being able to obtain a bonded body with improved bonding strength even after storage for a certain period. A copper fine particle dispersion and a method for producing a bonded body using the copper fine particle dispersion can be provided. That is, the present invention relates to the following [1] and [2]. [1] It contains copper nanoparticles A, carboxylic acid B having 6 to 14 carbon atoms, compound C represented by the following formula (1), and a dispersion medium D, the dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative, the content of the carboxylic acid B is 0.1% by mass or more, The content of the compound C is 0.05% by mass or more, A copper fine particle dispersion in which the total content of the carboxylic acid B and the compound C is 8% by mass or less. RO-(CH2CH2O) n -CH2-COOH (1) 〔In the formula (1), R is a hydrocarbon group having 6 to 14 carbon atoms, n is the average number of moles of ethyleneoxy groups added, and is a number of 0.5 or more and 20 or less.〕 [2] A method for manufacturing a joined body, including a step of heating with the copper fine particle dispersion according to [1] interposed between a plurality of metal members.

[0008] According to the present invention, it is possible to provide a copper fine particle dispersion capable of obtaining a joined body having improved joining strength even after being stored for a certain period, and a method for manufacturing a joined body using the copper fine particle dispersion.

[0009] [Copper fine particle dispersion] The copper fine particle dispersion of the present invention contains copper nanoparticles A, a carboxylic acid B having 6 to 14 carbon atoms, a compound C represented by the following formula (1), and a dispersion medium D. The dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative. The content of the carboxylic acid B is 0.1% by mass or more, the content of the compound C is 0.05% by mass or more, and the total content of the carboxylic acid B and the compound C is 8% by mass or less. RO-(CH2CH2O) n -CH2-COOH (1) In the formula (1), R is a hydrocarbon group having 6 to 14 carbon atoms, n is the average number of moles of ethyleneoxy groups added, and is a number of 0.5 or more and 20 or less. In this specification, "sinterability at low temperature" means that metal sintering occurs in a low-temperature nitrogen atmosphere, and is also referred to as "low-temperature sinterability". Also, the joinability of a plurality of metal members in a low-temperature nitrogen atmosphere is also referred to as "low-temperature joinability". Further, for example, the low-temperature joinability after storing the copper fine particle dispersion under the conditions of 25°C and 50% humidity for one month is also referred to as "low-temperature joinability after storage". Also, in this specification, "low temperature" means a temperature lower than the general sintering temperature (about 250 to 300 °C) when using a silver nanoparticle dispersion, for example, a temperature range of about 100 to 230 °C, and it is preferable that the sinterability and joinability are improved at a lower temperature.

[0010] According to the present invention, there is an effect that a joined body with improved joining strength can be obtained even after storage for a certain period. The reason is not clear, but it is considered as follows. The copper nanoparticles A contained in the copper microparticle dispersion according to the present invention are dispersed in a dispersion medium D containing at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative by a carboxylic acid B having 6 to 14 carbon atoms and a compound C represented by the formula (1). The carboxylic acid B having 6 to 14 carbon atoms has good coordination to the copper nanoparticles A, but due to its strong hydrophobicity, it is considered that the copper nanoparticles A coordinated with the carboxylic acid B are inferior in dispersibility in the hydrophilic dispersion medium D. Here, since the compound C having a hydrocarbon group, a carboxy group, and an ethyleneoxy group having 6 to 14 carbon atoms contains a hydrophilic group and a hydrophobic group in a well-balanced manner, it is considered that the compound C has good compatibility with the hydrophobic carboxylic acid B and the hydrophilic dispersion medium D, respectively. Therefore, in order to disperse the copper nanoparticles A in the dispersion medium D, by using a combination of the carboxylic acid B having 6 to 14 carbon atoms and the compound C represented by the formula (1), the dispersibility of the copper nanoparticles A coordinated with the carboxylic acid B in the dispersion medium D is effectively improved, and it is considered that the dispersion stability and storage stability of the copper microparticle dispersion are improved. In addition, since the carboxylic acid B having 6 to 14 carbon atoms is a low-molecular ligand, it is easy to volatilize, and further, the ethyleneoxy group of the compound C is easily decomposed at a low temperature by the copper nanoparticles A. Therefore, when sintering the copper nanoparticles A, the carboxylic acid B and the compound C do not interfere with the joining. Therefore, since the copper nanoparticles A are close to each other even in a low-temperature nitrogen atmosphere, it is considered that the low-temperature sinterability and low-temperature joinability are improved. For the above reasons, according to the copper microparticle dispersion of the present invention, the dispersion stability and storage stability of the copper microparticle dispersion are improved, and the low-temperature sinterability and low-temperature joinability are improved. Therefore, it is considered that a joined body with improved joining strength can be obtained even after storage for a certain period.

[0011] <Copper nanoparticles A> The copper microparticle dispersion according to the present invention contains copper nanoparticles A (hereinafter also referred to as "copper nanoparticles A"). From the viewpoint of improving conductivity, low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, the copper content in copper nanoparticles A is preferably 95% by mass or more, more preferably 98% by mass or more, still more preferably 99% by mass or more, and still more preferably substantially 100% by mass. Here, "substantially 100% by mass" means that it may include components contained unintentionally. Examples of components contained unintentionally include inevitable impurities.

[0012] From the viewpoint of improving the dispersion stability of the copper microparticle dispersion, the average particle size of copper nanoparticles A is preferably 100 nm or more, more preferably 130 nm or more, still more preferably 150 nm or more, and still more preferably 170 nm or more. From the viewpoint of improving low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, it is preferably 350 nm or less, more preferably 320 nm or less, still more preferably 300 nm or less, and still more preferably 280 nm or less. The average particle size of copper nanoparticles A is measured by the method described in the examples. The average particle size of copper nanoparticles A can be adjusted by the production conditions of copper nanoparticles A such as the reduction metal ratio, the type and amount of carboxylic acid B, and the reduction temperature.

[0013] The content of copper nanoparticles A in the copper microparticle dispersion according to the present invention is preferably more than 25% by mass, more preferably 30% by mass or more, still more preferably 40% by mass or more, still more preferably 50% by mass or more, still more preferably 55% by mass or more, from the viewpoint of improving low-temperature sinterability, low-temperature joining property, and low-temperature joining property after storage. From the viewpoint of improving the dispersion stability of the copper microparticle dispersion, it is preferably less than 97% by mass, more preferably 96% by mass or less, still more preferably 93% by mass or less, still more preferably 91% by mass or less. Considering these viewpoints comprehensively, the content of copper nanoparticles A in the copper microparticle dispersion according to the present invention is preferably more than 25% by mass and less than 97% by mass, more preferably 30% by mass or more and 96% by mass or less, still more preferably 40% by mass or more and 93% by mass or less, still more preferably 50% by mass or more and 91% by mass or less, still more preferably 55% by mass or more and 91% by mass or less.

[0014] <Carboxylic acid B> The copper nanoparticles A according to the present invention are dispersed in a carboxylic acid B having 6 to 14 carbon atoms from the viewpoint of improving the dispersion stability of the copper microparticle dispersion and improving low-temperature sinterability, low-temperature joining property, and low-temperature joining property after storage. The number of carbon atoms of the carboxylic acid B is 6 to 14, preferably 6 to 12, more preferably 6 to 10, still more preferably 6 to 8, from the viewpoint of improving the dispersion stability of the copper microparticle dispersion and improving low-temperature sinterability, low-temperature joining property, and low-temperature joining property after storage.

[0015] As the carboxylic acid B, both linear carboxylic acids and branched carboxylic acids can be used. However, from the viewpoint of improving the dispersion stability of the copper microparticle dispersion and improving low-temperature sinterability, low-temperature joining property, and low-temperature joining property after storage, linear carboxylic acids are preferred. Also, as the carboxylic acid B, both saturated carboxylic acids and unsaturated carboxylic acids can be used. However, from the viewpoint of easy availability, saturated carboxylic acids are preferred, saturated aliphatic carboxylic acids are more preferred, and saturated aliphatic monocarboxylic acids are still more preferred. As the saturated aliphatic monocarboxylic acid, from the viewpoint of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, at least one selected from hexanoic acid, caprylic acid, capric acid, lauric acid, and myristic acid is preferable, at least one selected from hexanoic acid, caprylic acid, capric acid, and lauric acid is more preferable, at least one selected from hexanoic acid, caprylic acid, and capric acid is still more preferable, and at least one selected from hexanoic acid and caprylic acid is still more preferable.

[0016] From the viewpoint of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, the content of carboxylic acid B in the copper fine particle dispersion according to the present invention is 0.1% by mass or more, preferably 0.3% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, and from the viewpoint of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, it is preferably 7.5% by mass or less, more preferably 6% by mass or less, still more preferably 5% by mass or less, still more preferably 4% by mass or less. Considering these viewpoints comprehensively, the content of carboxylic acid B in the copper fine particle dispersion according to the present invention is preferably 0.1% by mass or more and 7.5% by mass or less, more preferably 0.3% by mass or more and 6% by mass or less, still more preferably 0.3% by mass or more and 5% by mass or less, still more preferably 0.5% by mass or more and 4% by mass or less, still more preferably 0.6% by mass or more and 4% by mass or less.

[0017] <Compound C> The copper fine particle dispersion according to the present invention contains a compound C represented by the following formula (1) from the viewpoint of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage. RO-(CH2CH2O) n -CH2-COOH (1) In formula (1), R is a hydrocarbon group having 6 to 14 carbon atoms, n is the average number of added moles of ethyleneoxy groups, and is a number of 0.5 or more and 20 or less.

[0018] The number of carbon atoms of R in formula (1) is 6 or more, preferably 8 or more, from the viewpoint of improving the dispersion stability of the copper fine particle dispersion and improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage. From the viewpoint of improving the dispersion stability, low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, it is 14 or less, preferably 12 or less, more preferably 10 or less, and still more preferably 8 or less.

[0019] R in formula (1) may be linear or branched, but linear is preferred from the viewpoint of improving the dispersion stability of the copper fine particle dispersion and improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage. As the compound C, either a saturated compound or an unsaturated compound can be used, but a saturated compound is preferred from the viewpoint of easy availability.

[0020] n in formula (1) is 0.5 or more, preferably 2 or more, more preferably 4 or more, and still more preferably 6 or more from the viewpoint of improving the dispersion stability of the copper fine particle dispersion and improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage. From the viewpoint of improving the dispersion stability, low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, it is 20 or less, preferably 15 or less, more preferably 12 or less, and still more preferably 10 or less. Considering these viewpoints comprehensively, n in formula (1) is 0.5 or more and 20 or less, preferably 2 or more and 15 or less, more preferably 4 or more and 12 or less, and still more preferably 6 or more and 10 or less.

[0021] As the compound C, from the viewpoints of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, and the availability, in the formula (1), a compound in which R is a linear saturated alkyl group having 6 to 14 carbon atoms and n is 0.5 or more and 20 or less is preferable; in the formula (1), a compound in which R is a linear saturated alkyl group having 6 to 14 carbon atoms and n is 4 or more and 12 or less is more preferable; in the formula (1), a compound in which R is a linear saturated alkyl group having 8 to 12 carbon atoms and n is 6 or more and 10 or less is still more preferable; in the formula (1), a compound in which R is a linear saturated alkyl group having 8 carbon atoms and n is 6 or more and 10 or less is still more preferable.

[0022] From the viewpoints of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, the content of the compound C in the copper fine particle dispersion according to the present invention is 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more; from the viewpoints of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, it is preferably 7.5% by mass or less, more preferably 6% by mass or less, still more preferably 5% by mass or less, still more preferably 3.5% by mass or less, still more preferably 2.5% by mass or less, still more preferably 2% by mass or less, still more preferably 1.5% by mass or less. Considering these viewpoints comprehensively, the content of the compound C in the copper fine particle dispersion according to the present invention is preferably 0.05% by mass or more and 7.5% by mass or less, more preferably 0.05% by mass or more and 6% by mass or less, still more preferably 0.1% by mass or more and 5% by mass or less, still more preferably 0.3% by mass or more and 3.5% by mass or less, still more preferably 0.5% by mass or more and 2.5% by mass or less, still more preferably 0.5% by mass or more and 2% by mass or less, still more preferably 0.5% by mass or more and 1.5% by mass or less.

[0023] The total content of carboxylic acid B and compound C in the copper fine particle dispersion according to the present invention is preferably 0.85% by mass or more, more preferably 1% by mass or more, still more preferably 1.3% by mass or more, and still more preferably 1.5% by mass or more from the viewpoints of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, the low-temperature joining property, and the low-temperature joining property after storage. From the viewpoints of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, the low-temperature joining property, and the low-temperature joining property after storage, it is 8% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less, still more preferably 4.5% by mass or less, and still more preferably 3% by mass or less. Considering these viewpoints comprehensively, the total content of carboxylic acid B and compound C in the copper fine particle dispersion according to the present invention is preferably 0.85% by mass or more and 8% by mass or less, more preferably 0.85% by mass or more and 7% by mass or less, still more preferably 1% by mass or more and 5% by mass or less, still more preferably 1.3% by mass or more and 4.5% by mass or less, and still more preferably 1.5% by mass or more and 3% by mass or less.

[0024] The mass ratio of the content of compound C to the content of carboxylic acid B in the copper fine particle dispersion according to the present invention is preferably 0.05 or more, more preferably 0.1 or more, still more preferably 0.25 or more, still more preferably 0.3 or more, and still more preferably 0.4 or more from the viewpoints of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, the low-temperature joining property, and the low-temperature joining property after storage. From the viewpoints of improving the dispersion stability of the copper fine particle dispersion, improving the low-temperature sinterability, the low-temperature joining property, and the low-temperature joining property after storage, it is preferably 9 or less, more preferably 7.5 or less, still more preferably 7 or less, still more preferably 6.2 or less, still more preferably 4 or less, still more preferably 3.1 or less, and still more preferably 0.8 or less. Considering these viewpoints comprehensively, the mass ratio of the content of compound C to the content of carboxylic acid B in the copper fine particle dispersion according to the present invention is preferably 0.05 or more and 9 or less, more preferably 0.05 or more and 7 or less, still more preferably 0.1 or more and 6.2 or less, still more preferably 0.25 or more and 4 or less, still more preferably 0.3 or more and 3.1 or less, and still more preferably 0.4 or more and 0.8 or less.

[0025] <Dispersion medium D> The copper fine particle dispersion according to the present invention contains a dispersion medium D from the viewpoint of improving the dispersion stability of the copper fine particle dispersion and improving the storage stability and low-temperature joinability after storage of the copper fine particle dispersion. The dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin (boiling point: 290 ° C, molecular weight: 92), and glycerin derivative from the viewpoint of improving the dispersion stability of the copper fine particle dispersion and improving the storage stability and low-temperature joinability after storage of the copper fine particle dispersion.

[0026] Examples of the (poly)alkylene glycol include ethylene glycol (boiling point: 197 ° C, molecular weight: 62), propylene glycol (boiling point: 188 ° C, molecular weight: 76), diethylene glycol (boiling point: 244 ° C, molecular weight: 106), triethylene glycol (boiling point: 287 ° C, molecular weight: 150), tetraethylene glycol (boiling point: 327 ° C, molecular weight: 194), dipropylene glycol (boiling point: 232 ° C, molecular weight: 134), tripropylene glycol (boiling point: 273 ° C, molecular weight: 192), tetrapropylene glycol (boiling point: 300 ° C or higher, molecular weight: 250), polyethylene glycol (number average molecular weight is preferably 100 or more and 1000 or less, more preferably 150 or more and 600 or less, still more preferably 180 or more and 500 or less), polypropylene glycol (number average molecular weight is preferably 150 or more and 1000 or less, more preferably 180 or more and 600 or less, still more preferably 200 or more and 500 or less), 2-ethyl-1,3-hexanediol (boiling point: 244 ° C, molecular weight: 146), and the like.

[0027] Examples of the (poly)alkylene glycol derivative include compounds in which the hydroxy group at the terminal of the (poly)alkylene glycol is etherified or esterified. Examples of the compound in which the hydroxy groups at both ends of the polyalkylene glycol are etherified or esterified include diethylene glycol dimethyl ether (boiling point: 162 °C, molecular weight: 134), diethylene glycol dibutyl ether (boiling point: 254 °C, molecular weight: 218), triethylene glycol dimethyl ether (boiling point: 216 °C, molecular weight: 178), diethylene glycol monoethyl ether acetate (boiling point: 217 °C, molecular weight: 176), diethylene glycol monobutyl ether acetate (boiling point: 247 °C, molecular weight: 204), and the like. Examples of the compound in which the hydroxy group at one end of the polyalkylene glycol is etherified or esterified include diethylene glycol monoethyl ether (boiling point: 202 °C, molecular weight: 134), diethylene glycol monobutyl ether (boiling point: 231 °C, molecular weight: 162), and the like.

[0028] Examples of the terpene alcohol include monoterpene alcohols such as α-terpineol (boiling point: 219 °C, molecular weight: 154), linalool (boiling point: 198 °C, molecular weight: 154), geraniol (boiling point: 229 °C, molecular weight: 154), citronellol (boiling point: 225 °C, molecular weight: 156), and the like.

[0029] As the glycerin derivative, for example, there is no particular limitation as long as it is a solvent containing a structure derived from glycerin. For example, ether derivatives of glycerin, ester derivatives of glycerin, polyglycerin, alkylene oxide adducts of glycerin (such as ethylene oxide adducts and propylene oxide adducts), etc. can be mentioned. Examples of polyglycerin include diglycerin, triglycerin, etc. Examples of commercially available polyglycerin include polyglycerin #310, polyglycerin #500, polyglycerin #750, etc. manufactured by Sakamoto Yakuhin Kogyo Co., Ltd. Examples of ether derivatives of glycerin include 3-(2-ethylhexyloxy)-1,2-propanediol (boiling point: 325°C, molecular weight 204), etc. Examples of ester derivatives of glycerin include glyceryl tributyrate (boiling point: 305°C, molecular weight 302), etc.

[0030] From the viewpoint of improving the dispersion stability of the copper fine particle dispersion and improving the storage stability and low-temperature joining property after storage of the copper fine particle dispersion, the dispersion medium D preferably contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, and terpene alcohol. More preferably, it contains at least one selected from dipropylene glycol, tetraethylene glycol, polyethylene glycol (the number average molecular weight is preferably 100 or more and 1000 or less, more preferably 150 or more and 600 or less, still more preferably 180 or more and 500 or less), α-terpineol, and diethylene glycol monobutyl ether. Still more preferably, it contains at least one selected from dipropylene glycol, tetraethylene glycol, polyethylene glycol (number average molecular weight 180 or more and 500 or less), α-terpineol, and diethylene glycol monobutyl ether.

[0031] The boiling point of the dispersion medium D at 1 atm is preferably 180 °C or higher, more preferably 200 °C or higher, still more preferably 210 °C or higher, still more preferably 220 °C or higher, still more preferably 225 °C or higher, from the viewpoint of improving the storage stability of the copper fine particle dispersion and the low-temperature joining property after storage, and is preferably 400 °C or lower, more preferably 360 °C or lower, still more preferably 330 °C or lower, still more preferably 310 °C or lower, from the viewpoint of improving the low-temperature sintering property, the low-temperature joining property, and the low-temperature joining property after storage. When two or more kinds are used in combination as the dispersion medium D, the boiling point of the dispersion medium D is the weighted average value weighted by the content (% by mass) of each dispersion medium.

[0032] The molecular weight of the dispersion medium D is preferably 60 or higher, more preferably 100 or higher, still more preferably 110 or higher, still more preferably 130 or higher, from the viewpoint of improving the storage stability of the copper fine particle dispersion and the low-temperature joining property after storage, and is preferably 600 or lower, more preferably 450 or lower, still more preferably 400 or lower, still more preferably 350 or lower, still more preferably 330 or lower, from the viewpoint of improving the low-temperature sintering property, the low-temperature joining property, and the low-temperature joining property after storage. When two or more kinds are used in combination as the dispersion medium D, the molecular weight of the dispersion medium D is the weighted average value weighted by the content (% by mass) of each dispersion medium.

[0033] The total content of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative (hereinafter also referred to as "dispersion medium D1") in the dispersion medium D is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 98% by mass or more, still more preferably 99% by mass or more, still more preferably 99.9% by mass or more, still more preferably substantially 100% by mass, from the viewpoint of improving the storage stability of the copper fine particle dispersion and the low-temperature joining property after storage. Here, "substantially 100% by mass" means that it may include components contained unintentionally. Examples of the components contained unintentionally include the dispersion medium D other than the dispersion medium D1 contained in the dispersion medium D1.

[0034] The total content of (poly)alkylene glycol, (poly)alkylene glycol derivative, and terpene alcohol (hereinafter also referred to as "dispersion medium D2") in the dispersion medium D is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 98% by mass or more, still more preferably 99% by mass or more, still more preferably 99.9% by mass or more, still more preferably substantially 100% by mass, from the viewpoint of improving the storage stability of the copper fine particle dispersion and the low-temperature joinability after storage. Here, "substantially 100% by mass" means that it may include components contained unintentionally. Examples of the components contained unintentionally include the dispersion medium D other than the dispersion medium D2 contained in the dispersion medium D2.

[0035] The total content of dipropylene glycol, tetraethylene glycol, polyethylene glycol (number average molecular weight of 180 or more and 500 or less), α-terpineol, and diethylene glycol monobutyl ether (hereinafter also referred to as "dispersion medium D3") in the dispersion medium D is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 98% by mass or more, still more preferably 99% by mass or more, still more preferably 99.9% by mass or more, still more preferably substantially 100% by mass, from the viewpoint of improving the storage stability of the copper fine particle dispersion and the low-temperature joinability after storage. Here, "substantially 100% by mass" means that it may include components contained unintentionally. Examples of the components contained unintentionally include the dispersion medium D other than the dispersion medium D3 contained in the dispersion medium D3.

[0036] From the perspective of improving the dispersion stability of the copper microparticle dispersion, and enhancing the storage stability and low-temperature joining property after storage of the copper microparticle dispersion, the content of the dispersion medium D in the copper microparticle dispersion according to the present invention is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 6% by mass or more, still more preferably 6.5% by mass or more, and still more preferably 7.5% by mass or more. From the same perspective, it is preferably less than 10% by mass, more preferably 9.9% by mass or less, still more preferably 9.5% by mass or less, still more preferably 9% by mass or less, and still more preferably 8.5% by mass or less. Considering these perspectives comprehensively, the content of the dispersion medium D in the copper microparticle dispersion according to the present invention is preferably 3% by mass or more and less than 10% by mass, more preferably 4% by mass or more and 9.9% by mass or less, still more preferably 6% by mass or more and 9.5% by mass or less, still more preferably 6.5% by mass or more and 9% by mass or less, and still more preferably 7.5% by mass or more and 8.5% by mass or less.

[0037] From the perspective of suppressing the oxidation of copper, and improving the storage stability and low-temperature joining property after storage of the copper microparticle dispersion, the water content in the copper microparticle dispersion according to the present invention is preferably 5% by mass or less, more preferably 1% by mass or less, still more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, and still more preferably 0.01% by mass or less.

[0038] <Copper microparticles> The copper microparticle dispersion according to the present invention may further contain copper microparticles from the perspective of improving conductivity, low-temperature sinterability, low-temperature joining property, and low-temperature joining property after storage. From the perspective of improving conductivity, low-temperature sinterability, low-temperature joining property, and low-temperature joining property after storage, the copper content in the copper microparticles is preferably 95% by mass or more, more preferably 98% by mass or more, still more preferably 99% by mass or more, and still more preferably substantially 100% by mass. Here, "substantially 100% by mass" means that it may include components contained unintentionally. Examples of components contained unintentionally include inevitable impurities.

[0039] From the viewpoint of improving conductivity, low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, the average particle size of the copper microparticles is preferably more than 0.35 μm, more preferably 0.5 μm or more, still more preferably 0.7 μm or more, still more preferably 0.8 μm or more, and still more preferably 0.9 μm or more. From the viewpoint of improving the dispersion stability and storage stability of the copper microparticle dispersion and the low-temperature joinability after storage, it is preferably 10 μm or less, more preferably 7 μm or less, still more preferably 5 μm or less, still more preferably 3 μm or less, and still more preferably 2 μm or less. The average particle size of the copper microparticles is measured by the method described in the examples.

[0040] From the viewpoint of improving conductivity, low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, the content of the copper microparticles in the copper microparticle dispersion according to the present invention is preferably 5% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and still more preferably 25% by mass or more. From the viewpoints of improving conductivity, dispersion stability of the copper microparticle dispersion, storage stability of the copper microparticle dispersion, low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, it is preferably 65% by mass or less, more preferably 55% by mass or less, still more preferably 45% by mass or less, and still more preferably 35% by mass or less.

[0041] From the viewpoints of improving conductivity, storage stability of the copper microparticle dispersion, low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, the mass ratio of the content of the copper nanoparticles A to the total content of the copper nanoparticles A and the copper microparticles in the copper microparticle dispersion according to the present invention [copper nanoparticles A / (copper nanoparticles A + copper microparticles)] is preferably 0.3 or more, more preferably 0.4 or more, still more preferably 0.5 or more, and still more preferably 0.6 or more. From the viewpoints of improving conductivity, low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, it is preferably 1.0 or less, more preferably 0.9 or less, still more preferably 0.8 or less, and still more preferably 0.75 or less.

[0042] (Composition of copper microparticle dispersion) In the copper microparticle dispersion according to the present invention, from the viewpoints of improving the dispersion stability, storage stability, conductivity, low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage of the copper microparticle dispersion, the content of copper nanoparticles A is preferably more than 25% by mass and less than 97% by mass, the content of carboxylic acid B is preferably 0.1% by mass or more and 7.5% by mass or less, the content of compound C is 0.05% by mass or more and 7.5% by mass or less, the content of dispersion medium D is preferably 3% by mass or more and less than 10% by mass, and the content of copper microparticles is preferably 0% by mass or more and 65% by mass or less.

[0043] The copper microparticle dispersion according to the present invention may contain various additives as other components other than the above components, as long as the effects of the present invention are not inhibited. Examples of the additives include metal particles other than copper nanoparticles A and copper microparticles, sintering accelerators such as glass frit, antioxidants, viscosity modifiers, pH adjusters, buffers, defoamers, leveling agents, and volatilization inhibitors. Examples of the 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 the additive in the copper microparticle dispersion according to the present invention is preferably 1% by mass or less.

[0044] (Manufacture of copper microparticle dispersion) The copper microparticle dispersion according to the present invention can be obtained by a method of adding and mixing carboxylic acid B, compound C, and dispersion medium D, and optionally copper microparticles 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 carboxylic acid B, and optionally a solvent for dispersing the copper raw material compound and the reducing agent, reducing the copper raw material compound to obtain a dispersion of copper nanoparticles A, and then adding and mixing compound C, dispersion medium D, and optionally carboxylic acid B, copper microparticles, and various additives. Among them, from the viewpoints of improving the dispersion stability of the copper microparticle dispersion and improving the storage stability and low-temperature joinability after storage of the copper microparticle dispersion, after obtaining a dry powder of copper nanoparticles A containing carboxylic acid B in advance (hereinafter also referred to as "copper nanoparticle dry powder"), a method of adding and mixing compound C, dispersion medium D, and optionally carboxylic acid B, copper microparticles, and various additives is preferable. The copper nanoparticle dry powder can be obtained by mixing a copper raw material compound, a reducing agent, and carboxylic acid B, obtaining a dispersion of copper nanoparticles A in which the copper raw material compound is reduced by the reducing agent and dispersed by carboxylic acid B, and then drying the dispersion of copper nanoparticles A by freeze-drying or the like.

[0045] The copper raw material compound is not particularly limited as long as it is a compound containing copper. Examples of the copper raw material compound include copper sulfate, copper nitrate, cupric oxide, cuprous oxide, copper formate, copper acetate, copper oxalate, etc. The copper raw material compound can be used alone or in combination of two or more.

[0046] 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-based 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 bisulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, and sodium hypophosphite. The reducing agent may be used alone or in combination of two or more.

[0047] Examples of the solvent for dispersing the copper raw material compound and the reducing agent include water, methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, etc.

[0048] The temperature of the reduction reaction is preferably 5°C or higher, more preferably 10°C or higher, still more preferably 20°C or higher, still more preferably 30°C or higher, still more preferably 50°C or higher, still more preferably 60°C or higher from the viewpoint of reducing the particle size of copper nanoparticles A and making them uniform, and is preferably in the range of 100°C or lower, more preferably 90°C or lower, still more preferably 80°C or lower, still more preferably 75°C or lower from the viewpoint of stably producing copper nanoparticles. The reduction reaction may be carried out in an air atmosphere or in an inert gas atmosphere such as nitrogen gas.

[0049] In the production of the copper fine particle dispersion, from the viewpoint of removing impurities such as unreacted reducing agent and excess carboxylic acid B that does not contribute to the dispersion of copper nanoparticles A, the dispersion of copper nanoparticles A may be purified before freeze-drying. The method for purifying the dispersion of copper nanoparticles A is not particularly limited, and examples include membrane treatment such as dialysis and ultrafiltration; methods such as centrifugation treatment. Among them, from the viewpoint of efficiently removing impurities, membrane treatment is preferable, and dialysis is more preferable. As the material of the dialysis membrane used for dialysis, regenerated cellulose is preferable. The molecular weight cut-off of the dialysis membrane is preferably 1,000 or higher, more preferably 5,000 or higher, still more preferably 10,000 or higher, and is preferably 100,000 or lower, more preferably 70,000 or lower from the viewpoint of efficiently removing impurities. The copper fine particle dispersion according to the present invention can be obtained by further adding the above-mentioned various additives as necessary and performing a filtration treatment using a filter or the like.

[0050] The copper microparticle dispersion according to the present invention has good low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage, and thus can be used for forming conductive members of various electronic and electrical devices. The conductive member can preferably be used for a bonding agent such as solder; an antenna such as an RFID (radio frequency identifier) tag; a capacitor such as an MLCC (multi-layer ceramic capacitor); electronic paper; an image display device such as a liquid crystal display or an organic EL display; an organic EL element; an organic transistor; a wiring board such as a printed wiring board or a flexible wiring board; an organic solar cell; a sensor such as a flexible sensor. Among these, the copper microparticle dispersion according to the present invention is preferably used for joining a plurality of metal members from the viewpoints of low-temperature sinterability, low-temperature joinability, and low-temperature joinability after storage.

[0051] [Method for manufacturing a joined body] The method for manufacturing a joined body according to the present invention is a method for manufacturing a joined body including a step of heating with a copper microparticle dispersion interposed between a plurality of metal members, wherein the copper microparticle dispersion is the copper microparticle dispersion of the present invention described above. When the copper microparticle dispersion according to the present invention is used for joining a plurality of metal members, it is preferably used in a method for manufacturing a joined body including a step of heating with the copper microparticle dispersion interposed between a plurality of metal members.

[0052] From the viewpoints of joint strength and conductivity, the temperature of the heat treatment in the step of heating is preferably 100°C or higher, more preferably 150°C or higher, still more preferably 180°C or higher, and from the viewpoints of improving low-temperature sinterability and low-temperature joinability, it is preferably 230°C or lower, more preferably 220°C or lower, still more preferably 210°C or lower, and still more preferably 205°C or lower. The heat treatment in the heating step can be carried out either under non-pressure or under pressure. From the viewpoints of bonding strength and conductivity, under pressure is preferred. The pressure of the heat treatment in the heating step is preferably 5 MPa or more, more preferably 8 MPa or more, still more preferably 10 MPa or more, and still more preferably 15 MPa or more from the viewpoints of improving low-temperature sinterability and low-temperature joinability, and is preferably 50 MPa or less, more preferably 30 MPa or less, still more preferably 25 MPa or less, and still more preferably 20 MPa or less from the viewpoint of productivity. The time of the heat treatment in the heating step can be appropriately adjusted according to the temperature and pressure of the heat treatment. The atmosphere in the heating step may be an air atmosphere, an inert gas atmosphere such as a nitrogen gas atmosphere, or a reducing gas atmosphere such as a hydrogen gas atmosphere. However, from the viewpoints of suppressing oxidation of copper and safety, a nitrogen gas atmosphere is more preferred.

[0053] Examples of the metal members to be joined in the present invention include metal-based substrates or metal substrates such as gold substrates, gold-plated substrates, silver substrates, silver-plated metal substrates, copper substrates, palladium substrates, palladium-plated metal substrates, platinum substrates, platinum-plated metal substrates, aluminum substrates, nickel substrates, nickel-plated metal substrates, tin substrates, tin-plated metal substrates; and metal parts such as electrodes of electrical insulating substrates. The plurality of metal members used in the present invention may be of the same type or different types of metal members. Among these, the metal member preferably contains at least one selected from gold substrates, gold-plated substrates, silver substrates, silver-plated metal substrates, copper substrates, palladium substrates, palladium-plated metal substrates, platinum substrates, platinum-plated metal substrates, aluminum substrates, nickel substrates, nickel-plated metal substrates, tin substrates, tin-plated metal substrates, and metal parts of electrical insulating substrates. The joining of the metal members in the present invention can be used for joining chip components such as capacitors and resistors to circuit boards; joining semiconductor chips such as memories, diodes, transistors, ICs, and CPUs to lead frames or circuit boards; joining high-heat-generating semiconductor chips to cooling plates, etc.

[0054] As methods for applying the copper fine particle dispersion to a metal member, various coating methods such as slot die coating, dip coating, spray coating, spin coating, doctor blading, knife edge coating, bar coating, etc.; and various patterning printing methods such as stencil printing, screen printing, flexographic printing, gravure printing, offset printing, dispenser printing, inkjet printing, etc. can be mentioned. The amount of the copper fine particle dispersion applied to the metal member can be appropriately adjusted according to the size and type of the metal member to be joined.

[0055] The bonding strength of the joined body is preferably 10 MPa or more, more preferably 15 MPa or more. The bonding strength can be measured by the method described in the examples.

[0056] Regarding the above-described embodiments, the present invention further discloses the following embodiments. <1> It contains copper nanoparticles A, a carboxylic acid B having 6 to 14 carbon atoms, a compound C represented by the following formula (1), and a dispersion medium D. The dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative. The content of the carboxylic acid B is 0.1% by mass or more. The content of the compound C is 0.05% by mass or more. A copper fine particle dispersion in which the total content of the carboxylic acid B and the compound C is 8% by mass or less. RO-(CH2CH2O) n -CH2-COOH (1) 〔In formula (1), R is a hydrocarbon group having 6 to 14 carbon atoms, n is the average number of moles of ethyleneoxy groups added, and is a number from 0.5 to 20.〕 <2> It contains copper nanoparticles A, a carboxylic acid B having 6 to 14 carbon atoms, a compound C represented by the following formula (1), and a dispersion medium D. The dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative, the content of the copper nanoparticles A is more than 25% by mass and less than 97% by mass, the content of the carboxylic acid B is 0.1% by mass or more and 7.5% by mass or less, the content of the compound C is 0.05% by mass or more and 7.5% by mass or less, the total content of the carboxylic acid B and the compound C is 0.85% by mass or more and 8% by mass or less, the copper fine particle dispersion according to <1>, wherein the boiling point of the dispersion medium D is 180°C or higher and 400°C or lower. RO-(CH2CH2O) n -CH2-COOH (1) [In formula (1), R is a hydrocarbon group having 6 to 14 carbon atoms, n is the average number of added moles of ethyleneoxy groups, and is a number of 0.5 or more and 20 or less.] <3> containing copper nanoparticles A, a carboxylic acid B having 6 to 14 carbon atoms, a compound C represented by the following formula (1), and a dispersion medium D, the dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative, the content of the copper nanoparticles A is more than 25% by mass and less than 97% by mass, the content of the carboxylic acid B is 0.1% by mass or more and 7.5% by mass or less, the content of the compound C is 0.05% by mass or more and 7.5% by mass or less, the total content of the carboxylic acid B and the compound C is 0.85% by mass or more and 8% by mass or less, the copper fine particle dispersion according to <1> or <2>, wherein the molecular weight of the dispersion medium D is 60 or more and 600 or less. RO-(CH2CH2O) n -CH2-COOH (1) [In formula (1), R is a hydrocarbon group having 6 to 14 carbon atoms, n is the average number of moles of ethyleneoxy groups added, and is a number of 0.5 or more and 20 or less.] <4> It contains copper nanoparticles A, carboxylic acid B having 6 to 14 carbon atoms, compound C represented by the following formula (1), and dispersion medium D, wherein the dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative, the content of the copper nanoparticles A is 40% by mass or more and 93% by mass or less, the content of the carboxylic acid B is 0.3% by mass or more and 6% by mass or less, the content of the compound C is 0.05% by mass or more and 6% by mass or less, the total content of the carboxylic acid B and the compound C is 0.85% by mass or more and 7% by mass or less, the boiling point of the dispersion medium D is 180°C or more and 400°C or less, the molecular weight of the dispersion medium D is 60 or more and 600 or less, the copper fine particle dispersion according to any one of <1> to <3>. RO-(CH2CH2O) n -CH2-COOH (1) [In formula (1), R is a hydrocarbon group having 6 to 14 carbon atoms, n is the average number of moles of ethyleneoxy groups added, and is a number of 4 or more and 12 or less.] <5> It contains copper nanoparticles A, carboxylic acid B having 6 to 12 carbon atoms, compound C represented by the following formula (1), and dispersion medium D, wherein the dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, and terpene alcohol, the content of the copper nanoparticles A is 50% by mass or more and 91% by mass or less, the content of the carboxylic acid B is 0.3% by mass or more and 6% by mass or less, the content of the compound C is 0.05% by mass or more and 6% by mass or less, The total content of the carboxylic acid B and the compound C is 0.85% by mass or more and 7% by mass or less, the boiling point of the dispersion medium D is 200°C or higher and 400°C or lower, The copper fine particle dispersion according to any one of <1> to <4>, wherein the molecular weight of the dispersion medium D is 100 or more and 450 or less. RO-(CH2CH2O) n -CH2-COOH (1) [In formula (1), R is a hydrocarbon group having 8 to 12 carbon atoms, n is the average number of moles of ethyleneoxy groups added, and is a number from 4 to 12.] <6> The copper nanoparticles A, carboxylic acid B having 6 to 12 carbon atoms, compound C represented by the following formula (1), and dispersion medium D are contained, the dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, and terpene alcohol, the content of the copper nanoparticles A is 50% by mass or more and 91% by mass or less, the content of the carboxylic acid B is 0.5% by mass or more and 4% by mass or less, the content of the compound C is 0.5% by mass or more and 2.5% by mass or less, the total content of the carboxylic acid B and the compound C is 1% by mass or more and 5% by mass or less, the boiling point of the dispersion medium D is 220°C or higher and 400°C or lower, the molecular weight of the dispersion medium D is 130 or more and 400 or less, The copper fine particle dispersion according to any one of <1> to <5>, wherein the content of the dispersant D is 3% by mass or more and less than 10% by mass. RO-(CH2CH2O) n -CH2-COOH (1) [In formula (1), R is a hydrocarbon group having 8 to 12 carbon atoms, n is the average number of moles of ethyleneoxy groups added, and is a number from 6 to 10.] <7> The copper fine particle dispersion according to any one of <1> to <6>, wherein the average particle diameter of the copper nanoparticles A is 100 nm or more and 350 nm or less. <8> The copper microparticle dispersion according to any one of <1> to <7>, wherein the mass ratio of the content of the compound C to the content of the carboxylic acid B is 0.05 or more and 9 or less. <9> The copper microparticle dispersion according to any one of <1> to <8>, wherein the dispersion medium D contains at least one selected from dipropylene glycol, tetraethylene glycol, polyethylene glycol having a number average molecular weight of 180 or more and 500 or less, α-terpineol, and diethylene glycol monobutyl ether. <10> The copper microparticle dispersion according to any one of <1> to <9>, further containing copper microparticles, wherein the average particle diameter of the copper microparticles is more than 0.35 μm and 10 μm or less. <11> The copper microparticle dispersion according to <10>, wherein the content of the copper microparticles is 5% by mass or more and 65% by mass or less. <12> The copper microparticle dispersion according to any one of <1> to <11>, which is used for joining a plurality of metal members. <13> A method for manufacturing a joined body, comprising a step of interposing the copper microparticle dispersion according to any one of <1> to <11> between a plurality of metal members and heating. <14> The method for manufacturing a joined body according to <13>, wherein the temperature of the heat treatment in the step of heating is 230°C or lower. <15> The method for manufacturing a joined body according to <13> or <14>, wherein the atmosphere in the step of heating is an inert gas atmosphere. <16> The method for manufacturing a joined body according to any one of <13> to <15>, wherein the metal member contains at least one selected from the group consisting of 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, a tin-plated metal substrate, and the metal part of an electrically insulating substrate. <17> The method for manufacturing the bonded body according to any one of <13> to <16>, wherein the bonding of the metal member is any one selected from the group consisting of the bonding between a chip component and a circuit board, the bonding between a semiconductor chip and a lead frame or a circuit board, and the bonding between a highly heat-generating semiconductor chip and a cooling plate.

Example

[0057] Hereinafter, the present invention will be described in more detail 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 "%" are "parts by mass" and "% by mass" unless otherwise specified. Various physical properties were measured or calculated by the following methods.

[0058] [Average particle sizes of copper nanoparticles A and copper microparticles] Using a scanning electron microscope (manufactured by Hitachi High-Tech Corporation, field emission scanning electron microscope: S-4800), scanning electron microscope (SEM) images of copper nanoparticles A and copper microparticles were taken. The magnification was determined according to the particle size of the particles, and imaging was performed in the range of 5000 times to 150000 times. The SEM images were analyzed using image analysis software ImageJ (National Institutes of Health, USA), and the particle sizes were determined for 100 or more particles per sample, and their arithmetic mean values were taken as the average particle sizes of copper nanoparticles A and copper microparticles.

[0059] [Calculation of the content of carboxylic acid B in the dry powder of copper nanoparticles A containing carboxylic acid B] Using a differential thermal thermogravimetric simultaneous measurement device (TG / DTA) (manufactured by Hitachi High-Tech Science Corporation, trade name: STA7200RV), 10 mg of a sample (dry powder of copper nanoparticles A containing carboxylic acid B) was weighed into an aluminum pan cell, and the temperature was raised from 35°C to 550°C at a rate of 10°C / min under a nitrogen flow of 50 mL / min, and the mass reduction amount was measured. The mass reduction amount from 35°C to 550°C was taken as the mass of carboxylic acid B, and the remaining mass at 550°C was taken as the mass of copper nanoparticles A, and the content of carboxylic acid B was calculated by the following formula. Content of carboxylic acid B [mass%] = 100×(Mass reduction from 35°C to 550°C) / (Mass reduction from 35°C to 550°C + Residual mass at 550°C)

[0060] [Calculation of the content of carboxylic acid B in the dry powder of copper microparticles A containing carboxylic acid B] The sample was calculated in the same manner as [Calculation of the content of carboxylic acid B in the dry powder of copper nanoparticles A containing carboxylic acid B], except that the sample was changed to the dry powder of copper microparticles a containing carboxylic acid B.

[0061] (Synthesis of copper nanoparticle dry powder) Synthesis Example 1 (Production of copper nanoparticles A1) Into a 2L beaker, 50.0 g of copper oxide (manufactured by Nisshin KEMCO Co., Ltd., N-120) as a copper raw material compound, 4.40 g of hexanoic acid (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent), and 500 g of ethanol (95) (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) were added and stirred for 15 minutes. During the stirring, the temperature of the reaction solution was controlled at 70°C with an oil bath. Next, 63.0 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) placed in a 50 mL dropping funnel was added dropwise to the above mixture at 25°C over 20 minutes. Then, the reaction solution was stirred for 1 hour while controlling the temperature of the reaction solution at 70°C with 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 500PA bottle of a centrifugation sedimentation tube manufactured by the same company using a cooling centrifuge "himac CR22G" and a rotor (R12A, radius 15.1 cm) manufactured by Hitachi Koki Co., Ltd., and centrifuged at 2000 revolutions / minute with a centrifugal acceleration of 675G and held in this state for 30 minutes. 300 g of acetone (manufactured by Fujifilm Wako Pure Chemical Corporation, primary grade reagent) was added to the precipitate separated by centrifugation and stirred for 15 minutes for redispersion. Again, the entire amount of the redispersion was centrifuged under the same conditions, and the precipitate was separated. This operation was performed twice. Next, 300 g of methanol (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) was added to the precipitate and stirred for 15 minutes for redispersion. Again, the entire amount of the redispersion was centrifuged under the same conditions, and the precipitate was separated. This operation was performed twice. The precipitate of the refined copper nanoparticles was freeze-dried using a freeze dryer (manufactured by Tokyo Rika Kikai Co., Ltd., model: FDU-2110) attached with a dry chamber (manufactured by Tokyo Rika Kikai Co., Ltd., model: DRC-1000), thereby obtaining 38.0 g of copper nanoparticles A-1. The drying conditions were freezing at -25°C for 1 hour, vacuum drying at -10°C for 9 hours at 5 Pa, and further vacuum drying at 25°C for 5 hours at 5 Pa to obtain a dry powder of copper nanoparticles A1 containing hexanoic acid. The obtained copper nanoparticles had an average particle size of 250 nm and a hexanoic acid content of 0.9 mass%.

[0062] Synthesis Example 2 (Production of Copper Nanoparticles A3) The procedure was the same as in Synthesis Example 1 except that hexanoic acid was changed to stearic acid, and a dry powder of copper nanoparticles A3 containing stearic acid was obtained. The obtained copper nanoparticles A3 had an average particle size of 240 nm and a stearic acid content of 1.0 mass%.

[0063] (Synthesis of Copper Micro-Particles) Synthesis Example 3 (Production of Copper Micro-Particles a1) The procedure was the same as in Synthesis Example 1 except that the addition amount of hexanoic acid was changed from 4.40 g to 0.50 g, and a dry powder of copper micro-particles a1 containing hexanoic acid was obtained. The obtained copper micro-particles a1 had an average particle size of 1.0 μm and a hexanoic acid content of 0.3 mass%.

[0064] Synthesis Example 4 (Production of Copper Micro-Particles a2) The procedure was the same as in Synthesis Example 3 except that hexanoic acid was changed to lauric acid, and a dry powder of copper micro-particles a2 containing lauric acid was obtained. The obtained copper micro-particles a2 had an average particle size of 1.1 μm and a lauric acid content of 0.3 mass%.

[0065] (Synthesis of Compound C) Synthesis Example 5 (Production of Compound C1) According to the conventional method (such as JP-A-2008-303207), compound C1 (hydrate containing about 10% by mass) was obtained. The obtained compound C1 hydrate was frozen at -25°C for 1 hour 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), and then dried under reduced pressure at -10°C for 9 hours at 5 Pa, and further dried under reduced pressure at 25°C for 5 hours at 5 Pa to obtain compound C1 as a dry powder. For compound C1, R is an n-octyl group and n is 8.

[0066] Synthesis Example 6 (Production of Compound C2) The procedure was the same as in Synthesis Example 5 to obtain compound C2. For compound C2, R is a lauryl group and n is 10.

[0067] Synthesis Example 7 (Production of Compound C3) The procedure was the same as in Synthesis Example 5 to obtain compound C3. For compound C3, R is a lauryl group and n is 6.

[0068] Synthesis Example 8 (Production of Compound C4) The procedure was the same as in Synthesis Example 5 to obtain compound C4. For compound C4, R is an oleyl group and n is 9.

[0069] Example 1 (Preparation of Copper Fine Particle Dispersion) 0.49 g of dipropylene glycol (manufactured by Fujifilm Wako Pure Chemical Corporation, primary reagent), 0.5 g of tetraethylene glycol (manufactured by Fujifilm Wako Pure Chemical Corporation, primary reagent), 9.0 g of the dry powder of copper nanoparticles A1 containing hexanoic acid obtained in Synthesis Example 1, and 0.01 g of compound C1 obtained in Synthesis Example 5 were added to an agate mortar and kneaded until the dry powder was no longer visible to the naked eye, and the resulting mixed solution was transferred to a plastic bottle. The sealed plastic bottle was stirred at 2000 min -1 (2000 revolutions per minute) for 5 minutes to obtain copper fine particle dispersion 1.

[0070] (Production of Bonded Body) Using the obtained copper fine particle dispersion 1, a joined body was produced according to the following method. First, a stainless steel metal mask (thickness: 150 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 fine particle dispersion was applied onto the copper plate by stencil printing using a metal squeegee. Thereafter, it was dried at 120° C. for 10 minutes on an atmospheric pressure shamar hot plate (manufactured by AS ONE Corporation, HHP-441). Thereafter, a silicon chip (thickness: 400 μm) of 5 mm × 5 mm was prepared, and a silicon chip sputter-treated with titanium, nickel, and gold in this order was placed on the applied copper fine particle dispersion such that the gold was in contact with the copper fine particle dispersion. Thus, a laminate in which a copper plate, a copper fine particle dispersion, and a silicon chip were laminated in this order was obtained. The obtained laminate was fired by the following method to obtain a joined body. First, the laminate was set in a pressure firing machine (manufactured by Meisho Kiko Co., Ltd., HTM-1000), and nitrogen was flowed into the furnace at 500 mL / min to replace the air in the furnace with nitrogen. Thereafter, while pressurizing the laminate with the upper and lower heating heads at 20 MPa, the temperature of the heating heads was raised to 200° C. over 10 minutes. After the temperature rise, it was held at 200° C. for 150 seconds for sintering treatment to obtain a joined body. After sintering, the heating heads were water-cooled at -60° C. / min, and the joined body was taken out into the air at 100° C. or lower.

[0071] Examples 2 to 18, Comparative Examples 1 to 8 The copper fine particle dispersions and joined bodies of Examples 2 to 18 and Comparative Examples 1 to 8 were obtained in the same manner as in Example 1 except that the composition of the copper fine particle dispersion was changed to the composition shown in Table 1.

[0072] The raw materials used for the production of the copper fine particle dispersion are shown below. Dry powder of copper nanoparticles A2 containing lauric acid (manufactured by Mitsui Mining & Smelting Co., Ltd., CH200L1, average particle diameter 190 nm, lauric acid content 1.3 mass%) Hexanoic acid (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) Lauric acid (manufactured by Fujifilm Wako Pure Chemical Corporation, first grade reagent) Stearic acid (manufactured by FUJIFILM Wako Pure Chemical Corporation, special grade reagent) Dipropylene glycol (DPG, manufactured by FUJIFILM Wako Pure Chemical Corporation, first grade reagent) Tetraethylene glycol (TEG, manufactured by FUJIFILM Wako Pure Chemical Corporation, first grade reagent) PEG200 (manufactured by FUJIFILM Wako Pure Chemical Corporation, first grade reagent, polyalkylene glycol 200) PEG400 (manufactured by FUJIFILM Wako Pure Chemical Corporation, first grade reagent, polyalkylene glycol 400) α-Terpineol (manufactured by FUJIFILM Wako Pure Chemical Corporation, special grade reagent) Diethylene glycol monobutyl ether (manufactured by FUJIFILM Wako Pure Chemical Corporation, special grade reagent)

[0073] Using the copper microparticle dispersions and bonded bodies obtained in Examples 1 to 18 and Comparative Examples 1 to 8, the following evaluations were conducted.

[0074] [Bonding strength of the bonded body] [Bonding strength of the bonded body] According to the following procedure, the bonding strength of the bonded body was measured. Using a universal bond tester (Prospector, manufactured by Nordson Advanced Technology Corporation), the silicon chip of the bonded body was pushed horizontally at a test speed of 5 mm / min and a shear height of 50 μm, and the die shear strength of the bonded body was measured. This was done for three bonded bodies each, and the average value of the values obtained by measuring the three bonded bodies was taken as the bonding strength of the bonded body. The results are shown in Table 2.

[0075] [Storage stability of the copper microparticle dispersion] The copper microparticle dispersion was stored at 25°C and 50% humidity for one month, and then the bonding strength of the bonded body was measured by the same method as described above. The results are shown in Table 2.

[0076] [Table 1]

[0077] [Table 2]

[0078] From Table 2, for the copper fine particle dispersions of Examples 1 to 18, even in the case of pressure sintering at 200°C under nitrogen, the bonding strength was improved, and the bonding strength of the bonded body obtained after storage for one month was good. On the other hand, the copper fine particle dispersions of Comparative Examples 1 to 8 were not dispersible. From the above, it can be seen that the copper fine particle dispersion of the present invention has improved bonding strength and good storage stability even under the firing conditions of 200°C under nitrogen.

Claims

Claim 1: A copper microparticle dispersion containing copper nanoparticles A with an average particle diameter of 100 nm or more and 350 nm or less, carboxylic acid B with 6 to 14 carbon atoms, compound C represented by the following formula (1), and dispersion medium D, wherein the dispersion medium D contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative, the content of the carboxylic acid B is 0.1% by mass or more, the content of the compound C is 0.05% by mass or more, and the total content of the carboxylic acid B and the compound C is 8% by mass or less. RO-(CH 2 CH 2 O) n -CH 2 -COOH (1) 〔In formula (1), R is a hydrocarbon group with 6 to 14 carbon atoms, n is the average number of added moles of ethyleneoxy groups, and is a number from 0.5 to 20.〕

2. The copper microparticle dispersion according to Claim 1, wherein the content of the copper nanoparticles A is more than 25% by mass and less than 97% by mass.

3. The copper microparticle dispersion according to Claim 1 or 2, wherein the content of the carboxylic acid B is 7.5% by mass or less.

4. The copper microparticle dispersion according to any one of Claims 1 to 3, wherein the content of the compound C is 7.5% by mass or less.

5. The copper microparticle dispersion according to any one of Claims 1 to 4, wherein the total content of the carboxylic acid B and the compound C is 0.85% by mass or more.

6. The copper microparticle dispersion according to any one of Claims 1 to 5, wherein the compound C includes a compound in which in the formula (1), R is a linear saturated alkyl group with 6 to 14 carbon atoms and n is from 4 to 12.

7. The copper microparticle dispersion according to any one of Claims 1 to 6, wherein the mass ratio of the content of the compound C to the content of the carboxylic acid B is from 0.05 to 9.

8. The copper microparticle dispersion according to any one of Claims 1 to 7, wherein the content of the dispersion medium D is more than 3% by mass and less than 10% by mass.

9. The copper microparticle dispersion according to any one of Claims 1 to 8, wherein the boiling point of the dispersion medium D is 180°C or higher and the molecular weight of the dispersion medium D is 600 or less.

10. The copper microparticle dispersion according to any one of Claims 1 to 9, further containing copper microparticles with an average particle diameter of more than 0.35 μm and 10 μm or less.

11. The copper microparticle dispersion according to Claim 10, wherein the content of the copper microparticles is 5% by mass or more and 65% by mass or less.

12. The copper microparticle dispersion according to any one of Claims 1 to 11, which is used for joining a plurality of metal members.

13. A method for manufacturing a bonded body, comprising a step of heating with a copper fine particle dispersion according to any one of Claims 1 to 12 interposed between a plurality of metal members.

14. The method for manufacturing a bonded body according to Claim 13, wherein the heat treatment temperature in the heating step is 230°C or lower.

15. The method for manufacturing a bonded body according to Claim 13 or 14, wherein the atmosphere in the heating step is an inert gas atmosphere.

16. The method for manufacturing a bonded body according to any one of Claims 13 to 15, wherein the metal member includes at least one selected from the group consisting of 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, a tin-plated metal substrate, and a metal part of an electrically insulating substrate.

17. The method for manufacturing a bonded body according to any one of Claims 13 to 16, wherein the bonding of the metal members is any one selected from the group consisting of bonding between a chip component and a circuit board, bonding between a semiconductor chip and a lead frame or a circuit board, and bonding between a high-heat-generating semiconductor chip and a cooling plate.

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