Copper nanoparticle-containing composition

Abstract

SOLUTION: A present invention relates to a composition containing copper nanoparticle comprising copper nanoparticle A, monocarboxylic acid B, and organic solvent C, where the monocarboxylic acid B has a carbon number of 5 or more and 12 or less, and the monocarboxylic acid B has one or more functional groups or bonds selected from the group consisting of hydroxyl groups, ketone carbonyl groups, and ether bonds a method for manufacturing a composite using the composition containing copper nanoparticle, and a composite or electronic device using the composition containing copper nanoparticle.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copper nanoparticle-containing composition, a method for producing a bonded body using the copper nanoparticle-containing composition, and a bonded body or electronic device using the copper nanoparticle-containing composition. [Background technology]

[0002] Copper has excellent electrical conductivity and is therefore widely used as a wiring material, for example. Copper also has excellent thermal conductivity, so it is used as a heat transfer material, heat exchange material, heat dissipation material, etc., and further, taking advantage of this performance, it is sometimes used as a joining material for joining materials together.

[0003] In recent years, semiconductors known as power devices have become increasingly important as power conversion and control devices, such as inverters. Unlike semiconductors used for information processing, such as memory and microprocessors, power devices control large currents and generate a large amount of heat during operation. Therefore, bonding materials used in mounting power devices require not only high bonding strength but also heat resistance. However, lead-free solder, which is widely used as a bonding material these days, has the disadvantage of low heat resistance. Therefore, various techniques have been proposed to bond objects by using metal particle dispersions instead of solder, which are applied to the objects by various coating methods and then fired. Metal particle dispersions, in which metal particles are dispersed in a dispersing medium, have been proposed as compositions used in mounting. Silver or copper is typically used as the metal species in these metal particle dispersions. Silver does not form an oxide film at room temperature (25°C). Therefore, silver particle dispersions are fired without a reducing agent to form a silver continuum, which is then used to bond the objects. On the other hand, copper contains oxidized copper atoms because its oxidation state is stable at room temperature (25°C). Therefore, in order to bond objects to be bonded using a copper fine particle dispersion, it is necessary to reduce the oxidized copper atoms and then sinter them to form a continuous copper body.

[0004] JP 2020-053404 A (Patent Document 1) describes a copper paste containing copper powder and a liquid medium, with the aim of providing a copper paste with high bonding strength to the object to be bonded, wherein 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, and 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, and the mass proportion of the copper powder in the copper paste is 50% to 99%. WO 2018 / 030173 (Patent Document 2) describes a bonding composition containing silver nanoparticles, a dispersion medium, and a first carboxylic acid containing an oxygen atom in the carbon chain and attached to at least a portion of the surface of the silver nanoparticles, with the aim of providing a bonding composition for obtaining a bonding layer with high bonding strength. JP 2010-189681 A (Patent Document 3) describes a method for producing copper nanoparticles that have both oxidation resistance and bondability, and includes a specific step of producing copper nanoparticles having citric acid on the surface. The method also describes a bonding method using the copper nanoparticles produced by this method. Summary of the Invention

[0005] The present invention comprises copper nanoparticles A, a monocarboxylic acid B, and an organic solvent C, the monocarboxylic acid B has 5 or more and 12 or less carbon atoms, The present invention relates to a copper nanoparticle-containing composition, in which the monocarboxylic acid B has one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond, a method for producing a bonded body using the copper nanoparticle-containing composition, and a bonded body or electronic device using the copper nanoparticle-containing composition. DETAILED DESCRIPTION OF THE INVENTION

[0006] Metal particle dispersions that have been proposed as solder replacement bonding materials have higher heat resistance than solder, but there is still room for improvement in terms of bonding strength with the bonded objects. Furthermore, the operating temperatures of power devices have been increasing recently, reportedly reaching 250°C. Bonded bodies using conventional silver particle dispersions have insufficient heat resistance in a 250°C environment, resulting in a decrease in bonding strength. Furthermore, conventional copper particle dispersions have sometimes resulted in poor bonding strength in the resulting bonded bodies depending on the storage period. Therefore, silver particle dispersions with poor heat resistance in a 250°C environment and copper particle dispersions with poor storage stability are difficult to use in the implementation of next-generation power devices. Furthermore, until now, copper plating has been the mainstream method for forming wiring within electronic devices. However, copper plating generates a large amount of hazardous wastewater, resulting in a significant environmental impact. Therefore, metal microparticle dispersions have also been proposed as compositions for forming wiring in electronic devices. Metal microparticle dispersions can be formed by simply printing and firing the metal microparticle dispersion at the desired location, generating almost no waste and significantly reducing the environmental impact. Silver microparticle dispersions have been proposed for forming wiring in electronic devices. However, silver has a high electromigration potential, which can lead to short circuits between fine wiring formed using a silver microparticle dispersion and passing electricity through the silver microparticle dispersion. On the other hand, copper has a lower electromigration potential than silver, and thus copper microparticle dispersions have generally been used to form wiring in electronic devices. However, copper microparticle dispersions can experience an increase in resistivity and a decrease in conductivity over storage time. Patent Document 1 describes a copper paste in which copper particles treated with a hydrophobic fatty acid are dispersed in hydrophilic polyethylene glycol. When a bonded body was fabricated using the copper paste after one month of storage, the resulting bonded body exhibited poor bonding strength. Furthermore, when wiring was formed by printing and firing using the copper paste after one month of storage, it was found that the resistivity increased and the conductivity decreased. These phenomena are thought to be due to poor dispersion of the copper particles in the copper paste. The bonding composition described in Patent Document 2, which contains silver nanoparticles with a first carboxylic acid containing an oxygen atom in the carbon chain attached to the surface, exhibits excellent bonding strength and storage stability, but the resulting bonded body exhibits reduced bonding strength and poor heat resistance in an environment of 250°C. Furthermore, when this silver paste was used to print and bake a comb-shaped pattern with a line and space (L / S) of 400 μm / 400 μm to form wiring, and then current was passed through the printed wiring under high humidity conditions, it was found to cause a short circuit. In the bonding method described in Patent Document 3, which uses copper nanoparticles having citric acid on their surfaces, it is difficult to remove the citric acid that protects the copper nanoparticles during firing, and the resulting bonded body has poor bonding strength. Therefore, there is a need for further improvements in the dispersion stability of metal microparticles in a metal microparticle dispersion obtained by dispersing metal microparticles in a dispersion medium, the storage stability of the metal microparticle dispersion, the bondability and conductivity when fired under conditions of 200°C or higher but 300°C or lower, which are low temperatures for bonding or wiring formation using metal microparticles, and the heat resistance of the bonded body when kept in an environment of 250°C for a long period of time. The present invention relates to a copper nanoparticle-containing composition that can produce a bonded body that exhibits excellent bondability and conductivity when fired at low temperatures of 200°C or higher but 300°C or lower when forming bonds or wiring using metal fine particles, and that maintains high bond strength even after storage for a certain period of time, as well as a conductive structure with excellent conductivity, and that exhibits excellent heat resistance when the resulting bonded body is stored for an extended period of time in an environment of 250°C; a method for producing a bonded body using the copper nanoparticle-containing composition; and a bonded body or electronic device that uses the copper nanoparticle-containing composition.

[0007] The present inventors have discovered that copper nanoparticles are dispersed in an organic solvent using a monocarboxylic acid, the monocarboxylic acid having 5 to 12 carbon atoms, and the monocarboxylic acid having one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond. This improves the dispersion stability of the copper nanoparticles in the copper nanoparticle-containing composition, thereby improving the storage stability of the copper nanoparticle-containing composition. As a result, in bonding or wiring formation using metal fine particles, the bonding and conductivity are excellent when fired at low temperatures of 200°C to 300°C, and even after storage for a certain period of time, a bonded body having high bonding strength and a conductive structure with excellent conductivity can be obtained. The present inventors have discovered that the copper nanoparticle-containing composition has excellent heat resistance when the resulting bonded body is stored for a long period of time in an environment of 250°C, a method for producing a bonded body using the copper nanoparticle-containing composition, and a bonded body or electronic device using the copper nanoparticle-containing composition can be provided. That is, the present invention relates to the following [1] to [6]. [1] A composition comprising copper nanoparticles A, a monocarboxylic acid B, and an organic solvent C; the monocarboxylic acid B has 5 or more and 12 or less carbon atoms, The copper nanoparticle-containing composition, wherein the monocarboxylic acid B has one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond. [2] A method for producing a bonded body, comprising a step of interposing the copper nanoparticle-containing composition according to [1] between a plurality of bonded members and firing the mixture, At least one of the members to be joined is a metal plate, The method for producing a bonded body includes a step of holding the metal plate at a temperature of 200°C or higher for 30 seconds or more to sinter at least the copper nanoparticles A. [3] A bonded body having a bonding layer interposed between a plurality of bonded members, A bonded body, wherein the bonding layer comprises a sintered body of the copper nanoparticle-containing composition according to [1] above. [4] An electronic device comprising a conductive structure including a sintered body of the copper nanoparticle-containing composition according to [1] above. [5] Use of the copper nanoparticle-containing composition according to [1] above for joining a plurality of members to be joined. [6] Use of the copper nanoparticle-containing composition according to [1] above in a conductive structure of an electronic device.

[0008] According to the present invention, when forming bonds or wiring using metal fine particles, excellent bondability and conductivity can be obtained by firing at low temperatures of 200°C or higher and 300°C or lower, and a bonded body having high bond strength and a conductive structure with excellent conductivity can be obtained even after storage for a certain period of time. The obtained bonded body has excellent heat resistance when stored for a long period of time in an environment of 250°C. The present invention also provides a copper nanoparticle-containing composition, a method for producing a bonded body using the copper nanoparticle-containing composition, and a bonded body or electronic device using the copper nanoparticle-containing composition.

[0009] [Copper nanoparticle-containing composition] The copper nanoparticle-containing composition of the present invention contains copper nanoparticles A, monocarboxylic acid B, and organic solvent C, wherein the monocarboxylic acid B has 5 to 12 carbon atoms and has one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond. In the copper nanoparticle-containing composition of the present invention, the copper nanoparticles A are preferably dispersed in organic solvent C by monocarboxylic acid B, with organic solvent C serving as a dispersion medium. In this specification, "sinterability at low temperatures" means that metal sintering occurs at temperatures between 200°C and 300°C, and is also referred to as "low-temperature sinterability." "Bondability through firing at low temperatures" means the bondability between multiple joined components through metal sintering when fired at temperatures between 200°C and 300°C, and is also referred to as "low-temperature bondability." "Conductivity through firing at low temperatures" means conductivity through metal sintering when fired at temperatures between 200°C and 300°C, and is also referred to as "low-temperature conductivity." In this specification, the bondability of a bonded body obtained by firing a copper nanoparticle-containing composition stored for one month in an environment of 25°C and 50% humidity at 200°C to 300°C is referred to as "bondability after storage." Furthermore, the conductivity of a conductive structure obtained by firing a copper nanoparticle-containing composition stored for one month in an environment of 25°C and 50% humidity at 200°C to 300°C is referred to as "conductivity after storage." The bondability of a bonded body obtained using a copper nanoparticle-containing composition after storage in an environment at 250°C for 1000 hours is also referred to as "250°C heat resistance."

[0010] According to the present invention, the bonded body obtained using the copper nanoparticle-containing composition after storage for a certain period of time has excellent bonding strength and conductivity due to firing at low temperatures, and the conductive structure obtained using the copper nanoparticle-containing composition after storage for a certain period of time has excellent conductivity. It is possible to obtain a bonded body having excellent heat resistance at 250 ° C. The reason for this is not clear, but is thought to be as follows. The copper nanoparticle-containing composition of the present invention contains copper nanoparticles A, monocarboxylic acid B, and organic solvent C. In the copper nanoparticle-containing composition, copper nanoparticles A are dispersed in organic solvent C by monocarboxylic acid B. The monocarboxylic acid B has 5 or more carbon atoms, which provides steric repulsion. The monocarboxylic acid B also has affinity for copper nanoparticles A due to the carboxyl group and one or more functional groups or bonds selected from the group consisting of hydroxyl groups, ketonic carbonyl groups, and ether bonds. This effectively exerts electrostatic repulsion, suppressing aggregation of copper nanoparticles A in the copper nanoparticle-containing composition and contributing to improved dispersion stability of copper nanoparticles A in the copper nanoparticle-containing composition and storage stability of the copper nanoparticle-containing composition. Furthermore, monocarboxylic acid B has 12 or fewer carbon atoms and one or more functional groups or bonds selected from the group consisting of hydroxyl groups, ketonic carbonyl groups, and ether bonds, which is believed to facilitate mobility on the surface of copper nanoparticles A. Therefore, copper atoms are exposed on the surface of copper nanoparticles A, making it easier to form metallic bonds. This promotes necking between copper atoms due to low-temperature sintering, improving low-temperature bondability and low-temperature conductivity. Furthermore, it is believed that even after storing the copper nanoparticle-containing composition for a certain period of time, a bonded body with high bond strength and a conductive structure with excellent conductivity can be obtained. Furthermore, although fine voids exist in the bonding layer of the bonded body obtained by firing the copper nanoparticle-containing composition of the present invention, the monocarboxylic acid B has 12 or less carbon atoms and has one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond, and therefore the amount of monocarboxylic acid B remaining in the voids can be reduced.As a result, even in an environment of 250°C, the expansion of voids caused by repeated sintering due to the re-oxidation and re-reduction of copper by the remaining monocarboxylic acid B is suppressed, making it less likely that the bonding layer of the bonded body will change and improving heat resistance at 250°C.

[0011] <Copper nanoparticles A> In the present invention, copper nanoparticles A (hereinafter also simply referred to as "copper nanoparticles A") refer to an aggregate of ultrafine copper particles, and the copper nanoparticles A have an average particle size of 500 nm or less. Copper nanoparticles A are dispersed in organic solvent C by retaining monocarboxylic acid B, which will be described later, on their surfaces. It is believed that monocarboxylic acid B has the effect of suppressing aggregation of copper nanoparticles A in the copper nanoparticle-containing composition. In other words, it is believed that monocarboxylic acid B functions as a dispersant for copper nanoparticles A. The average particle size of the copper nanoparticles A is preferably 150 nm or more, more preferably 170 nm or more, even more preferably 190 nm or more, and even more preferably 200 nm or more, from the viewpoint of improving low-temperature sintering, low-temperature bondability, and low-temperature conductivity, and from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, low-temperature bondability and low-temperature conductivity, and bondability and conductivity after storage, it is preferably 300 nm or less, more preferably 260 nm or less, even more preferably 250 nm or less, even more preferably 240 nm or less, and even more preferably 230 nm or less. Taking these viewpoints into consideration, the average particle size of the copper nanoparticles A is preferably 150 nm or more and 300 nm or less, more preferably 170 nm or more and 300 nm or less, even more preferably 170 nm or more and 260 nm or less, even more preferably 190 nm or more and 250 nm or less, even more preferably 190 nm or more and 240 nm or less, and even more preferably 200 nm or more and 230 nm or less. In the present invention, even if the copper nanoparticles A contain those having a particle size of 500 nm or more, the effects of the present invention can be exhibited as long as the average particle size of the copper nanoparticles A is 500 nm or less. The average particle size of the copper nanoparticles A is measured by the method described in the examples.

[0012] The content of copper nanoparticles A in the copper nanoparticle-containing composition of the present invention is preferably 30% by mass or more, more preferably 40% 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 low-temperature bondability and low-temperature conductivity, and bondability and conductivity after storage. From the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, it is preferably 97% by mass or less, more preferably 95% by mass or less, even more preferably 93% by mass or less, and even more preferably 90% by mass or less. Taking these viewpoints into consideration, the content of copper nanoparticles A in the copper nanoparticle-containing composition of the present invention is preferably 30% by mass or more and 97% by mass or less, more preferably 40% by mass or more and 97% by mass or less, even more preferably 50% by mass or more and 97% by mass or less, even more preferably 50% by mass or more and 95% by mass or less, even more preferably 50% by mass or more and 93% by mass or less, and even more preferably 55% by mass or more and 90% by mass or less.

[0013] <Monocarboxylic acid B> In the present invention, monocarboxylic acid B (hereinafter also simply referred to as "monocarboxylic acid B") has 5 to 12 carbon atoms and one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bondability, low-temperature electrical conductivity, and bondability and electrical conductivity after storage, as well as improving heat resistance at 250°C. Monocarboxylic acid B has one carboxy group in its molecule and also has one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond. This is thought to enable an optimal balance between its affinity for the surface of copper nanoparticles A and its ability to be released from copper nanoparticles A during sintering.

[0014] Furthermore, because the carbon number of monocarboxylic acid B is 5 or more, the steric repulsion of monocarboxylic acid B is improved, which favorably stabilizes copper nanoparticles A in the copper nanoparticle-containing composition, improving the dispersion stability and storage stability of the copper nanoparticle-containing composition. Furthermore, because the carbon number of monocarboxylic acid B is 12 or less, elimination and migration of monocarboxylic acid from copper nanoparticles A during sintering proceeds rapidly, improving low-temperature sinterability. It is believed that the copper nanoparticle-containing composition can achieve both dispersion stability, storage stability, and low-temperature sinterability, while also improving low-temperature bondability, low-temperature conductivity, bondability and conductivity after storage, and heat resistance at 250°C. The number of carbon atoms of monocarboxylic acid B is preferably 5 or more and 10 or less, more preferably 5 or more and 8 or less, even more preferably 5 or more and 6 or less, and still more preferably 5, from the viewpoint of favorably stabilizing copper nanoparticles A in the copper nanoparticle-containing composition, achieving both dispersion stability and storage stability of the copper nanoparticle-containing composition and low-temperature sinterability, and improving low-temperature bondability, low-temperature conductivity, bondability and conductivity after storage, and heat resistance at 250°C. In the present invention, the number of carbon atoms of the monocarboxylic acid B means the number of carbon atoms including the number of carbon atoms of the functional group that the monocarboxylic acid B has.

[0015] Monocarboxylic acid B has one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond. When monocarboxylic acid B has these hydrophilic functional groups or bonds in addition to a carboxy group, it has an excellent balance of affinity to the surface of copper nanoparticles A and affinity with other components other than copper nanoparticles A, such as organic solvent C, that make up the copper nanoparticle-containing composition. This suppresses aggregation of copper nanoparticles A even after storing the copper nanoparticle-containing composition for a certain period of time, allowing copper nanoparticles A to be maintained in a well-dispersed state, and it is believed that the bonding strength and conductivity as originally designed can be expressed.

[0016] When monocarboxylic acid B has a hydroxy group, there are no particular restrictions on the bonding position of the hydroxy group. However, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C, it is preferable that the hydroxy group be bonded to a position away from the carboxy group, more preferably to the carbon atom farthest from the carboxy group or the carbon atom next farthest from the carboxy group, and even more preferably to the carbon atom farthest from the carboxy group. When monocarboxylic acid B has a ketonic carbonyl group, the bonding position of the ketonic carbonyl group is not particularly limited as long as it is other than the carbon atom at the end of the molecular chain. However, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, and improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C, it is preferable that the ketonic carbonyl group be bonded to a position far from the carboxy group, and it is more preferable that the ketonic carbonyl group be bonded to the carbon atom next farthest from the carboxy group. When monocarboxylic acid B has an ether bond, there are no restrictions on the position of the ether bond. However, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C, it is preferable that the ether bond be bonded at a position away from the carboxy group. In the present invention, the term "ether bond" means a "carbon-oxygen-carbon bond", and the term "position of the ether bond" means the position of the oxygen atom constituting the carbon-oxygen-carbon bond from the carboxy group.

[0017] Monocarboxylic acid B may have a combination of two or more selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond in the molecule. However, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C, it is preferable that monocarboxylic acid B has only one selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond. The number of one or more functional groups or bonds selected from the group consisting of hydroxy groups, ketonic carbonyl groups, and ether bonds contained in monocarboxylic acid B may be two or more, but is preferably one from the same viewpoint as above. From the above viewpoint, the monocarboxylic acid B is preferably at least one selected from the group consisting of a monocarboxylic acid having one hydroxy group, a monocarboxylic acid having one ketonic carbonyl group, and a monocarboxylic acid having one ether bond.

[0018] Specific examples of monocarboxylic acid B include, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bonding, low-temperature electrical conductivity, and bonding and electrical conductivity after storage, as well as improving heat resistance at 250°C, preferably one or more selected from the group consisting of 4-oxopentanoic acid (levulinic acid), 5-oxohexanoic acid, 6-hydroxyhexanoic acid, 2-hydroxy-n-octanoic acid, 12-hydroxydodecanoic acid, 2-methoxybutanoic acid, and 3-ethoxypropionic acid. The monocarboxylic acid B may be used alone or in combination of two or more kinds.

[0019] The copper nanoparticle-containing composition of the present invention may contain a carboxylic acid compound other than monocarboxylic acid B, as long as the effects of the present invention are not impaired. Specific examples of carboxylic acid compounds other than monocarboxylic acid B include monocarboxylic acids having less than 5 carbon atoms, monocarboxylic acids having more than 12 carbon atoms, tricarboxylic acids, tetracarboxylic acids, and polycarboxylic acids. In the copper nanoparticle-containing composition of the present invention, the content of monocarboxylic acid B in all carboxylic acid compounds is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, still more preferably 98% by mass or more, still more preferably 99% by mass or more, and still more preferably substantially 100% by mass, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C. In the present invention, the content of monocarboxylic acid B in all carboxylic acid compounds being substantially 100% by mass means that no carboxylic acid compounds other than monocarboxylic acid B are contained, but the presence of carboxylic acid compounds other than monocarboxylic acid B that are unintentionally contained in monocarboxylic acid B, specifically impurities contained in monocarboxylic acid B, is allowed.

[0020] The content of monocarboxylic acid B in the copper nanoparticle-containing composition of the present invention is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and even more preferably 0.7% by mass or more, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, and improving low-temperature bonding, low-temperature conductivity, and bonding and conductivity after storage. And from the viewpoint of improving 250 ° C. heat resistance, it is preferably 7% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, even more preferably 2% by mass or less, and even more preferably 1% by mass or less. Taking these viewpoints into consideration, the content of monocarboxylic acid B in the copper nanoparticle-containing composition of the present invention is preferably 0.1% by mass or more and 7% by mass or less, more preferably 0.3% by mass or more and 5% by mass or less, even more preferably 0.5% by mass or more and 3% by mass or less, even more preferably 0.7% by mass or more and 2% by mass or less, and even more preferably 0.7% by mass or more and 1% by mass or less.

[0021] The ratio of the mass of monocarboxylic acid B to the sum of the mass of copper nanoparticles A and the mass of monocarboxylic acid B in the copper nanoparticle-containing composition of the present invention (hereinafter sometimes referred to as "mass ratio [monocarboxylic acid B / (copper nanoparticles A + monocarboxylic acid B)]") is preferably 0.003 or more, more preferably 0.005 or more, even more preferably 0.007 or more, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, and improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage. Also, from the viewpoint of improving 250 ° C. heat resistance, it is preferably 0.015 or less, more preferably 0.013 or less, even more preferably 0.010 or less, and even more preferably 0.009 or less. Taking all these points into consideration, the mass ratio [monocarboxylic acid B / (copper nanoparticles A + monocarboxylic acid B)] is preferably 0.003 or more and 0.015 or less, more preferably 0.005 or more and 0.013 or less, even more preferably 0.005 or more and 0.010 or less, still more preferably 0.007 or more and 0.010 or less, and even more preferably 0.007 or more and 0.009 or less. The mass ratio [monocarboxylic acid B / (copper nanoparticles A+monocarboxylic acid B)] is measured by the method described in the Examples.

[0022] <Organic solvent C> The copper nanoparticle-containing composition of the present invention contains an organic solvent C for copper nanoparticle-containing compositions (hereinafter also referred to as "organic solvent C") as a dispersion medium for dispersing copper nanoparticles A. Preferred examples of the organic solvent C include one or more selected from the group consisting of hydrocarbons, alcohols, ethers, and esters. The organic solvent C may be used alone or in combination of two or more. The organic solvent C is preferably at least one selected from the group consisting of alcohols, ethers, and esters, and more preferably at least one selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, and (poly)alkylene glycol derivatives.

[0023] Examples of aliphatic monohydric alcohols include allyl alcohol, n-heptanol, n-octanol, 2-ethylhexyl alcohol, n-nonanol, n-decanol, lauryl alcohol, myristyl alcohol, cetyl alcohol, hexadecenol, stearyl alcohol, oleyl alcohol, and terpene alcohols. Among these, terpene alcohols are preferred as aliphatic monohydric alcohols. Preferred examples of terpene alcohols include monoterpene alcohols such as α-terpineol, linalool, geraniol, citronellol, and dihydroterpineol.

[0024] The (poly)alkylene glycol is at least one selected from the group consisting of alkylene glycols and polyalkylene glycols. Examples of alkylene glycols include ethylene glycol, propylene glycol, butylene glycol, and neopentyl glycol. Examples of polyalkylene glycols include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (number average molecular weight preferably 100 or more and 1000 or less, more preferably 150 or more and 600 or less, even more preferably 150 or more and 500 or less, and still more preferably 180 or more and 500 or less), dipropylene glycol, tripropylene glycol, polypropylene glycol (number average molecular weight preferably 150 or more and 1000 or less, more preferably 180 or more and 600 or less, and even more preferably 200 or more and 500 or less), and polytetramethylene glycol.

[0025] Examples of the (poly)alkylene glycol derivative include compounds in which the terminal hydroxy groups of the (poly)alkylene glycols 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. The (poly)alkylene glycol alkyl ether is at least one member selected from the group consisting of alkylene glycol alkyl ethers and polyalkylene glycol alkyl ethers. Examples of the (poly)alkylene glycol alkyl ether include (poly)alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol butyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether. The (poly)alkylene glycol monoalkyl ether acetate is at least one member selected from the group consisting of alkylene glycol monoalkyl ether acetates and polyalkylene glycol monoalkyl ether acetates. Examples of the (poly)alkylene glycol monoalkyl ether acetate include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

[0026] Among these, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bonding, low-temperature conductivity, and bonding and conductivity after storage, as well as improving heat resistance at 250°C, organic solvent C preferably contains one or more compounds selected from the group consisting of hydroxy group-containing compounds having at least one hydroxy group in the molecule (hereinafter also referred to as "hydroxy group-containing compounds") and ester group-containing compounds having at least one ester group in the molecule (hereinafter also referred to as "ester group-containing compounds"), and more preferably contains a hydroxy group-containing compound. In the present invention, monocarboxylic acid B is not included in the hydroxy group-containing compounds and ester group-containing compounds.

[0027] The hydroxy group-containing compound is preferably at least one selected from the group consisting of (poly)alkylene glycols and (poly)alkylene glycol alkyl ethers, and more preferably a (poly)alkylene glycol. The ester group-containing compound is preferably a (poly)alkylene glycol monoalkyl ether acetate.

[0028] The organic solvent C may be a combination of two or more hydroxy group-containing compounds, or a combination of two or more hydroxy group-containing compounds and other organic solvents. Preferred examples of a combination of two or more organic solvents C include a combination of two or more (poly)alkylene glycols, a combination of a (poly)alkylene glycol and an aliphatic monohydric alcohol, a combination of a (poly)alkylene glycol and a (poly)alkylene glycol monoalkyl ether, or a combination of a (poly)alkylene glycol and a (poly)alkylene glycol monoalkyl ether acetate. As a combination of two or more (poly)alkylene glycols, a combination of dipropylene glycol and tetraethylene glycol, or a combination of dipropylene glycol and polyethylene glycol is preferred. As a combination of a (poly)alkylene glycol and an aliphatic monohydric alcohol, a combination of polyethylene glycol and a terpene alcohol is preferred, and a combination of polyethylene glycol and α-terpineol is more preferred. As a combination of a (poly)alkylene glycol and a (poly)alkylene glycol monoalkyl ether, a combination of dipropylene glycol and diethylene glycol monobutyl ether, or a combination of polyethylene glycol and diethylene glycol monobutyl ether is preferred. A preferred combination of a (poly)alkylene glycol and a (poly)alkylene glycol monoalkyl ether acetate is a combination of polyethylene glycol and diethylene glycol monobutyl ether acetate.

[0029] The content of organic solvent C in the copper nanoparticle-containing composition of the present invention is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and even more preferably 7% by mass or more from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, improving low-temperature bonding, low-temperature conductivity, and bonding and conductivity after storage, and from the viewpoint of improving heat resistance at 250 ° C., and from the same viewpoint as above, it is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, even more preferably 15% by mass or less, and even more preferably 13% by mass or less. Taking these viewpoints into consideration, the content of organic solvent C in the copper nanoparticle-containing composition of the present invention is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 25% by mass or less, even more preferably 5% by mass or more and 20% by mass or less, even more preferably 7% by mass or more and 15% by mass or less, and even more preferably 7% by mass or more and 13% by mass or less.

[0030] The mass ratio of the content of organic solvent C to the content of monocarboxylic acid B in the copper nanoparticle-containing composition of the present invention [organic solvent C / monocarboxylic acid B] is preferably 1 or more, more preferably 3 or more, even more preferably 5 or more, still more preferably 7 or more, still more preferably 9 or more, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, improving low-temperature bonding, low-temperature conductivity, and bonding and conductivity after storage, and from the viewpoint of improving heat resistance at 250 ° C., and from the same viewpoint as above, preferably 20 or less, more preferably 17 or less, even more preferably 15 or less, still more preferably 14 or less, still more preferably 13 or less. Taking these viewpoints into consideration, the mass ratio of the content of organic solvent C to the content of monocarboxylic acid B in the copper nanoparticle-containing composition of the present invention [organic solvent C / monocarboxylic acid B] is preferably 1 or more and 20 or less, more preferably 3 or more and 17 or less, even more preferably 5 or more and 15 or less, still more preferably 7 or more and 14 or less, still more preferably 9 or more and 13 or less.

[0031] When organic solvent C contains one or more compounds selected from the group consisting of hydroxy group-containing compounds and ester group-containing compounds, in the copper nanoparticle-containing composition of the present invention, the total content of the hydroxy group-containing compounds and ester group-containing compounds in organic solvent C is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, still 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, and still more preferably substantially 100% by mass, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C. In the present invention, the total content of the hydroxy group-containing compound and the ester group-containing compound in the organic solvent C being substantially 100% by mass means that the organic solvent C does not contain any organic solvents other than the hydroxy group-containing compound and the ester group-containing compound, but the presence of organic solvents other than the hydroxy group-containing compound and the ester group-containing compound that are unintentionally contained in the hydroxy group-containing compound or the ester group-containing compound, specifically impurities contained in the hydroxy group-containing compound or the ester group-containing compound, is acceptable.

[0032] When organic solvent C contains a hydroxy group-containing compound, in the copper nanoparticle-containing composition of the present invention, the content of the hydroxy group-containing compound in organic solvent C is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, still 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, and still more preferably substantially 100% by mass, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C. In the present invention, the content of the hydroxy group-containing compound in the organic solvent C being substantially 100% by mass means that the organic solvent C does not contain any organic solvents other than the hydroxy group-containing compound, but the presence of organic solvents other than the hydroxy group-containing compound that are unintentionally contained in the hydroxy group-containing compound, specifically impurities contained in the hydroxy group-containing compound, is acceptable. In the copper nanoparticle-containing composition of the present invention, the total content of (poly)alkylene glycol and (poly)alkylene glycol alkyl ether in organic solvent C is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, still 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, and still more preferably substantially 100% by mass, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and from the viewpoint of improving heat resistance at 250°C. In the present invention, the total content of (poly)alkylene glycol and (poly)alkylene glycol alkyl ether in organic solvent C being substantially 100% by mass means that the organic solvent C does not contain any organic solvents other than the (poly)alkylene glycol and (poly)alkylene glycol alkyl ether, but the presence of organic solvents other than the (poly)alkylene glycol and (poly)alkylene glycol alkyl ether that are unintentionally contained in the (poly)alkylene glycol or (poly)alkylene glycol alkyl ether, specifically impurities contained in the (poly)alkylene glycol and (poly)alkylene glycol alkyl ether, is acceptable.

[0033] <Metal Microparticles D> From the viewpoint of improving low-temperature bondability, low-temperature electrical conductivity, and bondability and electrical conductivity after storage, as well as improving heat resistance at 250°C, the copper nanoparticle-containing composition of the present invention preferably further contains metal microparticles D. When metal microparticles D coexist with copper nanoparticles A in the copper nanoparticle-containing composition of the present invention, the copper nanoparticles A act as a binder to contribute to mutual bonding of the metal microparticles D, thereby enabling the development of high electrical conductivity and high bonding strength.

[0034] In the present invention, the metal microparticles D can be made of any metal, either singly or in combination of two or more. From the viewpoints of improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C, the metal microparticles D are preferably made of one or more metals selected from the group consisting of gold, platinum, silver, copper, nickel, bismuth, tin, and iron, more preferably one or more metals selected from the group consisting of gold, platinum, silver, and copper, even more preferably one or more metals selected from the group consisting of silver and copper, and even more preferably copper.

[0035] In the present invention, the metal microparticles D refer to an aggregate of metal fine particles having an average particle size of more than 500 nm. The average particle size of the metal microparticles D is preferably 0.6 μm or more, more preferably 0.65 μm or more, even more preferably 0.7 μm or more, still more preferably 0.75 μm or more, and even more preferably 0.8 μm or more from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, and improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage. In addition, from the viewpoint of heat resistance at 250 ° C., it is preferably 8 μm or less, more preferably 6 μm or less, even more preferably 5 μm or less, still more preferably 2 μm or less, and even more preferably 1 μm or less. Taking all these points into consideration, the average particle size of the metal microparticles D is preferably 0.6 μm or more and 8 μm or less, more preferably 0.65 μm or more and 6 μm or less, even more preferably 0.7 μm or more and 6 μm or less, even more preferably 0.7 μm or more and 5 μm or less, even more preferably 0.7 μm or more and 2 μm or less, even more preferably 0.7 μm or more and 1 μm or less, even more preferably 0.75 μm or more and 1 μm or less, and even more preferably 0.8 μm or more and 1 μm or less. In the present invention, even if the metal microparticles D contain those having a particle size of 500 nm or less, the effect of the present invention can be further improved if the average particle size exceeds 500 nm. The average particle size of the metal microparticles D is measured by the method described in the Examples. When the copper nanoparticle-containing composition of the present invention contains metal microparticles D, particles having an average particle size of 500 nm or less are considered to be copper nanoparticles A, and particles having an average particle size of more than 500 nm are considered to be metal microparticles D, as measured by the method described in the Examples.

[0036] When the copper nanoparticle-containing composition of the present invention further contains metal microparticles D, the organic solvent C used as the dispersion medium for the copper nanoparticle-containing composition is preferably a combination of polyethylene glycol and a terpene alcohol (preferably a combination of polyethylene glycol and α-terpineol), a combination of polyethylene glycol and diethylene glycol monobutyl ether, or a combination of polyethylene glycol and diethylene glycol monobutyl ether acetate. It is believed that these combinations, when combined with monocarboxylic acid B, produce a synergistic effect. The mechanism by which this effect is achieved is unclear, but all of these combinations contain polyethylene glycol, which has a high molecular weight but is easily decomposed at high temperatures, and has a balance of hydrophobicity and hydrophilicity suitable for monocarboxylic acid B, and is also easily volatile. Therefore, it is believed that by further containing metal microparticles D, even if the content of copper nanoparticles A is relatively reduced, efficient sintering of the particles occurs when the copper nanoparticle-containing composition is fired.

[0037] The content of metal microparticles D in the copper nanoparticle-containing composition of the present invention is preferably 5% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C.From the same viewpoints as above, the content is preferably 65% ​​by mass or less, more preferably 55% by mass or less, even more preferably 45% by mass or less, and even more preferably 35% by mass or less.

[0038] When the copper nanoparticle-containing composition of the present invention contains metal microparticles D, the mass ratio of the content of metal microparticles D to the content of copper nanoparticles A in the copper nanoparticle-containing composition of the present invention [metal microparticles D / copper nanoparticles A] is, from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, thereby improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250°C, preferably 0.01 or more, more preferably 0.1 or more, even more preferably 0.2 or more, still more preferably 0.3 or more, still more preferably 0.4 or more, and is preferably 3 or less, more preferably 2 or less, even more preferably 1.5 or less, still more preferably 1 or less, and still more preferably 0.7 or less.

[0039] The copper nanoparticle-containing composition of the present invention may contain various additives as components other than the components A to D, as long as the effects of the present invention are not impaired. Examples of such additives include dispersants, surfactants, antifoaming agents, and fillers. The copper nanoparticle-containing composition of the present invention may contain water as a component other than the components A to D. However, the content of water in the copper nanoparticle-containing composition of the present invention is preferably 1% by mass or less, more preferably 0.1% by mass or less, and even more preferably substantially 0% by mass. The water content in the copper nanoparticle-containing composition of the present invention being substantially 0% by mass means that the copper nanoparticle-containing composition does not intentionally contain water, but the presence of water unintentionally contained in the components used in the copper nanoparticle-containing composition is acceptable.

[0040] (Preparation of copper nanoparticle-containing composition) The copper nanoparticle-containing composition of the present invention can be prepared by preparing copper nanoparticles A in advance by a known method, and then mixing the prepared copper nanoparticles A with monocarboxylic acid B, organic solvent C, and, if necessary, metal microparticles D, and various additives (method (i)); or by using a dispersion of copper nanoparticles A dispersed in monocarboxylic acid B, if the dispersion medium of the dispersion is not organic solvent C, mixing organic solvent C, and, if necessary, metal microparticles D, and various additives (method (ii)). Among these, method (ii) is preferred from the viewpoint of improving the dispersion stability and storage stability of the copper nanoparticle-containing composition, improving low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, as well as improving heat resistance at 250 ° C. The method for mixing these is not particularly limited, and can be carried out by a conventionally known method using a mixer, a stirrer, etc. Specific methods include a method of kneading using a spatula on a plate-like object, a method of mixing using a mortar, and a method of kneading using a rotation-revolution type mixer.

[0041] The dispersion of copper nanoparticles A used in method (ii) can be obtained by maintaining a temperature of 50°C or higher and 100°C or lower in the presence of a copper raw material compound as a copper source for constituting copper nanoparticles A and monocarboxylic acid B in the presence of an organic solvent for preparing copper nanoparticles A. According to method (ii), copper nanoparticles A can be obtained in a form in which monocarboxylic acid B adheres to at least a portion of the surface of the copper nanoparticles A.

[0042] The copper source compound is not particularly limited, and examples thereof include nitrate, copper sulfate, copper chloride, cuprous oxide, copper oxide, copper acetate, and copper sulfide. The copper source compound may be used alone or in combination of two or more. Of these, copper oxide is preferred. The organic solvent used for preparing copper nanoparticles A is preferably an organic solvent other than organic solvent C. Preferred examples of the organic solvent for preparing copper nanoparticles A include alcohols, hydrocarbons, and ketones, with alcohols being more preferred, and one or more selected from the group consisting of methanol, ethanol, propanol, and butanol being even more preferred. In preparing a dispersion of copper nanoparticles A by method (ii), it is preferable to use a reducing agent in addition to the copper raw material compound, monocarboxylic acid B, and organic solvent for preparing copper nanoparticles A. The reducing agent is used to reduce the copper raw material compound and obtain copper as an elemental substance. Preferred examples of the reducing agent include carbon, hydrogen, carbon monoxide, hydrazine, metal hydrides, aldehyde group-containing compounds, and hydroxyl group-containing compounds. Among these, hydrazine is more preferred.

[0043] The obtained dispersion of copper nanoparticles A may be purified to remove the organic solvent used to prepare the copper nanoparticles A, residual raw materials, and by-products. Examples of purification methods include a method in which the obtained dispersion of copper nanoparticles A is left to stand or centrifuged for a certain period of time, the supernatant is removed to recover the precipitate, and the organic solvent for preparing copper nanoparticles A or the organic solvent for purifying copper nanoparticles A is added again, and the process of leaving to stand for a certain period of time or centrifuging is repeated a desired number of times; and a method in which the dissolved matter is removed using an ultrafiltration device. Suitable examples of organic solvents for purifying copper nanoparticles A include those exemplified above as organic solvents for preparing copper nanoparticles A. The purified copper nanoparticle A dispersion may be used in a copper nanoparticle-containing composition while still containing the organic solvent for preparing copper nanoparticles A or the organic solvent for purifying copper nanoparticles A. However, it is preferable to dry the copper nanoparticle A dispersion to remove the organic solvent for preparing copper nanoparticles A or the organic solvent for purifying copper nanoparticles A, and then incorporate the resulting dried powder of copper nanoparticles A containing monocarboxylic acid B into the copper nanoparticle-containing composition. The obtained dried powder of copper nanoparticles A containing monocarboxylic acid B can be mixed with organic solvent C, optionally metal microparticles D, and various additives to obtain a copper nanoparticle-containing composition. Methods for removing the organic solvent for preparing copper nanoparticles A or the organic solvent for purifying copper nanoparticles A from the copper nanoparticle A dispersion include atmospheric drying, reduced-pressure drying, and freeze-drying, but freeze-drying is preferred.

[0044] The copper nanoparticle-containing composition of the present invention can be interposed between multiple bonded members and fired to form a bonding layer containing a sintered body containing at least copper, which can bond multiple bonded members. In other words, the copper nanoparticle-containing composition of the present invention is preferably used as a bonding composition. Bonded bodies having such a bonding layer have high bonding strength, excellent heat resistance up to 250°C, and high electrical conductivity. From this perspective, the copper nanoparticle-containing composition of the present invention can be used as a bonding composition for bonding chip components such as capacitors and resistors to circuit boards; bonding semiconductor chips such as memories, diodes, transistors, ICs, and CPUs to lead frames or circuit boards; and bonding high-heat-generating semiconductor chips to heat-dissipating substrates.

[0045] [Method of manufacturing the bonded body] The method for producing a bonded body of the present invention includes a step (hereinafter also referred to as "step 1") of interposing the above-described copper nanoparticle-containing composition as a bonding composition between a plurality of members to be bonded and firing the resulting mixture.

[0046] In step 1, the copper nanoparticle-containing composition is preferably interposed between multiple bonded members by applying it between at least one of the bonded members and the other bonded members, i.e., between the first bonded member and the second bonded member. Various methods can be used to apply the copper nanoparticle-containing composition. Preferred methods for applying the copper nanoparticle-containing composition include screen printing, stencil printing, flexographic printing, gravure printing, dipping, spraying, bar coating, spin coating, inkjet printing, dispenser printing, pin transfer, brush coating, casting, and syringe coating. Among these, stencil printing is more preferred.

[0047] The atmosphere during firing in step 1 may be an air atmosphere, an inert gas atmosphere such as nitrogen, or a reducing gas atmosphere such as hydrogen gas, but a nitrogen atmosphere is more preferable from the viewpoints of inhibiting copper oxidation and safety. The firing temperature in step 1 is preferably 200°C or higher, more preferably 230°C or higher, even more preferably 240°C or higher, and preferably 300°C or lower, more preferably 280°C or lower, even more preferably 260°C or lower. In step 1, the time for which the predetermined temperature is maintained during firing is preferably 10 seconds or more, more preferably 60 seconds or more, and even more preferably 120 seconds or more. It is preferable to heat the first and second members to be joined while applying pressure to them during the firing in step 1. The pressure applied to the first and second members to be joined is preferably 10 MPa or more, more preferably 15 MPa or more, even more preferably 18 MPa or more, and is preferably 30 MPa or less, more preferably 28 MPa or less.

[0048] The material of the members to be joined used in the method for producing a bonded body of the present invention may be a single material or a combination of different materials. Preferred examples of the material of the members to be joined used in the method for producing a bonded body of the present invention include one or more selected from the group consisting of gold, platinum, silver, copper, iron, nickel, silicon, germanium, and indium. A preferred combination of the first and second members to be joined is a combination of the same or different materials selected from the group consisting of gold, silver, copper, and silicon, more preferably a combination of copper and copper or a combination of copper and silicon, and even more preferably a combination of copper and silicon. The members to be joined may have various shapes such as a plate shape. The members to be joined may be rigid or flexible. The thickness of the members to be joined may also be selected appropriately. At least one of the members to be joined is preferably a metal plate. When the members to be joined are metal plates, the members to be joined may be formed by coating, plating, or attaching a metal suitable for the members to the surface of glass, resin, or a metal other than the members to be joined.

[0049] When at least one of the members to be joined is a metal plate, step 1 preferably includes a step of holding the metal plate at a temperature of 200°C or higher for 30 seconds or more to sinter at least the copper nanoparticles A (hereinafter also referred to as the "sintering step"). The temperature of the metal plate in the sintering step is preferably 230°C or higher, more preferably 240°C or higher, and preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 260°C or lower. The time for which the metal plate is maintained at the above-mentioned predetermined temperature in the sintering step is preferably 60 seconds or more, more preferably 120 seconds or more. In the sintering process, it is preferable to apply pressure to the members to be joined. The pressure applied to the members to be joined in the sintering process is preferably 10 MPa or more, more preferably 15 MPa or more, even more preferably 18 MPa or more, and is preferably 30 MPa or less, more preferably 28 MPa or less.

[0050] The bond strength of the resulting bonded body is preferably 20 MPa or more, more preferably 25 MPa or more, and even more preferably 30 MPa or more. The bonding strength can be measured by the method used in the evaluation of low-temperature bonding properties described in the Examples. The resulting bonded body has a reduction in bonding strength after being held at 250° C. for 1000 hours, preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. The rate of decrease in bonding strength can be calculated by the method used in the evaluation of heat resistance at 250° C. described in the Examples.

[0051] In addition to the aforementioned bonding composition, the copper nanoparticle-containing composition of the present invention can also be used to form conductive structures such as wiring and electrodes with sufficiently low resistivity. Therefore, the copper nanoparticle-containing composition of the present invention can be suitably used in the production of electronic devices containing a conductive structure comprising a sintered body of the copper nanoparticle-containing composition, such as thin-film transistors, integrated circuits including thin-film transistors, RFID (radio frequency identifiers), flexible displays, organic electroluminescence (EL) displays, touch panels, organic electroluminescence (EL) elements, circuit boards, sensor devices, conductive pillars, and conductive materials for flip-chip mounting.

[0052] (Manufacturing of conductive structures) The method for producing the conductive structure of the present invention preferably includes a step of applying a copper nanoparticle-containing composition to a substrate and then firing the composition. By including the firing step (hereinafter also referred to as "Step I"), the medium in the applied copper nanoparticle-containing composition is evaporated and dried, and at least the copper nanoparticles A are sintered, thereby reducing the residual components in the conductive structure. Various methods can be used to apply the copper nanoparticle-containing composition, but the methods exemplified as the application method of the copper nanoparticle-containing composition in the above-mentioned method for producing a bonded body are preferred. Among them, stencil printing is more preferred.

[0053] In step I, the atmosphere during firing may be an air atmosphere, an inert gas atmosphere such as nitrogen, or a reducing gas atmosphere such as hydrogen gas, but a nitrogen atmosphere is more preferred from the viewpoints of inhibiting copper oxidation and safety. In step I, the firing temperature is preferably 200°C or higher, more preferably 230°C or higher, even more preferably 240°C or higher, and preferably 300°C or lower, more preferably 280°C or lower, even more preferably 260°C or lower. In step I, the time for which the above-mentioned predetermined temperature is maintained during firing can be appropriately selected depending on the firing temperature, but is preferably 1 minute or more, more preferably 3 minutes or more, even more preferably 5 minutes or more, and is preferably 60 minutes or less, more preferably 30 minutes or less, even more preferably 20 minutes or less. Examples of heating methods in step I include a method of heating by contacting a heater with the surface of the substrate opposite to the surface to which the copper nanoparticle-containing composition is applied; a method of storing the substrate to which the copper nanoparticle-containing composition is applied in a thermostatic device that can maintain a constant temperature; a method of heating the surface of the substrate to which the copper nanoparticle-containing composition is applied with hot air; a method of heating by bringing a heater close to the surface of the substrate to which the copper nanoparticle-containing composition is applied; a method of heating by steam curing using high-temperature steam at normal or high pressure; and a method of heating by irradiation with light such as near-infrared light or ultraviolet light. [Example]

[0054] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples. Various physical properties were measured or calculated by the following methods.

[0055] [Average particle size of copper nanoparticles A and metal microparticles D] Scanning electron microscope (SEM) images of copper nanoparticles A or metal microparticles D were taken using a scanning electron microscope (Hitachi High-Tech Corporation, field emission scanning electron microscope: S-4800). The magnification was determined according to the particle size, and images were taken at magnifications ranging from 5,000x to 150,000x. The SEM images were analyzed using image analysis software "ImageJ" (National Institutes of Health, USA), and the particle sizes of 100 or more particles per sample were determined. The arithmetic mean value of these particles was taken as the average particle size of copper nanoparticles A or metal microparticles D.

[0056] [Calculation of the ratio of the mass of monocarboxylic acid B to the sum of the mass of copper nanoparticles A and the mass of monocarboxylic acid B (mass ratio [monocarboxylic acid B / (copper nanoparticles A + monocarboxylic acid B)])] Using a simultaneous thermogravimetry and differential thermal analyzer (TG / DTA) "STA7200RV" (Hitachi High-Tech Science Corporation), 10 mg of sample (dried powder of copper nanoparticles A containing monocarboxylic acid B) was weighed into an aluminum pan 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 defined as the mass of monocarboxylic acid B, and the remaining mass at 550 ° C was defined as the mass of copper nanoparticles A. The ratio of the mass of carboxylic acid B to the sum of the mass of copper nanoparticles A and monocarboxylic acid B (mass ratio [monocarboxylic acid B / (copper nanoparticles A + monocarboxylic acid B)]) was calculated.

[0057] (Production of dry powder of copper nanoparticles A containing monocarboxylic acid B) Manufacturing Example 1 A 2 L beaker was charged with 50.0 g of copper oxide (Nisshin Chemco Corporation, Grade: N-120) as the copper source compound, 4.40 g of 4-oxopentanoic acid (levulinic acid) (Tokyo Chemical Industry Co., Ltd., purity: >97% by mass) as monocarboxylic acid B, and 500 g of ethanol (95) (Fujifilm Wako Pure Chemical Corporation, special grade reagent), and the mixture was stirred for 15 minutes. During stirring, the temperature of the mixture was controlled at 70 °C using an oil bath. Next, 63.0 g of hydrazine monohydrate (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in a 50 mL dropping funnel as a reducing agent and added dropwise to the mixed solution over 20 minutes at 25° C. Thereafter, the reaction solution was stirred for 1 hour while controlling the temperature at 70° C. in an oil bath, and then air-cooled to obtain a reddish-brown dispersion containing copper nanoparticles. The entire amount of the obtained dispersion was placed in a Hitachi Koki Co., Ltd. centrifuge sedimentation tube 500PA bottle using a refrigerated centrifuge "himacCR22G" and rotor (R12A, radius 15.1 cm), and centrifuged at 2,000 rpm with a centrifugal acceleration of 675G for 30 minutes. 300 g of acetone (Fujifilm Wako Pure Chemical Corporation, first-class reagent) was added to the precipitate separated by centrifugation, and the mixture was stirred for 15 minutes to redisperse. The entire amount of the redispersion was centrifuged again under the same conditions, and the precipitate was separated. This operation was repeated twice. Next, 300 g of methanol (Fujifilm Wako Pure Chemical Corporation, special grade reagent) was added to the precipitate and stirred for 15 minutes to redisperse it. The entire redispersion liquid was centrifuged again under the same conditions, and the precipitate was separated. This operation was repeated twice. The purified copper nanoparticle precipitate was freeze-dried using a freeze dryer (Tokyo Rikakikai Co., Ltd., Model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., Model: DRC-1000) to obtain 38.0 g of dried powder A-1 of copper nanoparticles A1 containing 4-oxopentanoic acid. The drying conditions were freezing at -25 °C for 1 hour, drying at -10 °C for 9 hours under reduced pressure at 5 Pa, and further drying at 25 °C for 5 hours under reduced pressure at 5 Pa. The average particle size of the obtained copper nanoparticles A1 was 200 nm, and the ratio of the mass of 4-oxopentanoic acid to the sum of the mass of copper nanoparticles A1 and the mass of 4-oxopentanoic acid was 0.009. The results are shown in Table 1.

[0058] Production Examples 2 to 7 and Comparative Production Examples 1 to 6 The same procedure as in Production Example 1 was carried out except that the monocarboxylic acid B was changed as shown in Table 1, and dried powders of copper nanoparticles A containing the monocarboxylic acid B shown in Table 1 were obtained. Table 1 shows the average particle size of the obtained copper nanoparticles A and the ratio of the mass of monocarboxylic acid B to the total mass of copper nanoparticles A and monocarboxylic acid B.

[0059] (Production of dry powder of silver nanoparticles containing monocarboxylic acid B) Comparative Manufacturing Example 7 Dry powder AC-7 of silver nanoparticles AC7 containing 5-oxohexanoic acid was obtained in the same manner as in Production Example 1, except that copper oxide was changed to silver oxide (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 4-oxopentanoic acid (levulinic acid) was changed to 5-oxohexanoic acid. The average particle size of the obtained silver nanoparticles AC7 was 170 nm, and the ratio of the mass of 5-oxohexanoic acid to the sum of the mass of the silver nanoparticles AC7 and the mass of 5-oxohexanoic acid was 0.011.

[0060] Comparative Example 8 Dry powder AC-8 of silver nanoparticles AC8 containing 12-hydroxydodecanoic acid was obtained in the same manner as in Comparative Production Example 7, except that 5-oxohexanoic acid was changed to 12-hydroxydodecanoic acid. The average particle size of the obtained silver nanoparticles AC8 was 220 nm, and the ratio of the mass of 12-hydroxydodecanoic acid to the sum of the mass of the silver nanoparticles AC8 and the mass of 12-hydroxydodecanoic acid was 0.009.

[0061] [Table 1]

[0062] Details of the monocarboxylic acid B and other carboxylic acids used in Production Examples 1 to 7 and Comparative Production Examples 1 to 8 are shown below. (Monocarboxylic acid B) 4-Oxopentanoic acid: Tokyo Chemical Industry Co., Ltd., purity: >97% by mass 5-Oxohexanoic acid: Tokyo Chemical Industry Co., Ltd., purity: >98% by mass 6-Hydroxyhexanoic acid: Sigma-Aldrich, purity: 95% by mass 2-Hydroxy-n-octanoic acid: Tokyo Chemical Industry Co., Ltd., purity: >98% by mass 12-Hydroxydodecanoic acid: Sigma-Aldrich, purity: 97% by mass 2-Methoxybutanoic acid: Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent 3-Ethoxypropionic acid: Tokyo Chemical Industry Co., Ltd., purity: >98% by mass (Other carboxylic acids) Pyruvic acid: Tokyo Chemical Industry Co., Ltd., purity: >97% by mass Lactic acid: Tokyo Chemical Industry Co., Ltd., purity: >85% by mass 16-Hydroxyhexadecanoic acid: Sigma-Aldrich, purity: 98% by mass Methoxyacetic acid: Tokyo Chemical Industry Co., Ltd., purity: >96% by mass Citric acid: Fujifilm Wako Pure Chemical Corporation, special grade reagent Hexanoic acid: Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent

[0063] Example 1 (Preparation of copper nanoparticle-containing composition) 0.5 g of dipropylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent) and 0.5 g of tetraethylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent) were used as organic solvent C, and 9.0 g of dried powder A-1 of copper nanoparticles A1 containing 4-oxopentanoic acid was added to an agate mortar and kneaded until the dried powder was no longer visible. The resulting mixture was transferred to a plastic bottle. The sealed plastic bottle was stirred at 2,000 rpm (2,000 revolutions / minute) for 5 minutes using a planetary centrifugal stirrer (Thinky Corporation, model: ARV-310) to obtain copper nanoparticle-containing composition 1.

[0064] (Manufacturing of Joints) Using the obtained copper nanoparticle-containing composition 1, a bonded body was produced according to the following method. First, a stainless steel metal mask (thickness: 150 μm) with three rows of 6 mm x 6 mm square openings was placed on a 30 mm x 30 mm copper plate (total thickness: 1 mm), and copper nanoparticle-containing composition 1 was applied to the copper plate by stencil printing using a metal squeegee. The copper plate was then heated and dried at 120 °C for 10 minutes on a Shamal hot plate (manufactured by AS ONE Corporation, model number: HHP-441) in an air atmosphere. A 5 mm x 5 mm silicon chip (thickness: 400 μm) was then prepared by sputtering titanium, nickel, and gold in this order. The silicon chip was then placed on the copper nanoparticle-containing composition 1 applied to the copper plate so that the gold was in contact with the copper nanoparticle-containing composition 1. This resulted in a laminate consisting of a copper plate, copper nanoparticle-containing composition 1, and silicon chip stacked in this order. The resulting laminate was fired in the following manner to obtain a bonded body. First, the laminate was placed in a pressure and heat bonding device (Meisho Kiko Co., Ltd., model number: HTM-1000), and nitrogen was flowed into the furnace at 500 mL / min to replace the air inside the furnace. The upper and lower heating heads were then used to apply pressure to the laminate at 20 MPa while the temperature of the heating heads was raised to 250°C over 10 minutes. After the temperature increase, the laminate was sintered by holding it at 250°C for 150 seconds to obtain a bonded body. After sintering, the heating heads were water-cooled at -60°C / min, and the bonded body was removed into air when the temperature of the heating heads dropped below 100°C.

[0065] Examples 2 to 17, Comparative Examples 1 to 9 The same procedure as in Example 1 was carried out except that the composition of the copper nanoparticle-containing composition was changed to the composition shown in Tables 2 and 3, and copper nanoparticle-containing compositions of Examples 2 to 17 and Comparative Examples 1 to 7, silver nanoparticle-containing compositions of Comparative Examples 8 and 9, and bonded bodies were obtained, respectively.

[0066] The raw materials used in producing the copper nanoparticle-containing composition and the silver nanoparticle-containing composition are shown below. (Other copper nanoparticles) Copper nanoparticles AC9: CH-0200L1 (manufactured by Mitsui Mining & Smelting Co., Ltd., particle size 190 nm, lauric acid content 1.3% by mass) (organic solvent C) Dipropylene glycol: Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent Tetraethylene glycol: Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent PEG200: Polyalkylene glycol 200, Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent, average molecular weight: 180-220 PEG400: Polyalkylene glycol 400, Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent, average molecular weight: 360-440 α-Terpineol: Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent Diethylene glycol monobutyl ether: Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent Diethylene glycol monobutyl ether acetate: Tokyo Chemical Industry Co., Ltd., purity: >98% by mass (Metal microparticles D) Copper microparticles D1: MA-C025 (Mitsui Mining & Smelting Co., Ltd., particle size 5.0 μm) Copper microparticles D2:1050Y (Mitsui Mining & Smelting Co., Ltd., particle size 0.8 μm)

[0067] The following evaluations were carried out using the bonded structures obtained in Examples 1 to 17 and Comparative Examples 1 to 9. The results are shown in Tables 2 and 3. <Evaluation> [Low temperature bondability] The bonding strength of each of the bonded bodies obtained in the examples and comparative examples was measured according to the following procedure. Using a universal bond tester (Nordson Advanced Technology Co., Ltd., product name: Material Tester, model number: Prospector), the silicon chip of the bonded assembly was pressed horizontally at a test speed of 5 mm / min and a shear height of 50 μm to measure the die shear strength of the bonded assembly. This test was performed on three bonded assembly pieces, and the average of the values ​​obtained from the measurements of the three bonded assembly pieces was used to evaluate the bond strength of the bonded assembly. The higher the bond strength value, the better the low-temperature bondability.

[0068] [Synchronization after storage] Each copper nanoparticle-containing composition or silver nanoparticle-containing composition obtained in the Examples and Comparative Examples was stored for one month in an environment of 25°C and 50% humidity, and then each bonded body was obtained in the same manner as in the production of the bonded body in Example 1. The bond strength of the bonded body was measured in the same manner as in the evaluation method for low-temperature bondability described above. The higher the bond strength value, the better the bondability after storage.

[0069] [250℃ heat resistance] The bonded bodies obtained in the examples and comparative examples were stored in an air atmosphere at 250°C for 1000 hours, and then the bond strength of the bonded bodies was measured using the same method as the above-mentioned low-temperature bondability evaluation method. The higher the bond strength value, the better the heat resistance at 250°C. The rate of decrease in bonding strength was calculated using the following formula. Decrease rate of bond strength (%) = (1 - (bond strength after storage / bond strength before storage)) x 100

[0070] [Table 2]

[0071] [Table 3]

[0072] From Tables 2 and 3, the copper nanoparticle-containing compositions of Examples 1 to 17 have excellent low-temperature bonding properties, and compared to the copper nanoparticle-containing compositions of Comparative Examples 1 to 7 that do not contain monocarboxylic acid B and the silver nanoparticle-containing compositions of Comparative Examples 8 and 9 that use silver nanoparticles AC7 and AC8, the copper nanoparticle-containing compositions of Examples 1 to 17 have excellent dispersion stability and storage stability, and the resulting bonded bodies have excellent heat resistance at 250 ° C. From the above, according to the present invention, it is possible to provide a copper nanoparticle-containing composition that has excellent dispersion stability and storage stability and excellent low-temperature bonding properties, and even after storing the copper nanoparticle-containing composition for a certain period of time, a bonded body having high bonding strength can be obtained by low-temperature firing at 200 ° C. or higher and 300 ° C. or lower, and further, a bonded body having excellent heat resistance in an environment of 250 ° C. can be obtained.

[0073] Example 18 (Manufacturing of conductive structures) Using the copper nanoparticle-containing composition 1 obtained in Example 1, a conductive structure was obtained according to the following method. First, a stainless steel metal mask (thickness: 50 μm) with a 10 mm × 10 mm square opening was placed on a 40 mm × 10 mm glass slide (total thickness: 1 mm), and copper nanoparticle-containing composition 1 was applied to the glass slide by stencil printing using a metal squeegee. Then, it was placed on a Shamal hot plate (manufactured by AS ONE Corporation, model number: HHP-441), and a separable flask lid connected to a nitrogen pipe was placed on top. It was then heated at 250 °C for 10 minutes while flowing nitrogen at 5 L / min.

[0074] Comparative Example 10 A conductive structure was obtained in the same manner as in Example 18, except that the copper nanoparticle-containing composition C6 obtained in Comparative Example 6 was used instead of the copper nanoparticle-containing composition 1 in Example 18.

[0075] The conductive structures obtained in Example 18 and Comparative Example 10 were evaluated as follows. The results are shown in Table 4. <Evaluation> [Low temperature conductivity] The volume resistivity of each conductive structure obtained in the examples and comparative examples was measured according to the following procedure. First, the obtained conductive structure was peeled off from the slide glass, and the thickness t of the conductive structure was measured using a micrometer. Next, the conductive structure was measured using a resistivity meter (main body: Loresta-GP, four-point probe: PSP probe, both manufactured by Mitsubishi Chemical Analytech Co., Ltd.). The thickness t of the conductive structure measured above was input into the resistivity meter to display the volume resistivity. Similar measurements were taken at other locations on the conductive structure, and the volume resistivity ρv was obtained by arithmetic averaging the values ​​at a total of three locations. The lower the volume resistivity ρv, the better the low-temperature conductivity.

[0076] [Conductivity after storage] Each copper nanoparticle-containing composition obtained in the examples and comparative examples was stored for one month in an environment of 25°C and 50% humidity, and then each conductive structure was obtained in the same manner as in the production of the conductive structure in Example 18, and then measured using the same method as the above-mentioned low-temperature conductivity evaluation method. The lower the volume resistivity ρv, the better the conductivity after storage.

[0077] [Table 4]

[0078] From Table 4, it can be seen that the copper nanoparticle-containing composition of Example 18 has excellent low-temperature conductivity and is also superior in conductivity after storage compared to the copper nanoparticle-containing composition of Comparative Example 10, which does not contain monocarboxylic acid B. Therefore, it can be seen that the copper nanoparticle-containing composition of Example 18 has excellent dispersion stability and storage stability, and also has excellent low-temperature conductivity of the resulting conductive structure. From the above, according to the present invention, it is possible to provide a copper nanoparticle-containing composition that is excellent in dispersion stability and storage stability and low-temperature conductivity, and a conductive structure that is excellent in low-temperature conductivity can be obtained even after storing the copper nanoparticle-containing composition for a certain period of time. [Industrial Applicability]

[0079] According to the present invention, when forming bonds or wiring using metal fine particles, excellent bondability and conductivity can be obtained by firing at low temperatures of 200°C or higher and 300°C or lower, and a bonded body having high bond strength and a conductive structure with excellent conductivity can be obtained even after storage for a certain period of time. The obtained bonded body has excellent heat resistance when maintained for a long period of time in an environment of 250°C. A copper nanoparticle-containing composition, a method for producing a bonded body using the copper nanoparticle-containing composition, and a bonded body or electronic device using the copper nanoparticle-containing composition can be provided. In the present invention, because copper nanoparticles are used, a highly reliable electronic device in which electromigration is suppressed can be provided.

Claims

1. A copper nanoparticle dry powder for preparing a copper nanoparticle-containing composition, comprising copper nanoparticles A and an organic solvent C, The copper nanoparticles A and the monocarboxylic acid B are contained, the monocarboxylic acid B has 5 or more and 12 or less carbon atoms, The copper nanoparticle dry powder for preparing a copper nanoparticle-containing composition, wherein the monocarboxylic acid B has one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond.

2. The copper nanoparticle dry powder for preparing a copper nanoparticle-containing composition according to claim 1, wherein the copper nanoparticles A have an average particle size of 150 nm or more and 300 nm or less.

3. 2. The copper nanoparticle dry powder for preparing a copper nanoparticle-containing composition according to claim 1, wherein the ratio of the mass of the monocarboxylic acid B to the sum of the mass of the copper nanoparticles A and the mass of the monocarboxylic acid B in the copper nanoparticle dry powder is 0.003 or more and 0.015 or less.

4. 2. The copper nanoparticle dry powder for preparing a copper nanoparticle-containing composition according to claim 1, wherein the monocarboxylic acid B is at least one selected from the group consisting of 4-oxopentanoic acid, 5-oxohexanoic acid, 6-hydroxyhexanoic acid, 2-hydroxy-n-octanoic acid, 12-hydroxydodecanoic acid, 2-methoxybutanoic acid, and 3-ethoxypropionic acid.

5. A copper nanoparticle dry powder for preparing a copper nanoparticle-containing composition as described in claim 1, wherein the monocarboxylic acid B is held on the surface of the copper nanoparticle A.

6. A step of preparing a copper nanoparticle-containing composition comprising the copper nanoparticle dry powder for preparing a copper nanoparticle-containing composition according to any one of claims 1 to 5 and an organic solvent C; A firing step of interposing the copper nanoparticle-containing composition between a plurality of members to be joined and firing the mixture, At least one of the members to be joined is a metal plate, The firing step includes a step of holding the metal plate at a temperature of 200°C or higher for 30 seconds or more to sinter at least the copper nanoparticles A.

7. A method for manufacturing a bonded body as described in claim 6, wherein the rate of decrease in bond strength after holding the bonded body at 250°C for 1000 hours is 20% or less.

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