Composition containing copper nanoparticles

Abstract

The present invention relates to a copper nanoparticle-containing composition containing copper nanoparticles (A), a monocarboxylic acid (B), and an organic solvent (C), a method for producing a bonded body using the copper nanoparticle-containing composition, and a bonded body or an electronic device using the copper nanoparticle-containing composition, the copper nanoparticle-containing composition containing copper nanoparticles (A), a monocarboxylic acid (B), and an organic solvent (C), and a monocarboxylic acid (B) having 5-12 carbon atoms and having one or more functional groups or bonds selected from the group consisting of a hydroxyl group, a ketocarbonyl group, and an ether bond.

Description

Technical Field

[0001] The present invention relates to a composition containing copper nanoparticles, a method for manufacturing a bonded body using the composition containing copper nanoparticles, and a bonded body or an electronic device using the composition containing copper nanoparticles. Background Art

[0002] Copper is widely used as a wiring material due to its excellent electrical conductivity.

[0003] In addition, since copper also has excellent thermal conductivity, it is also used as a heat transfer material, a heat exchange material, a heat dissipation material, etc., and sometimes this property is further utilized to be used as a bonding material for bonding materials to each other.

[0004] In recent years, as power conversion and control devices such as converters, the importance of semiconductors called power devices has been gradually increasing. Different from information processing semiconductors such as memories or microprocessors, power devices are used to control large currents, and the amount of heat dissipated during operation increases. Therefore, the bonding material for mounting power devices is required to have not only bonding strength but also heat resistance. However, the lead-free solder widely used recently has the disadvantage of low heat resistance. Therefore, various techniques have been proposed in the industry to use a metal particle dispersion instead of solder, coat it on an object by various coating methods and perform firing to bond the objects to be bonded, and as a composition for mounting, a metal particle dispersion in which metal particles are dispersed in a dispersion medium has been proposed. As the metal type of this metal particle dispersion, silver or copper is mainly used. Silver does not have an oxide film at room temperature (25°C). Therefore, for the silver particle dispersion, firing is performed in the absence of a reducing agent to form a continuous body of silver, thereby bonding the objects to be bonded. On the other hand, the oxidation state of copper is stable at room temperature (25°C), so it contains copper atoms in an oxidized state. Therefore, in order to bond the objects to be bonded using a copper particle dispersion, the copper atoms in the oxidized state must be reduced and fired to form a continuous body of copper.

[0005] In Japanese Patent Laid-Open No. 2020-053404 (Patent Document 1), the purpose is to provide a copper paste with a higher bonding strength to the object to be bonded, and it describes a copper paste containing copper powder and a liquid medium, the liquid medium contains polyethylene glycol, the average particle size of the primary particles of the copper particles constituting the copper powder is 0.03 μm or more and 1.0 μm or less, a fatty acid having 6 to 18 carbon atoms is applied to the surface of the copper particles, and the crystal grain size of the (111) plane is 50 nm or less, and the mass ratio of the copper powder in the copper paste is 50% or more and 99% or less.

[0006] In International Publication No. 2018 / 030173 (Patent Document 2), the object is to provide a bonding composition for obtaining a bonding layer with high bonding strength, and there is described a bonding composition containing silver nanoparticles, a dispersion medium, and a first carboxylic acid having an oxygen atom in a carbon chain attached to at least a part of the surface of the above silver nanoparticles.

[0007] In Japanese Unexamined Patent Application Publication No. 2010 - 189681 (Patent Document 3), the object is to provide a method for producing copper nanoparticles having both oxidation resistance and bondability, and there is described a method for producing copper nanoparticles having a specified step of producing copper nanoparticles having citric acid on the surface, and there is also described a bonding method using the copper nanoparticles produced by this production method. SUMMARY OF THE INVENTION

[0008] The present invention relates to a composition containing copper nanoparticles, a method for manufacturing a bonded body using the composition containing copper nanoparticles, and a bonded body or an electronic device using the composition containing copper nanoparticles. The composition containing copper nanoparticles contains copper nanoparticle A, monocarboxylic acid B, and organic solvent C.

[0009] The monocarboxylic acid B has 5 to 12 carbon atoms.

[0010] The monocarboxylic acid B has one or more functional groups or bonds selected from a hydroxyl group, a ketone carbonyl group, and an ether bond. DETAILED DESCRIPTION OF THE INVENTION

[0011] Compared with solder, the metal particle dispersion proposed so far as a bonding material instead of solder has higher heat resistance, but there is still room for improvement in terms of the bonding strength with the object to be bonded. In addition, recently, the driving temperature of power devices has a tendency to rise, and it is said to reach 250°C. For a bonded body using a silver particle dispersion of the prior art, there is a situation where the heat resistance at 250°C is insufficient and the bonding strength is reduced. In addition, for a copper particle dispersion of the prior art, there is a situation where the bonding strength of the obtained bonded body deteriorates depending on its storage time. Therefore, such a silver particle dispersion with poor heat resistance at 250°C and a copper particle dispersion with poor storage stability are difficult to be used in the mounting of next-generation power devices.

[0012] In addition, up to now, forming wiring within an electronic device by copper plating has been the mainstream technology. However, copper plating discharges a lot of harmful waste liquid, so the environmental burden is relatively large. Therefore, as a composition for forming wiring of an electronic device, a metal particle dispersion has been proposed. For a metal particle dispersion, wiring can be formed simply by printing at a position where wiring is desired to be formed and then firing. Therefore, almost no waste is generated, thus significantly reducing the environmental burden. When forming wiring of an electronic device, a silver particle dispersion has been proposed. However, the electromigration of silver is relatively large, and there is a problem that when using the silver particle dispersion to form fine wiring and electricity flows through it, a short circuit occurs between the wirings. On the other hand, compared with silver, the electromigration of copper is smaller. Therefore, up to now, a copper particle dispersion has generally been used to form wiring of an electronic device. However, for a copper particle dispersion, sometimes its resistivity increases and its conductivity decreases according to the storage time.

[0013] Regarding the copper paste in which copper particles coated with a hydrophobic fatty acid are dispersed by hydrophilic polyethylene glycol as described in Patent Document 1, when a bonded body is produced using the copper paste stored for 1 month, poor bonding strength of the obtained bonded body can be seen. In addition, it is known that when wiring is formed by printing and firing the copper paste stored for 1 month, the resistivity increases and the conductivity decreases. It is considered that these phenomena are caused by poor dispersion of the copper particles in the copper paste.

[0014] The bonding composition containing silver nanoparticles described in Patent Document 2 (wherein a first carboxylic acid having an oxygen atom in its carbon chain is attached to the surface of the silver nanoparticles) has excellent bonding strength and storage stability. However, the bonding strength of the obtained bonded body decreases in an environment of 250 °C, and poor heat resistance can be seen. In addition, it is known that when this silver paste is printed into a comb shape with a line and space (L / S) of 400 μm / 400 μm and fired to form wiring, a short circuit occurs when electricity flows under high humidity conditions.

[0015] In the bonding method using copper nanoparticles having citric acid on their surfaces as described in Patent Document 3, it is difficult to remove citric acid protecting the copper nanoparticles during firing, and poor bonding strength of the obtained bonded body can be seen.

[0016] Therefore, further improvement in the following properties is required: that is, the dispersion stability of metal particles in a metal particle dispersion obtained by dispersing metal particles in a dispersion medium and the storage stability of the metal particle dispersion, the bondability, conductivity, and heat resistance of the bonded body when firing is carried out under conditions that are low temperature (i.e., 200 °C or more and 300 °C or less) in bonding or wiring formation using metal particles.

[0017] The present invention relates to a composition containing copper nanoparticles, a method for manufacturing a bonded body using the composition containing copper nanoparticles, and a bonded body or an electronic device using the composition containing copper nanoparticles. By using the composition containing copper nanoparticles of the present invention, the following effects can be obtained: namely, excellent bondability and conductivity are achieved by firing under conditions belonging to low temperature (200 °C or higher and 300 °C or lower) in the formation of bonding or wiring using metal fine particles, and even after being stored for a certain period of time, a bonded body having a high bonding strength and a conductive structure having excellent conductivity can be obtained, and the obtained bonded body has excellent heat resistance when maintained in an environment of 250 °C for a long time.

[0018] The inventors have found that it is possible to provide a composition containing copper nanoparticles, a method for manufacturing a bonded body using the composition containing copper nanoparticles, and a bonded body or an electronic device using the composition containing copper nanoparticles. Among them, the composition containing copper nanoparticles is formed by dispersing copper nanoparticles in an organic solvent with a monocarboxylic acid. The monocarboxylic acid has 5 to 12 carbon atoms, and the monocarboxylic acid has one or more functional groups or bonds selected from a hydroxyl group, a ketone carbonyl group, and an ether bond. Therefore, the dispersion stability of the copper nanoparticles in the composition containing copper nanoparticles is improved, and the storage stability of the composition containing copper nanoparticles is improved. As a result, excellent bondability and conductivity are achieved by firing under conditions belonging to low temperature (that is, 200 °C or higher and 300 °C or lower) in the formation of bonding or wiring using metal fine particles, and even after being stored for a certain period of time, a bonded body having a high bonding strength and a conductive structure having excellent conductivity can be obtained, and the obtained bonded body has excellent heat resistance when maintained in an environment of 250 °C for a long time.

[0019] That is, the present invention relates to the following [1] to [6].

[0020] [1] A composition containing copper nanoparticles, wherein the composition contains copper nanoparticles A, a monocarboxylic acid B, and an organic solvent C,

[0021] The monocarboxylic acid B has 5 to 12 carbon atoms,

[0022] The monocarboxylic acid B has one or more functional groups or bonds selected from a hydroxyl group, a ketone carbonyl group, and an ether bond.

[0023] [2] A method for manufacturing a bonded body, which includes: a step of firing in a state where the composition containing copper nanoparticles described in [1] above is interposed between a plurality of members to be bonded,

[0024] At least one of the members to be bonded is a metal plate,

[0025] This process includes the step of maintaining the metal plate at a temperature of 200 °C or higher for 30 seconds or longer to sinter at least copper nanoparticles A.

[0026] [3] A joined body, wherein there is a joining layer interposed between a plurality of members to be joined.

[0027] This joining layer contains a sintered body of the composition containing copper nanoparticles as described in [1] above.

[0028] [4] An electronic device, which contains: a conductive structure including a sintered body of the composition containing copper nanoparticles as described in [1] above.

[0029] [5] Use of the composition containing copper nanoparticles as described in [1] above in joining a plurality of members to be joined.

[0030] [6] Use of the composition containing copper nanoparticles as described in [1] above in the conductive structure of an electronic device.

[0031] According to the present invention, a composition containing copper nanoparticles, a method for manufacturing a joined body using the composition containing copper nanoparticles, and a joined body or an electronic device using the composition containing copper nanoparticles can be provided. By the composition containing copper nanoparticles of the present invention, the following effects can be obtained: namely, excellent joinability and conductivity achieved by firing under conditions that are low temperature (i.e., 200 °C or higher and 300 °C or lower) in joining or wiring formation using metal fine particles, and a joined body having a high joining strength and a conductive structure having excellent conductivity can be obtained even after being stored for a certain period of time, and the obtained joined body has excellent heat resistance when maintained in an environment of 250 °C for a long time.

[0032] [Composition containing copper nanoparticles]

[0033] The composition containing copper nanoparticles of the present invention contains copper nanoparticles A, monocarboxylic acid B, and organic solvent C. The monocarboxylic acid B has 5 to 12 carbon atoms, and the monocarboxylic acid B has one or more functional groups or bonds selected from a hydroxyl group, a keto carbonyl group, and an ether bond. In the composition containing copper nanoparticles of the present invention, the copper nanoparticles A are preferably dispersed in the organic solvent C through the monocarboxylic acid B using the organic solvent C as a dispersion medium.

[0034] In addition, in this specification, "sinterability at low temperature" means that metal sintering occurs at a temperature above 200°C and below 300°C, and is also referred to as "low-temperature sinterability". "Bondability achieved by firing at low temperature" means the bondability between multiple bonded members achieved by metal sintering during firing at a temperature above 200°C and below 300°C, and is also referred to as "low-temperature bondability". In addition, "electric conductivity achieved by firing at low temperature" means the electric conductivity achieved by metal sintering during firing at a temperature above 200°C and below 300°C, and is also referred to as "low-temperature electric conductivity".

[0035] In addition, in this specification, the bondability of the bonded body obtained by firing the composition containing copper nanoparticles after being stored for 1 month in an environment of 25°C and 50% humidity at a temperature above 200°C and below 300°C is referred to as "bondability after storage". In addition, the electric conductivity of the conductive structure obtained by firing the composition containing copper nanoparticles after being stored for 1 month in an environment of 25°C and 50% humidity at a temperature above 200°C and below 300°C is referred to as "electric conductivity after storage".

[0036] In addition, the bondability of the bonded body obtained by using the composition containing copper nanoparticles after being stored for 1000 hours in an environment of 250°C is also referred to as "heat resistance at 250°C".

[0037] According to the present invention, the following effects can be obtained: the bondability and electric conductivity achieved by firing at low temperature are excellent, the bonded body obtained by using the composition containing copper nanoparticles after being stored for a certain period of time has a high bonding strength, in addition, the conductive structure obtained by using the composition containing copper nanoparticles after being stored for a certain period of time has excellent electric conductivity, and further, a bonded body with excellent heat resistance at 250°C can be obtained. Although the reason is not clear, it is considered as follows.

[0038] The composition containing copper nanoparticles of the present invention contains copper nanoparticle A, monocarboxylic acid B, and organic solvent C. It is considered that in the above composition containing copper nanoparticles, copper nanoparticle A is dispersed in organic solvent C by monocarboxylic acid B, and the monocarboxylic acid B effectively exhibits the electrostatic repulsion force generated by the carboxyl group by using the steric repulsion force obtained with 5 or more carbon atoms and the affinity for copper nanoparticle A obtained from the carboxyl group and one or more functional groups or bonds selected from hydroxyl group, ketone carbonyl group, and ether bond, inhibits the aggregation of copper nanoparticle A in the composition containing copper nanoparticles, and contributes to improving the dispersion stability of copper nanoparticle A in the composition containing copper nanoparticles and the storage stability of the composition containing copper nanoparticles. Further, since the monocarboxylic acid B has 12 or less carbon atoms and has one or more functional groups or bonds selected from hydroxyl group, ketone carbonyl group, and ether bond, it is easy to move on the surface of copper nanoparticle A. Therefore, it is considered that copper atoms are exposed on the surface of copper nanoparticle A and it is easy to form metal bonds, whereby necking formation between copper atoms is carried out by low-temperature sintering, improving low-temperature joinability and low-temperature conductivity. Further, even after the composition containing copper nanoparticles is stored for a certain period of time, a joined body having a high joining strength and a conductive structure having excellent conductivity can be obtained.

[0039] Further, it is considered that although there are fine pores in the joining layer of the joined body obtained by firing the composition containing copper nanoparticles of the present invention, since the monocarboxylic acid B has 12 or less carbon atoms and has one or more functional groups or bonds selected from hydroxyl group, ketone carbonyl group, and ether bond, the monocarboxylic acid B remaining in the pores can be reduced. As a result, even in an environment of 250°C, the expansion of the pores caused by repeated sintering due to the reoxidation and re-reduction of copper caused by the remaining monocarboxylic acid B is suppressed, the joining layer of the joined body is not easily changed, and the heat resistance at 250°C is also improved.

[0040] <Copper Nanoparticle A>

[0041] In the present invention, copper nanoparticle A (hereinafter, also simply referred to as "copper nanoparticle A") is an aggregate of ultrafine particles of copper, and it means that the average particle size of the copper nanoparticle A is 500 nm or less. Copper nanoparticle A is dispersed in organic solvent C by holding the following monocarboxylic acid B on its surface. It is considered that monocarboxylic acid B has the effect of inhibiting the aggregation of copper nanoparticle A in the composition containing copper nanoparticles. In other words, it is considered that monocarboxylic acid B functions as a dispersant for copper nanoparticle A.

[0042] From the viewpoints of improving low-temperature sinterability, low-temperature joinability, and low-temperature conductivity, the average particle diameter of the copper nanoparticles A is preferably 150 nm or more, more preferably 170 nm or more, still more preferably 190 nm or more, and even more preferably 200 nm or more. Further, from the viewpoints of improving the dispersion stability and storage stability of the composition containing the copper nanoparticles, improving the low-temperature joinability and low-temperature conductivity, and the joinability and conductivity after storage, it is preferably 300 nm or less, more preferably 260 nm or less, still more preferably 250 nm or less, even more preferably 240 nm or less, and even more preferably 230 nm or less. Considering these viewpoints comprehensively, the average particle diameter 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, still 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.

[0043] In the present invention, even if the copper nanoparticles A contain particles having a particle diameter of 500 nm or more, as long as the average particle diameter of the copper nanoparticles A is 500 nm or less, the effects of the present invention can be exhibited.

[0044] The average particle diameter of the copper nanoparticles A is measured by the method described in the examples.

[0045] From the viewpoints of improving the low-temperature joinability and low-temperature conductivity, and the joinability and conductivity after storage, the content of the copper nanoparticles A in the composition containing the copper nanoparticles of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and even more preferably 55% by mass or more. Further, from the viewpoint of improving the dispersion stability and storage stability of the composition containing the copper nanoparticles, it is preferably 97% by mass or less, more preferably 95% by mass or less, still more preferably 93% by mass or less, and even more preferably 90% by mass or less. Considering these viewpoints comprehensively, the content of the copper nanoparticles A in the composition containing the copper nanoparticles 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, still more preferably 50% 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.

[0046] <Monocarboxylic acid B>

[0047] In the present invention, from the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, bondability and conductivity after storage, and improving the heat resistance at 250°C, the monocarboxylic acid B (hereinafter also simply referred to as "monocarboxylic acid B") has 5 to 12 carbon atoms and has one or more functional groups or bonds selected from a hydroxyl group, a keto carbonyl group, and an ether bond.

[0048] The monocarboxylic acid B has one carboxyl group in its molecule and further has one or more functional groups or bonds selected from a hydroxyl group, a keto carbonyl group, and an ether bond. Therefore, it is considered that the balance between the affinity for the surface of the copper nanoparticles A and the detachability from the copper nanoparticles A during sintering can be optimized.

[0049] In addition, it is considered that since the monocarboxylic acid B has 5 or more carbon atoms, the steric repulsion force of the monocarboxylic acid B can be increased, so that the copper nanoparticles A can be well stabilized in the composition containing copper nanoparticles, and the dispersion stability and storage stability of the composition containing copper nanoparticles can be improved. Moreover, since the monocarboxylic acid B has 12 or fewer carbon atoms, the detachment or transfer of the monocarboxylic acid from the copper nanoparticles A during sintering can be carried out rapidly, thereby improving the low-temperature sinterability. The dispersion stability and storage stability of the composition containing copper nanoparticles and the low-temperature sinterability can be balanced, and the low-temperature bondability, low-temperature conductivity, bondability and conductivity after storage, and heat resistance at 250°C can be improved.

[0050] From the viewpoints of well stabilizing the copper nanoparticles A in the composition containing copper nanoparticles, balancing the dispersion stability and storage stability of the composition containing copper nanoparticles and the low-temperature sinterability, and improving the low-temperature bondability, low-temperature conductivity, bondability and conductivity after storage, and heat resistance at 250°C, the number of carbon atoms of the monocarboxylic acid B is preferably 5 to 10, more preferably 5 to 8, further preferably 5 to 6, and even more preferably 5.

[0051] In the present invention, the number of carbon atoms of the monocarboxylic acid B refers to the number of carbon atoms including the carbon atoms of the functional groups possessed by the monocarboxylic acid B.

[0052] The monocarboxylic acid B has one or more functional groups or bonds selected from a hydroxyl group, a keto carbonyl group, and an ether bond. It is considered that when the monocarboxylic acid B has these hydrophilic functional groups or bonds in addition to the carboxyl group, the balance between the affinity for the surface of the copper nanoparticles A and the affinity for other components such as the organic solvent C constituting the composition containing copper nanoparticles other than the copper nanoparticles A is excellent. Even after the composition containing copper nanoparticles is stored for a certain period of time, the aggregation of the copper nanoparticles A can be inhibited, and the copper nanoparticles A can be maintained in a well-dispersed state, showing the bonding strength and conductivity designed initially.

[0053] In the case where the monocarboxylic acid B has a hydroxyl group, there is no particular limitation on the bonding position of the hydroxyl group. From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bonding property, low-temperature conductivity, and the bonding property and conductivity after storage, and improving the heat resistance at 250 °C, it is preferably bonded to a position far from the carboxyl group, more preferably bonded to a carbon atom at the position farthest from the carboxyl group or a carbon atom at the position second farthest from the carboxyl group, and further preferably bonded to a carbon atom at the position farthest from the carboxyl group.

[0054] In the case where the monocarboxylic acid B has a ketocarbonyl group, there is no particular limitation on the bonding position of the ketocarbonyl group, as long as it is a position other than the carbon atom at the end of the molecular chain. From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bonding property, low-temperature conductivity, and the bonding property and conductivity after storage, and improving the heat resistance at 250 °C, it is preferably bonded to a position far from the carboxyl group, more preferably bonded to a carbon atom at the position secondarily (secondly) far from the carboxyl group.

[0055] In the case where the monocarboxylic acid B has an ether bond, there is no limitation on the position of the ether bond. From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bonding property, low-temperature conductivity, and the bonding property and conductivity after storage, and improving the heat resistance at 250 °C, it is preferably bonded to a position far from the carboxyl group.

[0056] In the present invention, "ether bond" means "carbon-oxygen-carbon bond", and "position of the ether bond" means the position of the oxygen atom constituting the carbon-oxygen-carbon bond from the carboxyl group.

[0057] The monocarboxylic acid B may combine two or more selected from a hydroxyl group, a ketocarbonyl group, and an ether bond in the molecule. From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bonding property, low-temperature conductivity, and the bonding property and conductivity after storage, and improving the heat resistance at 250 °C, it is preferably to have only one selected from a hydroxyl group, a ketocarbonyl group, and an ether bond.

[0058] The number of one or more functional groups or bonds selected from a hydroxyl group, a ketocarbonyl group, and an ether bond contained in the monocarboxylic acid B may be two or more. From the same viewpoints as above, it is preferably one.

[0059] As described above, from the same viewpoints as above, the monocarboxylic acid B is preferably one or more selected from a monocarboxylic acid having one hydroxyl group, a monocarboxylic acid having one ketocarbonyl group, and a monocarboxylic acid having one ether bond.

[0060] As specific examples of monocarboxylic acid B, from the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250°C, one or more selected from 4-oxopentanoic acid (levulinic acid), 5-oxohexanoic acid, 6-hydroxyhexanoic acid, 2-hydroxynoctanoic acid, 12-hydroxydodecanoic acid, 2-methoxybutyric acid, and 3-ethoxypropionic acid are preferred.

[0061] Regarding monocarboxylic acid B, one kind can be used alone, or two or more kinds can be used in combination.

[0062] The composition containing copper nanoparticles of the present invention may also contain a carboxylic acid compound other than monocarboxylic acid B within the range not impairing the effects of the present invention. As specific examples of the carboxylic acid compound other than monocarboxylic acid B, monocarboxylic acids having less than 5 carbon atoms, monocarboxylic acids having more than 12 carbon atoms, tricarboxylic acids, tetracarboxylic acids, and polycarboxylic acids can be cited.

[0063] In the composition containing copper nanoparticles of the present invention, from the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250°C, 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, further preferably 95% by mass or more, further more preferably 98% by mass or more, further more preferably 99% by mass or more, and further more preferably substantially 100% by mass.

[0064] In the present invention, "the content of monocarboxylic acid B in all carboxylic acid compounds is substantially 100% by mass" means that carboxylic acid compounds other than monocarboxylic acid B are not included, but the presence of carboxylic acid compounds other than monocarboxylic acid B that are not deliberately included in monocarboxylic acid B is allowed. Specifically, the presence of impurities contained in monocarboxylic acid B is allowed.

[0065] From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, and improving the low-temperature joining property, low-temperature conductivity, and joining property and conductivity after storage, the content of monocarboxylic acid B in the composition containing copper nanoparticles of the present invention is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more. And from the viewpoint of improving the heat resistance at 250 °C, it is preferably 7% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, even more preferably 2% by mass or less, even more preferably 1% by mass or less. Considering these viewpoints comprehensively, the content of monocarboxylic acid B in the composition containing copper nanoparticles 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, still 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, even more preferably 0.7% by mass or more and 1% by mass or less.

[0066] From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, and improving the low-temperature joining property, low-temperature conductivity, and joining property and conductivity after storage, the ratio of the mass of monocarboxylic acid B to the total mass of copper nanoparticle A and monocarboxylic acid B in the composition containing copper nanoparticles of the present invention (hereinafter sometimes referred to as "mass ratio [monocarboxylic acid B / (copper nanoparticle A + monocarboxylic acid B)]") is preferably 0.003 or more, more preferably 0.005 or more, still more preferably 0.007 or more. And from the viewpoint of improving the heat resistance at 250 °C, it is preferably 0.015 or less, more preferably 0.013 or less, still more preferably 0.010 or less, even more preferably 0.009 or less. Considering these viewpoints comprehensively, the mass ratio [monocarboxylic acid B / (copper nanoparticle 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, still more preferably 0.005 or more and 0.010 or less, even more preferably 0.007 or more and 0.010 or less, even more preferably 0.007 or more and 0.009 or less.

[0067] The mass ratio [monocarboxylic acid B / (copper nanoparticle A + monocarboxylic acid B)] is measured by the method described in the examples.

[0068] <Organic solvent C>

[0069] In the composition containing copper nanoparticles of the present invention, as a dispersion medium for dispersing copper nanoparticle A, an organic solvent C for the composition containing copper nanoparticles (hereinafter also referred to as "organic solvent C") is contained.

[0070] As the organic solvent C, for example, preferably, one or more selected from hydrocarbons, alcohols, ethers, and esters can be cited. Regarding the organic solvent C, one kind can be used alone or two or more kinds can be used in combination.

[0071] As the organic solvent C, more preferably, one or more selected from alcohols, ethers, and esters can be cited, and further preferably, one or more selected from aliphatic monohydric alcohols, (poly)alkylene glycols, and (poly)alkylene glycol derivatives can be cited.

[0072] As the aliphatic monohydric alcohol, for example, allyl alcohol, n-heptanol, n-octanol, 2-ethylhexanol, n-nonanol, n-decanol, lauryl alcohol, myristyl alcohol, cetyl alcohol, hexadecenol, stearyl alcohol, oleyl alcohol, and terpenol can be cited. Among these, the aliphatic monohydric alcohol is preferably terpenol. As the terpenol, for example, preferably, monoterpenols such as α-terpineol, linalool, geraniol, citronellol, and dihydroterpineol can be cited.

[0073] (Poly)alkylene glycol is one or more selected from alkylene glycol and polyalkylene glycol.

[0074] As the alkylene glycol, for example, ethylene glycol, propylene glycol, butylene glycol, and neopentyl glycol can be cited.

[0075] As the polyalkylene glycol, for example, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (the number average molecular weight is preferably 100 or more and 1000 or less, more preferably 150 or more and 600 or less, further preferably 150 or more and 500 or less, and further more preferably 180 or more and 500 or less), dipropylene glycol, tripropylene glycol, polypropylene glycol (the number average molecular weight is preferably 150 or more and 1000 or less, more preferably 180 or more and 600 or less, further preferably 200 or more and 500 or less), and polytetramethylene glycol can be cited.

[0076] As the (poly)alkylene glycol derivative, for example, a compound in which the hydroxyl group at the terminal of the above (poly)alkylene glycol is etherified or esterified can be cited. Specifically, one or more selected from (poly)alkylene glycol alkyl ethers and (poly)alkylene glycol monoalkyl ether acetates can be cited.

[0077] (Poly)alkylene glycol alkyl ether is one or more selected from alkylene glycol alkyl ether and polyalkylene glycol alkyl ether.

[0078] As the (poly)alkylene glycol alkyl ether, for example, (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 can be cited.

[0079] (Poly)alkylene glycol monoalkyl ether acetate is one or more selected from alkylene glycol monoalkyl ether acetate and polyalkylene glycol monoalkyl ether acetate.

[0080] 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.

[0081] Among these, from the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250 °C, the organic solvent C preferably contains one or more selected from 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.

[0082] In addition, in the present invention, the monocarboxylic acid B is not included in the hydroxy group-containing compound and the ester group-containing composition.

[0083] As the hydroxy group-containing compound, one or more selected from (poly)alkylene glycols and (poly)alkylene glycol alkyl ethers are preferred, and (poly)alkylene glycols are more preferred.

[0084] As the ester group-containing compound, (poly)alkylene glycol monoalkyl ether acetate is preferred.

[0085] As the organic solvent C, two or more hydroxy group-containing compounds can be combined, or two or more hydroxy group-containing compounds and other organic solvents can be combined. As an example of combining two or more organic solvents C, 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 is preferred.

[0086] 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.

[0087] As a combination of a (poly)alkylene glycol and an aliphatic monohydric alcohol, a combination of polyethylene glycol and terpene alcohol is preferred, and a combination of polyethylene glycol and α-terpineol is more preferred.

[0088] As a combination of (poly)alkylene glycol and (poly)alkylene glycol monoalkyl ether, it is preferably a combination of dipropylene glycol and diethylene glycol monobutyl ether, or a combination of polyethylene glycol and diethylene glycol monobutyl ether.

[0089] As a combination of (poly)alkylene glycol and (poly)alkylene glycol monoalkyl ether acetate, it is preferably a combination of polyethylene glycol and diethylene glycol monobutyl ether acetate.

[0090] From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250°C, the content of organic solvent C in the composition containing copper nanoparticles of the present invention is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, still further preferably 7% by mass or more. And, from the same viewpoints as above, it is preferably 30% by mass or less, more preferably 25% by mass or less, further preferably 20% by mass or less, still further preferably 15% by mass or less, still further preferably 13% by mass or less. Considering these viewpoints comprehensively, the content of organic solvent C in the composition containing copper nanoparticles 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, further preferably 5% by mass or more and 20% by mass or less, still further preferably 7% by mass or more and 15% by mass or less, still further preferably 7% by mass or more and 13% by mass or less.

[0091] From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250°C, the mass ratio [organic solvent C / monocarboxylic acid B] of the content of organic solvent C in the composition containing copper nanoparticles of the present invention to the content of monocarboxylic acid B is preferably 1 or more, more preferably 3 or more, further preferably 5 or more, still further preferably 7 or more, still further preferably 9 or more. And, from the same viewpoints as above, it is preferably 20 or less, more preferably 17 or less, further preferably 15 or less, still further preferably 14 or less, still further preferably 13 or less. Considering these viewpoints comprehensively, the mass ratio [organic solvent C / monocarboxylic acid B] of the content of organic solvent C in the composition containing copper nanoparticles of the present invention to the content of monocarboxylic acid B is preferably 1 or more and 20 or less, more preferably 3 or more and 17 or less, further preferably 5 or more and 15 or less, still further preferably 7 or more and 14 or less, still further preferably 9 or more and 13 or less.

[0092] When the organic solvent C contains one or more selected from hydroxyl group-containing compounds and ester group-containing compounds, in the composition containing copper nanoparticles of the present invention, from the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250°C, the total content of the hydroxyl group-containing compound and the ester group-containing compound in the organic solvent C is preferably 40% by mass or more, more preferably 50% by mass or more, still 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, still more preferably substantially 100% by mass.

[0093] In the present invention, "the total content of the hydroxyl group-containing compound and the ester group-containing compound in the organic solvent C is substantially 100% by mass" means that no organic solvent other than the hydroxyl group-containing compound and the ester group-containing compound is included, but the presence of an organic solvent other than the hydroxyl group-containing compound and the ester group-containing compound that is not deliberately included in the hydroxyl group-containing compound or the ester group-containing compound is allowed. Specifically, the presence of impurities contained in the hydroxyl group-containing compound or the ester group-containing compound is allowed.

[0094] When the organic solvent C contains a hydroxyl group-containing compound, in the composition containing copper nanoparticles of the present invention, from the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250°C, the content of the hydroxyl group-containing compound in the organic solvent C is preferably 40% by mass or more, more preferably 50% by mass or more, still 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, still more preferably substantially 100% by mass.

[0095] In the present invention, "the content of the hydroxyl group-containing compound in the organic solvent C is substantially 100% by mass" means that no organic solvent other than the hydroxyl group-containing compound is included, but the presence of an organic solvent other than the hydroxyl group-containing compound that is not deliberately included in the hydroxyl group-containing compound is allowed. Specifically, the presence of impurities contained in the hydroxyl group-containing compound is allowed.

[0096] In the composition containing copper nanoparticles of the present invention, from the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250°C, the total content of (poly)alkylene glycol and (poly)alkylene glycol alkyl ether in the organic solvent C is preferably 40% by mass or more, more preferably 50% by mass or more, further 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.

[0097] In the present invention, "the total content of (poly)alkylene glycol and (poly)alkylene glycol alkyl ether in the organic solvent C is substantially 100% by mass" means that no organic solvents other than (poly)alkylene glycol and (poly)alkylene glycol alkyl ether are included, but the presence of organic solvents other than (poly)alkylene glycol and (poly)alkylene glycol alkyl ether that are not deliberately included in the (poly)alkylene glycol or (poly)alkylene glycol alkyl ether is permitted. Specifically, the presence of impurities contained in the (poly)alkylene glycol and (poly)alkylene glycol alkyl ether is permitted.

[0098] <Metal fine particle D>

[0099] From the viewpoints of improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250°C, the composition containing copper nanoparticles of the present invention preferably further contains metal fine particle D. In the composition containing copper nanoparticles of the present invention, by coexisting metal fine particle D with copper nanoparticle A, it is possible to help copper nanoparticle A bond the metal fine particles D to each other as an adhesive, exhibit a high conductivity, and also exhibit a high bonding strength.

[0100] In the present invention, regarding metal fine particle D, any one metal can be used alone or two or more arbitrary metals can be used in combination. From the viewpoints of improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250°C, it is preferably one or more selected from gold, platinum, silver, copper, nickel, bismuth, tin, and iron, more preferably one or more selected from gold, platinum, silver, and copper, further preferably one or more selected from silver and copper, and still more preferably copper.

[0101] In the present invention, the metal fine particles D are an aggregate of fine particles of a metal, meaning that their average particle diameter exceeds 500 nm. From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, and improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, the average particle diameter of the metal fine particles D is preferably 0.6 μm or more, more preferably 0.65 μm or more, further preferably 0.7 μm or more, still further preferably 0.75 μm or more, still further preferably 0.8 μm or more. Also, from the viewpoint of heat resistance at 250 °C, it is preferably 8 μm or less, more preferably 6 μm or less, further preferably 5 μm or less, still further preferably 2 μm or less, still further preferably 1 μm or less. Considering these viewpoints comprehensively, the average particle diameter of the metal fine particles 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, further preferably 0.7 μm or more and 6 μm or less, still further preferably 0.7 μm or more and 5 μm or less, still further preferably 0.7 μm or more and 2 μm or less, still further preferably 0.7 μm or more and 1 μm or less, still further preferably 0.75 μm or more and 1 μm or less, still further preferably 0.8 μm or more and 1 μm or less.

[0102] In the present invention, even if the metal fine particles D contain particles having a particle diameter of 500 nm or less, as long as the average particle diameter exceeds 500 nm, the effects of the present invention can be further improved.

[0103] The average particle diameter of the metal fine particles D is measured by the method described in the examples.

[0104] In addition, when the composition containing copper nanoparticles of the present invention contains the metal fine particles D, in the measurement performed by the method described in the examples, the particles having an average particle diameter of 500 nm or less are regarded as the copper nanoparticles A, and the particles having an average particle diameter exceeding 500 nm are regarded as the metal fine particles D.

[0105] In the case where the composition containing copper nanoparticles of the present invention further contains metal fine particles D, the organic solvent C as the dispersion medium of the composition containing copper nanoparticles is preferably a combination of polyethylene glycol and terpene alcohol (wherein, 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 considered that: if it is these combinations, a synergistic effect is exhibited when combined with monocarboxylic acid B. Although the mechanism for exerting this effect is not clear, the reason is considered as follows: These combinations all contain polyethylene glycol having a relatively high molecular weight but being easily decomposed at high temperatures, and have a balance of hydrophobicity and hydrophilicity suitable for monocarboxylic acid B, and also have the property of being easily volatilized. Therefore, by further containing metal fine particles D, even when the content ratio of copper nanoparticles A relatively decreases, when firing the composition containing copper nanoparticles, the sintering of the particles can still be carried out efficiently.

[0106] From the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250 °C, the content of metal fine particles D in the composition containing copper nanoparticles of the present invention is preferably 5% by mass or more, more preferably 15% by mass or more, further preferably 20% by mass or more, still more preferably 25% by mass or more, and, from the same viewpoints as above, is preferably 65% by mass or less, more preferably 55% by mass or less, further preferably 45% by mass or less, still more preferably 35% by mass or less.

[0107] In the case where the composition containing copper nanoparticles of the present invention contains metal fine particles D, from the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving the low-temperature bondability, low-temperature conductivity, and bondability and conductivity after storage, and improving the heat resistance at 250 °C, the mass ratio [metal fine particles D / copper nanoparticles A] of the content of metal fine particles D in the composition containing copper nanoparticles of the present invention to the content of copper nanoparticles A is preferably 0.01 or more, more preferably 0.1 or more, further 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, further preferably 1.5 or less, still more preferably 1 or less, still more preferably 0.7 or less.

[0108] The composition containing copper nanoparticles of the present invention may also contain various additives as other components in addition to the above components A to D within a range that does not hinder the effects of the present invention. Examples of such additives include: dispersants, surfactants, defoamers, and fillers.

[0109] The copper nanoparticle-containing composition of the present invention may contain water as another component in addition to the above-mentioned components A to D. The water content 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 further preferably substantially 0% by mass.

[0110] In the present invention, “the content of water in the copper nanoparticle-containing composition is substantially 0 mass %” means that the copper nanoparticle-containing composition does not intentionally contain water, but the presence of water not intentionally contained in the components used in the copper nanoparticle-containing composition is allowed.

[0111] (Preparation of Composition Containing Copper Nanoparticles)

[0112] Regarding the preparation of the composition containing copper nanoparticles of the present invention, there are exemplified the following methods: method (i), which is to prepare copper nanoparticles A in advance by a known method, and to mix monocarboxylic acid B, organic solvent C, metal fine particles D contained as required, and various additives to the prepared copper nanoparticles A; method (ii), which is to use a dispersion of copper nanoparticles A dispersed by monocarboxylic acid B, and when the dispersion medium of the dispersion is not organic solvent C, to mix organic solvent C, and further to mix metal fine particles D contained as required, and various additives. Among these, method (ii) is preferred from the viewpoints of improving the dispersion stability and storage stability of the composition containing copper nanoparticles, improving low-temperature bonding, low-temperature conductivity, bonding and conductivity after storage, and improving heat resistance at 250°C.

[0113] There is no particular limitation on the method for mixing these, and the mixture can be mixed by a known method using a blender, a stirrer, etc. Specific methods include: a method of mixing with a spatula on a plate-like object, a method of mixing with a mortar, and a method of mixing with a rotation-revolution type stirring device.

[0114] The dispersion of copper nanoparticles A used in method (ii) can be obtained by maintaining the temperature of a copper raw material compound and a monocarboxylic acid B, which are a supply source of copper constituting copper nanoparticles A, within a range of 50° C. to 100° C. 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 the monocarboxylic acid B is attached to at least a portion of the surface of copper nanoparticles A.

[0115] The copper raw material compound is not particularly limited. For example, nitrates, copper sulfate, copper chloride, cuprous oxide, copper oxide, copper acetate, and copper sulfide can be cited. In addition, regarding the copper raw material compound, one kind can be used alone or two or more kinds can be used in combination. Among these, the copper raw material compound is preferably copper oxide.

[0116] As the organic solvent for the preparation of copper nanoparticles A, it is preferable to use an organic solvent other than organic solvent C. Suitable examples of the organic solvent for the preparation of copper nanoparticles A preferably include alcohols, hydrocarbons, and ketones, more preferably alcohols, and further preferably one or more selected from methanol, ethanol, propanol, and butanol.

[0117] In the preparation of the dispersion of copper nanoparticles A by method (ii), in addition to using the copper raw material compound, monocarboxylic acid B, and the organic solvent for the preparation of copper nanoparticles A, it is preferable to also use a reducing agent in combination. The purpose of using the reducing agent is to reduce the copper raw material compound to obtain elemental copper. As the reducing agent, for example, carbon, hydrogen, carbon monoxide, hydrazine, or metal hydrides, aldehyde group-containing compounds, and hydroxyl group-containing compounds can be preferably cited. Among these, hydrazine is more preferable.

[0118] The obtained dispersion of copper nanoparticles A can be refined to remove the organic solvent for the preparation of copper nanoparticles A or the remaining raw materials or by-products.

[0119] As the refining method, for example, the following methods can be cited: allowing the obtained dispersion of copper nanoparticles A to stand or centrifuging for a certain period of time, removing the supernatant, recovering the precipitate, adding again the organic solvent for the preparation of copper nanoparticles A or the organic solvent for the refining of copper nanoparticles A and performing the operation of standing or centrifuging for a certain period of time, and repeating this operation the required number of times; removing the dissolved substances through an ultrafiltration device.

[0120] Suitable examples of the organic solvent for the refining of copper nanoparticles A preferably include the organic solvents exemplified in the above-mentioned organic solvents for the preparation of copper nanoparticles A.

[0121] The dispersion of the refined copper nanoparticles A can be directly used in the composition containing copper nanoparticles in a state containing the organic solvent for the preparation of copper nanoparticles A or the organic solvent for the refining of copper nanoparticles A. However, it is preferably to dry the dispersion of copper nanoparticles A to remove the organic solvent for the preparation of copper nanoparticles A or the organic solvent for the refining of copper nanoparticles A, and formulate the composition containing copper nanoparticles in the form of a dry powder of copper nanoparticles A containing monocarboxylic acid B. The obtained dry powder of copper nanoparticles A containing monocarboxylic acid B is mixed with the organic solvent C, the metal fine particles D contained as required, and various additives, thereby enabling the composition containing copper nanoparticles to be obtained. As a method for removing the organic solvent for the preparation of copper nanoparticles A or the organic solvent for the refining of copper nanoparticles A from the dispersion of copper nanoparticles A, atmospheric drying, reduced-pressure drying, and freeze-drying can be mentioned, and freeze-drying is preferred.

[0122] For the composition containing copper nanoparticles of the present invention, by firing it while interposing it between a plurality of members to be joined, a joining layer including a sintered body containing at least copper can be formed, and the plurality of members to be joined can be joined through this joining layer. That is, the composition containing copper nanoparticles of the present invention is preferably used as a joining composition. The joined body having this joining layer has a high joining strength, excellent heat resistance at 250 °C, and also has high conductivity. From this viewpoint, the composition containing copper nanoparticles of the present invention can be used as a joining composition in the following situations: joining of chip components such as capacitors and resistors to a circuit board; joining of semiconductor chips such as memories, diodes, transistors, ICs (Integrated Circuits), and CPUs (Central Processing Units) to a lead frame or a circuit board; and joining of a highly heat-generating semiconductor chip to a heat dissipation substrate, etc.

[0123] [Method for manufacturing a joined body]

[0124] The method for manufacturing the joined body of the present invention includes a step of firing in a state where the above composition containing copper nanoparticles as a joining composition is interposed between a plurality of members to be joined (hereinafter, also referred to as "step 1").

[0125] In Step 1, as a method of interposing a composition containing copper nanoparticles between a plurality of members to be joined, preferably, a method of coating is carried out between at least one of the members to be joined and other members to be joined, that is, between a first member to be joined and a second member to be joined. As a method of coating the composition containing copper nanoparticles, various methods can be used. As a method of coating the composition containing copper nanoparticles, for example, preferably, screen printing method, stencil printing method, flexographic printing method, gravure printing method, dipping method, spraying method, bar coating method, spin coating method, inkjet method, dispenser method, needle plate transfer method, coating method using a brush, casting method, or syringe method can be cited. Among these, the stencil printing method is more preferable.

[0126] In Step 1, the atmosphere during firing can be an air atmosphere, an inert gas atmosphere such as nitrogen, or a reducing gas atmosphere such as hydrogen. From the viewpoints of suppressing oxidation of copper and safety, a nitrogen atmosphere is more preferable.

[0127] In Step 1, the firing temperature is preferably 200°C or higher, more preferably 230°C or higher, and further preferably 240°C or higher. Also, it is preferably 300°C or lower, more preferably 280°C or lower, and further preferably 260°C or lower.

[0128] In Step 1, the time for maintaining the temperature at the above-specified temperature during firing is preferably 10 seconds or longer, more preferably 60 seconds or longer, and further preferably 120 seconds or longer.

[0129] During firing in Step 1, preferably, heating is carried out while applying pressure to the first member to be joined and the second member to be joined. The pressure applied to the first member to be joined and the second member to be joined is preferably 10 MPa or higher, more preferably 15 MPa or higher, and further preferably 18 MPa or higher. Also, it is preferably 30 MPa or lower, more preferably 28 MPa or lower.

[0130] The material of the member to be joined used in the method for manufacturing the joined body of the present invention can be a single material or a material composed of a plurality of different types of materials. As the material of the member to be joined used in the method for manufacturing the joined body of the present invention, for example, preferably, one or more selected from gold, platinum, silver, copper, iron, nickel, silicon, germanium, and indium can be cited.

[0131] As a preferable combination of the first member to be joined and the second member to be joined, a combination of the same type or different types selected from gold, silver, copper, and silicon is preferable, a combination of copper and copper or a combination of copper and silicon is more preferable, and a combination of copper and silicon is further preferable.

[0132] As the shape of the member to be joined, various shapes such as a plate shape can be cited. The member to be joined can be rigid or flexible. Regarding the thickness of the member to be joined, it can also be appropriately selected.

[0133] Preferably, at least one of the members to be joined is a metal plate.

[0134] In the case where the member to be joined is a metal plate, the member to be joined can be in a form obtained by appropriately applying, plating, or attaching a metal to the surface of glass, resin, or a metal other than the member to be joined.

[0135] In the case where 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 longer to sinter at least copper nanoparticles A (hereinafter, also referred to as "sintering treatment step").

[0136] The temperature of the metal plate in the sintering treatment 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 further preferably 260°C or lower.

[0137] The time for holding the metal plate at the above specified temperature in the sintering treatment step is preferably 60 seconds or longer, more preferably 120 seconds or longer.

[0138] In the sintering treatment step, it is preferable to apply pressure to the member to be joined. In the sintering treatment step, the pressure applied to the member to be joined is preferably 10 MPa or higher, more preferably 15 MPa or higher, further preferably 18 MPa or higher, and preferably 30 MPa or lower, more preferably 28 MPa or lower.

[0139] The joining strength of the obtained joined body is preferably 20 MPa or higher, more preferably 25 MPa or higher, and further preferably 30 MPa or higher.

[0140] The joining strength can be measured by the method used in the evaluation of low-temperature joinability described in the examples.

[0141] The rate of decrease in the joining strength after holding the obtained joined body at 250°C for 1000 hours is preferably 20% or lower, more preferably 15% or lower, and further preferably 10% or lower.

[0142] The rate of decrease in the joining strength can be calculated by the method used in the evaluation of heat resistance at 250°C described in the examples.

[0143] In addition, as a use other than the above-described bonding composition, the composition containing copper nanoparticles of the present invention can be used to form conductive structures such as wirings and electrodes having a sufficiently low resistivity. Therefore, the composition containing copper nanoparticles of the present invention can be suitably used for manufacturing electronic devices containing a conductive structure (the conductive structure includes a sintered body of the composition containing copper nanoparticles), such as thin film transistors, integrated circuits including thin film transistors, RFID (Radio Frequency Identifier), flexible displays, organic EL (Electroluminescence) displays, touch panels, organic EL elements, circuit boards, sensor devices, conductive columns, conductive materials for flip chip mounting, and the like.

[0144] (Manufacture of Conductive Structure)

[0145] The method for manufacturing the conductive structure of the present invention is preferably a method including a step of applying a composition containing copper nanoparticles to a substrate and then firing. By including the firing step (hereinafter, also referred to as "Step I"), the medium in the applied composition containing copper nanoparticles can be evaporated and dried, and further, at least copper nanoparticles A can be sintered to reduce the residual components in the conductive structure.

[0146] As a method for applying the composition containing copper nanoparticles, various methods can be used, and preferably, the methods exemplified as the coating method of the composition containing copper nanoparticles in the above-described method for manufacturing the bonded body can be mentioned. Among these, the template printing method is more preferable.

[0147] In Step I, the atmosphere during firing can be an air atmosphere, an inert gas atmosphere such as nitrogen, or a reducing gas atmosphere such as hydrogen. From the viewpoints of suppressing oxidation of copper and safety, a nitrogen atmosphere is more preferable.

[0148] In Step I, the firing temperature is preferably 200 °C or higher, more preferably 230 °C or higher, further preferably 240 °C or higher, and preferably 300 °C or lower, more preferably 280 °C or lower, further preferably 260 °C or lower.

[0149] In Step I, the time for maintaining the temperature at the above-specified temperature during firing can be appropriately selected according to the firing temperature, preferably 1 minute or longer, more preferably 3 minutes or longer, further preferably 5 minutes or longer, and preferably 60 minutes or shorter, more preferably 30 minutes or shorter, further preferably 20 minutes or shorter.

[0150] As the method of heating in Process I, examples include: a method of heating by bringing a heater into contact with the surface of the substrate on the side opposite to the surface to which the composition containing copper nanoparticles is applied; a method of storing the substrate to which the composition containing copper nanoparticles is applied in a thermostatic device capable of maintaining a fixed temperature; a method of heating the surface of the substrate to which the composition containing copper nanoparticles is applied with hot air; a method of heating by bringing a heater close to the surface of the substrate to which the composition containing copper nanoparticles is applied; a method of heating by steam curing using high-temperature steam under normal pressure or high pressure; a method of heating by irradiating light such as near-infrared light or ultraviolet light, etc.

[0151] [Examples]

[0152] Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to these examples.

[0153] Various physical properties were measured or calculated by the following methods.

[0154] [Average particle size of copper nanoparticles A and metal fine particles D]

[0155] Using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, field emission scanning electron microscope: S-4800), a scanning electron microscope (SEM) image of copper nanoparticles A or metal fine particles D was taken. The magnification was determined according to the particle size and was taken in the range of 5,000 times to 150,000 times. The SEM image was analyzed using image analysis software ImageJ (National Institutes of Health, USA). For each sample, the particle size was determined for more than 100 particles, and the arithmetic mean of these was set as the average particle size of copper nanoparticles A or metal fine particles D.

[0156] [Calculation of the ratio of the mass of monocarboxylic acid B to the total mass 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)])]

[0157] Using a differential thermal gravimetric synchronous measurement device (TG / DTA) STA7200RV (manufactured by Hitachi High-Technologies Science Corporation), 10 mg of a sample (dry powder of copper nanoparticles A containing monocarboxylic acid B) was weighed and placed in an aluminum crucible. Under a nitrogen gas flow rate of 50 mL / minute, the temperature was raised from 35°C to 550°C at a rate of 10°C / minute, and the mass reduction was measured. The mass reduction from 35°C to 550°C was set as the mass of monocarboxylic acid B, and the residual mass at 550°C was set as the mass of copper nanoparticles A, and the ratio of the mass of monocarboxylic acid B to the total mass 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)]) was calculated.

[0158] (Manufacture of dry powder of copper nanoparticles A containing monocarboxylic acid B)

[0159] Production Example 1

[0160] 50.0 g of copper oxide (manufactured by Nisshin Chemco Co., Ltd., grade: N-120) as a copper raw material compound, 4.40 g of 4-oxopentanoic acid (levulinic acid) as monocarboxylic acid B (Tokyo Chemical Industry Co., Ltd., purity: >97% by mass), and 500 g of ethanol (95) (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) were placed in a 2-L beaker and stirred for 15 minutes. During stirring, the temperature of the mixed solution was controlled at 70 °C by an oil bath.

[0161] Next, 63.0 g of hydrazine hydrate (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) as a reducing agent was placed in a 50-mL dropping funnel and added dropwise to the above mixed solution at 25 °C over 20 minutes. After that, while controlling the temperature of the reaction solution at 70 °C by an oil bath, the mixture was stirred for 1 hour, and then air-cooled to obtain a reddish-brown dispersion containing copper nanoparticles.

[0162] Using a cooling centrifuge himac CR22G and rotor (R12A, radius 15.1 cm) manufactured by Hitachi High-Tech Corporation, the entire amount of the obtained dispersion was added to a 500PA bottle of a centrifuge tube manufactured by the same company, and a centrifugal acceleration of 675 G was applied at 2,000 revolutions per minute and maintained in this state for 30 minutes. 300 g of acetone (manufactured by Fujifilm Wako Pure Chemical Corporation, first grade reagent) was added to the precipitate separated by centrifugation, and the mixture was stirred for 15 minutes to redisperse it. Again, the entire amount of the redispersed solution was centrifuged under the same conditions, and the precipitate was separated. This operation was performed twice.

[0163] Next, 300 g of methanol (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) was added to the precipitate, and the mixture was stirred for 15 minutes to redisperse it. Again, the entire amount of the redispersed solution was centrifuged under the same conditions, and the precipitate was separated. This operation was performed twice.

[0164] Using a freeze dryer (manufactured by Tokyo Rika Kikai Co., Ltd., model: FDU-2110) equipped with a drying chamber (manufactured by Tokyo Rika Kikai Co., Ltd., model: DRC-1000), the precipitate of refined copper nanoparticles was freeze-dried to obtain 38.0 g of dry powder A-1 of copper nanoparticles A1 containing 4-oxopentanoic acid. The drying conditions were as follows: frozen at -25°C for 1 hour, dried under reduced pressure at 5 Pa at -10°C for 9 hours, and further dried under reduced pressure at 5 Pa at 25°C for 5 hours. 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 total mass of copper nanoparticles A1 and the mass of 4-oxopentanoic acid was 0.009. The results are shown in Table 1.

[0165] Production Examples 2 to 7 and Comparative Production Examples 1 to 6

[0166] Except for changing the monocarboxylic acid B as shown in Table 1, the same procedure as in Production Example 1 was carried out to obtain the dry powders of copper nanoparticles A containing monocarboxylic acid B shown in Table 1. 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 the mass of monocarboxylic acid B.

[0167] (Production of dry powder of silver nanoparticles containing monocarboxylic acid B)

[0168] Comparative Production Example 7

[0169] Copper oxide was changed to silver oxide (FUJIFILM Wako Pure Chemical Corporation, special grade reagent), and 4-oxopentanoic acid (levulinic acid) was changed to 5-oxohexanoic acid. Otherwise, the same procedure as in Production Example 1 was carried out to obtain the dry powder AC-7 of silver nanoparticles AC7 containing 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 total mass of silver nanoparticles AC7 and the mass of 5-oxohexanoic acid was 0.011.

[0170] Comparative Production Example 8

[0171] Except for changing 5-oxohexanoic acid to 12-hydroxydodecanoic acid, the same procedure as in Comparative Production Example 7 was carried out to obtain the dry powder AC-8 of silver nanoparticles AC8 containing 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 total mass of silver nanoparticles AC8 and the mass of 12-hydroxydodecanoic acid was 0.009.

[0172] [Table 1]

[0173] Table 1

[0174]

[0175] *1: The ratio of the mass of monocarboxylic acid B to the total mass of the mass of copper nanoparticles A and the mass of monocarboxylic acid B.

[0176] However, compare the ratio of the mass of monocarboxylic acid B to the total mass of the mass of silver nanoparticles and the mass of monocarboxylic acid B in Production Example 7 and Comparative Production Example 8.

[0177] 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 as follows.

[0178] (Monocarboxylic acid B)

[0179] 4 - Oxopentanoic acid: manufactured by Tokyo Chemical Industry Co., Ltd., purity: > 97% by mass.

[0180] 5 - Oxohexanoic acid: manufactured by Tokyo Chemical Industry Co., Ltd., purity: > 98% by mass.

[0181] 6 - Hydroxyhexanoic acid: manufactured by Sigma - Aldrich, purity: 95% by mass.

[0182] 2 - Hydroxyoctanoic acid: manufactured by Tokyo Chemical Industry Co., Ltd., purity: > 98% by mass.

[0183] 12 - Hydroxydodecanoic acid: manufactured by Sigma - Aldrich, purity: 97% by mass.

[0184] 2 - Methoxybutyric acid: manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent.

[0185] 3 - Ethoxypropionic acid: manufactured by Tokyo Chemical Industry Co., Ltd., purity: > 98% by mass.

[0186] (Other carboxylic acids)

[0187] Pyruvic acid: manufactured by Tokyo Chemical Industry Co., Ltd., purity: > 97% by mass.

[0188] Lactic acid: manufactured by Tokyo Chemical Industry Co., Ltd., purity: > 85% by mass.

[0189] 16 - Hydroxyhexadecanoic acid: manufactured by Sigma - Aldrich, purity: 98% by mass.

[0190] Methoxyacetic acid: manufactured by Tokyo Chemical Industry Co., Ltd., purity: > 96% by mass.

[0191] Citric acid: manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent.

[0192] Hexanoic acid: manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent.

[0193] Example 1

[0194] (Preparation of Composition Containing Copper Nanoparticles)

[0195] Add 0.5 g of dipropylene glycol (manufactured by Fujifilm Wako Pure Chemical Corporation, first-grade reagent) as organic solvent C, 0.5 g of tetraethylene glycol (manufactured by Fujifilm Wako Pure Chemical Corporation, first-grade reagent), and 9.0 g of dry powder A-1 of copper nanoparticle A1 containing 4-oxopentanoic acid into an agate mortar, and knead until the dry powder is no longer visible to the naked eye. Transfer the obtained mixed solution into a polymer bottle. Tightly stopper the polymer bottle and stir it for 5 minutes at 2,000 rpm (2,000 revolutions per minute) using a rotation revolution type stirring device (manufactured by Thinky Corporation, model: ARV-310) to obtain Composition 1 containing copper nanoparticles.

[0196] (Manufacture of Bonded Body)

[0197] The obtained Composition 1 containing copper nanoparticles was used to manufacture a bonded body according to the following method.

[0198] First, place a stainless-steel metal shield (thickness: 150 μm) with 3 columns of 6 mm × 6 mm square openings on a 30 mm × 30 mm copper plate (total thickness: 1 mm), and coat Composition 1 containing copper nanoparticles on the copper plate by stencil printing using a metal squeegee. Then, in an atmospheric atmosphere, heat and dry it on a Shamal hot plate (manufactured by AS ONE Corporation, model: HHP-441) at 120 °C for 10 minutes. Then, prepare a silicon chip obtained by sequentially performing sputtering treatments of titanium, nickel, and gold on a 5 mm × 5 mm silicon chip (thickness: 400 μm), and place the silicon chip on Composition 1 containing copper nanoparticles coated on the copper plate in such a way that gold is in contact with Composition 1 containing copper nanoparticles. Thus, a laminate was obtained by sequentially laminating a copper plate, Composition 1 containing copper nanoparticles, and a silicon chip.

[0199] The obtained laminate was fired by the following method to obtain a bonded body.

[0200] First, the laminate was installed in a pressure heating bonding device (manufactured by Meisho Kiko Co., Ltd., model: HTM-1000), and nitrogen was allowed to flow into the furnace at 500 mL / min to replace the air in the furnace with nitrogen. After that, while pressing the laminate at 20 MPa with the upper and lower heating heads, the temperature of the heating heads was raised to 250 °C over 10 minutes. After the temperature rise, sintering treatment was carried out at 250 °C for 150 seconds to obtain a bonded body. After the sintering treatment, the heating heads were water-cooled at -60 °C / min, and when the temperature of the heating heads became 100 °C or lower, the bonded body was taken out into the air.

[0201] Examples 2 to 17, Comparative Examples 1 to 9

[0202] Except for changing the composition of the composition containing copper nanoparticles to the compositions shown in Tables 2 and 3, the same procedure as in Example 1 was followed to obtain the compositions containing copper nanoparticles of Examples 2 to 17 and Comparative Examples 1 to 7, the compositions containing silver nanoparticles of Comparative Examples 8 to 9, and the bonded bodies, respectively.

[0203] The raw materials for manufacturing the composition containing copper nanoparticles and the composition containing silver nanoparticles are as follows.

[0204] (Other copper nanoparticles)

[0205] Copper nanoparticles AC9: CH-0200L1 (manufactured by Mitsui Mining & Smelting Co., Ltd., particle size 190 nm, lauric acid content 1.3 mass%).

[0206] (Organic solvent C)

[0207] Dipropylene glycol: Manufactured by Fujifilm Wako Pure Chemical Corporation, first grade reagent.

[0208] Tetraethylene glycol: Manufactured by Fujifilm Wako Pure Chemical Corporation, first grade reagent.

[0209] PEG200: Polyalkylene glycol 200, manufactured by Fujifilm Wako Pure Chemical Corporation, first grade reagent, average molecular weight: 180 - 220.

[0210] PEG400: Polyalkylene glycol 400, manufactured by Fujifilm Wako Pure Chemical Corporation, first grade reagent, average molecular weight: 360 - 440.

[0211] α-Terpineol: Manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent.

[0212] Diethylene glycol monobutyl ether: Manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent.

[0213] Diethylene Glycol Monobutyl Ether Acetate: Tokyo Chemical Industry Co., Ltd., Purity: >98 mass%.

[0214] (Metal fine particle D)

[0215] Copper fine particle D1: MA-C025 (manufactured by Mitsui Mining & Smelting Co., Ltd., particle size 5.0 μm).

[0216] Copper fine particle D2: 1050Y (manufactured by Mitsui Mining & Smelting Co., Ltd., particle size 0.8 μm).

[0217] Using the bonded bodies obtained in Examples 1 to 17 and Comparative Examples 1 to 9, the following evaluations were carried out. The results are shown in Tables 2 and 3.

[0218] <Evaluation>

[0219] [Low-temperature bondability]

[0220] In the following order, the bond strength of each bonded body obtained in the examples and comparative examples was measured.

[0221] Using a universal bond strength testing machine (manufactured by Nordson Advanced Technology Co., Ltd., product name: Material Testing Machine, model: Prospector), the silicon chip of the bonded body was pressed horizontally at a test speed of 5 mm / minute and a shear height of 50 μm, and the chip shear strength of the bonded body was measured. Three bonded bodies were measured for each, and the average value of the values obtained by measuring the three bonded bodies was set as the bond strength of the bonded body, and the low-temperature bondability was evaluated. The higher the value of the bond strength, the more excellent the low-temperature bondability.

[0222] [Bondability after storage]

[0223] Each composition containing copper nanoparticles or silver nanoparticles obtained in the examples and comparative examples was stored in an environment of 25°C and 50% humidity for one month. After that, each bonded body was obtained by the same method as the manufacture of the bonded body in Example 1. Then, the bond strength of the bonded body was measured by the same method as the above evaluation method for low-temperature bondability. The higher the value of the bond strength, the more excellent the bondability after storage.

[0224] [Heat resistance at 250°C]

[0225] Each bonded body obtained in the examples and comparative examples was stored in an atmosphere at 250°C for 1000 hours. Then, the bond strength of the bonded body was measured by the same method as the above evaluation method for low-temperature bondability. The higher the value of the bond strength, the more excellent the heat resistance at 250°C.

[0226] In addition, the rate of decrease in the bonding strength is calculated according to the following formula.

[0227] Rate of decrease in bonding strength (%) = (1 - (bonding strength after storage / bonding strength before storage)) × 100

[0228]

[0229]

[0230] As can be seen from Table 2 and Table 3, the compositions containing copper nanoparticles of Examples 1 to 17 have excellent low-temperature bondability. Compared with the compositions containing copper nanoparticles of Comparative Examples 1 to 7 that do not contain monocarboxylic acid B and the compositions containing silver nanoparticles of Comparative Examples 8 and 9 using silver nanoparticles AC7 and AC8, the bondability after storage is excellent. Therefore, the dispersion stability and storage stability of the compositions containing copper nanoparticles of Examples 1 to 17 are excellent. In addition, the obtained bonded bodies have excellent heat resistance at 250°C. As described above, according to the present invention, a composition containing copper nanoparticles with excellent dispersion stability, storage stability, and low-temperature bondability can be provided. Even after storing the composition containing copper nanoparticles for a certain period of time, a bonded body with a high bonding strength can be obtained by low-temperature firing at 200°C or higher and 300°C or lower. Further, a bonded body with excellent heat resistance in an environment of 250°C can be obtained.

[0231] Example 18

[0232] (Manufacture of Conductive Structure)

[0233] A conductive structure was obtained using the composition 1 containing copper nanoparticles obtained in Example 1 according to the following method.

[0234] First, a stainless-steel metal shield (thickness: 50 μm) having a 10 mm × 10 mm square opening was placed on a 40 mm × 10 mm glass slide (total thickness: 1 mm). The composition 1 containing copper nanoparticles was coated on the glass slide by template printing using a metal squeegee. Then, it was placed on a Shamal hot plate (manufactured by AS ONE Corporation, model: HHP-441), the lid of a separable flask connected to a nitrogen pipe was covered, and while flowing nitrogen at 5 L / minute, it was heated at 250°C for 10 minutes.

[0235] Comparative Example 10

[0236] In Example 18, except that the composition C6 containing copper nanoparticles obtained in Comparative Example 6 was used instead of the composition 1 containing copper nanoparticles, a conductive structure was obtained in the same manner as in Example 18.

[0237] The following evaluations were performed using the conductive structures obtained in Example 18 and Comparative Example 10. The results are shown in Table 4.

[0238] <Evaluation>

[0239] [Low-temperature conductivity]

[0240] The volume resistivity of each conductive structure obtained in the examples and comparative examples was measured in the following order.

[0241] First, the obtained conductive structure was peeled off from the glass slide, and the thickness t of the conductive structure was measured using a micrometer.

[0242] Secondly, the above conductive structure was measured using a resistivity meter (main body: Loresta-GP, four-probe type probe: PSP probe, both manufactured by Mitsubishi Chemical Analytech Co., Ltd.). The volume resistivity was displayed by inputting the thickness t of the measured conductive structure into the above resistivity meter. The other parts of the above conductive structure were also measured in the same manner, and the volume resistivity ρv was obtained based on the arithmetic mean of a total of three places. The lower the value of the volume resistivity ρv, the more excellent the low-temperature conductivity.

[0243] [Conductivity after storage]

[0244] Each composition containing copper nanoparticles obtained in the examples and comparative examples was stored in an environment of 25°C and 50% humidity for one month. Then, each conductive structure was obtained by the same method as the production of the conductive structure in Example 18, and then measured by the same method as the above evaluation method for low-temperature conductivity. The lower the value of the volume resistivity ρv, the more excellent the conductivity after storage.

[0245] [Table 4]

[0246] Table 4

[0247]

[0248] As can be seen from Table 4, the composition containing copper nanoparticles of Example 18 has excellent low-temperature conductivity, and also has excellent conductivity after storage compared with the composition containing copper nanoparticles of Comparative Example 10 that does not contain monocarboxylic acid B. Therefore, the dispersion stability and storage stability of the composition containing copper nanoparticles of Example 18 are excellent, and in addition, the low-temperature conductivity of the obtained conductive structure is also excellent. As described above, according to the present invention, it is also possible to provide a composition containing copper nanoparticles with excellent dispersion stability, storage stability, and low-temperature conductivity, and even after storing the composition containing copper nanoparticles for a certain period of time, a conductive structure with excellent low-temperature conductivity can be obtained.

[0249] [Industrial applicability]

[0250] According to the present invention, it is possible to provide a composition containing copper nanoparticles, a method for manufacturing a bonded body using the composition containing copper nanoparticles, and a bonded body or an electronic device using the composition containing copper nanoparticles. By the composition containing copper nanoparticles of the present invention, the following effects can be obtained: namely, excellent bondability and conductivity achieved by firing under conditions belonging to low temperature (i.e., 200 °C or higher and 300 °C or lower) in the formation of bonding or wiring using metal fine particles, and even after being stored for a certain period of time, a bonded body having a high bonding strength and a conductive structure having excellent conductivity can be obtained, and the obtained bonded body has excellent heat resistance when kept at 250 °C for a long time. In the present invention, since copper nanoparticles are used, it is possible to provide an electronic device with high reliability in which electromigration is suppressed.

Claims

1. A composition containing copper nanoparticles, wherein, it contains copper nanoparticle A, monocarboxylic acid B, and organic solvent C, the monocarboxylic acid B has 5 or more and 12 or fewer carbon atoms, the monocarboxylic acid B has one or more functional groups or bonds selected from a hydroxyl group, a ketone carbonyl group, and an ether bond.

2. The composition containing copper nanoparticles according to claim 1, wherein, the average particle size of the copper nanoparticle A is 150 nm or more and 300 nm or less.

3. The composition containing copper nanoparticles according to claim 1 or 2, wherein, the ratio of the mass of the monocarboxylic acid B in the composition containing copper nanoparticles to the total mass of the copper nanoparticle A and the monocarboxylic acid B is 0.003 or more and 0.015 or less.

4. The composition containing copper nanoparticles according to any one of claims 1 to 3, wherein, the monocarboxylic acid B is one or more selected from 4-oxopentanoic acid, 5-oxohexanoic acid, 6-hydroxyhexanoic acid, 2-hydroxyoctanoic acid, 12-hydroxydodecanoic acid, 2-methoxybutyric acid, and 3-ethoxypropionic acid.

5. The composition containing copper nanoparticles according to any one of claims 1 to 4, wherein, the organic solvent C contains one or more selected from a hydroxyl group-containing compound having at least one hydroxyl group in the molecule and an ester group-containing compound having at least one ester group in the molecule.

6. The composition containing copper nanoparticles according to claim 5, wherein, the hydroxyl group-containing compound is one or more selected from (poly)alkylene glycols and (poly)alkylene glycol alkyl ethers.

7. The composition containing copper nanoparticles according to claim 5 or 6, wherein, the ester group-containing compound is (poly)alkylene glycol monoalkyl ether acetate.

8. The composition containing copper nanoparticles according to any one of claims 1 to 7, wherein, it further contains metal microparticle D.

9. The composition containing copper nanoparticles according to claim 8, wherein, the average particle size of the metal microparticle D is 0.6 μm or more and 8 μm or less.

10. A method for manufacturing a bonded body, wherein, including: a step of firing in a state where the composition containing copper nanoparticles according to any one of claims 1 to 9 is interposed between a plurality of members to be bonded, at least one of the members to be bonded is a metal plate, this step includes: a step of holding the metal plate at a temperature of 200 °C or more for 30 seconds or more and performing a sintering treatment on at least the copper nanoparticle A.

11. The method for manufacturing a bonded body according to claim 10, wherein, the rate of decrease in the bonding strength after holding the obtained bonded body at 250 °C for 1000 hours is 20% or less.

12. A bonded body, wherein, it has a bonding layer interposed between a plurality of members to be bonded, the bonding layer contains a sintered body of the composition containing copper nanoparticles according to any one of claims 1 to 9.

13. An electronic device, wherein, it contains: a conductive structure including a sintered body of the composition containing copper nanoparticles according to any one of claims 1 to 9.

14. Use of the composition containing copper nanoparticles according to any one of claims 1 to 9 in joining of a plurality of joined members.

15. Use of the composition containing copper nanoparticles according to any one of claims 1 to 9 in a conductive structure of an electronic device.

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