Copper particles, conductive paste, substrate, and method for producing copper particles

Abstract

The copper particles have a carbon content of from 0.1% by mass to 2.5% by mass (inclusive) as calculated by the following method. The method for calculating the carbon content comprises the following steps: weighing 0.5 g of copper particles, adding 1.5 g of tungsten powder, 0.5 g of iron powder and 0.5 g of tin powder as a combustion improver, and measuring in oxygen gas flow by using a carbon-sulfur analysis device under the conditions that the flow is 3L / min, the combustion method is high-frequency heating, the combustion time is 60 seconds and the detection method is infrared absorption, thereby calculating the carbon content.

Description

Technical Field

[0001] The present invention relates to copper particles, a conductive paste, a substrate, and a method for manufacturing copper particles. Background Art

[0002] A low-temperature co-fired ceramic substrate (LTCC substrate) is a substrate obtained by co-firing a wiring conductor and a ceramic substrate simultaneously. The LTCC substrate has excellent heat resistance and moisture resistance, and exhibits good frequency characteristics in high-frequency circuits. Therefore, it is widely used in applications for in-vehicle electronic substrates. The wiring conductors in the LTCC substrate use a conductive paste containing copper particles.

[0003] Conductive pastes containing copper particles are widely used. As technologies related to the method for manufacturing copper particles, for example, the contents described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-052284) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2020-050888) can be cited.

[0004] Patent Document 1 describes a method for manufacturing metal fine particles, which is characterized in that in a liquid in which a metal compound is dissolved or dispersed, in the presence of gelatin, in a method for obtaining metal fine particles by reducing metal ions contained in the metal compound, the particle diameter of the metal fine particles is controlled by selecting the type of gelatin. According to this method for manufacturing metal fine particles, metal fine particles having a desired average particle diameter can be easily manufactured.

[0005] Patent Document 2 describes a method for manufacturing easily pulverizable copper powder, which includes a pH treatment step of bringing copper powder manufactured by a wet method into contact with an alkaline aqueous solution having a pH of 8 to 14 or an acidic aqueous solution having a pH of 0 to 4. According to this method for manufacturing easily pulverizable copper powder, easily pulverizable copper powder can be obtained in which the burden of the pulverization and classification steps from a dry cake is reduced and the remaining of secondary particles is sufficiently reduced.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-052284.

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-050888. Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] For an LTCC substrate, since the wiring conductor and the ceramic substrate are co-fired simultaneously, a high sintering start temperature is required for the copper particles used in the wiring conductor.

[0012] The present invention has been completed in view of the above circumstances, and provides copper particles having a high firing start temperature, a conductive paste and a substrate using the copper particles, and a method for manufacturing copper particles having a high firing start temperature.

[0013] Means for solving the problem

[0014] The inventor of the present invention repeatedly conducted intensive research to achieve the above problems, and found that the firing start temperature of copper particles having a carbon content of 0.1% by mass or more and 2.5% by mass or less is high, thereby completing the present invention.

[0015] [1] A kind of copper particles, wherein the copper particles are copper particles having a carbon content of 0.1% by mass or more and 2.5% by mass or less calculated by the following method.

[0016] [Method for calculating carbon content]

[0017] Weigh 0.5 g of copper particles, add 1.5 g of tungsten powder, 0.5 g of iron powder and 0.5 g of tin powder as combustion aids, and use a carbon-sulfur analyzer to measure under the conditions of an oxygen flow rate of 3 L / min, a combustion method of high-frequency heating, a combustion time of 60 seconds, and a detection method of infrared absorption method to calculate the carbon content.

[0018] [2] A kind of copper particles, wherein, among the copper particles described in the above [1], the copper particles are copper particles having a shrinkage rate of 1.0% and a temperature of 650 °C or higher calculated by the following method.

[0019] [Method for calculating the temperature of shrinkage rate of 1.0%]

[0020] Weigh 1 g of copper particles, fill them into a cylindrical molding die with a diameter of 5 mm, and press and mold the copper particles by a hydraulic press (spray pressure: 10 MPa). Crush the particles obtained by the press molding to obtain a particle sample. Weigh 0.67 g of the particle sample, fill it into a cylindrical molding die with a diameter of 5 mm, and press and mold the particle sample by a hydraulic press (spray pressure: 10 MPa) to obtain a cylindrical particle with a diameter of 5 mm and a height of 5 mm as a measurement sample.

[0021] Use a thermomechanical analyzer to measure under the conditions of an Ar flow rate of 200 mL / min, a measurement load of 10 mN, a measurement temperature range of 23 to 1000 °C, and a heating rate of 5 °C / min to calculate the temperature of shrinkage rate of 1.0%.

[0022] [3] A kind of copper particles, wherein, among the copper particles described in the above [1] or [2], the D of the copper particles calculated by the following method 90The particle size is 0.1 μm or more and 5.0 μm or less.

[0023] [D 90 Method for calculating particle size]

[0024] Mix 0.1 g of copper particles with 1 mL of an aqueous dispersant solution containing 0.1% by mass. Using a laser diffraction / scattering particle size measuring device, irradiate ultrasonic waves into the device for 5 min, then measure the cumulative volume 90% particle size of the copper particles, and calculate D 90 Particle size.

[0025] [4] A kind of copper particles, wherein, among the copper particles described in any one of the foregoing [1] to [3], the D 50 calculated by the following method for the particle size of the copper particles is 0.05 μm or more and 5.0 μm or less.

[0026] [D 50 Method for calculating particle size]

[0027] Mix 0.1 g of copper particles with 1 mL of an aqueous dispersant solution containing 0.1% by mass. Using a laser diffraction / scattering particle size measuring device, irradiate ultrasonic waves into the device for 5 min, then measure the cumulative volume 50% particle size of the copper particles, and calculate D 50 Particle size.

[0028] [5] A kind of copper particles, wherein, among the copper particles described in any one of the foregoing [1] to [4], the proportion of copper particles with a particle size of 20 μm or more calculated by the following method is 0.8% or less based on volume.

[0029] [Method for calculating the proportion of copper particles with a particle size of 20 μm or more]

[0030] Mix 0.1 g of copper particles with 1 mL of an aqueous dispersant solution containing 0.1% by mass. Using a laser diffraction / scattering particle size measuring device, irradiate ultrasonic waves into the device for 5 min, then measure the cumulative volume particle size distribution of the copper particles, and calculate the proportion of copper particles with a particle size of 20 μm or more.

[0031] [6] A method for manufacturing copper particles, which is a method for manufacturing the copper particles described in any one of the foregoing [1] to [5], wherein the manufacturing method includes: a step of dispersing a divalent copper compound in a solvent in the presence of a dispersant; and a step of reducing the divalent copper compound to obtain a copper particle dispersion (A).

[0032] [7] A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in the foregoing [6], it further includes a step of removing the dispersant from the copper particle dispersion (A).

[0033] [8] A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in [7] above, in the step of removing the dispersant, the pH of the copper particle dispersion (A) is 7.0 or more and 14.0 or less.

[0034] [9] A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of [6] to [8] above, the dispersant contains at least one selected from the group consisting of gelatin, casein, sodium caseinate, ammonium caseinate, starch, dextrin, agar, sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, ammonium polyacrylate, stearic acid, polyethylene glycol, citric acid, aniline, and derivatives of aniline.

[0035]

[10] A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in [9] above, the dispersant contains gelatin.

[0036]

[11] A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of [6] to

[10] above, when the copper compound is set to 100 parts by mass in the step of dispersing the copper compound, the content of the dispersant is 0.1 part by mass or more and 3.0 parts by mass or less.

[0037]

[12] A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of [6] to

[11] above, the step of obtaining the copper particle dispersion (A) includes: a step of reducing the copper compound to obtain a copper compound dispersion (B); and a step of adjusting the pH of the copper compound dispersion (B) to 9.0 or more and 14.0 or less.

[0038]

[13] A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in

[12] above, in the step of obtaining the copper compound dispersion (B), the solvent is heated to 10°C or more and 70°C or less.

[0039]

[14] A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in

[12] or

[13] above, in the step of obtaining the copper compound dispersion (B), the reducing agent contains ascorbic acid.

[0040]

[15] A conductive paste, wherein the conductive paste contains the copper particles described in any one of [1] to [5] above or copper particles obtained by the method for manufacturing copper particles described in any one of [6] to

[14] above.

[0041]

[16] A substrate, wherein the substrate contains the conductive paste described in the foregoing

[15] or a sintered body of the conductive paste.

[0042]

[17] The substrate as described in the foregoing

[16] , wherein the substrate is a low-temperature fired laminated ceramic substrate.

[0043] Effects of the Invention

[0044] According to the present invention, it is possible to provide copper particles having a high firing start temperature, a conductive paste using the copper particles and a substrate, and a method for manufacturing copper particles having a high firing start temperature. Detailed Embodiments

[0045] Hereinafter, embodiments of the present invention will be described.

[0046] [Copper Particles]

[0047] The carbon content rate of the copper particles of the present embodiment is 0.1% by mass or more and 2.5% by mass or less. The carbon content rate of the copper particles of the present embodiment is preferably 0.3% by mass or more, more preferably 0.4% by mass or more, further preferably 0.5% by mass or more, further preferably 0.8% by mass or more, further preferably 1.0% by mass or more, and preferably 2.3% by mass or less, more preferably 2.0% by mass or less, further preferably 1.9% by mass or less. When the carbon content rate is above the above lower limit value, the firing start temperature of the copper particles becomes high, so it is preferred. When the carbon content rate is below the above upper limit value, the firing start temperature of the copper particles becomes high, and when the copper particles are used in a conductive paste, the conductivity is less likely to decrease, so it is preferred.

[0048] The carbon content rate of the copper particles can be controlled, for example, by the type, addition amount of the dispersant when manufacturing the copper particles, the method of removing the dispersant, and the like.

[0049] Here, the carbon content rate of the copper particles can be calculated by the following method.

[0050] [Calculation Method of Carbon Content Rate]

[0051] Weigh 0.5 g of copper particles, add 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder as combustion aids, and use a carbon and sulfur analyzer to measure under the conditions of an oxygen flow rate of 3 L / min, a combustion method of high-frequency heating, a combustion time of 60 seconds, and a detection method of infrared absorption method to calculate the carbon content rate.

[0052] The copper particles of this embodiment may also contain elements other than copper and carbon. Examples of elements other than copper and carbon include oxygen, nitrogen, chlorine, boron, etc. When the total copper particles are 100% by mass, the content rate of elements other than copper and carbon is preferably 5.0% by mass or less, more preferably 3.0% by mass or less. The lower limit value of the content rate of elements other than copper and carbon is not particularly limited. For example, it may be 0.1% by mass or more, or may be 1.0% by mass or more.

[0053] The D of the copper particles of this embodiment 90 particle size is preferably 0.1 μm or more, more preferably 0.3 μm or more, further preferably 0.4 μm or more, further preferably 0.5 μm or more, further preferably 0.7 μm or more, further preferably 0.9 μm or more, further preferably 1.0 μm or more, and preferably 5.0 μm or less, more preferably 4.5 μm or less, further preferably 4.0 μm or less, further preferably 3.0 μm or less, further preferably 2.0 μm or less. The D 90 When the particle size is below the above upper limit value, when the conductive paste containing copper particles is used for the LTCC substrate, the LTCC substrate can be further miniaturized, so it is preferred. The D 90 When the particle size is above the above lower limit value, the processability of the copper particles is improved, so it is preferred.

[0054] Here, the D 90 particle size is calculated by the following method.

[0055] [Calculation method of D 90 particle size]

[0056] Mix 0.1 g of copper particles with 1 mL of an aqueous solution of a dispersant with a concentration of 0.1% by mass. Use a laser diffraction / scattering particle size measuring device. After irradiating ultrasonic waves into the device for 5 minutes, measure the cumulative volume 90% particle size of the copper particles, and calculate the D 90 particle size.

[0057] As the dispersant for copper particle size measurement, a known dispersant used when measuring the particle size of copper particles can be used. For example, polyoxyethylene-based nonionic surfactants such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monooleate; nonionic surfactants such as polyoxyethylene octylphenyl ether; etc. can be used.

[0058] The D of the copper particles of this embodiment 50The particle size is preferably 0.05 μm or more, more preferably 0.10 μm or more, further preferably 0.30 μm or more, further preferably 0.50 μm or more, further preferably 0.80 μm or more, further preferably 1.0 μm or more, and preferably 5.0 μm or less, more preferably 4.0 μm or less, further preferably 3.0 μm or less, further preferably 2.0 μm or less, further preferably 1.2 μm or less. D 50 When the particle size is below the above upper limit value, in the case of using the conductive paste containing copper particles for an LTCC substrate, the LTCC substrate can be further miniaturized, so it is preferred. D 50 When the particle size is above the above lower limit value, the processability of the copper particles is improved, so it is preferred.

[0059] Here, D 50 The particle size is calculated by the following method.

[0060] [D 50 Method for calculating the particle size]

[0061] Mix 0.1 g of copper particles with 1 mL of an aqueous dispersant solution of 0.1 mass%. Using a laser diffraction / scattering particle size measuring device, after irradiating the inside of the device with ultrasonic waves for 5 minutes, measure the cumulative volume 50% particle size of the copper particles and calculate D 50 the particle size.

[0062] As the dispersant for copper particle size measurement, a known dispersant used when measuring the particle size of copper particles can be used. For example, polyoxyethylene-based nonionic surfactants such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monooleate; nonionic surfactants such as polyoxyethylene octylphenyl ether; etc. can be used.

[0063] For the copper particles of the present embodiment, the proportion of copper particles with a particle size of 20 μm or more is preferably 0.8% or less based on volume, more preferably 0.5% or less based on volume, further preferably 0.3% or less based on volume, further preferably 0.2% or less based on volume, further preferably 0.1% or less based on volume, and further preferably 0.0% based on volume. When the proportion of copper particles with a particle size of 20 μm or more is below the above upper limit value, in the case of using the conductive paste containing copper particles for an LTCC substrate, the LTCC substrate can be further miniaturized, so it is preferred.

[0064] The proportion of copper particles with a particle size of 20 μm or more can be controlled, for example, by the type and addition amount of the dispersant during the manufacture of copper particles, the method of removing the dispersant, the pH adjustment time in the reduction process, etc.

[0065] Here, the proportion of copper particles with a particle size of 20 μm or more is calculated by the following method.

[0066] [Method for calculating the proportion of copper particles with a particle size of 20 μm or more]

[0067] Mix 0.1 g of copper particles with 1 mL of an aqueous solution of a dispersant at 0.1 mass%, and using a laser diffraction / scattering particle size measuring device, irradiate ultrasonic waves into the device for 5 min, then measure the cumulative volume particle size distribution of the copper particles, and calculate the proportion of copper particles with a particle size of 20 μm or more.

[0068] As the dispersant for copper particle size measurement, a known dispersant used when measuring the particle size of copper particles can be used. For example, polyoxyethylene-based nonionic surfactants such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monooleate; nonionic surfactants such as polyethyleneglycol octylphenyl ether; etc. can be used.

[0069] The firing start temperature of the copper particles in this embodiment is high. The firing start temperature can be evaluated by the temperature at which the copper particles reach a certain specified shrinkage rate measured using a thermomechanical analyzer. It should be noted that the firing start temperature in this embodiment is defined as the temperature at a shrinkage rate of 1.0%.

[0070] For the copper particles of this embodiment, the temperature at a shrinkage rate of 1.0% is preferably 650 °C or higher, more preferably 700 °C or higher, further preferably 730 °C or higher, further preferably 800 °C or higher, and further preferably 850 °C or higher. When the temperature at a shrinkage rate of 1.0% is above the above lower limit value, in the case of using the conductive paste containing copper particles for an LTCC substrate, co-firing of the wiring conductor and the ceramic substrate can be carried out more effectively, so it is preferred.

[0071] Here, the temperature at a shrinkage rate of 1.0% is calculated by the following method.

[0072] [Method for calculating the temperature at a shrinkage rate of 1.0%]

[0073] Weigh 1 g of copper particles, fill them into a cylindrical molding die with a diameter of 5 mm, and press and mold the copper particles using a hydraulic press (ejection pressure 10 MPa). Crush the pellets obtained by the press molding to obtain a pellet sample. Weigh 0.67 g of the pellet sample, fill it into a cylindrical molding die with a diameter of 5 mm, and press and mold the pellet sample using a hydraulic press (ejection pressure 10 MPa) to obtain a cylindrical pellet with a diameter of 5 mm and a height of 5 mm as the measurement sample.

[0074] Using a thermomechanical analyzer, measurements were carried out under the conditions of an Ar flow rate of 200 mL / min, a measurement load of 10 mN, a measurement temperature range of 23 to 1000 °C, and a heating rate of 5 °C / min, and the temperature at a shrinkage rate of 1.0% was calculated.

[0075] For the copper particles of the present embodiment, the temperature at a shrinkage rate of 0.5% is preferably 500 °C or higher, more preferably 550 °C or higher, further preferably 600 °C or higher, further preferably 650 °C or higher, further preferably 700 °C or higher, and further preferably 730 °C or higher. When the temperature at a shrinkage rate of 0.5% is above the above lower limit value, when the conductive paste containing copper particles is used for an LTCC substrate, co-firing of the wiring conductor and the ceramic substrate can be carried out more efficiently, so it is preferred.

[0076] Here, the temperature at a shrinkage rate of 0.5% is calculated by the following method.

[0077] [Method for calculating the temperature at a shrinkage rate of 0.5%]

[0078] Weigh 1 g of copper particles and fill them into a cylindrical molding die with a diameter of 5 mm. Press and mold the copper particles with an oil pressure press (spray pressure: 10 MPa). Crush the particles obtained by press molding to obtain a particle sample. Weigh 0.67 g of the particle sample and fill it into a cylindrical molding die with a diameter of 5 mm. Press and mold the particle sample with an oil pressure press (spray pressure: 10 MPa) to obtain a cylindrical particle with a diameter of 5 mm and a height of 5 mm as a measurement sample.

[0079] Using a thermomechanical analyzer, measurements were carried out under the conditions of an Ar flow rate of 200 mL / min, a measurement load of 10 mN, a measurement temperature range of 23 to 1000 °C, and a heating rate of 5 °C / min, and the temperature at a shrinkage rate of 0.5% was calculated.

[0080] The copper particles of the present embodiment can be used, for example, in conductive pastes, coatings, inks, etc., and are preferably used in conductive pastes.

[0081] [Manufacturing method of copper particles]

[0082] The manufacturing method of the copper particles of the present embodiment is not particularly limited and can be manufactured by a wet reduction method, a disproportionation method, etc. From the viewpoint of being able to further reduce the particle size of the copper particles, it is preferred to manufacture the copper particles of the present embodiment by a wet reduction method.

[0083] Preferably, the manufacturing method of the copper particles of the present embodiment includes: a step of dispersing a divalent copper compound in a solvent in the presence of a dispersant; and a step of reducing the divalent copper compound to obtain a copper particle dispersion (A).

[0084] The method for manufacturing copper particles according to the present embodiment can provide a method for manufacturing copper particles with a high firing start temperature. Further, the method for manufacturing copper particles according to the present embodiment can provide a method for manufacturing copper particles with a high firing start temperature and capable of reducing the content of copper particles with a large primary particle size.

[0085] For the copper particles obtained by the method for manufacturing copper particles according to the present embodiment, the content of copper particles with a large primary particle size can be reduced. The content of copper particles with a large primary particle size can be evaluated by magnifying and observing the copper particles using a scanning electron microscope.

[0086] Hereinafter, each process of the preferred manufacturing method will be specifically described.

[0087] (Process of dispersing a divalent copper compound in a solvent in the presence of a dispersant)

[0088] The process of dispersing a divalent copper compound in a solvent in the presence of a dispersant is carried out by adding a divalent copper compound to a solvent such as water and stirring, and then adding a dispersant.

[0089] As the divalent copper compound, for example, at least one selected from the group consisting of copper sulfate, copper oxide, copper chloride, copper carbonate, copper nitrate, etc. can be used. Preferably, copper sulfate can be used.

[0090] As the dispersant, for example, at least one selected from the group consisting of protein-based dispersants such as gelatin, casein, sodium caseinate, ammonium caseinate; natural rubber-based dispersants such as gum arabic; natural polymer-based dispersants such as starch, dextrin, agar, sodium alginate; cellulose-based dispersants such as hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose; vinyl-based dispersants such as polyvinyl alcohol, polyvinylpyrrolidone; acrylic-based dispersants such as sodium polyacrylate, ammonium polyacrylate; higher fatty acid-based dispersants such as stearic acid; synthetic polymer-based dispersants such as polyethylene glycol; polycarboxylic acid-based dispersants such as citric acid; dispersants composed of aniline or their derivatives, etc. can be used. Preferably, it contains at least one selected from the group consisting of gelatin, casein, sodium caseinate, ammonium caseinate, starch, dextrin, agar, sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, ammonium polyacrylate, stearic acid, polyethylene glycol, citric acid, aniline, and derivatives of aniline. More preferably, it contains at least one selected from the group consisting of gelatin, casein, sodium caseinate, and ammonium caseinate. Further preferably, it contains gelatin.

[0091] The dispersant is preferably a protein-based dispersant, more preferably gelatin.

[0092] Examples of gelatin used as a dispersant include gelatin obtained from raw materials containing collagen, such as the bones and skins of mammals such as cows and pigs; the bones, skins, and scales of fish such as sharks and tilapia.

[0093] From the viewpoint of improving the dispersibility of copper particles, the weight-average molecular weight of the gelatin used as the dispersant in this embodiment is preferably 25,000 or more, more preferably 50,000 or more, further preferably 75,000 or more, and further preferably 100,000 or more. And from the viewpoint of improving the processability of the dispersion liquid, it is preferably 500,000 or less, more preferably 400,000 or less, further preferably 350,000 or less, and further preferably 300,000 or less.

[0094] Here, the weight-average molecular weight of the gelatin is a value measured by the test method for photographic gelatin (Photographic and Gelatin Industries, PAGI method).

[0095] From the viewpoint of improving the dispersibility of copper particles, the number-average molecular weight of the gelatin used as the dispersant in this embodiment is preferably 10,000 or more, more preferably 15,000 or more, further preferably 20,000 or more. And from the viewpoint of improving the processability of the dispersion liquid, it is preferably 70,000 or less, more preferably 60,000 or less, and further preferably 50,000 or less.

[0096] Here, the number-average molecular weight of the gelatin is a value measured by the PAGI method.

[0097] In the step of dispersing the copper compound, when the copper compound is 100 parts by mass, the content of the dispersant is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, further preferably 1.0 part by mass or more. And it is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, and further preferably 2.0 parts by mass or less. When the content of the dispersant is within the above range, the dispersibility of the copper particles is improved, and it is easy to make the carbon content rate of the obtained copper particles fall within a preferable range, so it is preferable.

[0098] (Step of reducing the copper compound to obtain the copper particle dispersion liquid (A))

[0099] The step of reducing the copper compound to obtain the copper particle dispersion (A) is carried out by adding a reducing agent to the dispersion obtained by the step of dispersing the divalent copper compound in the presence of a dispersant and reducing the copper compound. Preferably, the step of reducing the copper compound to obtain the copper particle dispersion (A) includes: a step of reducing the copper compound to obtain a copper compound dispersion (B); and a step of adjusting the pH of the copper compound dispersion (B) to 9.0 or more and 14.0 or less.

[0100] The step of reducing the copper compound to obtain the copper compound dispersion (B) is carried out by adding a reducing agent to the dispersion obtained by the step of dispersing the divalent copper compound in the presence of a dispersant and reducing the copper compound.

[0101] Examples of the reducing agent that can be used include at least one selected from the group consisting of ascorbic acid; hydrazine-based reducing agents such as hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine hydrate; sodium borohydride; sodium sulfite; sodium bisulfite; sodium thiosulfate; sodium nitrite; sodium hyponitrite; phosphorous acid; sodium phosphite; hypophosphorous acid; sodium hypophosphite; aldehydes; alcohols; amines; sugars, etc.

[0102] Preferably, in the step of reducing the copper compound to obtain the copper compound dispersion (B), the reducing agent contains ascorbic acid.

[0103] In the step of reducing the copper compound to obtain the copper compound dispersion (B), the temperature of the solvent is preferably 10°C or higher, more preferably 20°C or higher, further preferably 30°C or higher, and preferably 70°C or lower, more preferably 60°C or lower, further preferably 55°C or lower, further preferably 50°C or lower, further preferably 45°C or lower.

[0104] The step of adjusting the pH of the copper compound dispersion (B) to 9.0 or more and 14.0 or less is carried out by adding an aqueous sodium hydroxide solution or the like to adjust the pH.

[0105] In the step of adjusting the pH of the copper compound dispersion (B) to 9.0 or more and 14.0 or less, the time for adjusting the pH is preferably 15 minutes or more, more preferably 20 minutes or more, and preferably 80 minutes or less, more preferably 50 minutes or less, further preferably 40 minutes or less.

[0106] The step of reducing the copper compound to obtain the copper particle dispersion (A) can also include a step of reducing the copper compound dispersion (B) after the step of adjusting the pH of the copper compound dispersion (B) to 9.0 or more and 14.0 or less.

[0107] After the step of adjusting the pH to 9.0 or higher and 14.0 or lower, the step of reducing the copper compound dispersion (B) is carried out by adding a reducing agent to the copper compound dispersion (B) and reducing the copper compound. The reducing agent is, for example, the same as the reducing agent used in the step of reducing the copper compound to obtain the copper compound dispersion (B), but a reducing agent containing hydrazine is preferably used.

[0108] (Step of removing the dispersant from the copper particle dispersion (A))

[0109] More preferably, the method for producing copper particles of the present embodiment further includes a step of removing the dispersant from the copper particle dispersion (A).

[0110] The step of removing the dispersant from the copper particle dispersion (A) is carried out by adding a removing agent to the copper particle dispersion (A) and removing the dispersant.

[0111] As the removing agent, for example, an aqueous solution of a hydroxide salt such as an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide; ion-exchanged water; etc. can be used. An aqueous solution of a hydroxide salt is preferably used, and an aqueous solution of sodium hydroxide is more preferably used.

[0112] In the step of removing the dispersant from the copper particle dispersion (A), the pH of the copper particle dispersion (A) is preferably 7.0 or higher, more preferably 8.0 or higher, further preferably 9.0 or higher, further preferably 10.0 or higher, further preferably 11.0 or higher, further preferably 11.5 or higher, further preferably 12.0 or higher, and preferably 14.0 or lower, more preferably 13.5 or lower, further preferably 13.0 or lower.

[0113] In the step of removing the dispersant from the copper particle dispersion (A), in addition to the removing agent, a reducing agent can also be added. As the reducing agent, for example, hydrazine can be cited. By adding the reducing agent, an effect of suppressing the oxidation of the copper particles in the copper particle dispersion (A) can be obtained.

[0114] (Other steps)

[0115] The method for producing copper particles of the present embodiment can also include a surface treatment step, a solid-liquid separation step, etc.

[0116] The surface treatment step is carried out, for example, by treating the surface of the copper particles with a surface treatment agent such as a saturated fatty acid salt such as sodium stearate or an unsaturated fatty acid salt such as sodium oleate. By treating the surface of the copper particles, it is possible to easily bring the carbon content rate of the obtained copper particles into a preferred range.

[0117] When the divalent copper compound is 100 parts by mass, the content of the surface treatment agent is preferably 0.05 part by mass or more, more preferably 0.07 part by mass or more, still more preferably 0.10 part by mass or more, and is preferably 0.50 part by mass or less, more preferably 0.30 part by mass or less, still more preferably 0.25 part by mass or less.

[0118] The solid-liquid separation step is carried out, for example, by separating the copper particles from the solvent using filtration, centrifugation, or the like.

[0119] [Conductive paste]

[0120] The conductive paste of the present embodiment contains the copper particles of the present embodiment or the copper particles obtained by the method for producing copper particles of the present embodiment.

[0121] When the total conductive paste is 100% by mass, for example, the content of the copper particles in the conductive paste of the present embodiment is 1% by mass or more, 5% by mass or more, 10% by mass or more, and is 99% by mass or less, 97% by mass or less, 94% by mass or less.

[0122] In addition, the conductive paste of the present embodiment may further contain a binder resin.

[0123] The binder resin contains, for example, at least one selected from the group consisting of polyester resin, polyurethane resin, polyamide resin, polyvinyl chloride resin, polyacrylamide resin, polyether resin, acrylic resin, melamine resin, vinyl resin, phenolic resin, epoxy resin, urea resin, vinyl acetate resin, polybutadiene resin, vinyl chloride-vinyl acetate copolymer resin, fluororesin, silicone resin, rosin, rosin ester, chlorinated polyolefin resin, modified chlorinated polyolefin resin, chlorinated polyurethane resin, cellulose-based resin, polyethylene glycol, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, and the like.

[0124] The conductive paste of the present embodiment may further contain a solvent containing at least one of water and an organic solvent. The organic solvent may be either a hydrophobic solvent or a hydrophilic solvent.

[0125] Examples of the hydrophobic solvent include mineral oil, fatty acid, alcohol, hydrocarbon, and the like.

[0126] Examples of the hydrophilic solvent include alkylene glycols such as ethylene glycol and propylene glycol; polyhydric alcohols such as glycerol; sugar alcohols; lower alcohols such as ethanol, methanol, propanol, and butanol; glycol ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; aliphatic amines such as methylamine and triethylamine; alkanolamines such as ethanolamine and triethanolamine; amides such as N-methylacetamide and N-methylformamide; and the like.

[0127] The organic solvent can be used alone or in combination of two or more kinds.

[0128] The conductive paste of the present embodiment is coated on a substrate by, for example, an inkjet method, a screen printing method, etc., and after drying, it is heated to form a conductive component such as a wiring or a thin film containing copper particles.

[0129] The conductive paste of the present embodiment can be manufactured by a known method. For example, a mixer such as a three-roll mill, a bead mill, a ball mill, a planetary mixer, or a disperser can be used to mix the above-mentioned respective materials to manufacture the conductive paste.

[0130] [Substrate]

[0131] The substrate of the present embodiment contains the conductive paste of the present embodiment or a sintered body of the conductive paste of the present embodiment. For example, the conductive paste of the present embodiment is coated on a predetermined area of a substrate.

[0132] The substrate of the present embodiment is, for example, a low-temperature co-fired ceramic substrate (LTCC substrate), a printed circuit board, a flexible substrate, etc., and preferably an LTCC substrate. The firing start temperature of the copper particles of the present embodiment is high, and the firing start temperature of the conductive paste containing the copper particles of the present embodiment is also high. The LTCC substrate containing the conductive paste of the present embodiment can fire the wiring conductor and the ceramic substrate simultaneously, and thus is preferred.

[0133] The substrate of the present embodiment is used, for example, as an in-vehicle electronic substrate, a substrate for a high-frequency module, a substrate for a semiconductor package, etc.

[0134] The substrate of the present embodiment can be manufactured by a known method. For example, the conductive paste of the present embodiment is screen-printed on a predetermined area of a green sheet, and the green sheets printed with a plurality of conductive pastes are laminated to form a laminate, and the laminate is fired to manufacture the substrate.

[0135] It should be noted that the present invention is not limited to the foregoing embodiments, and modifications, improvements, etc. within the scope capable of achieving the object of the present invention are also included in the present invention.

[0136] Examples

[0137] Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to any of the descriptions in these Examples and Comparative Examples.

[0138] [Measurement]

[0139] In the present Example, various measurements were performed by the following methods.

[0140] (Carbon content ratio)

[0141] Weigh 0.5 g of copper particles and add them as a combustion aid to 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder. Using a carbon-sulfur analyzer (manufactured by Horiba, Ltd., product name: EMIA-820W), measure under the conditions of an oxygen flow rate of 3 L / min, a combustion method of high-frequency heating, a combustion time of 60 seconds, and a detection method of infrared absorption method, and calculate the carbon content rate.

[0142] (Particle size)

[0143] D 90 Particle size

[0144] Mix 0.1 g of copper particles with 1 mL of a 0.1 mass% aqueous dispersant solution. Using a laser diffraction / scattering particle size analyzer (manufactured by Horiba, Ltd., product name: LA-960V2), after irradiating the inside of the device with ultrasonic waves for 5 minutes, measure the cumulative volume 90% particle size of the copper particles and calculate D. 90 Particle size.

[0145] D 50 Particle size

[0146] Mix 0.1 g of copper particles with 1 mL of a 0.1 mass% aqueous dispersant solution. Using a laser diffraction / scattering particle size analyzer (manufactured by Horiba, Ltd., product name: LA-960V2), after irradiating the inside of the device with ultrasonic waves for 5 minutes, measure the cumulative volume 50% particle size of the copper particles and calculate D. 50 Particle size.

[0147] Proportion of copper particles with a particle size of 20 μm or more

[0148] Mix 0.1 g of copper particles with 1 mL of a 0.1 mass% aqueous dispersant solution. Using a laser diffraction / scattering particle size analyzer (manufactured by Horiba, Ltd., product name: LA-960V2), after irradiating the inside of the device with ultrasonic waves for 5 minutes, measure the cumulative volume particle size distribution of the copper particles and calculate the proportion of copper particles with a particle size of 20 μm or more.

[0149] (Evaluation of coarse particles)

[0150] Using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, product name: Regulus8230), observe the copper particles magnified 25,000 times. Observe any 10 locations in the copper particles and evaluate according to the following criteria.

[0151] A (Good): There are no plate-like particles (coarse particles) with a primary particle size of 20 μm or more.

[0152] B (Bad): There are plate-like particles (coarse particles) with a primary particle size of 20 μm or more.

[0153] (Temperature at a shrinkage rate of 0.5%)

[0154] Weigh 1 g of copper particles and fill them into a cylindrical molding die with a diameter of 5 mm. Press the copper particles using a hydraulic press (ejection pressure: 10 MPa) to form a shape. Crush the particles obtained by the pressure molding to obtain particle samples. Weigh 0.67 g of the particle samples, fill them into a cylindrical molding die with a diameter of 5 mm, and press the particle samples using a hydraulic press (ejection pressure: 10 MPa) to obtain cylindrical particles with a diameter of 5 mm and a height of 5 mm as the samples for measurement.

[0155] Use a thermomechanical analyzer (manufactured by NETZSCH, Germany, product name: TMA4000SA) to measure under the conditions of an Ar flow rate of 200 mL / min, a measurement load of 10 mN, a measurement temperature range of 23 - 1000 °C, and a heating rate of 5 °C / min, and calculate the temperature at a shrinkage rate of 0.5%.

[0156] (Temperature at a shrinkage rate of 1.0%)

[0157] Weigh 1 g of copper particles and fill them into a cylindrical molding die with a diameter of 5 mm. Press the copper particles using a hydraulic press (ejection pressure: 10 MPa) to form a shape. Crush the particles obtained by the pressure molding to obtain particle samples. Weigh 0.67 g of the particle samples, fill them into a cylindrical molding die with a diameter of 5 mm, and press the particle samples using a hydraulic press (ejection pressure: 10 MPa) to obtain cylindrical particles with a diameter of 5 mm and a height of 5 mm as the samples for measurement.

[0158] Use a thermomechanical analyzer (manufactured by NETZSCH, Germany, product name: TMA4000SA) to measure under the conditions of an Ar flow rate of 200 mL / min, a measurement load of 10 mN, a measurement temperature range of 23 - 1000 °C, and a heating rate of 5 °C / min, and calculate the temperature at a shrinkage rate of 1.0%.

[0159] [Example 1]

[0160] (Process of dispersing a divalent copper compound in a solvent in the presence of a dispersant)

[0161] First, add 670 g of copper sulfate (manufactured by JX Metals Co., Ltd.) as a divalent copper compound to 2.26 L of ion-exchanged water, stir using a stirrer (manufactured by HEIDON, product name: BL300), and add the dispersant solution prepared by the method described below to obtain a dispersion.

[0162] Preparation method of the dispersant solution

[0163] As a dispersant, 10.7 g of gelatin (from bovine bone, manufactured by Wako Pure Chemical Industries, Ltd., weight-average molecular weight 100,000 to 300,000) was added to 0.5 L of ion-exchanged water, and the mixture was stirred using a magnetic stirrer (manufactured by IKA Works, Inc., Germany, product name: C-MAG HS4 digital) to prepare a dispersant solution.

[0164] (Step of reducing a copper compound to obtain a copper particle dispersion (A))

[0165] To the dispersion, a reducing agent solution prepared by the method described below was added. The dispersion was heated to 40 °C and stirred for 3 minutes to reduce the copper compound, obtaining a copper compound dispersion (B). Then, at a solution temperature of 40 °C, a 24 mass% aqueous sodium hydroxide solution was added to the copper compound dispersion (B) until the pH of the solution reached 10.6. At this time, the adjustment time until the pH of the solution reached 10.6 was 30 minutes. 400 g of hydrazine (manufactured by Wako Pure Chemical Industries, Ltd.) as a reducing agent was added to the copper compound dispersion (B) with the adjusted pH, and the solution was heated to 60 °C and stirred for 60 minutes to reduce the copper compound, obtaining a copper particle dispersion (A).

[0166] Method for preparing the reducing agent solution

[0167] 472 g of ascorbic acid (manufactured by Wako Pure Chemical Industries, Ltd.) as a reducing agent was added to 2.0 L of ion-exchanged water, and the mixture was stirred using a magnetic stirrer (manufactured by IKA Works, Inc., Germany, product name: C-MAG HS4 digital) to prepare a reducing agent solution.

[0168] (Step of removing the dispersant from the copper particle dispersion (A))

[0169] After stopping the stirring of the copper particle dispersion (A) and removing the supernatant, 5050 g of a 1.2 mass% aqueous sodium hydroxide solution was added as a removing agent to remove the dispersant, and the mixture was stirred for 10 minutes. After stopping the stirring again and removing the supernatant, an aqueous reducing agent solution prepared by adding 27 g of hydrazine (manufactured by Wako Pure Chemical Industries, Ltd.) to ion-exchanged water was added to the copper particle dispersion (A), and the solution was heated to 50 °C and stirred for 20 minutes. At this time, the pH of the copper particle dispersion (A) was 12.5.

[0170] (Surface treatment step)

[0171] To the copper particle dispersion (A) from which the dispersant had been removed, a surface treatment agent dispersion prepared by adding 0.84 g of sodium stearate (manufactured by Kanto Chemical Co., Inc.) to 0.5 L of ion-exchanged water was added as a surface treatment agent to obtain a copper particle dispersion.

[0172] (Solid-liquid separation process)

[0173] The obtained copper particle dispersion is subjected to solid-liquid separation by centrifugation to obtain copper particles.

[0174] [Example 2]

[0175] In Example 1, 5000 g of ion-exchanged water was added to replace 5050 g of 1.2 mass% sodium hydroxide aqueous solution in the step of removing the dispersant, hydrazine was not added, the pH of the copper particle dispersion (A) was set to 10.5, and 4.2 g of sodium stearate in the surface treatment step was used. Otherwise, the same procedure as in Example 1 was carried out to obtain copper particles.

[0176] [Example 3]

[0177] In Example 2, the step of removing the dispersant was not carried out. Otherwise, the same procedure as in Example 2 was carried out to obtain copper particles.

[0178] [Example 4]

[0179] In Example 3, the time until the pH of the solution reached 10.6 in the step of reducing the copper compound to obtain the copper particle dispersion (A) was set to 70 minutes. Otherwise, the same procedure as in Example 3 was carried out to obtain copper particles.

[0180] [Comparative Example 1]

[0181] In Example 3, gelatin as a dispersant was not added. Otherwise, the same procedure as in Example 3 was carried out to obtain copper particles.

[0182] The above measurements were respectively carried out on the copper particles obtained in Examples 1 to 4 and Comparative Example 1. The results are shown in Table 1. It should be noted that in Table 1, "-" means not measured.

[0183] Table 1

[0184]

[0185] From Table 1, it can be understood that by setting the carbon content rate of the copper particles to 0.1 mass% or more and 2.5 mass% or less, the temperature at which the shrinkage rate is 1.0% can be made higher. That is, it can be known that the firing start temperature of the copper particles of the present embodiment is high.

[0186] From Table 1, it can be understood that by making the proportion of copper particles having a particle size of 20 μm or more 0.8% or less on a volume basis, the temperature at which the shrinkage rate is 1.0% can be made higher.

[0187] As can be understood from Table 1, the above manufacturing method includes a step of dispersing a divalent copper compound in a solvent in the presence of a dispersant and a step of reducing the divalent copper compound to obtain a copper particle dispersion (A). The step of obtaining the copper particle dispersion (A) includes a step of reducing the copper compound to obtain a copper compound dispersion (B) and a step of adjusting the pH of the copper compound dispersion (B) to 9.0 or more and 14.0 or less. The temperature at which the shrinkage rate of the copper particles obtained by this manufacturing method is 1.0% is high, and there are no coarse particles.

[0188] As can be understood from Table 1, the above manufacturing method of copper particles includes a step of dispersing a divalent copper compound in a solvent in the presence of a dispersant, a step of reducing the divalent copper compound to obtain a copper particle dispersion (A), and a step of removing the dispersant from the copper particle dispersion (A). The temperature at which the shrinkage rate of the copper particles obtained by this manufacturing method of copper particles, that is, Examples 1 and 2, is 0.5% is high, and there are no coarse particles. On the other hand, although the copper particles obtained by a manufacturing method without performing the step of removing the dispersant from the copper particle dispersion (A), that is, Example 3, have no coarse particles, the temperature at which the shrinkage rate is 0.5% is low. The copper particles obtained by a manufacturing method without performing the step of dispersing the divalent copper compound in a solvent and the step of removing the dispersant from the copper particle dispersion (A), that is, Comparative Example 1, have coarse particles, and the temperature at which the shrinkage rate is 0.5% is low.

[0189] This application is based on Japanese Patent Application No. 2022-160531, Japanese Patent Application No. 2022-160532, Japanese Patent Application No. 2022-160533, and Japanese Patent Application No. 2022-160534 filed on October 4, 2022, and claims the priority of this Japanese patent application. The entire content of this Japanese patent application is incorporated herein by reference.

[0190] The present invention can be implemented in the following manner.

[0191] [1a] A copper particle, wherein the proportion of copper particles having a particle diameter of 20 μm or more calculated by the following method is 0.8% or less on a volume basis.

[0192] [Method for calculating the proportion of copper particles having a particle diameter of 20 μm or more]

[0193] Mix 0.1 g of copper particles with 1 mL of an aqueous dispersant solution having a concentration of 0.1% by mass. Using a laser diffraction / scattering particle size measuring device, irradiate ultrasonic waves into the device for 5 minutes, and then measure the cumulative volume particle size distribution of the copper particles to calculate the proportion of copper particles having a particle diameter of 20 μm or more.

[0194] [2a] A copper particle, wherein, among the copper particles described in the foregoing [1a], the D 90 particle size calculated by the following method is 0.1 μm or more and 5.0 μm or less.

[0195] [D 90 Method for calculating particle size]

[0196] Mix 0.1 g of copper particles with 1 mL of an aqueous dispersant solution of 0.1 mass%, use a laser diffraction / scattering particle size measuring device, irradiate ultrasonic waves into the device for 5 min, measure the cumulative volume 90% particle size of the copper particles, and calculate D 90 particle size.

[0197] [3a] A copper particle, wherein, among the copper particles described in the foregoing [1a] or [2a], the D 50 particle size calculated by the following method is 0.05 μm or more and 5.0 μm or less.

[0198] [D 50 Method for calculating particle size]

[0199] Mix 0.1 g of copper particles with 1 mL of an aqueous dispersant solution of 0.1 mass%, use a laser diffraction / scattering particle size measuring device, irradiate ultrasonic waves into the device for 5 min, measure the cumulative volume 50% particle size of the copper particles, and calculate D 50 particle size.

[0200] [4a] A copper particle, wherein, among the copper particles described in any one of the foregoing [1a] to [3a], the temperature at which the shrinkage rate of the copper particle is 1.0% is 650 °C or higher.

[0201] [Method for calculating the temperature at which the shrinkage rate is 1.0%]

[0202] Weigh 1 g of copper particles, fill them into a cylindrical molding die with a diameter of 5 mm, and press-mold the copper particles with a hydraulic press (ejection pressure 10 MPa). Crush the particles obtained by press-molding to obtain a particle sample. Weigh 0.67 g of the particle sample, fill it into a cylindrical molding die with a diameter of 5 mm, and press-mold the particle sample with a hydraulic press (ejection pressure 10 MPa) to obtain a cylindrical particle with a diameter of 5 mm and a height of 5 mm as a measurement sample.

[0203] Use a thermomechanical analyzer to perform measurements under the conditions of an Ar flow rate of 200 mL / min, a measurement load of 10 mN, a measurement temperature range of 23 to 1000 °C, and a heating rate of 5 °C / min, and calculate the temperature at which the shrinkage rate is 1.0%.

[0204] [5a]A copper particle, wherein, among the copper particles described in any one of the foregoing [1a] to [4a], the carbon content rate of the copper particle calculated by the following method is 0.1% by mass or more and 2.5% by mass or less.

[0205] [Method for calculating carbon content rate]

[0206] Weigh 0.5 g of copper particles, add 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder as combustion aids, and use a carbon-sulfur analyzer to measure under the conditions of an oxygen flow rate of 3 L / min, a combustion method of high-frequency heating, a combustion time of 60 seconds, and a detection method of infrared absorption method to calculate the carbon content rate.

[0207] [6a]A conductive paste, wherein the conductive paste contains the copper particles described in any one of the foregoing [1a] to [5a].

[0208] [7a]A substrate, wherein the substrate contains the conductive paste described in the foregoing [6a] or a sintered body of the conductive paste.

[0209] [8a]The substrate according to the foregoing [7a], wherein the substrate is a low-temperature fired multilayer ceramic substrate.

[0210] The present invention can also be implemented in the following manner.

[0211] [1b]A method for manufacturing copper particles, wherein the method for manufacturing copper particles includes: a step of dispersing a divalent copper compound in a solvent in the presence of a dispersant; and a step of reducing the copper compound to obtain a copper particle dispersion (A). The step of obtaining the copper particle dispersion (A) includes: a step of reducing the copper compound to obtain a copper compound dispersion (B); and a step of adjusting the pH of the copper compound dispersion (B) to 9.0 or more and 14.0 or less. The dispersant contains at least one selected from the group consisting of gelatin, casein, sodium caseinate, ammonium caseinate, starch, dextrin, agar, sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, ammonium polyacrylate, stearic acid, polyethylene glycol, citric acid, aniline, and derivatives of aniline.

[0212] [2b]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in the foregoing [1b], when the copper compound is set to 100 parts by mass in the step of dispersing the copper compound, the content of the dispersant is 0.1 part by mass or more and 3.0 parts by mass or less.

[0213] [3b]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in the foregoing [1b] or [2b], the dispersant contains gelatin.

[0214] [4b]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of the foregoing [1b] to [3b], it further includes a step of removing the dispersant from the copper particle dispersion (A).

[0215] [5b]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in the foregoing [4b], in the step of removing the dispersant, the pH of the copper particle dispersion (A) is 7.0 or more and 14.0 or less.

[0216] [6b]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of the foregoing [1b] to [5b], in the step of obtaining the copper compound dispersion (B), the solvent is heated to 10°C or more and 70°C or less.

[0217] [7b]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of the foregoing [1b] to [6b], in the step of obtaining the copper compound dispersion (B), the reducing agent contains ascorbic acid.

[0218] [8b]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of the foregoing [1b] to [7b], the carbon content rate of the obtained copper particles is 0.1 mass% or more and 2.5 mass% or less.

[0219] [9b]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of the foregoing [1b] to [8b], the D 90 particle size of the obtained copper particles is 0.1 μm or more and 5.0 μm or less.

[0220] [10b]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of the foregoing [1b] to [9b], the D 50 particle size of the obtained copper particles is 0.05 μm or more and 5.0 μm or less.

[0221] [11b]A conductive paste, wherein the conductive paste contains copper particles obtained by the method for manufacturing copper particles described in any one of the foregoing [1b] to [10b].

[0222] [12b]A substrate, wherein the substrate contains the conductive paste described in the foregoing [11b] or a sintered body of the conductive paste.

[0223]

[13] The substrate as described in [12b] above, wherein the substrate is a low-temperature fired laminated ceramic substrate.

[0224] The present invention can also be implemented in the following manner.

[0225] [1c] A method for manufacturing copper particles, wherein the method for manufacturing copper particles includes: a step of dispersing a divalent copper compound in a solvent in the presence of a dispersant; a step of reducing the divalent copper compound to obtain a copper particle dispersion (A); and a step of removing the dispersant from the copper particle dispersion (A).

[0226] [2c] A method for manufacturing copper particles, wherein in the method for manufacturing copper particles described in [1c] above, in the step of removing the dispersant, the pH of the copper particle dispersion (A) is 7.0 or more and 14.0 or less.

[0227] [3c] A method for manufacturing copper particles, wherein in the method for manufacturing copper particles described in [1c] or [2c] above, the dispersant includes at least one selected from the group consisting of gelatin, casein, sodium caseinate, ammonium caseinate, starch, dextrin, agar, sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, ammonium polyacrylate, stearic acid, polyethylene glycol, citric acid, aniline, and derivatives of aniline.

[0228] [4c] A method for manufacturing copper particles, wherein in the method for manufacturing copper particles described in [3c] above, the dispersant includes gelatin.

[0229] [5c] A method for manufacturing copper particles, wherein in the method for manufacturing copper particles described in any one of [1c] to [4c] above, when the copper compound is set to 100 parts by mass in the step of dispersing the copper compound, the content of the dispersant is 0.1 part by mass or more and 3.0 parts by mass or less.

[0230] [6c] A method for manufacturing copper particles, wherein in the method for manufacturing copper particles described in any one of [1c] to [5c] above, the step of obtaining the copper particle dispersion (A) includes: a step of reducing the copper compound to obtain a copper compound dispersion (B); and a step of adjusting the pH of the copper compound dispersion (B) to 9.0 or more and 14.0 or less.

[0231] [7c] A method for manufacturing copper particles, wherein in the method for manufacturing copper particles described in [6c] above, in the step of obtaining the copper compound dispersion (B), the solvent is heated to 10°C or more and 70°C or less.

[0232] [8c]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in the foregoing [6c] or [7c], in the step of obtaining the copper compound dispersion (B), the reducing agent contains ascorbic acid.

[0233] [9c]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of the foregoing [1c] to [8c], the carbon content rate of the obtained copper particles is 0.1% by mass or more and 2.5% by mass or less.

[0234] [10c]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of the foregoing [1c] to [9c], the D 90 particle size is 0.1 μm or more and 5.0 μm or less.

[0235] [11c]A method for manufacturing copper particles, wherein, in the method for manufacturing copper particles described in any one of the foregoing [1c] to [10c], the D 50 particle size is 0.05 μm or more and 5.0 μm or less.

[0236] [12c]A conductive paste, wherein the conductive paste contains copper particles obtained by the method for manufacturing copper particles described in any one of the foregoing [1c] to [11c].

[0237] [13c]A substrate, wherein the substrate contains the conductive paste described in the foregoing [12c] or a sintered body of the conductive paste.

[0238] [14c]The substrate according to the foregoing [13c], wherein the substrate is a low-temperature fired laminated ceramic substrate.

Claims

1. A copper particle, wherein, the copper particle is a copper particle having a carbon content of 0.1% by mass or more and 2.5% by mass or less calculated by the following method, Method for calculating the carbon content: Weigh 0.5 g of copper particles, add 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder as combustion aids, and use a carbon-sulfur analyzer to measure under the conditions of an oxygen flow rate of 3 L / min, a combustion method of high-frequency heating, a combustion time of 60 seconds, and a detection method of infrared absorption method to calculate the carbon content.

2. The copper particle according to claim 1, wherein, the copper particle is a copper particle having a temperature of 650°C or higher at which the shrinkage rate is 1.0% calculated by the following method, Method for calculating the temperature at which the shrinkage rate is 1.0%: Weigh 1 g of copper particles, fill them into a cylindrical molding die with a diameter of 5 mm, press and mold the copper particles with an ejection pressure of 10 MPa using a hydraulic press, crush the particles obtained by the press molding to obtain a particle sample, weigh 0.67 g of the particle sample, fill it into a cylindrical molding die with a diameter of 5 mm, and press and mold the particle sample with an ejection pressure of 10 MPa using a hydraulic press to obtain a cylindrical particle with a diameter of 5 mm and a height of 5 mm as a measurement sample. Use a thermomechanical analyzer to measure under the conditions of an Ar flow rate of 200 mL / min, a measurement load of 10 mN, a measurement temperature range of 23 - 1000°C, and a heating rate of 5°C / min to calculate the temperature at which the shrinkage rate is 1.0%.

3. The copper particle according to claim 1 or 2, wherein, The D of the copper particles calculated by the following method 90 has a particle size of 0.1 μm or more and 5.0 μm or less, D 90 Method for calculating particle size: Mix 0.1 g of copper particles with 1 mL of an aqueous dispersant solution containing 0.1 mass%, and after irradiating the inside of the device with ultrasonic waves for 5 min using a laser diffraction / scattering particle size measuring device, measure the cumulative volume 90% particle size of the copper particles and calculate D 90 Particle size.

4. The copper particle according to any one of claims 1 to 3, wherein, The D of the copper particles calculated by the following method 50 The particle size is 0.05 μm or more and 5.0 μm or less, D 50 Calculation method of particle size: Mix 0.1 g of copper particles with 1 mL of an aqueous dispersant solution containing 0.1% by mass, and after irradiating ultrasonic waves into the device for 5 min using a laser diffraction / scattering particle size measuring device, measure the cumulative volume 50% particle size of the copper particles and calculate D 50 Particle size.

5. The copper particle according to any one of claims 1 to 4, wherein, the proportion of copper particles having a particle size of 20 μm or more calculated by the following method is 0.8% or less based on volume, Method for calculating the proportion of copper particles having a particle size of 20 μm or more: Mix 0.1 g of copper particles with 1 mL of a 0.1% by mass aqueous solution of a dispersant, use a laser diffraction / scattering particle size analyzer, irradiate ultrasonic waves into the device for 5 min, and then measure the cumulative volume particle size distribution of the copper particles to calculate the proportion of copper particles having a particle size of 20 μm or more.

6. A method for manufacturing copper particles, which is a method for manufacturing the copper particles according to any one of claims 1 to 5, wherein, the manufacturing method includes: a step of dispersing a divalent copper compound in a solvent in the presence of a dispersant; and a step of reducing the divalent copper compound to obtain a copper particle dispersion (A).

7. The method for manufacturing copper particles according to claim 6, wherein, the method for manufacturing copper particles further includes a step of removing the dispersant from the copper particle dispersion (A).

8. The method for manufacturing copper particles according to claim 7, wherein, in the step of removing the dispersant, the pH of the copper particle dispersion (A) is 7.0 or more and 14.0 or less.

9. The method for manufacturing copper particles according to any one of claims 6 to 8, Among them, the dispersant includes at least one selected from the group consisting of gelatin, casein, sodium caseinate, ammonium caseinate, starch, dextrin, agar, sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, ammonium polyacrylate, stearic acid, polyethylene glycol, citric acid, aniline, and derivatives of aniline.

10. The method for producing copper particles according to claim 9, wherein, the dispersant includes gelatin.

11. The method for producing copper particles according to any one of claims 6 to 10, wherein, when the copper compound is set to 100 parts by mass in the step of dispersing the copper compound, the content of the dispersant is 0.1 part by mass or more and 3.0 parts by mass or less.

12. The method for producing copper particles according to any one of claims 6 to 11, wherein, the step of obtaining the copper particle dispersion (A) includes: a step of reducing the copper compound to obtain a copper compound dispersion (B); and a step of adjusting the pH of the copper compound dispersion (B) to 9.0 or more and 14.0 or less.

13. The method for producing copper particles according to claim 12, wherein, in the step of obtaining the copper compound dispersion (B), the solvent is heated to 10°C or more and 70°C or less.

14. The method for producing copper particles according to claim 12 or 13, wherein, in the step of obtaining the copper compound dispersion (B), the reducing agent includes ascorbic acid.

15. A conductive paste, wherein, the conductive paste includes the copper particles according to any one of claims 1 to 5 or the copper particles obtained by the method for producing copper particles according to any one of claims 6 to 14.

16. A substrate, wherein, the substrate includes the conductive paste according to claim 15 or a sintered body of the conductive paste.

17. The substrate according to claim 16, wherein, the substrate is a low-temperature fired multilayer ceramic substrate.

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