Copper granules, copper granule production methods, conductive adhesives, and substrates.

Abstract

The invention relates to copper particles such that the values ​​obtained by dividing the particle diameter D95 (H2O) by the particle diameter D10 (H2O), each calculated by the following particle diameter measurement 1, are 4.20 or less. [Particle diameter measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1% by mass aqueous dispersion solution, and the particle size distribution based on the volume of the copper particles is measured by a laser diffraction / scattering particle diameter measuring device after irradiating the device with ultrasound for 5 minutes, from which the particle diameter values ​​D10 (H2O), D50 (H2O) and D95 ​​(H2O) are obtained.

Description

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

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

[0002] As a technique relating to copper particles, for example, the technique described in Patent Document 1 can be mentioned.

[0003] Patent Document 1 describes copper powder produced by a wet method, which has an absolute value of a zeta potential of 20 mV or more. It also describes that the copper powder in Patent Document 1 can reduce the burden of the crushing and classification processes from a dried cake, while also providing easily crushable copper powder with a sufficiently reduced amount of residual secondary particles.

[0004] Japanese Patent Application Laid-Open No. 2020-50947

[0005] The present invention provides copper particles with improved packing properties, a method for producing copper particles that can obtain copper particles with improved packing properties, and a conductive paste and substrate that use the copper particles.

[0006] According to the present invention, there are provided copper particles, a method for producing copper particles, a conductive paste, and a substrate, as shown below.

[0007] [1] D calculated by the following particle size measurement 1 ９５ Particle size (H ２ O) to D １０ Particle size (H ２ Copper particles having a value of 4.20 or less when divided by 0.01 wt % of the dispersant solution. [Particle size measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture is irradiated with ultrasonic waves in a laser diffraction / scattering particle size measurement device for 5 minutes. Then, the volume-based particle size distribution of the copper particles is measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２ [2] The values ​​of D calculated by the particle size measurement 1 are obtained. ９５ Particle size (H ２ O) to D １０ Particle size (H ２[3] The copper particles according to the above [1], wherein the value obtained by dividing by the particle diameter (D) calculated by the particle diameter measurement 1 is 1.10 or more. ９５ Particle size (H ２ O) to D １０ Particle size (H ２ [4] The copper particles according to [1] or [2], wherein the value obtained by subtracting the particle diameter D calculated by the particle diameter measurement 1 is 0.05 μm or more and 1.50 μm or less. ９５ Particle size (H ２ [5] The copper particles according to any one of [1] to [3], wherein the diameter D calculated by the particle diameter measurement 1 is 0.20 μm or more and 2.00 μm or less. １０ Particle size (H ２ [6] The copper particles according to any one of [1] to [4], wherein the diameter D calculated by the particle diameter measurement 1 is 0.05 μm or more and 0.50 μm or less. ５０ Particle size (H ２ [7] The copper particles according to any one of [1] to [5], wherein the diameter D calculated by the following particle diameter measurement 2 is 0.10 μm or more and 1.00 μm or less. ５０ [Particle size measurement 2] The copper particles according to any one of [1] to [6], having a particle size (img) of 0.10 μm or more and 1.00 μm or less, are obtained by image analysis of an image obtained by a scanning electron microscope. １０ Particle size (img), D ５０ Particle size (img), and D ９０ [8] The particle diameter (img) value calculated by the particle diameter measurement 1 is obtained. ５０ Particle size (H ２ O) is calculated by the particle size measurement 2 below. ５０ The copper particles according to any one of [1] to [7], wherein the value obtained by dividing by the particle diameter (img) is 1.50 or less. [Particle diameter measurement 2] An image obtained by a scanning electron microscope is analyzed to determine the D １０ Particle size (img), D ５０ Particle size (img), and D ９０The particle diameter (img) values ​​are obtained, respectively. [9] Copper particles according to any one of [1] to [8], wherein the temperature at which a shrinkage rate of 1.0% calculated by the shrinkage rate measurement described below is 200°C or higher. [Shrinkage Rate Measurement] 1 g of copper particles is weighed out and filled into a cylindrical molding die having a diameter of 5 mm, and the copper particles are press-molded using a hydraulic press (discharge pressure of 10 MPa). The pellets obtained by press molding are crushed to obtain a granule sample. 0.67 g of the granule sample is weighed out and filled into a cylindrical molding die having a diameter of 5 mm, and the granule sample is press-molded using a hydraulic press (discharge pressure of 10 MPa), to obtain a cylindrical pellet having a diameter of 5 mm and a height of 5 mm as a measurement sample. Using a thermomechanical analyzer, measurements are taken under the conditions of Ar flow rate: 200 mL / min, measurement load: 10 mN, measurement temperature range: 23 to 1000°C, and temperature rise rate: 5°C / min, and the temperature at which the shrinkage rate reaches 1.0% is calculated.

[10] The tap density measured in accordance with JIS Z2512:2012 is 2.5 g / cm ３

[11] The copper particles according to any one of [1] to

[10] , having an oxygen content of 0.70% by mass or less as measured in accordance with JIS H1067:2002.

[12] The copper particles according to any one of [1] to

[11] , having a carbon content of 1.50% by mass or less as calculated by the carbon content measurement described below. [Carbon Content Measurement] 0.5 g of copper particles is weighed, and 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder are added as combustion improvers. The carbon content is calculated using a carbon / sulfur analyzer under the following conditions: in an oxygen stream, a flow rate of 3 L / min, a combustion method using high-frequency heating, a combustion time of 60 seconds, and a detection method using infrared absorption.

[13] The method for producing copper particles according to any one of [1] to

[12] , comprising step (A) of drying hydrous copper particles while vibrating them, wherein the moisture content of the hydrous copper particles is 30% by mass or less, when the total weight of the hydrous copper particles is taken as 100% by mass.

[14] The method for producing copper particles according to

[13] , wherein the moisture content of the hydrous copper particles is 5% by mass or more, when the total weight of the hydrous copper particles is taken as 100% by mass.

[15] The method for producing copper particles according to

[13] or

[14] , wherein in step (A), the hydrous copper particles are dried using a vibration dryer.

[16] The method for producing copper particles according to any one of

[13] to

[15] , wherein in step (A), the drying temperature is 30°C or more and 100°C or less.

[17] The method for producing copper particles according to any one of

[13] to

[16] , wherein in step (A), the drying time is 10 minutes or more and 24 hours or less.

[18] The method for producing copper particles according to any one of

[13] to

[17] , further comprising: a step (B) of preparing a copper particle dispersion liquid (a); and a step (C) of performing solid-liquid separation of the copper particle dispersion liquid (a) to obtain the hydrated copper particles.

[19] The method for producing copper particles according to

[18] , wherein in the step (C), the hydrated copper particles are obtained by at least one method selected from a centrifugation method and a filtration method.

[20] The method for producing copper particles according to

[18] or

[19] , wherein step (B) comprises: step (B-1) of dispersing a divalent copper compound in a solvent in the presence of a dispersant; and step (B-2) of reducing the divalent copper compound to obtain a copper particle dispersion (a).

[21] The method for producing copper particles according to

[20] , wherein in step (B-1), the dispersant comprises 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 an aniline derivative.

[22] A conductive paste comprising the copper particles according to any one of [1] to

[12] above, or copper particles obtained by the method for producing copper particles according to any one of

[13] to

[21] above.

[23] A substrate comprising the conductive paste according to

[22] above or a sintered body of the conductive paste.

[24] The substrate according to

[23] above, which is a low-temperature co-fired ceramic substrate.

[0008] According to the present invention, it is possible to provide copper particles with improved packing property, a method for producing copper particles that can obtain copper particles with improved packing property, and a conductive paste and a substrate that use the copper particles.

[0009] Hereinafter, embodiments of the present invention will be described. Unless otherwise specified, the numerical range "A to B" represents A or more and B or less.

[0010] Copper particles are used, for example, as a conductive paste. Furthermore, a conductive paste containing copper particles is used, for example, as a wiring conductor for a substrate. When a conductive paste containing copper particles is used as a wiring conductor for a substrate, the conductive paste may be filled into via holes in the substrate. Therefore, there is a need to further improve the filling rate of copper particles in via holes. The present invention provides copper particles with improved filling property, a method for producing copper particles that can obtain copper particles with improved filling property, and a conductive paste and a substrate using the copper particles.

[0011] Furthermore, according to the method for producing copper particles of this embodiment, the proportion of powdery copper particles in the copper particles obtained after step (A) can be further increased. Here, powdery copper particles refer to copper particles that are in powder form without being subjected to a crushing process in a mortar or the like. If the proportion of powdery copper particles in the copper particles obtained after step (A) is further increased, the production process can be further simplified and the yield of copper particles can be further improved.

[0012] [Copper particles] The copper particles of this embodiment, D ９５ Particle size (H ２ O) to D １０ Particle size (H ２ The value obtained by dividing by D is 4.20 or less. ９５ Particle size (H ２ O) to D １０ Particle size (H ２ From the viewpoint of further improving the filling property, the value obtained by dividing the total mass of the polymer by the total mass of the polymer (MnO) is preferably 4.10 or less, more preferably 4.00 or less, even more preferably 3.90 or less, and still more preferably 3.80 or less. The lower limit is not particularly limited, but may be, for example, 1.10 or more, 1.30 or more, 1.50 or more, or 1.80 or more.

[0013] According to the study by the present inventors, D ９５ Particle size (H ２ O) to D １０ Particle size (H ２ It has been found that the packing property of copper particles can be improved by adjusting the value obtained by dividing the D of copper particles by the D of copper particles to fall within the above range. ９５ Particle size (H ２ O) to D １０ Particle size (H ２ This is the first time that we have found that the measure of the value obtained by dividing the packing density by the packing density (density) ... is effective as a design index for improving the packing density of copper particles.

[0014] D ９５ Particle size (H ２ O) to D １０ Particle size (H ２The value obtained by dividing by (1 / 0) can be controlled, for example, by adjusting the conditions for drying the copper particles when producing the copper particles, more specifically, by drying the copper particles while vibrating them, adjusting the moisture content of the copper particles before drying, etc.

[0015] D of the copper particles of this embodiment １０ Particle size (H ２ O) is preferably 0.05 μm or more, more preferably 0.10 μm or more, even more preferably 0.15 μm or more, even more preferably 0.20 μm or more, even more preferably 0.25 μm or more, and is preferably 0.50 μm or less, more preferably 0.45 μm or less, even more preferably 0.40 μm or less.

[0016] D of the copper particles of this embodiment ５０ Particle size (H ２ O) is preferably 0.10 μm or more, more preferably 0.20 μm or more, even more preferably 0.25 μm or more, even more preferably 0.30 μm or more, even more preferably 0.35 μm or more, even more preferably 0.40 μm or more, and is preferably 1.00 μm or less, more preferably 0.80 μm or less, even more preferably 0.70 μm or less, even more preferably 0.65 μm or less, even more preferably 0.60 μm or less.

[0017] D of the copper particles of this embodiment ９５ Particle size (H ２ O) is preferably 0.20 μm or more, more preferably 0.30 μm or more, even more preferably 0.40 μm or more, and still more preferably 0.50 μm or more, and from the viewpoint of further improving the filling property, it is preferably 2.00 μm or less, more preferably 1.80 μm or less, even more preferably 1.60 μm or less, and still more preferably 1.50 μm or less.

[0018] The copper particles of this embodiment, D ９５ Particle size (H ２ O) to D １０ Particle size (H ２From the viewpoint of further improving the filling property, the value obtained by subtracting the thickness (μm) of the filler particles (μm) from the total thickness (μm) of the filler particles (μm), is preferably 1.50 μm or less, more preferably 1.40 μm or less, even more preferably 1.30 μm or less, even more preferably 1.20 μm or less, and even more preferably 1.10 μm or less. The lower limit is not particularly limited, but may be, for example, 0.05 μm or more, 0.10 μm or more, 0.20 μm or more, or 0.25 μm or more.

[0019] Here, D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２ O) means the value calculated by particle size measurement 1.

[0020] [Particle size measurement 1] 0.1 g of copper particles was mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture was irradiated with ultrasonic waves in a laser diffraction / scattering particle size measurement device for 5 minutes. After that, the volume-based particle size distribution of the copper particles was measured. １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２ In particle size measurement 1, the dispersant refers to polyoxyethylene (20) sorbitan monolaurate.

[0021] D of the copper particles of this embodiment １０ The particle size (img) is preferably 0.05 μm or more, more preferably 0.10 μm or more, and preferably 0.50 μm or less, more preferably 0.40 μm or less.

[0022] D of the copper particles of this embodiment ５０ The particle size (img) is preferably 0.10 μm or more, more preferably 0.20 μm or more, even more preferably 0.30 μm or more, and is preferably 1.00 μm or less, more preferably 0.80 μm or less, even more preferably 0.60 μm or less.

[0023] D of the copper particles of this embodiment ９０The particle size (img) is preferably 0.20 μm or more, more preferably 0.40 μm or more, even more preferably 0.50 μm or more, and preferably 2.00 μm or less, more preferably 1.80 μm or less, even more preferably 1.50 μm or less, even more preferably 1.20 μm or less.

[0024] Here, D １０ Particle size (img), D ５０ Particle size (img), and D ９０ The particle diameter (img) means the value calculated by particle diameter measurement 2.

[0025] [Particle size measurement 2] The image obtained by the scanning electron microscope was analyzed to determine the D １０ Particle size (img), D ５０ Particle size (mg), and D ９０ The particle diameter (mg) values ​​are obtained. More specifically, D １０ Particle size (img), D ５０ Particle size (mg), and D ９０ The particle size (img) means a value calculated by the method described in the Examples.

[0026] The copper particles of this embodiment, D ５０ Particle size (H ２ O) to D ５０ From the viewpoint of further improving the packing property, the value obtained by dividing by the particle size (img) is preferably 1.50 or less, more preferably 1.45 or less, even more preferably 1.40 or less, and even more preferably 1.35 or less. The lower limit is not particularly limited, but may be, for example, 0.50 or more, 0.60 or more, or 0.70 or more.

[0027] From the viewpoint of further improving filling properties, the oxygen content of the copper particles of this embodiment, measured in accordance with JIS H1067:2002, is preferably 0.70% by mass or less, preferably 0.68% by mass or less, more preferably 0.67% by mass or less, even more preferably 0.66% by mass or less, even more preferably 0.65% by mass or less, and even more preferably 0.63% by mass or less. The lower limit is not particularly limited, but may be, for example, 0.01% by mass or more, 0.10% by mass or more, 0.20% by mass or more, 0.30% by mass or more, 0.40% by mass or more, or 0.45% by mass or more.

[0028] According to the study of the present inventors, it was found that the packing property of copper particles can be further improved by adjusting the oxygen content of copper particles to the above-mentioned range. That is, the present invention is the first to discover that the measure of the oxygen content of copper particles is effective as a design index for further improving the packing property of copper particles.

[0029] The oxygen content of copper particles can be controlled, for example, by adjusting the conditions for drying the copper particles when producing the copper particles, more specifically, by drying the copper particles while vibrating them, or by adjusting the moisture content of the copper particles before drying.

[0030] From the viewpoint of further suppressing a decrease in electrical conductivity, the carbon content of the copper particles of this embodiment is preferably 1.50% by mass or less, more preferably 1.00% by mass or less, even more preferably 0.80% by mass or less, even more preferably 0.75% by mass or less, even more preferably 0.70% by mass or less, even more preferably 0.65% by mass or less, even more preferably 0.62% by mass or less, and even more preferably 0.60% by mass or less. The lower limit is not particularly limited, but may be, for example, 0.01% by mass or more, 0.10% by mass or more, 0.20% by mass or more, 0.30% by mass or more, or 0.40% by mass or more. Here, the carbon content refers to the value calculated by the following carbon content measurement.

[0031] [Carbon Content Measurement] 0.5 g of copper particles was weighed, and 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder were added as combustion improvers. Measurement was then carried out using a carbon / sulfur analyzer in an oxygen stream at a flow rate of 3 L / min, under the conditions of high-frequency heating as the combustion method, combustion time of 60 seconds, and infrared absorption as the detection method, to calculate the carbon content.

[0032] The copper particles of this embodiment may contain elements other than copper, oxygen, and carbon. Examples of the other elements include nitrogen, chlorine, boron, etc. The content of the other elements is not particularly limited and may be an appropriate amount.

[0033] The temperature at which the copper particles of this embodiment achieve a shrinkage of 1.0% is preferably 200°C or higher, more preferably 300°C or higher, even more preferably 400°C or higher, even more preferably 500°C or higher, even more preferably 600°C or higher, even more preferably 650°C or higher, and even more preferably 700°C or higher. The upper limit is not particularly limited, but may be, for example, 1000°C or lower, 950°C or lower, or 900°C or lower. When the temperature at which the shrinkage of 1.0% is achieved is equal to or higher than the lower limit, this is preferable because, when a conductive paste containing copper particles is used in a low-temperature co-fired ceramic substrate, the wiring conductor and the ceramic substrate can be co-fired more efficiently. Here, the temperature at which the shrinkage of 1.0% is achieved refers to the value calculated by the following shrinkage measurement.

[0034] [Shrinkage Measurement] 1 g of copper particles was weighed and filled into a cylindrical molding die with a diameter of 5 mm, and the copper particles were press-molded using a hydraulic press (discharge pressure of 10 MPa). The pellets obtained by press molding were crushed to obtain a granule sample. 0.67 g of the granule sample was weighed and filled into a cylindrical molding die with a diameter of 5 mm, and the granule sample was press-molded using a hydraulic press (discharge pressure of 10 MPa) to obtain a cylindrical pellet with a diameter of 5 mm and a height of 5 mm as a measurement sample. Measurement was performed using a thermomechanical analyzer under the following conditions: Ar flow rate: 200 mL / min, measurement load: 10 mN, measurement temperature range: 23 to 1000°C, and heating rate: 5°C / min, and the temperature at which a shrinkage rate of 1.0% was calculated.

[0035] The copper particles of this embodiment preferably have a tap density of 2.5 g / cm as measured in accordance with JIS Z2512:2012. ３ More preferably, 2.8 g / cm ３ More preferably, 3.0 g / cm ３ More preferably, 3.2 g / cm ３ More preferably, 3.5 g / cm ３ The upper limit is not particularly limited, but is, for example, 5.0 g / cm ３ or less, and ３ or less, and ３ or less, and ３ It may be the following:

[0036] [Uses of Copper Particles] The copper particles of this embodiment can be used, for example, in conductive pastes, paints, inks, etc., and can be preferably used in conductive pastes.

[0037] [Method for producing copper particles] The method for producing copper particles of this embodiment is not particularly limited, and examples include a wet reduction method and a disproportionation method. Among these, the wet reduction method is preferred from the viewpoint of reducing the particle diameter of the copper particles.

[0038] The method for producing copper particles of this embodiment preferably includes a step (A) of drying the hydrous copper particles while vibrating them, and more preferably includes the step (A), a step (B) of preparing a copper particle dispersion (a), and a step (C) of performing solid-liquid separation of the copper particle dispersion (a) to obtain hydrous copper particles. Here, in this embodiment, the hydrous copper particles refer to a copper particle cake containing moisture, and refer to copper particles in a state after solid-liquid separation of the copper particle dispersion (a) and before drying.

[0039] Below, each step of a preferred embodiment of the method for producing copper particles of this embodiment will be described.

[0040] <Step (A) of drying the hydrous copper particles while vibrating> The method for producing copper particles of this embodiment preferably includes step (A) of drying the hydrous copper particles while vibrating them.

[0041] The moisture content of the hydrous copper particles, when the entire hydrous copper particles are taken as 100% by mass, is preferably 30% by mass or less, more preferably 28% by mass or less, even more preferably 25% by mass or less, even more preferably 23% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of adjusting the particle size and oxygen content of the copper particles within appropriate ranges, further improving the packing property of the obtained copper particles, and further increasing the proportion of powdery copper particles in the obtained copper particles.The lower limit is not particularly limited, but may be, for example, 5% by mass or more, 7% by mass or more, or 10% by mass or more. Note that the moisture content of the hydrous copper particles means the moisture content of the hydrous copper particles before drying.

[0042] In step (A), the drying temperature is preferably 30°C or higher, more preferably 40°C or higher, even more preferably 45°C or higher, even more preferably 50°C or higher, and even more preferably 60°C or higher, from the viewpoint of further increasing the proportion of powdery copper particles in the obtained copper particles, and is preferably 100°C or lower, more preferably 95°C or lower, even more preferably 90°C or lower, and even more preferably 80°C or lower, from the viewpoint of further increasing the proportion of powdery copper particles in the obtained copper particles.

[0043] In step (A), from the viewpoint of further increasing the proportion of powdery copper particles in the obtained copper particles, the drying time is preferably 10 minutes or more, more preferably 30 minutes or more, even more preferably 60 minutes or more, even more preferably 80 minutes or more, even more preferably 120 minutes or more, and even more preferably 150 minutes or more, and from the viewpoint of further improving productivity, it is preferably 24 hours or less, more preferably 12 hours or less, even more preferably 5 hours or less, and even more preferably 4 hours or less.

[0044] Step (A) may be carried out under reduced pressure or normal pressure, but is preferably carried out under reduced pressure.

[0045] In step (A), the method for drying the hydrous copper particles while vibrating them is not particularly limited, but it is preferable to dry the hydrous copper particles using a vibration dryer, and it is more preferable to dry the hydrous copper particles using a vertical vibration dryer. As the vertical vibration dryer, for example, a small vibration dryer VU-15 (manufactured by Chuo Kakoki Co., Ltd.) can be used.

[0046] <Step (B) of Preparing Copper Particle Dispersion Liquid (a)> The method for producing copper particles according to this embodiment preferably includes step (B) of preparing copper particle dispersion liquid (a).

[0047] The copper particle dispersion liquid (a) means a solution in which copper particles are dispersed in a solvent such as water. The solvent preferably contains water.

[0048] Step (B) preferably includes step (B-1) of dispersing a divalent copper compound in a solvent in the presence of a dispersant, and step (B-2) of reducing the divalent copper compound to obtain copper particle dispersion liquid (a).

[0049] The step (B-1) of dispersing a divalent copper compound in a solvent in the presence of a dispersant is carried out, for example, by adding a divalent copper compound to a solvent such as water, stirring the mixture, and then adding a dispersant.

[0050] The divalent copper compound includes, for example, at least one selected from the group consisting of copper sulfate, copper oxide, copper chloride, copper carbonate, copper nitrate, etc., and preferably includes copper sulfate.

[0051] The dispersant is not particularly limited, but preferably 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 aniline derivatives, more preferably includes at least one selected from the group consisting of gelatin, casein, sodium caseinate, and ammonium caseinate, and even more preferably includes gelatin.

[0052] In step (B-1), the content of the dispersant, relative to 100 parts by mass of the copper compound, is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1.0 part by mass or more, and is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, even more preferably 2.0 parts by mass or less, from the viewpoint of further improving the dispersibility of the copper particles.

[0053] The step (B-2) of reducing the divalent copper compound to obtain the copper particle dispersion liquid (a) is carried out, for example, by adding a reducing agent to the dispersion liquid obtained in the step (B-1) and reducing the divalent copper compound to obtain copper particles.

[0054] The reducing agent includes at least one selected from the group consisting of, for example, ascorbic acid; hydrazine-based reducing agents such as hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine hydrate; sodium borohydride; sodium sulfite; sodium hydrogen sulfite; sodium thiosulfate; sodium nitrite; sodium hyponitrite; phosphorous acid; sodium phosphite; hypophosphorous acid; sodium hypophosphite; aldehydes; alcohols; amines; and sugars.

[0055] Step (B-2) may be carried out under heating conditions to further promote the reduction of the divalent copper compound. The heating temperature is not particularly limited, but may be, for example, 10°C or higher, 20°C or higher, and 90°C or lower, or 80°C or lower.

[0056] In step (B-2), the reduction step may be performed only once or multiple times, but it is preferable to perform the reduction step multiple times. That is, step (B-2) preferably includes a first reduction step and a second reduction step.

[0057] In the first reduction step, the reducing agent preferably includes ascorbic acid. In the second reduction step, the reducing agent preferably includes a hydrazine-based reducing agent, more preferably hydrazine.

[0058] The method may further include a step of adjusting the pH of the dispersion between the first reduction step and the second reduction step. The step of adjusting the pH of the dispersion is, for example, a step of adjusting the pH to 9.0 or more and 14.0 or less. The step of adjusting the pH of the dispersion is carried out, for example, by adding a pH adjuster such as an aqueous sodium hydroxide solution to the dispersion.

[0059] The copper particle dispersion liquid (a) may have the dispersant removed. The dispersant can be removed, for example, by adding a remover to the copper particle dispersion liquid (a). Examples of the remover include an aqueous solution of a hydroxide salt, such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution; ion-exchanged water; and the like.

[0060] The copper particles in the copper particle dispersion liquid (a) may be surface-treated by treating the surfaces of the copper particles with a surface treating agent such as a saturated fatty acid salt such as sodium stearate or an unsaturated fatty acid salt such as sodium oleate.

[0061] <Step (C) of Obtaining Hydrous Copper Particles by Solid-Liquid Separation of Copper Particle Dispersion (a)> The copper particle manufacturing method of the present embodiment preferably includes step (C) of obtaining hydrous copper particles by solid-liquid separation of the copper particle dispersion (a). Here, the copper particle dispersion (a) in step (C) includes copper particle dispersion (a) that has been subjected to treatments such as removal of the dispersant and surface treatment.

[0062] The method for obtaining hydrous copper particles by solid-liquid separation of the copper particle dispersion liquid (a) is not particularly limited. For example, the hydrous copper particles can be obtained by at least one method selected from the group consisting of centrifugation, filtration, decantation, etc. Among these, from the viewpoint of adjusting the water content of the hydrous copper particles to an appropriate range, it is preferable to obtain the hydrous copper particles by at least one method selected from centrifugation and filtration.

[0063] <Other Steps> The method for producing copper particles according to the present embodiment may include other steps as appropriate. Examples of the other steps include a crushing step.

[0064] [Conductive Paste] The conductive paste of this embodiment contains the copper particles of this embodiment or copper particles obtained by the copper particle manufacturing method of this embodiment. The content of the copper particles in the conductive paste of this embodiment may be, for example, 1 mass % or more, 5 mass % or more, or 10 mass % or more, and may be 99 mass % or less, 97 mass % or less, or 94 mass % or less, when the entire conductive paste is taken as 100 mass %.

[0065] The conductive paste of this embodiment may further include a binder resin, such as 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, phenol 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, and polyvinylpyrrolidone.

[0066] The conductive paste of this 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.

[0067] The hydrophobic solvent may be, for example, at least one selected from the group consisting of mineral oil, fatty acid, alcohol, hydrocarbon, and the like.

[0068] Examples of the hydrophilic solvent include at least one selected from the group consisting of alkanediols such as ethylene glycol and propylene glycol; polyhydric alcohols such as glycerin; 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; and amides such as N-methylacetamide and N-methylformamide.

[0069] The organic solvent may be used alone or in combination of two or more kinds.

[0070] The conductive paste of this embodiment can be applied to a substrate by, for example, an inkjet method or a screen printing method, dried, and then heated to form a conductive member such as copper particle-containing wiring or a thin film.

[0071] The conductive paste of this embodiment can be produced by a known method, for example, by mixing the above-described materials using a mixer such as a three-roll mill, a bead mill, a ball mill, a planetary mixer, or a disper.

[0072] [Substrate] The substrate of the present embodiment includes the conductive paste of the present embodiment or a sintered body of the conductive paste of the present embodiment. The substrate of the present embodiment includes, for example, a coating film of the conductive paste of the present embodiment or a sintered body of the conductive paste of the present embodiment in a predetermined region of a base material.

[0073] The substrate of this embodiment is, for example, a low-temperature co-fired ceramic substrate, a printed circuit board, a flexible substrate, or the like, and is preferably a low-temperature co-fired ceramic substrate.

[0074] The substrate of this embodiment is used, for example, as an electronic substrate for an automobile, a substrate for a high frequency module, a substrate for a semiconductor package, and the like.

[0075] The substrate of this embodiment can be manufactured by a known method, for example, by screen-printing the conductive paste of this embodiment in a predetermined region of a substrate (e.g., a green sheet), stacking a plurality of substrates on which the conductive paste has been printed to form a laminate, and firing the laminate to manufacture the substrate.

[0076] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.

[0077] The present embodiment will be described in detail below based on examples and comparative examples, but the present embodiment is not limited to the descriptions of these examples.

[0078] Example 1 Step (B-1) of Dispersing a Divalent Copper Compound in a Solvent in the Presence of a Dispersant First, 670 g of copper sulfate (manufactured by JX Nippon Mining & Metals Corporation) was added as a divalent copper compound to 2.26 L of ion-exchanged water, and the mixture was stirred using a stirrer (manufactured by HEIDON, product name: BL300). A dispersant solution prepared by the method described below was then added to obtain a dispersion. (Method of Preparing Dispersant Solution) As a dispersant, 10.7 g of gelatin (derived from bovine bone, manufactured by FUJIFILM 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, product name: C-MAG HS4 digital) to prepare a dispersant solution.

[0079] <Step (B-2) of Reducing a Divalent Copper Compound to Obtain a Copper Particle Dispersion Liquid (a)> A reducing agent solution prepared by the method described below was added to the dispersion liquid. The dispersion liquid was heated to 40°C and stirred for 3 minutes to reduce the copper compound, thereby obtaining a copper compound dispersion liquid (b). Subsequently, a 24% by mass aqueous sodium hydroxide solution was added to the copper compound dispersion liquid (b) at a solution temperature of 40°C until the pH of the solution reached 10.6. At this time, the time required to adjust the pH of the solution to 10.6 was 30 minutes. 400 g of hydrazine (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added as a reducing agent to the pH-adjusted copper compound dispersion liquid (b), and the solution was heated to 60°C and stirred for 60 minutes to reduce the copper compound, thereby obtaining a copper particle dispersion liquid (a). (Method for preparing reducing agent solution) As a reducing agent, 472 g of ascorbic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to 2.0 L of ion-exchanged water, and the mixture was stirred with a magnetic stirrer (manufactured by IKA Corporation, product name: C-MAG HS4 digital) to prepare a reducing agent solution.

[0080] <Step of Removing Dispersant> After stopping the stirring of the copper particle dispersion (a) and removing the supernatant, 5050 g of a 1.2 mass% sodium hydroxide aqueous solution was added as a dispersant remover and stirred for 10 minutes. After stopping the stirring again and removing the supernatant, a reducing agent aqueous solution prepared by adding 27 g of hydrazine (manufactured by Fujifilm 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.

[0081] <Surface Treatment Step> To the copper particle dispersion liquid (a) from which the dispersant had been removed, 0.84 g of sodium stearate (manufactured by Kanto Chemical Co., Inc.) was added as a surface treatment agent to 0.5 L of ion-exchanged water to prepare a surface treatment agent dispersion liquid, and the surface of the copper particles was then treated by adding the surface treatment agent dispersion liquid to the copper particle dispersion liquid (a).

[0082] <Step (C) of Obtaining Hydrous Copper Particles by Solid-Liquid Separation of Copper Particle Dispersion Liquid (a)> The surface-treated copper particle dispersion liquid (a) was subjected to solid-liquid separation using a centrifuge (manufactured by Kokusan Co., Ltd., product name: H-36) at a rotation speed of 3500 rpm for 5 minutes to obtain hydrous copper particles. The moisture content of the obtained hydrous copper particles was 13% by mass, where the total amount of the hydrous copper particles was taken as 100% by mass.

[0083] <Step (A) of drying hydrous copper particles while vibrating> 817 g of hydrous copper particles were dried while vibrating using a vertical vibration dryer under reduced pressure conditions at a drying temperature of 50°C and a drying time of 180 minutes to obtain copper particles. Here, the vertical vibration dryer used was a small vibration dryer VU-15 (manufactured by Chuo Kakoki Co., Ltd.) equipped with an adapter attached to the reduced pressure filter section and an extended barrel section. The obtained copper particles weighed 708 g. The proportion of powdery copper particles in the obtained copper particles was 59% by mass, and the proportion of clumped copper particles was 41% by mass. Here, powdery copper particles refer to copper particles that are powdery without being subjected to a crushing treatment in a mortar or the like. Clumped copper particles refer to copper particles other than powdery copper particles. The inventors believe that the powdery copper particles were obtained by crushing the clumped copper particles by vibration drying.

[0084] [Example 3] Hydrous copper particles were obtained in the same manner as in Example 1. The moisture content of the obtained hydrous copper particles is shown in Table 1.

[0085] <Step (A) of drying hydrous copper particles while vibrating> Copper particles were obtained by drying hydrous copper particles while vibrating them in the same manner as in Example 1, except that the amount of hydrous copper particles charged, the drying temperature, and the drying time were set to the conditions shown in Table 1. The amount of the obtained copper particles, the proportion of powdery copper particles, and the proportion of chunky copper particles in the obtained copper particles are shown in Table 1.

[0086] [Examples 2 and 4] Copper particle dispersions (a) were obtained by carrying out surface treatment in the same manner as in Example 1.

[0087] <Step (C) of Obtaining Hydrous Copper Particles by Solid-Liquid Separation of Copper Particle Dispersion (a)> The surface-treated copper particle dispersion (a) was subjected to solid-liquid separation by suction filtration using qualitative filter paper (manufactured by ADVANTEC, product name: No. 131) to obtain hydrous copper particles. The moisture content of the obtained hydrous copper particles is shown in Table 1.

[0088] <Step (A) of drying hydrous copper particles while vibrating> Each copper particle was obtained by drying hydrous copper particles while vibrating in the same manner as in Example 1, except that the amount of hydrous copper particles charged, the drying temperature, and the drying time were set to the conditions shown in Table 1. The amount of the obtained copper particles, the proportion of powdery copper particles, and the proportion of chunky copper particles in the obtained copper particles are shown in Table 1.

[0089] Comparative Example 1 Hydrous copper particles were obtained in the same manner as in Example 1. The moisture content of the obtained hydrous copper particles is shown in Table 1.

[0090] <Step of drying hydrous copper particles> 150 g of hydrous copper particles were dried under reduced pressure conditions using a tray dryer (Yamato Scientific Co., Ltd., constant temperature tray dryer DX602) at a drying temperature of 50°C for a drying time of 720 minutes to obtain copper particles. In Comparative Example 1, the copper particles were dried without vibration. The amount of obtained copper particles was 108 g. The proportion of clumped copper particles was 100 mass%.

[0091] <Crushing Step> The lump copper particles were crushed in a mortar to obtain powdered copper particles.

[0092] [Comparative Example 2] Copper particles were obtained in the same manner as in Comparative Example 1, except that the reducing agent aqueous solution was not added in the step of removing the dispersant. The amount of the obtained copper particles, the proportion of powdery copper particles in the obtained copper particles, and the proportion of lump copper particles in the obtained copper particles are shown in Table 1.

[0093] Comparative Example 3 A copper particle dispersion liquid (a) was obtained by carrying out a surface treatment in the same manner as in Example 1.

[0094] <Step (C) of Obtaining Hydrous Copper Particles by Solid-Liquid Separation of Copper Particle Dispersion Liquid (a)> The surface-treated copper particle dispersion liquid (a) was manually decanted to obtain hydrous copper particles. The moisture content of the obtained hydrous copper particles is shown in Table 1.

[0095] <Step (A) of drying hydrous copper particles while vibrating> Copper particles were obtained by drying hydrous copper particles while vibrating them in the same manner as in Example 1, except that the amount of hydrous copper particles, drying temperature, and drying time were set to the conditions shown in Table 1. The amount of the obtained copper particles, the proportion of powdery copper particles, and the proportion of chunky copper particles in the obtained copper particles are shown in Table 1.

[0096] [Measurements] The following measurements were carried out in each example and comparative example. Here, the copper particles were obtained in the form of powder copper particles and lump copper particles, but various measurements were carried out on the powder copper particles.

[0097] <Particle size (H ２ O) 0.1 g of copper particles was mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture was irradiated with ultrasonic waves in a laser diffraction / scattering particle size analyzer (manufactured by Horiba, Ltd., product name: LA-960V2) for 5 minutes, after which the volume-based particle size distribution of the copper particles was measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２ The dispersant used was polyoxyethylene (20) sorbitan monolaurate.

[0098] <Particle diameter (img)> Copper particles were observed under a magnified magnification (10K magnification) using a scanning electron microscope to obtain an image obtained by a scanning electron microscope (SEM image). The SEM image was analyzed using image processing software ImageJ to obtain the particle diameter (img). １０ Particle size (img), D ５０ Particle size (mg), and D ９０The particle diameter (img) values ​​were obtained for each. Specifically, the particle diameter was calculated by the following procedure. 1. The SEM image was imported into the image processing software ImageJ. 2. The scale of the SEM image was set as Known Distance using Set Scale. 3. The contrast threshold was adjusted using Threshold, and the image was binarized. 4. Particles were separated from the binarized image using the Watershed method. 5. The particle diameter was calculated using Analyze Particles. The number of copper particles used to calculate the particle diameter was 200 or more. 6. From the obtained values, the volume-based particle size distribution was calculated using the Area value, and D １０ Particle size (img), D ５０ Particle size (img), and D ９０ The particle size (img) values ​​were obtained for each.

[0099] Based on the particle diameter value obtained by the above measurement method, D ９５ Particle size (H ２ O) to D １０ Particle size (H ２ O), D ９５ Particle size (H ２ O) to D １０ Particle size (H ２ O) and D ５０ Particle size (H ２ O) to D ５０ The values ​​were divided by the particle size (img) to calculate the respective values.

[0100] <Oxygen Content> The oxygen content was calculated in accordance with JIS H1067:2002 using a nitrogen / oxygen analyzer (manufactured by LECO Corporation, product name: ON836).

[0101] <Carbon Content> 0.5 g of copper particles was weighed, and 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder were added as combustion improvers. Measurement was performed using a carbon / sulfur analyzer (manufactured by HORIBA, Ltd., product name: EMIA-820W) in an oxygen stream under the following conditions: flow rate: 3 L / min, combustion method: high-frequency heating, combustion time: 60 sec, detection method: infrared absorption method, and the carbon content was calculated.

[0102] <Temperature at which shrinkage rate reaches 1.0%> 1 g of copper particles was weighed and filled into a cylindrical molding die with a diameter of 5 mm. The copper particles were press-molded using a hydraulic press (discharge pressure of 10 MPa). The pellets obtained by press molding were crushed to obtain a granule sample. 0.67 g of the granule sample was weighed and filled into a cylindrical molding die with a diameter of 5 mm. The granule sample was press-molded using a hydraulic press (discharge pressure of 10 MPa) to obtain a cylindrical pellet with a diameter of 5 mm and a height of 5 mm as a measurement sample. Measurement was performed using a thermomechanical analyzer (manufactured by NETZSCH, product name: TMA4000SA) under the following conditions: Ar flow rate: 200 mL / min, measurement load: 10 mN, measurement temperature range: 23 to 1000°C, and heating rate: 5°C / min, and the temperature at which shrinkage rate reaches 1.0% was calculated.

[0103] <Tap Density> The tap density was measured in accordance with JIS Z2512:2012.

[0104] The results of each measurement are shown in Table 1. ９５ Particle size (H ２ O) to D １０ Particle size (H ２ O) is "D ９５ (H) / D １０ (H)," "D ９５ Particle size (H ２ O) to D １０ Particle size (H ２ The value obtained by subtracting "D ９５ (H)-D １０ (H)" and "D ５０ Particle size (H ２ O) to D ５０ The value divided by the particle diameter (mg) is "D ５０ (H) / D ５０ (i)" In Table 1, "-" means that the measurement was not performed.

[0105]

[0106] From Table 1, the tap density of the copper particles of the example is D ５０ It can be seen that the tap density is improved compared to the copper particles of the comparative example, which have a similar particle diameter (img) value. In other words, it can be seen that the copper particles of this embodiment have improved packing properties.

[0107] From Table 1, it can be seen that the copper particle manufacturing method of the example improves the proportion of powdery copper particles in the obtained copper particles compared to the copper particle manufacturing methods of comparative examples 1 and 2. In other words, it can be seen that the copper particle manufacturing method of this embodiment can further improve the proportion of powdery copper particles in the obtained copper particles.

[0108] This application claims priority based on Japanese Patent Application Nos. 2023-169397, 2023-169398, and 2023-169399, filed on September 29, 2023, the disclosures of which are incorporated herein in their entireties.

[0109] The present invention can also take the following aspects.

[0110] [1a] Copper particles having an oxygen content of 0.70% by mass or less as measured in accordance with JIS H1067:2002. [2a] The copper particles according to [1a], having a carbon content of 1.50% by mass or less as calculated by the carbon content measurement described below. [Carbon Content Measurement] 0.5 g of copper particles are weighed, and 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder are added as combustion improvers. The carbon content is calculated using a carbon / sulfur analyzer in an oxygen stream under the following conditions: flow rate: 3 L / min, combustion method: high-frequency heating, combustion time: 60 sec, and detection method: infrared absorption method. [3a] The copper particles according to [1a] or [2a], having a temperature of 200°C or higher at which a shrinkage rate of 1.0% is calculated by the shrinkage rate measurement described below. [Shrinkage Rate Measurement] 1 g of copper particles is weighed out and filled into a cylindrical molding die with a diameter of 5 mm, and the copper particles are press-molded using a hydraulic press (discharge pressure of 10 MPa). The pellets obtained by press molding are crushed to obtain a granule sample. 0.67 g of the granule sample is weighed out and filled into a cylindrical molding die with a diameter of 5 mm, and the granule sample is press-molded using a hydraulic press (discharge pressure of 10 MPa) to obtain a cylindrical pellet with a diameter of 5 mm and a height of 5 mm as a measurement sample. Measurement is performed using a thermomechanical analyzer 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 which the shrinkage rate reaches 1.0% is calculated. [4a] The tap density measured in accordance with JIS Z2512:2012 is 2.5 g / cm ３ [5a] The copper particles according to any one of [1a] to [3a], wherein D calculated by the following particle diameter measurement 1 ５０ Particle size (H ２ [Particle size measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture is irradiated with ultrasonic waves in a laser diffraction / scattering particle size measurement device for 5 minutes. Then, the volume-based particle size distribution of the copper particles is measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H２ [6a] The values ​​of D calculated by the following particle size measurement 1 are obtained. １０ Particle size (H ２ [Particle size measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture is irradiated with ultrasonic waves in a laser diffraction / scattering particle size measurement device for 5 minutes. Then, the volume-based particle size distribution of the copper particles is measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２ [7a] The values ​​of D calculated by the following particle size measurement 1 are obtained. ９５ Particle size (H ２ [Particle size measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture is irradiated with ultrasonic waves in a laser diffraction / scattering particle size measurement device for 5 minutes. Then, the volume-based particle size distribution of the copper particles is measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２

[0023] The values ​​of (0) and (10) are obtained, respectively. [8a] A conductive paste comprising the copper particles according to any one of [1a] to [7a]. [9a] A substrate comprising the conductive paste according to [8a] or a sintered body of the conductive paste. [10a] The substrate according to [9a], which is a low-temperature co-fired ceramic substrate.

[0111] The present invention can also take the following aspects.

[0112] [1b] A method for producing copper particles, comprising a step (A) of drying hydrous copper particles while vibrating them, wherein the moisture content of the hydrous copper particles is 30% by mass or less, when the total weight of the hydrous copper particles is taken as 100% by mass. [2b] A method for producing copper particles as described in [1b], wherein the moisture content of the hydrous copper particles is 5% by mass or more, when the total weight of the hydrous copper particles is taken as 100% by mass. [3b] A method for producing copper particles as described in [1b] or [2b], wherein in step (A), the hydrous copper particles are dried using a vibration dryer. [4b] A method for producing copper particles as described in any of [1b] to [3b], wherein in step (A), the drying temperature is 30°C or more and 100°C or less. [5b] A method for producing copper particles as described in any of [1b] to [4b], wherein in step (A), the drying time is 10 minutes to 24 hours. [6b] The method for producing copper particles according to any one of [1b] to [5b], further comprising: step (B) of preparing a copper particle dispersion liquid (a); and step (C) of obtaining the hydrated copper particles by performing solid-liquid separation of the copper particle dispersion liquid (a). [7b] The method for producing copper particles according to [6b], wherein in step (C), the hydrated copper particles are obtained by at least one method selected from centrifugation and filtration. [8b] The method for producing copper particles according to [6b] or [7b], wherein step (B) comprises: step (B-1) of dispersing a divalent copper compound in a solvent in the presence of a dispersant; and step (B-2) of reducing the divalent copper compound to obtain the copper particle dispersion liquid (a). [9b] The method for producing copper particles according to [8b], wherein in step (B-1), the dispersant comprises 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 aniline derivatives. [10b] The method for producing copper particles according to any one of [1b] to [9b], wherein the temperature at which the copper particles have a shrinkage of 1.0% calculated by the following shrinkage measurement is 200°C or higher.[Shrinkage Measurement] 1 g of copper particles was weighed and filled into a cylindrical mold with a diameter of 5 mm. The copper particles were press-molded using a hydraulic press (discharge pressure of 10 MPa). The pellets obtained by press molding were crushed to obtain a granule sample. 0.67 g of the granule sample was weighed and filled into a cylindrical mold with a diameter of 5 mm. The granule sample was press-molded using a hydraulic press (discharge pressure of 10 MPa) to obtain a cylindrical pellet with a diameter of 5 mm and a height of 5 mm as a measurement sample. Measurement was performed using a thermomechanical analyzer under the following conditions: Ar flow rate: 200 mL / min, measurement load: 10 mN, measurement temperature range: 23 to 1000°C, and heating rate: 5°C / min, and the temperature at which the shrinkage rate reached 1.0% was calculated. [11b] The tap density of the copper particles measured in accordance with JIS Z2512:2012 was 2.5 g / cm. ３ [12b] The method for producing copper particles according to any one of [1b] to [10b], wherein D calculated by the following particle diameter measurement 1 of the copper particles. ５０ Particle size (H ２ [Particle size measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture is irradiated with ultrasonic waves in a laser diffraction / scattering particle size measurement device for 5 minutes. Then, the volume-based particle size distribution of the copper particles is measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２ [13b] The value of D calculated by the following particle diameter measurement 1 of the copper particles is obtained. １０ Particle size (H ２ [Particle size measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture is irradiated with ultrasonic waves in a laser diffraction / scattering particle size measurement device for 5 minutes. Then, the volume-based particle size distribution of the copper particles is measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H２ O), and D ９５ Particle size (H ２ [14b] The value of D calculated by the following particle diameter measurement 1 of the copper particles is obtained. ９５ Particle size (H ２ [Particle size measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture is irradiated with ultrasonic waves in a laser diffraction / scattering particle size measurement device for 5 minutes. Then, the volume-based particle size distribution of the copper particles is measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２ [15b] The value of D calculated by the following particle diameter measurement 1 of the copper particles is obtained. ９５ Particle size (H ２ O) to D １０ Particle size (H ２ [Particle size measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1 mass % dispersant aqueous solution, and the mixture is irradiated with ultrasonic waves in a laser diffraction / scattering particle size measurement device for 5 minutes. Then, the volume-based particle size distribution of the copper particles is measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２

[0023] The carbon content of the copper particles is 1.50% by mass or less, as calculated by the carbon content measurement described below. [Carbon Content Measurement] 0.5 g of copper particles is weighed, and 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder are added as combustion improvers. The carbon content is calculated using a carbon / sulfur analyzer in an oxygen stream under the following conditions: a flow rate of 3 L / min, a combustion method using high-frequency heating, a combustion time of 60 seconds, and a detection method using infrared absorption. [18b] A conductive paste containing copper particles obtained by the copper particle production method described in any one of [1b] to [17b]. [19b] A substrate comprising the conductive paste according to [18b] above or a sintered body of the conductive paste. [20b] The substrate according to [19b] above, which is a low-temperature co-fired ceramic substrate.

Claims

1. D calculated by the particle size measurement 1 below ９５ Particle size (H ２ O) to D １０ Particle size (H ２ [Particle size measurement 1] 0.1 g of copper particles are mixed with 1 mL of a 0.1 mass% dispersant aqueous solution, and the mixture is irradiated with ultrasonic waves in a laser diffraction / scattering type particle size measurement device for 5 minutes, after which the volume-based particle size distribution of the copper particles is measured, and D １０ Particle size (H ２ O), D ５０ Particle size (H ２ O), and D ９５ Particle size (H ２ O) values ​​are obtained respectively.

2. D calculated by the particle size measurement 1. ９５ Particle size (H ２ O) to D １０ Particle size (H ２ 2. The copper particles according to claim 1, wherein the value obtained by dividing the total mass of the copper particles by the mass of the copper particles is 1.10 or more.

3. D calculated by the particle size measurement 1. ９５ Particle size (H ２ O) to D １０ Particle size (H ２ 3. The copper particles according to claim 1 or 2, wherein the value obtained by subtracting the particle diameter (μm) of the copper particle is 0.05 μm or more and 1.50 μm or less.

4. D calculated by the particle size measurement 1 ９５ Particle size (H ２ The copper particles according to any one of claims 1 to 3, wherein O) is 0.20 μm or more and 2.00 μm or less.

5. D calculated by the particle size measurement 1 １０ Particle size (H ２ The copper particles according to any one of claims 1 to 4, wherein O) is 0.05 μm or more and 0.50 μm or less.

6. D calculated by the particle size measurement 1 ５０ Particle size (H ２ The copper particles according to any one of claims 1 to 5, wherein O) is 0.10 μm or more and 1.00 μm or less.

7. D calculated by particle size measurement 2 below ５０ The copper particles according to any one of claims 1 to 6, having a particle diameter (img) of 0.10 μm or more and 1.00 μm or less. [Particle diameter measurement 2] The image obtained by a scanning electron microscope is analyzed to obtain a particle diameter of 0.10 μm or more and 1.00 μm or less. １０ Particle size (img), D ５０ Particle size (img) and D ９０ The particle size (img) values ​​are obtained for each.

8. D calculated by the particle size measurement 1 ５０ Particle size (H ２ O) is calculated by the following particle size measurement 2. ５０ The copper particles according to any one of claims 1 to 7, wherein the value divided by the particle diameter (img) is 1.50 or less. [Particle diameter measurement 2] An image obtained by a scanning electron microscope is analyzed to obtain D １０ Particle size (img), D ５０ Particle size (img) and D ９０ The particle size (img) values ​​are obtained for each.

9. The copper particles according to any one of claims 1 to 8, wherein the temperature at which the shrinkage rate reaches 1.0% calculated by the following shrinkage rate measurement is 200°C or higher. [Shrinkage Rate Measurement] 1 g of copper particles is weighed out, filled into a cylindrical molding die having a diameter of 5 mm, and the copper particles are press-molded using a hydraulic press (discharge pressure of 10 MPa). The pellets obtained by press molding are crushed to obtain a granule sample. 0.67 g of the granule sample is weighed out, filled into a cylindrical molding die having a diameter of 5 mm, and the granule sample is press-molded using a hydraulic press (discharge pressure of 10 MPa), to obtain a cylindrical pellet having a diameter of 5 mm and a height of 5 mm as a measurement sample. Measurement is performed using a thermomechanical analyzer under the conditions of Ar flow rate: 200 mL / min, measurement load: 10 mN, measurement temperature range: 23 to 1000°C, and heating rate: 5°C / min, and the temperature at which the shrinkage rate reaches 1.0% is calculated.

10. The tap density measured in accordance with JIS Z2512:2012 is 2.5 g / cm ３ The copper particles according to any one of claims 1 to 9.

11. Copper particles according to any one of claims 1 to 10, having an oxygen content of 0.70 mass% or less, measured in accordance with JIS H1067:2002.

12. Copper particles according to any one of claims 1 to 11, having a carbon content of 1.50% by mass or less as calculated by the following carbon content measurement: [Carbon content measurement] 0.5 g of copper particles is weighed, and 1.5 g of tungsten powder, 0.5 g of iron powder, and 0.5 g of tin powder are added as combustion improvers, and the carbon content is calculated using a carbon / sulfur analyzer under the conditions of an oxygen stream, a flow rate of 3 L / min, a combustion method of high-frequency heating, a combustion time of 60 sec, and a detection method of infrared absorption.

13. A method for producing copper particles as described in any one of claims 1 to 12, comprising a step (A) of drying hydrous copper particles while vibrating them, wherein the moisture content of the hydrous copper particles is 30% by mass or less when the entire hydrous copper particles are taken as 100% by mass.

14. A method for producing copper particles as described in claim 13, wherein the moisture content of the hydrated copper particles is 5% by mass or more when the entire hydrated copper particles are taken as 100% by mass.

15. A method for producing copper particles as described in claim 13 or 14, wherein in step (A), the hydrated copper particles are dried using a vibration dryer.

16. A method for producing copper particles described in any one of claims 13 to 15, wherein in step (A), the drying temperature is 30°C or higher and 100°C or lower.

17. A method for producing copper particles described in any one of claims 13 to 16, wherein in step (A), the drying time is 10 minutes or more and 24 hours or less.

18. A method for producing copper particles as described in any one of claims 13 to 17, further comprising: a step (B) of preparing a copper particle dispersion liquid (a); and a step (C) of subjecting the copper particle dispersion liquid (a) to solid-liquid separation to obtain the hydrous copper particles.

19. The method for producing copper particles described in claim 18, wherein in step (C), the hydrated copper particles are obtained by at least one method selected from a centrifugation method and a filtration method.

20. A method for producing copper particles as described in claim 18 or 19, wherein the step (B) comprises a step (B-1) of dispersing a divalent copper compound in a solvent in the presence of a dispersant, and a step (B-2) of reducing the divalent copper compound to obtain a copper particle dispersion liquid (a).

21. A method for producing copper particles as described in claim 20, wherein in step (B-1), the dispersing agent comprises 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 aniline derivatives.

22. A conductive paste comprising copper particles according to any one of claims 1 to 12, or copper particles obtained by the method for producing copper particles according to any one of claims 13 to 21.

23. A substrate comprising the conductive paste according to claim 22 or a sintered body of said conductive paste.

24. The substrate of claim 23 which is a low temperature co-fired ceramic substrate.