JP2016102249A - Method for producing electrolytic copper powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing electrolytic copper powders capable of inexpensively producing electrolytic copper powders fine and excellent in oxidation resistance in the method for producing electrolytic copper powder by an electrolytic process capable of producing copper powders with high purity.SOLUTION: Provided is a method for producing electrolytic copper powders characterized in that an acidic solution containing copper ions, (meth)acryl amide and chloride ions is stored into an electrolytic tank provided with an anode and a cathode, and the surface of the cathode is conducted with current density at which hydrogen gas is generated, and electrolysis is performed. Then, the obtained electrolytic copper powders being a single crystal metal in which the edge parts form chamfered polyhedral shape, and having a crystal structure made of a face-centered cubic.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing electrolytic copper powder, and more particularly to a method for producing electrolytic copper powder that can be suitably used as a material such as a conductive paste and has excellent oxidation resistance.

  In order to form wiring layers, electrodes, and the like in electronic devices, conductive pastes using metal fillers such as silver powder and copper powder, such as resin pastes and fired pastes, are frequently used. A metal filler paste of silver powder or copper powder is applied or printed on various base materials, and is subjected to heat curing or heat baking treatment to form a conductive film to be a wiring layer, an electrode or the like.

  Specifically, the resin-type conductive paste is made of a metal filler, a resin, a curing agent, a solvent, etc., printed on a conductor circuit pattern or terminal, and heated and cured at 100 ° C. to 200 ° C. to become a conductive film. Form wirings and electrodes. In the resin-type conductive paste, since the thermosetting resin is cured and contracted by heat, the metal fillers are pressed and brought into contact with each other so that the metal fillers overlap each other, and as a result, an electrically connected current path is formed. Since this resin-type conductive paste is processed at a curing temperature of 200 ° C. or lower, it is used for a substrate using a heat-sensitive material such as a printed wiring board.

  The firing type conductive paste is made of a metal filler, glass, solvent, etc., printed on a conductor circuit pattern or terminal, and heated and fired at a high temperature of 600 ° C. to 800 ° C. to form a conductive film. An electrode is formed. In the baking type conductive paste, the metal filler is sintered by being processed at a high temperature, and the conductivity is ensured. Since this fired conductive paste is processed at such a high firing temperature, it cannot be used for a printed wiring board using a resin material, but the metal filler is sintered by high temperature processing. Low resistance can be realized. Therefore, the fired conductive paste is used for an external electrode of a multilayer ceramic capacitor.

  As a metal filler used in these resin-type conductive pastes and fired-type conductive pastes, silver powder has been conventionally used, but due to the trend of cost reduction, it is cheaper than silver powder in recent years. There is a growing tendency to use copper powder.

  When the conductive paste using copper powder is heated to a high temperature in an oxidizing atmosphere, the copper metal is oxidized, so that it is difficult to heat and is generally fired at a high temperature in an inert atmosphere.

  Moreover, as a manufacturing method of the copper powder used as a raw material, an electrolytic method, an atomizing method, a wet method in which a reducing agent is added in a solution and the like are known.

  Specifically, the copper powder obtained by the electrolytic method has a feature that a high-purity product can be obtained, but most of the electrolytic copper powder is precipitated in a dendritic shape and has a coarse particle size of 10 μm or more. In particular, it was not suitable for use as a filler for a fired conductive paste.

  In addition, the atomizing method is a method in which a jet fluid is blown into a molten metal flow in which a metal is melted at a high temperature as shown in Patent Document 1, for example, and an impurity is included when the metal is melted. There are problems that it is easy to oxidize when sprayed, and that copper fine particles of 1 μm or less cannot be produced.

  The wet method is a method in which copper ions in a solution are reduced and precipitated with a reducing agent. Specifically, for example, as shown in Patent Document 2, an alkali agent is added to a solution containing a copper salt to cause reaction to precipitate copper hydroxide, and then a reducing agent is added to reduce to cuprous oxide. Further, a secondary reducing agent is added to reduce the metal copper to obtain copper powder. Such a wet method has the advantage that very fine copper fine powder of submicron can be produced, but impurities in the solution are likely to be mixed into the product, and an expensive reducing agent is used. In addition, there is a problem in that manufacturing costs are required due to the time and expense required for processing the waste liquid after manufacturing.

  Furthermore, the copper powder obtained by the atomization method or the wet method described above is a polycrystalline powder and has grain boundaries in the powder. For this reason, there exists a fault that a specific surface area becomes large and oxidation resistance falls.

  In general, when a conductive paste is used for an IC substrate, a printed circuit board, or the like, in order to form a fine pattern, it is required to have excellent oxidation resistance, fine quality and good dispersibility. However, in the case of metal powders, particularly copper powders, the oxidation tends to proceed more easily as the particle diameter becomes finer, so there is a need for a method for obtaining a copper powder that is fine and excellent in oxidation resistance. It has been.

  For example, Patent Document 3 proposes a method of obtaining single crystal copper fine powder by a gas phase reaction. The copper powder obtained by the method of Patent Document 3 is a chamfered polyhedral single crystal by observation using a scanning electron microscope (SEM), and the powder particles are single crystal, so the surface is smooth. It has the feature of having no defects and excellent oxidation resistance. However, in the production of copper powder by gas phase reaction, cuprous chloride is reacted with a reducing gas at a high temperature of 700 ° C. or higher to obtain single crystal copper powder, which complicates the mechanism of the apparatus and increases production costs. Further, there is a problem that the obtained copper powder is remelted.

  Thus, a method suitable for producing a fine copper powder excellent in oxidation resistance industrially at low cost has not been proposed yet.

Japanese Patent No. 4342746 Japanese Patent No. 4406738 Japanese Patent Publication No. 6-76609

  The present invention has been proposed in view of the above-described circumstances, and in an electrolytic copper powder production method by an electrolytic method capable of producing high-purity copper powder, an electrolytic copper powder that is fine and excellent in oxidation resistance is obtained. It aims at providing the manufacturing method of the electrolytic copper powder which can be manufactured cheaply.

  The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, a single crystal that is fine but excellent in oxidation resistance is obtained by using an electrolytic solution with a composition added with a specific additive and conducting electrolysis by applying current at a current density that generates hydrogen gas to the cathode. The present inventors have found that the electrolytic copper powder can be obtained at low cost and have completed the present invention. That is, the present invention provides the following.

  (1) According to a first aspect of the present invention, an acidic solution containing copper ions, (meth) acrylamides, and chloride ions is accommodated in an electrolytic cell provided with an anode and a cathode, and the cathode On the other hand, it is a method for producing electrolytic copper powder, characterized in that electrolysis is performed by energizing the cathode surface with a current density at which hydrogen gas is generated.

  (2) A second invention according to the present invention is characterized in that, in the first invention, the electrolytic copper fine powder has a polyhedral shape with chamfered ends, and the crystal structure is a face-centered cubic structure. It is a manufacturing method of electrolytic copper powder.

  (3) According to a third aspect of the present invention, the concentration of the (meth) acrylamides and chloride ions is such that the primary particle diameter of the electrolytic copper powder is in the range of 0.1 μm to 5 μm. The method for producing an electrolytic copper powder is characterized by adjusting the amount of current.

  According to the method for producing electrolytic copper powder according to the present invention, it is possible to produce high-purity and single-crystal electrolytic copper powder at low cost. The single crystal electrolytic copper powder obtained by this production method is fine and has high surface stability and excellent oxidation resistance, and can be suitably used as a material for conductive paste and the like.

4 is a photographic view showing an SEM observation image of the copper powder obtained in Example 1. FIG. 4 is a photographic view showing an SEM observation image of the copper powder obtained in Example 2. FIG. 4 is a photographic view showing an SEM observation image of the copper powder obtained in Example 3. FIG. 4 is a photographic view showing an SEM observation image of the copper powder obtained in Comparative Example 1. FIG.

  Hereinafter, a specific embodiment (hereinafter referred to as “the present embodiment”) of a method for producing an electrolytic copper powder according to the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention.

<< 1. Method for producing electrolytic copper powder >>
The method for producing electrolytic copper powder according to the present embodiment is a method for producing a single crystal copper powder by electrolyzing a solution containing a copper salt (copper ion). Specifically, an acidic solution containing copper ions, (meth) acrylamides, and chloride ions is contained in an electrolytic cell equipped with an anode and a cathode, and hydrogen is applied to the cathode surface with respect to the cathode. It is characterized in that electrolysis is carried out with a current density generated by gas.

  According to this manufacturing method, it is possible to obtain electrolytic copper powder having high purity and substantially single crystal. Specifically, it has a polyhedral shape with chamfered ends (corners), and a substantially single-crystal electrolytic copper powder of face-centered cubic single crystals or twin grains can be obtained. This single crystal electrolytic copper powder is fine, has high surface stability and excellent oxidation resistance, and has excellent dispersibility when used in a paste.

[Electrolytic solution composition]
The solution containing the copper salt, that is, the electrolytic solution is not particularly limited as long as it is a composition in which copper is precipitated by electrolysis. However, in consideration of industrial mass production, an acidic solution containing copper sulfate and sulfuric acid is used. Preferably there is.

  The copper concentration and free acid concentration in the solution are not particularly limited as long as they are dissolved to such an extent that they do not become supersaturated, but the concentration of metal copper is 5 g / L to 30 g as a concentration that can be produced industrially stably. / L is preferable. The free acid concentration is also preferably in the range of about 50 g / L to 300 g / L.

  In the present embodiment, (meth) acrylamides and chloride ions are allowed to coexist in an acidic solution containing a copper salt. “(Meth) acryl” means acrylic or methacrylic.

As (meth) acrylamides, for example, those represented by the following general formula (I) can be contained. In general formula (I), R ₁ is a hydrogen atom or a methyl group, and R ₂ and R ₃ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a C ₁ to C ₁ having a hydroxyl group. 4 alkyl groups are preferred. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, and the like. Examples of the alkyl group include those having one or more hydroxyl groups in these alkyl groups.

  Specific examples of (meth) acrylamides include acrylamide, N-methylacrylamide, N-ethylacrylamide, N- (2-hydroxyethyl) acrylamide, N- (2-hydroxypropyl) acrylamide, and N, N-dimethylacrylamide. N, N-diethylacrylamide, N-methyl-N-ethylacrylamide, N-methyl-N- (2-hydroxyethyl) acrylamide, N-methyl-N- (2-hydroxypropyl) acrylamide, N-ethyl-N -(2-hydroxyethyl) acrylamide, N-ethyl-N- (2-hydroxypropyl) acrylamide, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N- (2-hydroxyethyl) methacrylamide, N -(2-Hide Xylpropyl) methacrylamide, N, N-dimethylmethacrylamide, N, N-diethylmethacrylamide, N-methyl-N-ethylmethacrylamide, N-methyl-N- (2-hydroxypropyl) methacrylamide, N-ethyl- N- (2-hydroxypropyl) methacrylamide and the like can be mentioned. In addition, these (meth) acrylamides can be used individually or in combination of 2 or more types.

  The addition amount of (meth) acrylamides is preferably an amount that is 25 mg / L or more as the concentration in the electrolytic solution. By adding such a concentration in the electrolytic solution, it is possible to more effectively produce a single crystal copper powder that is fine and excellent in oxidation resistance. The upper limit of the addition amount is not particularly limited, and even if it is excessively added, the above-described effects are not impaired, but the cost increases industrially, so the concentration in the electrolytic solution is 1000 mg / L or less. Is preferred. When two or more types of (meth) acrylamides are used in combination, the total addition amount thereof is the amount described above.

  As described above, in the present embodiment, chloride ions are contained together with (meth) acrylamides. Although the detailed mechanism is unknown, single-crystal copper that is fine and excellent in oxidation resistance by causing an electrolytic reaction in the presence of (meth) acrylamides and chloride ions in this way. Powder can be deposited.

  Specifically, the chloride ion source is not particularly limited, and hydrochloric acid, sodium chloride, potassium chloride, and the like can be used.

  Moreover, it is preferable to add chloride ion so that the concentration in the electrolytic solution is 10 mg / L or more. The upper limit value of the addition amount is not particularly limited, but it is industrially expensive, so that the concentration in the electrolyte is preferably 500 mg / L or less.

  In the present embodiment, it is more preferable to adjust the concentration of (meth) acrylamides and the concentration of chloride ions in the electrolytic solution, and a fine single crystal copper powder can be produced. Specifically, a single crystal copper powder having a more preferable size in the range of primary particle diameter (average particle diameter (D50)) of 0.1 μm to 5 μm can be deposited on the cathode plate.

[Electrolytic treatment]
In the method for producing electrolytic copper powder according to the present embodiment, the electrolytic solution (solution containing copper ions) having the above-described composition is placed in an electrolytic cell (electrolyzer) including an anode (anode) and a cathode (cathode). Electrolysis is performed by applying a direct current between the anode and the cathode. In addition, electrolysis can be performed by the general electrolysis method using the electrolytic cell provided with an anode and a cathode.

  Specifically, any of a soluble electrode and an insoluble electrode can be used as the anode. As the soluble electrode, a copper plate can be used, and a copper piece can be used in a basket made of an insoluble metal such as titanium. On the other hand, as the insoluble electrode, an electrode in which a metal such as platinum or iridium is coated on the surface of a metal plate having corrosion resistance such as titanium can be used. As this insoluble electrode, electrodes called DSA, DSE, etc. are commercially available.

  When a soluble electrode is used as the anode, it may take time to replenish the electrolytic cell with copper as the anode copper dissolves, or the distance from the cathode may increase and the current density distribution may become uneven. On the other hand, when an insoluble electrode is used, there is no advantage in that the current density distribution can be kept constant because there is no increase in the distance from the cathode due to dissolution from the anode. In electrolysis using an insoluble electrode, a copper component corresponding to electrodeposited copper is added to a copper salt such as copper oxide to maintain a constant copper concentration in the electrolyte.

  Further, the cathode is not particularly limited as long as it is an electrically conductive material and is a metal having corrosion resistance to the electrolyte. For example, an electrode made of copper, stainless steel, titanium or the like can be used for the sulfuric acid acidic solution. Among these, it is preferable to use a titanium plate as a cathode. The titanium plate is not so strong in adhesion with the deposited copper, and the deposited copper powder can be easily peeled off and separated and recovered. In addition, as a method of peeling the deposited copper powder, it can carry out by well-known methods, such as the method of scraping off using a scraper etc., the method of applying a mechanical impact with respect to a cathode plate, and knocking off.

  Here, in the present embodiment, when a direct current is applied to an electrolytic cell including the anode plate and the cathode plate as described above to cause an electrolytic reaction, the current density applied to the cathode is defined as the cathode plate. It is important to set the current density so that hydrogen gas is generated by the decomposition of water simultaneously with copper deposition on the surface. Thereby, it is possible to effectively deposit a single-crystal copper powder having a fine polyhedral shape with chamfered ends. Under the condition of constant current in which hydrogen is not generated, copper deposited on the surface of the cathode plate is deposited in a so-called metal film state, so that fine particulate copper powder cannot be deposited.

  Adjustment of the current density at which hydrogen is generated may be determined by visually observing that hydrogen gas is generated from the cathode and bubbles are floated on the liquid surface of the electrolytic cell while actually energized. In addition, an electrolyte solution having the same composition is subjected to polarization measurement using an electrochemical means such as a potentiostat at the same solution temperature as during electrolysis, and a current density at which hydrogen gas is generated is obtained from the obtained polarization curve. You may make it energize with the electric current value which becomes.

  Further, the amount of current to be applied can be determined based on a value obtained by obtaining the current density at which hydrogen gas is generated by the method described above and multiplying this by the electrode area of the cathode. In order to make single crystallization more reliably, it is better to set the current amount larger than the standard, but even if the current amount is increased extremely, the effect is only increased by increasing the generation of hydrogen gas and increasing the power cost. Does not improve.

  Specifically, it is preferable to adjust the current amount such that single crystal copper powder having a primary particle size (average particle size (D50)) in the range of 0.1 μm to 5 μm is deposited on the cathode plate.

  The applied current may be a direct current, and may be a so-called PR method in which the direction of the current is changed periodically.

  A part of the copper powder deposited on the cathode plate under such electrolysis conditions may be aggregated. In that case, it is preferable to crush by a simple physical crushing method or the like. As a crushing method, for example, a method of crushing by applying ultrasonic waves in a solution, a method of crushing copper powder in a solution or once dried copper powder using a pulverizer such as a mixer, etc. It can be carried out.

≪2. Single-crystal electrolytic copper powder >>
The electrolytic copper powder according to the present embodiment is a substantially single-crystal electrolytic copper powder manufactured by the above-described manufacturing method using electrolysis. Here, “substantially single crystal” means not only single crystal grains but also twin grains having few grain boundaries.

  Specifically, the electrolytic copper powder according to the present embodiment is a single-crystal or twin-grain copper powder having a polyhedral shape with chamfered edges (corners) and a crystal structure of a face-centered cubic structure. (Refer to the photograph figure of FIGS. 1-3). The “polyhedron shape” refers to a shape having two or more planes on the surface. The electrolytic copper powder is fine and preferably has a primary particle size (average particle size (D50)) of 0.1 μm to 5 μm.

  The electrolytic copper powder according to the present embodiment is high purity because it is manufactured by an electrolysis method, and is fine, while it is a single crystal particle, so its appearance is smooth and has defects. No crystallinity, good stability (high surface stability), and excellent oxidation resistance. From this, for example, when used as a material (metal filler) of a conductive paste, it exhibits excellent dispersibility in which it is uniformly dispersed without agglomeration in the resin. Further, by having oxidation resistance, the conductive paste using the electrolytic copper powder as a metal filler can be appropriately subjected to a baking treatment such as high-temperature baking even in an oxidizing atmosphere.

  Hereinafter, examples of the present invention will be described together with comparative examples to be described specifically. However, the present invention is not limited to the following examples.

≪Evaluation method≫
With respect to the single crystal copper powder obtained in the following examples and comparative examples, the shape was observed and the crystal plane was measured by the following methods.

(Observation of shape)
With a scanning electron microscope (SEM) (manufactured by JEOL Ltd., JSM-7100F), 20 fields were arbitrarily observed with a field of magnification of 10,000 times, and the appearance of the copper powder contained in the field of view was observed.

(Measurement of crystal plane)
It measured with the X-ray-diffraction measuring apparatus (XRD) (the product name X'Pert PRO by the PAN artificial company).

(Measurement of average particle size)
The average particle diameter (D50) of the obtained copper powder was measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., HRA9320 X-100).

≪Example, comparative example≫
[Example 1]
In an electrolytic cell having an electrolytic solution capacity of 100 liters, a titanium electrode plate having a size of 200 mm × 200 mm as a cathode and a copper anode plate having a size of 200 mm × 200 mm as an anode are arranged so that the distance between the surfaces becomes 100 mm. One by one was inserted, and direct current was passed through it to deposit copper powder on the cathode plate. The opposite surfaces of the anode and the cathode that do not face each other were masked on the entire surface using a masking tape for plating.

  As the electrolytic solution, copper sulfate pentahydrate was used, and the composition was such that the copper ion concentration was 5 g / L and the sulfuric acid concentration was 100 g / L. In addition, N, N-dimethylacrylamide (manufactured by Kanto Chemical Co., Inc.) was added to the electrolytic solution so that the concentration in the electrolytic solution was 150 mg / L, and a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was further added. It added so that it might become 20 mg / L as the chlorine ion (chloride ion) density | concentration in electrolyte solution.

Then, the electrolytic solution whose concentration was adjusted in this manner was circulated at a flow rate of 15 L / min using a metering pump while maintaining the temperature at 30 ° C. Then, electricity was applied at a current density of 15 A / dm ² (1500 A / m ² ), in which hydrogen gas was generated by decomposition of copper, and copper powder was deposited on the cathode plate. The copper powder deposited on the cathode is mechanically scraped to the bottom of the electrolytic cell using a scraper and periodically collected. The collected copper powder is washed with pure water and then placed in a vacuum dryer for drying. I let you.

  The shape of the copper powder thus obtained was observed by the method using the SEM described above. FIG. 1 shows a photograph of a representative shape as an observation result. As can be seen from the photograph in FIG. 1, the deposited copper powder had a polyhedral shape with chamfered ends. Moreover, it was confirmed by the measurement of the crystal plane by XRD that the obtained copper powder was a face-centered cubic metal single crystal having a (111) plane and a twin grain copper powder. The average particle diameter (D50) of the obtained copper powder was 3.6 μm.

[Example 2]
An electrolytic solution having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 100 g / L is used, and N, N-diethylmethacrylamide is used as the electrolytic solution so that the concentration in the electrolytic solution is 300 mg / L. Further, a hydrochloric acid solution was added so as to have a chloride ion concentration of 250 mg / L. Using such an electrolytic solution, copper powder was deposited on the cathode plate at a current density of 20 A / dm ² (2000 A / m ² ) at which hydrogen gas was generated. The other conditions were the same as in Example 1.

  The obtained copper powder was observed by SEM as in Example 1. FIG. 2 shows a photograph of a representative shape as an observation result. As can be seen from the photograph in FIG. 2, the deposited copper powder had a polyhedral shape with chamfered ends. Further, the measurement of the crystal plane by XRD confirmed that it was a face-centered cubic metal single crystal having a (111) plane and a copper powder of twin particles. Moreover, the average particle diameter (D50) of the obtained copper powder was 1.4 μm.

[Example 3]
As the electrolytic solution, a composition having a copper ion concentration of 20 g / L and a sulfuric acid concentration of 150 g / L was used, and N-ethyl-N- (2-hydroxyethyl) acrylamide (manufactured by Kanto Chemical Co., Ltd.) was used as the electrolytic solution. Was added to a concentration of 500 mg / L in the electrolytic solution, and a hydrochloric acid solution was added to a concentration of 400 mg / L as the chloride ion concentration. Using such an electrolyte, copper powder was deposited on the cathode plate at a current density of 25 A / dm ² (2500 A / m ² ) at which hydrogen gas was generated. The other conditions were the same as in Example 1.

  The obtained copper powder was observed by SEM as in Example 1. FIG. 3 shows a photograph of a representative shape as an observation result. As can be seen from the photograph in FIG. 3, the deposited copper powder had a polyhedral shape with chamfered ends. Further, the measurement of the crystal plane by XRD confirmed that it was a face-centered cubic metal single crystal having a (100) plane and a copper powder of twin particles. Moreover, the average particle diameter (D50) of the obtained copper powder was 0.6 μm.

[Comparative Example 1]
Electrolysis was performed in the electrolyte without adding (meth) acrylamides and chloride ions to deposit copper powder on the cathode plate. The other conditions were the same as in Example 1.

  The obtained copper powder was observed by SEM as in Example 1. FIG. 4 shows a photograph of a representative shape as an observation result. As can be seen from the photograph in FIG. 4, the deposited copper powder is a dendritic copper powder in which granular copper powder particles are aggregated, and is confirmed to be a coarse copper powder having a size of 40 μm or more. It was done.

[Comparative Example 2]
Electrolysis is performed at a current density of 5 A / dm ² (500 A / m ² ) at a current density that does not generate hydrogen under the condition that (meth) acrylamides and chloride ions are added to the electrolyte, and copper is deposited on the cathode plate. Precipitated. The other conditions were the same as in Example 3.

In Comparative Example 2, as a result of electrolysis, a copper film having a metallic luster was uniformly deposited on the cathode, and a copper powder that did not form a copper powder was deposited.

Claims (3)

  An acidic solution containing copper ions, (meth) acrylamides, and chloride ions is contained in an electrolytic cell equipped with an anode and a cathode, and hydrogen gas is generated on the surface of the cathode with respect to the cathode. A method for producing electrolytic copper powder, characterized in that electrolysis is performed by applying current at a current density.   2. The method for producing electrolytic copper powder according to claim 1, wherein the electrolytic copper powder has a polyhedral shape with chamfered ends, and the crystal structure has a face-centered cubic structure. The concentration of the (meth) acrylamides and chloride ions and the amount of current are adjusted so that the primary particle diameter of the electrolytic copper powder is in the range of 0.1 μm to 5 μm. Item 3. A method for producing an electrolytic copper powder according to Item 1 or 2.