KR101613601B1 - Copper powder - Google Patents

Abstract

The present invention relates to a copper powder containing copper powder particles on a dendritic surface, and is intended to provide a novel copper powder which suppresses the influence of residual chlorine and improves the tendency to oxidize. A copper content containing dendritic phase copper powder particles which exhibits a dendrite phase, wherein the concentration of chlorine contained in the copper powder is 5 wtppm to 250 wtppm and the pH of the copper measured in accordance with JIS K 5101-17-2 (Hereinafter referred to as " copper powder of the present invention ").

Description

Copper {COPPER POWDER}

The present invention relates to a copper powder which can be suitably used as a conductive filler contained in a conductive paste or the like.

BACKGROUND ART [0002] Conductive pastes are widely used in the formation of electric circuits, the formation of external electrodes of ceramic capacitors, the formation of various conductive films, and the like, in which a conductive filler is dispersed in a vehicle comprising a resin-based binder and a solvent.

Conventionally, silver has been used as a conductive filler contained in this kind of conductive paste. However, the use of copper powder is inexpensive, migration is difficult to occur, and solderability is excellent, so that conductive paste using copper powder has been widely used.

The dendritic copper-based particles obtained by the electrolytic method have a larger number of contacts between the particles than the spherical copper-based particles, so that when used as the conductive material for the conductive paste, So that the conductive property can be enhanced. Therefore, for example, in the production of a semiconductor device, in the application such as filling a wiring connection hole or the like with a conductive paste, it is sufficient if conductivity conduction capable of transmitting an electric signal is taken, Dendritic copper particles capable of achieving conductivity in small amounts are particularly useful.

With respect to such dendritic copper powder, for example, Patent Document 1 discloses a copper powder for a solderable conductive paint, which is a rod obtained by pulverizing particulate dendritic copper powder and has an oil absorption (JIS K5101) of 20 ml / Or less, a maximum particle diameter of 44 占 퐉 or less, an average particle diameter of 10 占 퐉 or less, and a hydrogen reduction loss of 0.5% or less.

Patent Document 2 discloses a method in which a grease is added and mixed with a resinous electrolytic copper powder having an average particle diameter of 20 to 35 탆 and a bulkiness density of 0.5 to 0.8 g / cm 3, and the surface of the electrolytic copper powder is coated with a grease And then pulverized and pulverized by an impact plate type jet mill.

Patent Documents 3 and 4 disclose an electrolytic copper powder particle showing a dendritic phase as a heat pipe constituent raw material.

Patent Document 5 relates to a method for producing a dendrite-phase electrolytic copper powder and describes a method for electrolytically adding chlorine to an electrolytic solution as a production method for making the dendrite form of electrolytic copper uniform .

Japanese Patent Application Laid-Open No. 06-158103 Japanese Patent Application Laid-Open No. 2000-80408 Japanese Patent Application Laid-Open No. 2008-122030 Japanese Patent Application Laid-Open No. 2009-047383 Japanese Patent Application Laid-Open No. 1-247584

As described in Patent Document 5, it is known that, when copper is produced by the electrolytic solution, copper is added to the electrolytic solution to make the copper powder particles finer while maintaining the shape of the dendrite-like particles.

When the electrolytic solution is actually electrolyzed by adding chlorine, it is difficult to coat the copper powder with a uniform thickness when the conductivity of the obtained copper powder is lower than an expected value due to the influence of residual chlorine, or when silver is coated on copper powder particles And the like. It has also been found that the copper content obtained in this manner, that is, the copper content containing the copper powder particles on the dendritic basis, is remarkably deteriorated over time such as oxidation and corrosion.

Therefore, the present invention relates to a copper powder containing copper powder particles on a dendritic phase, and is intended to provide a new copper powder which suppresses the influence of residual chlorine and improves the oxidizing property.

The present invention relates to a copper powder containing dendritic phase copper powder particles showing a dendritic phase, wherein the concentration of chlorine contained in the copper powder is 5 wtppm to 250 wtppm and the copper content is measured in accordance with JIS K 5101-17-2 (Hereinafter referred to as " copper powder of the present invention ") characterized in that the pH of the copper powder is 5 to 9.

Since the copper powder of the present invention is a copper powder containing copper powder particles in the form of dendrites, the number of contact points between the particles is larger than that of the copper powder comprising spherical copper powder particles. Therefore, when used as a conductive material for a conductive paste , And the conductive property can be increased even when the amount of the conductive material is reduced.

Further, by adjusting the concentration of chlorine contained in the copper powder of the present invention to 5 wtppm to 250 wtppm, adverse effects due to residual chlorine can be effectively suppressed. For example, when copper particles are coated with silver, Can be coated.

Further, the copper powder of the present invention succeeded in improving the deterioration of the oxidative property and the corrosiveness with time, by adjusting the pH of the copper powder to 5 to 9.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a model diagram for explaining the particle shape of dendrite-phase copper powder particles. Fig.

Hereinafter, embodiments of the present invention will be described in detail. However, the scope of the present invention is not limited to the following embodiments.

<Characteristics of Bon-guri>

The copper powder (referred to as &quot; copper powder &quot;) according to the present embodiment is a copper powder containing dendritic copper powder (referred to as "copper powder").

As shown in Fig. 1, the "dendritic phase copper powder particle" in the present copper has, when observed under an electron microscope (500 to 20,000 times), one main axis and a plurality of branches Or two-dimensional or three-dimensionally grown copper powder particles. At this time, the main axis indicates a rod-shaped portion on which a plurality of branches are branched.

Particularly, it is particularly preferable that the present copper particles show a dendrite phase having the following characteristics when observed under an electron microscope (500 to 20,000 times).

The thickness a of the main axis is preferably 0.3 mu m to 5.0 mu m, more preferably 0.4 mu m or more, or 4.5 mu m or less, particularly 0.5 mu m or more or 4.0 mu m or less. When the thickness a of the main axis of the dendrites is 0.3 mu m or less, there is a possibility that branches grow hard because the main axis is not rigid. On the other hand, when the main axis is thicker than 5.0 mu m, the particles tend to aggregate, There is a possibility of quality.

The length b (the &quot; branch length b &quot;) of the longest branches out of the branches extending from the main axis indicates the degree of growth of the dendrites, and is preferably from 0.8 mu m to 12.0 mu m. Among them, it is more preferable to be 1.0 占 퐉 or more or 10.0 占 퐉 or less, particularly 1.2 占 퐉 or more or 8.0 占 퐉 or less. When the branch length b is less than 0.8 占 퐉, the dendrites do not sufficiently grow. On the other hand, if the branch length b exceeds 12.0 占 퐉, the flowability of the copper component may be lowered and handling may become difficult.

The number of branches (the number of branches / the long diameter L) with respect to the major axis L of the main axis indicates a large number of branches of the dendrites, and it is preferable that the number of branches is 0.5 / 탆 to 4.0 / 탆, Mu] m or more and 3.5 [mu] m / [mu] m or less, more preferably 0.8 / mu m or more or 3.0 / mu m or less. When the number of branches / the long diameter L is not less than 0.5 / 탆, the number of branches is sufficiently large and sufficient contact can be ensured. On the other hand, if the number of branches / long diameter L is less than 4.0 / It is possible to prevent the fluidity from being deteriorated.

However, when observed with an electron microscope (500 to 20,000 times), if most of the particles are occupied by the dendritic phase particles as described above, even if particles having other shapes are mixed, An effect similar to that of copper can be obtained. Therefore, from this viewpoint, the copper powder of the present invention is characterized in that the copper powder particles on the dendritic phase account for at least 80% by number, preferably at least 90% by number of the whole copper powder particles when observed under an electron microscope (500 to 20,000 times) If it is present, it may contain copper particles in the form of videndrite which are not recognized as dendrites.

As described above, in order to develop the dendritic shape of the copper particle, it is preferable to carry out electrolysis by adding chlorine to the electrolytic solution under predetermined electrolysis conditions using an electrolytic apparatus described later.

(Containing chlorine concentration)

The concentration of the chlorine contained in the copper powder, that is, the concentration of chlorine contained in the copper powder is preferably 5 wtppm to 250 wtppm, more preferably 10 wtppm or more or 220 wtppm or less, particularly 20 wtppm or more or 200 wtppm or less, particularly 30 wtppm or more or 180 wtppm or less .

When the concentration of chlorine contained in the copper powder is not more than 250 wtppm, adverse effects due to the residual chlorine can be effectively suppressed. For example, when silver is coated on the copper powder particles, the copper can be coated with a uniform thickness. The contained chlorine concentration of the copper powder may be less than 5 wtppm, but about 5 wtppm is the detection limit of the contained chlorine concentration.

In order to adjust the concentration of chlorine contained in the present copper powder to 5 to 250 wtppm, it is preferable to conduct an alkali treatment to bring the copper just obtained after electrolysis into contact with an alkaline solution having a pH of 8 or more. That is, in order to produce the copper powder containing the dendrite-shaped copper powder particles as described above, electrolysis is preferably performed using an electrolytic solution to which chlorine is added. However, in such a case, simply cleaning with pure water causes chlorine to remain in the particles, so that adverse effects due to the residual chlorine can not be effectively suppressed. Thus, by removing the chlorine contained in the inside of the particle, at least the vicinity of the surface which adversely affects the inside by the alkali treatment as described above, the concentration of chlorine contained in the present copper powder is controlled to be 5 wtppm to 250 wtppm to effectively suppress the adverse effect by residual chlorine For example, copper can be coated with a uniform thickness when silver particles are coated on copper particles.

Incidentally, it has been confirmed that the concentration of chlorine contained in the copper powder can not be set to 5 to 250 ppm by weight, as a result of cleaning with pure water instead of the alkali treatment with an alkali solution having a pH of 8 or more.

(Powder pH)

The powder pH of the present copper powder (measured in accordance with JIS K 5101-17-2) is preferably 5 to 9, more preferably 5.5 or more, or 8 or less, and especially 6 or more or 7.5 or less.

When the powder pH of the present copper powder is 5 to 9, deterioration with time due to oxidation and corrosion of the copper powder surface can be effectively suppressed.

As a method for adjusting the pH of the powder of the present copper powder to 5 to 9, for example, there can be mentioned a method of alkali treatment of the copper powder immediately after electrolysis.

(D50)

The volume cumulative particle diameter D50 measured by a D50 of the present copper powder, that is, a particle size distribution measured by a laser diffraction scattering type particle size distribution analyzer is preferably 3 mu m to 30 mu m, more preferably 5 mu m or more or 25 mu m or less, More preferably 20 mu m or less, particularly 15 mu m or less. When D50 is 3 m or more, viscosity adjustment is easy, and when D50 is 30 m or less, it can be applied to various conductive pastes.

(Specific surface area)

The specific surface area measured by the BET one-point method of the present copper is preferably from 0.30 to 1.50 m 2 / g. If it is significantly smaller than 0.30 m &lt; 2 &gt; / g, it is difficult to obtain the effect represented by the dendritic phase copper because the branch is not developed and is close to the pine cone or sphere. On the other hand, if it is remarkably larger than 1.50 m 2 / g, the branches of the dendrites become excessively thin, and problems such as breakage of branches in the paste processing step may occur, and the conductivity may be deteriorated rather.

Therefore, the specific surface area of the present copper component measured by the BET one-point method is preferably 0.30 to 1.50 m 2 / g, more preferably 0.40 m 2 / g or 1.40 m 2 / g or less, and particularly 1.00 m 2 / g or less Do.

(Oxygen concentration)

The oxygen concentration of the present copper powder is preferably 0.20 mass% or less.

When the oxygen concentration of the present copper component is 0.20 mass% or less, the conductivity can be further improved. From this viewpoint, the oxygen concentration of the present copper powder is more preferably 0.18 mass% or less, particularly preferably 0.15 mass% or less.

In order to reduce the oxygen concentration of the present copper particle to 0.20 mass% or less, there is a method of controlling the oxygen concentration and the drying temperature in the dry atmosphere or performing the alkali treatment as described above. However, the present invention is not limited to this method.

&Lt; Preparation method of copper-containing powder >

This copper powder can be produced by a predetermined electrolytic method.

As an electrolytic solution, for example, a positive electrode and a negative electrode are immersed in a sulfuric acid-acidic electrolytic solution containing copper ions and a direct current is flowed through the electrolytic solution to deposit copper on the surface of the negative electrode in a powder form, , Followed by washing and scraping by a sputtering method, followed by drying and, if necessary, sieving, and the like, to produce an electrolytic copper powder.

In the electrolysis, it is preferable to add chlorine to the electrolytic solution to adjust the chlorine concentration of the electrolytic solution to 3 to 300 mg / L, particularly 5 to 200 mg / L.

Further, when copper powder is produced by the electrolytic method, copper ions in the electrolytic solution are consumed along with precipitation of copper, so that the copper ion concentration of the electrolytic solution in the vicinity of the electrode plate is reduced and the electrolytic efficiency is lowered as it is. Therefore, in order to increase the electrolytic efficiency in general, it is preferable to circulate the electrolytic solution in the electrolytic bath so that the copper ion concentration of the electrolytic solution between the electrodes does not become thin.

However, in order to develop the dendrite of each copper particle, in other words, in order to promote the growth of branches extending from the main axis, it is preferable that the concentration of copper ions in the vicinity of the electrode is low. Therefore, in the production of the copper powder, the size of the electrolytic cell, the number of electrodes, the distance between the electrodes, and the circulating amount of the electrolytic solution are adjusted so that the copper ion concentration of the electrolytic solution in the vicinity of the electrode is adjusted to be low. At this time, it is preferable to adjust so that the copper ion concentration of the electrolytic solution between the electrodes always becomes at least thinner than the copper ion concentration of the electrolytic solution at the bottom of the electrolytic bath.

In order to adjust the particle size of the dendrite-phase copper particles, an appropriate condition may be set based on the technical knowledge within the above-described conditions. For example, in order to obtain dendritic copper particles having a large particle size, the copper concentration is preferably set to a relatively high concentration within the above preferable range, and the current density is set to a relatively low density within the preferable range And the electrolysis time is preferably set to a relatively long time within the preferable range. When it is intended to obtain copper particles of dendritic phase having a small particle size, it is preferable to set each condition by the above-mentioned thinking method. For example, the copper concentration may be 1 g / l to 10 g / l, the current density may be 100 A / m 2 to 3000 A / m 2, and the electrolysis time may be 3 minutes to 3 hours.

After the electrolysis, the electrolytically precipitated copper powder is washed with water as required and then mixed with water to form a slurry or a copper powder cake. Thereafter, an alkaline solution having a pH of 8 or more is mixed and stirred , It is preferable to reduce the concentration of chlorine contained in the copper powder by washing with water or the like by conducting an alkali treatment to bring the copper powder and the alkali solution into contact with each other.

In the alkali treatment, it is preferable to adjust the pH of the slurry or the copper cake after precipitation of the electrolytic copper to 8 or more, preferably 9 or more, or 12 or less, especially 10 or more or 11 or less.

Examples of the alkaline agent for use in the alkali treatment include ammonium carbonate solution, caustic soda solution, sodium bicarbonate, potassium hydroxide, ammonia water, and the like.

The surface of the electrolytic copper particle may be subjected to an oxidation resistance treatment using an organic material to form an organic material layer on the surface of the copper particle. It is not always necessary to form an organic material layer, but it is more preferable to form it by taking into account the change over time due to oxidation of the copper particle surface.

The organic material used for this oxidation-resistance treatment is not particularly limited, and examples thereof include glue, gelatin, organic fatty acids, and coupling agents.

The oxidation-resistance treatment method, that is, the method of forming the organic material layer may be either a dry method or a wet method. In the case of the dry method, a method of mixing an organic substance and a copper powder particle by a V-type mixer or the like, and a method of adding an organic substance to a slurry of a water-copper particle slurry and adsorbing it on the surface in a wet method. However, it is not limited to these.

For example, a method of adhering an organic substance to the surface of a copper powder by mixing an aqueous solution containing a copper powder cake and a desired organic substance with an organic solvent after alkaline treatment after electrolytic copper precipitation is a preferred example.

<Applications>

Since this copper powder has excellent conductivity characteristics, the copper powder can be suitably used as a main constituent material of various conductive materials such as a conductive resin composition such as a conductive paste and a conductive adhesive, and also as a conductive paint.

It is also possible to use other copper as a main constituent material of various conductive materials such as conductive paste and conductive resin composition such as conductive paste by mixing the copper with the copper.

For example, in order to produce a conductive paste, a conductive paste can be prepared by mixing the present copper powder with a binder and a solvent, and if necessary, with a curing agent, a coupling agent, a corrosion inhibitor, and the like.

Here, examples of the binder include liquid epoxy resin, phenol resin, unsaturated polyester resin, and the like, but are not limited thereto.

Examples of the solvent include terpineol, ethyl carbitol, carbitol acetate, and butyl cellosolve.

As the curing agent, 2-ethyl-4-methylimidazole and the like can be given.

Examples of the corrosion inhibitor include benzothiazole, benzimidazole, and the like.

The conductive paste can be used to form a circuit pattern on a substrate to form various electric circuits. For example, a printed wiring board or an electric circuit or an external electrode of various electronic parts can be formed by applying or printing to a fired substrate or an untreated substrate, heating the substrate, or pressing and baking if necessary.

Particularly, copper dendrites of this copper component are especially developed, and the number of contact points between the particles is increased, so that even when the content of the conductive powder is reduced, excellent conductivity characteristics can be obtained. For example, And is suitable as a conductive paste material for use in filling a wiring connection hole or the like.

In fabricating semiconductor devices, a plurality of wiring trenches (via holes or contact holes) for electrically interconnecting the wiring trenches or multilayer wiring lines connecting elements are provided. Aluminum has been conventionally used as a conductive material to be filled in these wiring trenches and wiring connection holes. However, aluminum has been used as a conductive material in recent years due to high integration and miniaturization of semiconductor devices, And a conductive paste containing copper powder as a conductive material is used to fill the wiring connection hole or the like. In this kind of application, it is not necessary to conduct a large amount of current, and it is sufficient if the electric signal can be conducted.

Further, the present copper particles can be used as a core material, and a part or all of their surfaces can be covered with a different kind of conductive material such as gold, silver, nickel, tin, or the like.

At this time, since the present copper content reduces the residual chlorine, silver can be uniformly coated when copper is coated on copper particles by a substitution method, for example.

<Explanation of Terms>

In the present specification, when expressed as "X to Y" (where X and Y are arbitrary numbers), "not less than X and not more than Y" Y &quot;.

In addition, when expressed as &quot; X or more &quot; (X is an arbitrary number), unless otherwise specified, it includes the meaning of &quot; preferably larger than X &quot;, and when expressed as &quot; Y or less &quot; , And &quot; preferably smaller than Y &quot; unless otherwise specified.

[Example]

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following examples.

(Example 1)

9 sheets of an SUS negative electrode plate and an insoluble positive electrode plate (DSE (manufactured by Permeelec Electrode Co., Ltd.)) were placed in an electrolytic cell having a size of 2.5 m x 1.1 m x 1.5 m (about 4 m) And a copper sulfate solution as an electrolytic solution was circulated at 30 L / min. Then, a positive electrode and a negative electrode were immersed in this electrolytic solution, and a direct current was passed through the electrolytic solution to carry out electrolysis to deposit copper in powder form on the surface of the negative electrode .

At this time, electrolysis was carried out for 30 minutes by adjusting the Cu concentration of the circulating electrolyte to 10 g / L, the sulfuric acid (H ₂ SO ₄ ) concentration to 100 g / L, the chlorine concentration to 50 mg / L, and the current density to 800 A / . The pH of the solution at this time was 1.

The copper ion concentration of the electrolytic solution between the electrodes was always kept lower than the copper ion concentration of the electrolytic solution at the bottom of the electrolytic bath during electrolysis.

Copper precipitated on the surface of the negative electrode was mechanically scraped off and recovered and then washed to obtain a hydrous copper cake equivalent to 1 kg of copper. This cake was dispersed in 3 liters of water to prepare a slurry. An ammonium carbonate solution was added until the pH of the slurry reached pH 9, and the mixture was stirred and alkalized. Thereafter, the impurities were removed by washing with pure water.

Subsequently, 1 L of an aqueous solution of 10 g / L of industrial gelatin (Nitta gelatin shale) was added and stirred, followed by drying at 80 캜 for 6 hours under reduced pressure (1 × 10 ^-3 Pa) to obtain an electrolytic copper sample (sample).

The electrolytic copper powder (sample) thus obtained was observed using a scanning electron microscope (SEM), and at least 90% of the copper powder particles had one main axis, and a plurality of branches from the main axis Or a dendritic phase grown diagonally at a three-dimensionally divergent angle.

(Examples 2 and 3)

In the alkali treatment of Example 1, the alkali treatment was performed by adding ammonia water until pH 11 was attained in Example 2 instead of adding the ammonium carbonate solution until pH 9 was reached, and in Example 3 , caustic soda was added until the pH was 14, and alkali treatment was carried out. Electrolytic copper (sample) was obtained in the same manner as in Example 1 except for this point.

The electrolytic copper powder (sample) thus obtained was observed using a scanning electron microscope (SEM), and at least 90% of the copper powder particles had one main axis, and a plurality of branches from the main axis Or a dendritic phase grown diagonally at a three-dimensionally divergent angle.

(Example 4)

9 sheets of an SUS negative electrode plate and an insoluble positive electrode plate (DSE (manufactured by Permeelec Electrode Co., Ltd.)) were placed in an electrolytic cell having a size of 2.5 m x 1.1 m x 1.5 m (about 4 m) And a copper sulfate solution as an electrolytic solution was circulated at 30 L / min. Then, a positive electrode and a negative electrode were immersed in this electrolytic solution, and a direct current was passed through the electrolytic solution to carry out electrolysis to deposit copper in powder form on the surface of the negative electrode .

At this time, electrolysis was carried out for 10 minutes by adjusting the Cu concentration of the circulating electrolytic solution to 5 g / l, the sulfuric acid (H ₂ SO ₄ ) concentration to 80 g / l and the chlorine concentration to 100 mg / l and the current density to 1200 A / . The pH of the solution at this time was 1.

The copper ion concentration of the electrolytic solution between the electrodes was always kept lower than the copper ion concentration of the electrolytic solution at the bottom of the electrolytic bath during electrolysis.

Then, the copper precipitated on the surface of the negative electrode was mechanically scraped off and recovered, and then washed to obtain a functional copper cake equivalent to 1 kg of copper. This cake was dispersed in 3 liters of water to prepare a slurry, and an ammonium carbonate solution was added until the pH became 9, followed by stirring to alkalize. Thereafter, the impurities were removed by washing with pure water.

Subsequently, 1 L of an aqueous solution of 10 g / L of industrial gelatin (Nitta gelatin shale) was added and stirred, followed by drying at 80 캜 for 6 hours under reduced pressure (1 × 10 ^-3 Pa) to obtain an electrolytic copper sample (sample).

The electrolytic copper powder (sample) thus obtained was observed using a scanning electron microscope (SEM), and at least 90% of the copper powder particles had one main axis, and a plurality of branches from the main axis Or a dendritic phase grown diagonally at a three-dimensionally divergent angle.

(Examples 5 and 6)

In the alkali treatment of Example 4, the alkali treatment was performed by adding ammonia water until pH 11 was attained in Example 5 instead of adding the ammonium carbonate solution until pH 9 was reached, and in Example 6 , caustic soda was added until the pH was 14, and alkali treatment was carried out. Electrolytic copper (sample) was obtained in the same manner as in Example 4 except for this point.

The electrolytic copper powder (sample) thus obtained was observed using a scanning electron microscope (SEM), and at least 90% of the copper powder particles had one main axis, and a plurality of branches from the main axis Or a dendritic phase grown diagonally at a three-dimensionally divergent angle.

(Example 7)

9 sheets of an SUS negative electrode plate and an insoluble positive electrode plate (DSE (manufactured by Permeelec Electrode Co., Ltd.)) were placed in an electrolytic cell having a size of 2.5 m x 1.1 m x 1.5 m (about 4 m) And a copper sulfate solution as an electrolytic solution was circulated at 30 L / min. Then, a positive electrode and a negative electrode were immersed in this electrolytic solution, and a direct current was passed through the electrolytic solution to carry out electrolysis to deposit copper in powder form on the surface of the negative electrode .

At this time, electrolysis was carried out for 10 minutes by adjusting the Cu concentration of the circulating electrolytic solution to 20 g / L, the sulfuric acid (H ₂ SO ₄ ) concentration to 80 g / L, the chlorine concentration to 20 mg / L, and the current density to 500 A / . The pH of the solution at this time was 1.

The copper ion concentration of the electrolytic solution between the electrodes was always kept lower than the copper ion concentration of the electrolytic solution at the bottom of the electrolytic bath during electrolysis.

Then, the copper precipitated on the surface of the negative electrode was mechanically scraped off and recovered, and then washed to obtain a functional copper cake equivalent to 1 kg of copper. This cake was dispersed in 3 liters of water to prepare a slurry, and an ammonium carbonate solution was added until the pH became 9, followed by stirring to alkalize. Thereafter, the impurities were removed by washing with pure water.

Subsequently, 1 L of an aqueous solution of 10 g / L of industrial gelatin (Nitta gelatin shale) was added and stirred, followed by drying at 80 캜 for 6 hours under reduced pressure (1 × 10 ^-3 Pa) to obtain an electrolytic copper sample (sample).

The electrolytic copper powder (sample) thus obtained was observed using a scanning electron microscope (SEM), and at least 90% of the copper powder particles had one main axis, and a plurality of branches from the main axis Or a dendritic phase grown diagonally at a three-dimensionally divergent angle.

(Examples 8 and 9)

In the alkali treatment of Example 4, instead of adding the ammonium carbonate solution until the pH of the solution became 9, an ammonium carbonate solution was added until pH 8.5 was reached in Example 8, In Example 9, an ammonium carbonate solution was added until the pH became 8.0, and alkali treatment was carried out. Electrolytic copper (sample) was obtained in the same manner as in Example 1 except for this point.

The electrolytic copper powder (sample) thus obtained was observed using a scanning electron microscope (SEM), and at least 90% of the copper powder particles had one main axis, and a plurality of branches from the main axis Or a dendritic phase grown diagonally at a three-dimensionally divergent angle.

(Comparative Example 1)

In Example 1, copper precipitated on the surface of the negative electrode was mechanically scraped off and recovered, and then washed to obtain a hydrous copper cake equivalent to 1 kg of copper. The cake was washed with pure water to remove impurities and then stirred with 1 l of an aqueous solution of 10 g / l of industrial gelatin (Nitta gelatin shale) and dried at 80 캜 for 6 hours in a reduced pressure state (1 × 10 ^-3 Pa) Electrolytic copper (sample) was obtained. The other points were produced in the same manner as in Example 1.

The electrolytic copper powder (sample) thus obtained was observed using a scanning electron microscope (SEM), and at least 90% of the copper powder particles had one main axis, and a plurality of branches from the main axis Or divergent phase that diverges diagonally and grows three-dimensionally.

(Comparative Example 2)

In Example 4, the copper precipitated on the surface of the negative electrode was mechanically scraped off and recovered, and then washed to obtain a functional copper cake equivalent to 1 kg of copper. The cake was washed with pure water to remove impurities and then stirred with 1 l of an aqueous solution of 10 g / l of industrial gelatin (Nitta gelatin shale) and dried at 80 캜 for 6 hours in a reduced pressure state (1 × 10 ^-3 Pa) Electrolytic copper (sample) was obtained. The other points were produced in the same manner as in Example 4.

The electrolytic copper powder (sample) thus obtained was observed using a scanning electron microscope (SEM). As a result, at least 90% of the copper powder particles had one main axis, and a plurality of branches were obliquely It was confirmed that the dendrite phase grown in three dimensions was branched.

= Evaluation method =

The copper powder (sample) obtained in the Examples and Comparative Examples was evaluated as follows.

&Lt; Observation of particle shape &

The shape of each of 500 particles was observed at an arbitrary 100 field of view with a scanning electron microscope (2,000 times), and the thickness a of the major axis ("main axis thickness a") and the length of the longest branch among the branches extending from the main axis b ("Branch length b"), and the number of branches ("branch number / long diameter L") with respect to the major axis of the main axis.

&Lt; Particle size measurement &

The measurement sample (copper content) was taken in a small amount of beaker, and 2 or 3 drops of a 3% Triton X solution (Kanto Kagaku Co., Ltd.) was added to the dispersion to obtain a 0.1% SN Dispersant 41 solution , And then dispersed for 2 minutes using an ultrasonic disperser TIP? 20 (manufactured by Nippon Seiki Seisakusho Co., Ltd.) to prepare a sample for measurement.

The measurement sample was measured for volume accumulation standard D50 using a laser diffraction scattering type particle size distribution analyzer MT3300 (manufactured by Nikkiso Co., Ltd.), and is shown in Table 1.

&Lt; Measurement of specific surface area &

The specific surface area was measured by a BET one-point method with a Mantecex Co., Ltd. monosubstrate and is shown in Table 1 as BET.

&Lt; Measurement of concentration of chlorine contained &

The copper content obtained in the examples and comparative examples was completely dissolved in nitric acid, and the chlorine concentration in the obtained solution was measured by a spectrophotometer to measure the concentration of contained chlorine.

&Lt; Measurement of oxygen concentration >

The copper (sample) obtained in the examples and comparative examples was heated and melted in a He atmosphere using "EMGA-820ST" manufactured by Horiba Seisakusho Shuzo Co., and the oxygen concentration (wt%) was measured.

&Lt; Measurement of powder pH &

The pH of the powder of the copper powder obtained in the Examples and Comparative Examples was measured in accordance with the measuring method prescribed in JIS K 5101-17-2.

&Lt; Silver coating evaluation &

25 kg of the electrolytic copper obtained in the examples and comparative examples were poured into 50 L of pure water kept at 50 캜 and stirred well. Separately, 9.0 liters of silver nitrate was added to 10 liters of pure water to prepare a silver nitrate solution. The silver nitrate solution was added to the solution in which the copper powder was previously dissolved. In this state, agitation was carried out for 2 hours to obtain a silver-coated copper powder slurry.

Next, after filtration of the silver-coated copper powder slurry by vacuum filtration, after the filtration, 1200 g of EDTA (ethylenediamine acetic acid) was dissolved in 12 l of pure water, and then the filtrate was washed with 6.0 l of pure water EDTA. Thereafter, it was dried at 120 DEG C for 3 hours to obtain silver-coated copper powder.

Then, the surface of the silver-coated copper powder thus obtained was observed with an Auger electron spectroscopic apparatus to evaluate whether or not the silver was covered with a uniform thickness. In this case, the case where silver was entirely coated and the case where the portion where the copper was exposed was not evaluated was evaluated as &quot; uniform &quot;, and the case where the portion where the copper was exposed and the copper was exposed was evaluated as &quot; .

&Lt; Evaluation of oxidative property &

The electrolytic copper powders obtained in Examples and Comparative Examples were evaluated for oxidative deterioration and corrosive deterioration by a high temperature and high humidity test at 85 ° C and 85RH% for 100 hours. Thus, it is possible to evaluate whether or not it is easily oxidized or corroded over time.

[Table 1]

(Review)

From the foregoing examples and comparative examples and the results of the tests conducted so far, it is possible to effectively suppress the adverse effect of the residual chlorine when the concentration of chlorine contained in the copper powder is 5 to 250 wtppm, and when the copper particles are coated with silver, It can be coated with one thickness.

It was also found that when the pH of the powder of the copper powder was 5 to 9, the deterioration of oxidation and deterioration of corrosion over time could be suppressed.

Claims (4)

A copper powder obtained by an electrolytic solution using an electrolytic solution containing chlorine and containing dendritic phase copper powder particles showing a dendrite phase,
The concentration of chlorine contained in the copper particle is from 30 to 250 wtppm and the pH of the copper measured according to JIS K 5101-17-2 is from 5 to 9 and the specific surface area measured by the BET 1 point method Is in the range of 0.40 to 1.50 m ² / g. The method according to claim 1,
And the oxygen concentration is 0.20 mass% or less. 3. The method according to claim 1 or 2,
Wherein the volume cumulative particle diameter D50 measured by the laser diffraction scattering type particle size distribution measuring apparatus is 3 mu m to 30 mu m. 3. The method according to claim 1 or 2,
When viewed from a copper particle by using a scanning electron microscope (SEM), shows a dendrites phase having one main axis, a plurality of branches branching obliquely from the main axis and grown two-dimensionally or three-dimensionally, The length a of the longest branch among the branches extending from the main axis is 0.8 to 12.0 mu m and the number of branches (the number of branches / Wherein the copper particles exhibiting a dendritic phase having a diameter of from 0.5 to 4.0 / μm are contained in at least 80% by number of the total copper particles.

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