JPH0610014A - Production of copper fine powder - Google Patents

Abstract

PURPOSE:To obtain the spherical copper powder having narrow width of grain sizes distribution and prescribed grain sizes by reducing copper compd. by hydrazine in the aq. soln. containing acetic acid. CONSTITUTION:Copper compd. (e.g. copper oxide, copper carbonate, copper acetate, copper sulfate, etc.) is suspended or dissolved in the aq. soln. containing acetic acid. Hydrazine (e.g. hydrazine hydrate, hydrazine sulfate, hydrazine soln. containing compd. anhydride) is added to the aq. soln. containing copper compd. and the copper compd. is reduced. Then, the spherical copper powder which has narrow width of grain sizes distribution for example 2.3mum average grain sizes and 100% of its are in 1-10mum grain sizes range is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine copper powder by a wet method, and more particularly to a method for producing spherical fine copper powder having a narrow particle size distribution width and a controlled good particle size.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed as methods for obtaining fine copper powder. The method for producing fine copper powder having an average particle size in the particle size range of about 10 μm or less, which is relevant to the present invention, includes atomizing molten copper, electrolytic deposition on a cathode, and mechanically There are methods such as crushing. However, in all of these conventional methods, the average particle size is as large as 10 μm or more, and fine powder of 10 μm or less can be obtained only after some sort of classification operation after production, which also has a wide particle size distribution and is difficult to control the particle size. There is a problem that is.

Further, a so-called gas evaporation method in which copper is forcibly evaporated in an inert gas, a plasma flame method in which copper coarse powder is blown into a plasma flame to volatilize and agglomerate, and a so-called arc plasma in a hydrogen-rich gas is used. Conventional methods such as the hydrogen plasma method and the method of adding sodium borohydride to a copper ion solution to reduce and precipitate ultrafine copper powder (JP-A-58-224103) have a small average particle diameter of usually 0.1 μm or less. ,
It is bulky, has a large specific surface area, is easily oxidized, and has the drawbacks of expensive equipment and poor mass productivity.

On the other hand, although it is known that copper ions are reduced with hydrazine or a hydrazine compound and deposited as metallic copper (New Experimental Chemistry Lecture 8 “Synthesis of Inorganic Compounds (1)”, Tokyo Kagaku Dojin), these According to the method of reducing copper ions with hydrazine (compound), fine copper powder can be obtained, but the particle size distribution is wide, the shape is irregular, and it is difficult to control the particle size, and copper powder of constant quality is obtained. It has the drawback of being difficult.

Among them, in the method of reducing and precipitating from a solution of copper carbonate with hydrazine (Japanese Patent Publication No. 59-12723), spherical copper powder can be obtained, but it has a drawback that the particle size distribution is wide due to aggregation. There is also a method of adding a surfactant to a solution of copper sulfate and reducing and precipitating with hydrazine to obtain monodispersed copper fine powder (JP-A-62-77407).
other). However, since the surfactant inhibits the growth of the deposited copper powder, it is difficult to obtain copper powder having a large particle size, and the average particle size is 2
In order to obtain copper powder of μm or more, it is necessary to suppress the addition amount of the surfactant, and as a result, a certain amount of aggregation cannot be avoided,
It has the drawback that the particle size distribution is also quite wide.

The present invention solves the above-mentioned problems of the conventional method and provides a method for producing spherical copper fine powder which can be easily controlled to an appropriate particle size of about 1 to 10 μm and has a small particle size distribution width. The purpose is to provide.

[0007]

The method of the present invention is to reduce a copper compound with hydrazine in an aqueous solution containing acetic acid, thereby solving the above-mentioned problems.

Although the process of the reduction reaction in the present invention has not been clearly clarified, the present inventors have found that acetic acid acts as a kind of surfactant and at the same time, a copper complex compound is deposited on the copper surface. It is speculated that a spherical and monodispersed copper powder is obtained by the reduction. The particle size of the copper powder can be controlled by adjusting the reduction temperature, the amount of hydrazine added, and the like.

As the copper compound, any of copper oxide, cuprous oxide, copper carbonate, copper acetate, copper sulfate, copper nitrate and the like can be used, but a salt with a strong acid such as copper sulfate and copper nitrate is used. In comparison with those using copper oxide, cuprous oxide, copper carbonate, and copper acetate, has a lower PH during reduction, slows down the reduction reaction, and becomes a copper powder with a large particle size. Examples of hydrazine include hydrazine hydrate, anhydrous hydrazine, and hydrazine sulfate.These hydrazines are usually added to an aqueous solution containing acetic acid.
Add about 1 to 3 times the equivalent of the theoretical amount required for copper powder production.
The reaction is usually carried out at a reducing temperature of 40 to 90 ° C. for 1 to 48 hours.

Thus, according to the present invention, a spherical monodispersed copper powder having an average particle size of 1 to 10 μm having a small particle size distribution width can be obtained. When the particle size of the copper powder is smaller than 1 μm, when it is made into a paste, the agglomeration becomes intense, the screen is clogged, the wicking property becomes large, the leveling becomes poor, and the printed surface becomes not smooth. Conversely 10
If it is larger than μm, a dense film cannot be formed and the conductive circuit becomes unstable.

[0011]

Example 1 600 g of copper oxide was suspended in 4 liters of water and 500 g of acetic acid, 300 g of hydrazine hydrate was added, and the suspension was heated at 90 ° C. for 4 hours.
Reacted for hours. As a result, the average particle size is 2.4 μm,
A spherical copper powder having a small particle size distribution width in which 100% of the particle size distribution was 1 to 10 μm was obtained.

[0012]

Example 2 540 g of copper oxide was suspended in 4 liters of water and 500 g of acetic acid, 280 g of hydrazine hydrate was added, and the suspension was heated at 90 ° C. for 8 hours.
Reacted for hours. As a result, the average particle size was 2.9 μm,
A spherical copper powder having a small particle size distribution width in which 100% of the particle size distribution was 1 to 10 μm was obtained.

[0013]

Example 3 930 g of copper carbonate was suspended in 4 liters of water and 500 g of acetic acid, 300 g of hydrazine hydrate was added, and the suspension was heated at 90 ° C. for 4 hours.
Reacted for hours. As a result, the average particle size is 2.3 μm,
A spherical copper powder having a small particle size distribution width in which 100% of the particle size distribution was 1 to 10 μm was obtained.

[0014]

EXAMPLE 4 2 kg of copper sulfate pentahydrate was suspended in 2.5 l of water and 500 g of acetic acid, and 350 g of hydrazine hydrate was added,
The reaction was carried out at 90 ° C for 48 hours. As a result, spherical copper powder having an average particle size of 6.3 μm and a small particle size distribution width of 90% in a particle size distribution of 1 to 10 μm was obtained.

[0015]

Comparative Example 1 2 kg of copper sulfate pentahydrate was dissolved in 5 l of water. Next, add 350 g of hydrazine hydrate,
The reaction was carried out for 8 hours. As a result, a copper powder having an average particle size of 8.5 μm and a large particle size distribution width of 30% in a particle size distribution of 1 to 10 μm was obtained.

[0016]

Comparative Example 2 1350 g of copper carbonate was suspended in 4 liters of water, 300 g of hydrazine hydrate was added, and the mixture was reacted at 90 ° C. for 4 hours. As a result, a copper powder having a wide particle size distribution with an average particle size of 2.8 μm and 40% in the particle size distribution of 1 to 10 μm was obtained.

[0017]

Comparative Example 3 2 kg of copper sulfate pentahydrate was dissolved in 5 l of water,
A copper sulfate aqueous solution was used. Surfactant C is added to this copper sulfate aqueous solution.
2.0 g of ₁₀ H ₂₁ NHCH ₂ COONa was added. Next, 350 g of hydrazine hydrate was added and reacted at 90 ° C. for 48 hours. As a result, a copper powder having an average particle size of 2.6 μm and a particle size distribution of 70% in 1 to 10 μm and having a wide particle size distribution width was obtained.

[0018]

Comparative Example 4 2 kg of copper sulfate pentahydrate was dissolved in 5 l of water,
Add 130 g of sodium borohydride and add 4 at 90 ° C.
Reacted for hours. As a result, the particle size of the obtained copper powder was 0.
It was 1 μm or less.

[0019]

As described above, according to the present invention,
Spherical copper fine powder having a very small particle size distribution range can be obtained, which can be easily controlled to an appropriate particle size of about 1 to 10 μm.
Copper fine powder that can be widely used for various purposes including screen printing can be produced at low cost.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Ushijima 2-8-2 Hikoshima Nishiyama-cho, Shimonoseki City, Yamaguchi Prefecture

Claims (1)

[Claims] 1. A method for producing a fine copper powder, which comprises reducing a copper compound with hydrazine in an aqueous solution containing acetic acid.