JPH086130B2 - Method for producing copper powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for producing fine-grained copper powder used for copper paste and the like.

[Conventional technology]

Most of the copper powder used in the copper paste has a particle size of 1 μm to 10 μm, but the copper powder having a particle size of 1 μm or less is highly active, and when used in the copper paste and baked on the substrate, the chemistry at the interface with the substrate is high. The characteristic feature is that the adhesive strength is improved by the dynamic bonding, and a dense and high-quality copper electrode can be formed. In order to produce such fine copper powder, various production methods such as an electrolysis method, a spraying method, a gas reduction method, and a mechanical pulverization method have been conventionally known, but these methods are time-consuming to produce. ,
There are problems that impurities are easily mixed in and that the particles of the produced copper powder are large and the particle diameter is irregular.

In order to solve such a problem, the present applicant mixed a copper-containing solution containing copper carbonate with hydrazine or a hydrazine compound, and produced copper powder by reducing and precipitating the copper powder by heating the mixture. A method was proposed (Japanese Patent Publication No. 59-12723). According to this method, fine copper powder with high purity can be produced, and since copper powder is obtained by a liquid phase reaction, there is a feature that special equipment and advanced technology are not required and the production is simple.

[Problems to be Solved by the Invention]

However, when the copper powder is manufactured by the above method, as shown in FIG. 1, the average particle size of the copper powder is about 1 to 2 μm, and the particle size distribution width is 0.4 to 3 μm, and the variation in particle size is relatively large.
Further, there is a problem that it is difficult to obtain ultrafine particles of 1 μm or less.

Then, the 1st objective of this invention is to provide the manufacturing method of the copper powder which can obtain the ultrafine particle whose average particle diameter is 1 micrometer or less.

A second object is to provide a method for producing a copper powder with a small variation in particle size.

[Means for solving the problem]

In order to achieve the above object, the invention according to claim 1 comprises the steps of mixing a copper-containing solution containing copper pyrophosphate with hydrazine or a hydrazine compound, and heating the mixture solution to 20 to 150 ° C. And a step of reducing and precipitating the copper powder, the method comprising the steps of:

Further, the invention according to claim 2 is a step of mixing a copper-containing solution containing copper formate with hydrazine or a hydrazine compound, and a step of heating the mixed solution to 20 to 150 ° C. to reduce and precipitate copper powder. And a method for producing a copper powder containing

[Action]

In the invention according to claim 1, when copper pyrophosphate is used as the copper salt, and hydrazine or a hydrazine compound which is a reducing agent is mixed with this aqueous solution and heat-treated, copper in the copper salt is reduced and precipitated, and copper carbonate is removed. Ultrafine copper powder having a smaller particle size than that used and having an average particle size of 1 μm or less is obtained.

The proper temperature for the heat treatment is in the range of 20 ° C to 150 ° C.
The reason is that if the temperature is lower than 20 ° C., the reduction precipitation of the copper powder is insufficient, and if the temperature exceeds 150 ° C., the particle size of the copper powder reduced and precipitated is large, and the variation in the particle size becomes large.

The heating time is not particularly limited, but is preferably 2 hours or more at which copper pyrophosphate in the mixed solution almost completes the reaction.

Examples of the hydrazine or the hydrazine compound include hydrazine itself, hydrazine hydrate, hydrazine hydrate, hydrazine sulfate, hydrazonium sulfate, and hydrazonium chloride.

As for the mixing ratio of copper pyrophosphate and hydrazine or a hydrazine compound, for example, when hydrazine hydrate is used as the hydrazine compound, 1 to 15 moles of hydrazine hydrate are suitable with respect to 1 mole of copper pyrophosphate. The reason is that if it is less than 1 mol, the reaction rate is slow and it is not suitable for mass production, and if it exceeds 15 mol, copper powder in the form of fine particles in yield and particle size cannot be obtained.

Further, in the invention described in claim 2, copper formate is used as the copper salt, and the particle size of the precipitated copper powder is larger than that when copper carbonate is used, but the particle size distribution width is small and homogeneous copper powder. Is obtained. The conditions such as the heating temperature, the heating time, and the mixing ratio are the same as those of the invention described in claim 1.

〔Example〕

-First Example- 250 g of copper pyrophosphate was dissolved in 3000 cc of water, and hydrazine hydrate was added thereto and mixed. Then mix this mixture with 100
A precipitate powder was obtained after heating at ℃ for 3 hours. This one
The solution was left standing for cooling for a while, the solution was filtered at room temperature using a glass filter, washed with water of PH7, washed with acetone and dried.

The particle size of the copper powder obtained in this way is ultrafine particles with an average particle size of about 0.6 μm as shown in Fig. 1, is a spherical powder with little aggregation and good dispersibility, and is highly pure with almost no impurities. It was the one.

This copper powder is mixed with glass frit and organic varnish to form a copper paste, and is also used as a fine powder additive to the paste. Since the above copper powder has good dispersibility, it was uniformly mixed with the glass frit and the organic varnish to obtain a homogeneous paste. This paste is printed and applied on a ceramic substrate or the like, and then baked in a non-oxidizing atmosphere such as nitrogen. The electrodes and circuit patterns obtained in this way had good solderability and sufficient adhesive strength, and a thick film circuit with high reliability could be obtained.

-Second Example- 350 g of copper formate was dissolved in 3000 cc of water, and hydrazine hydrate was added thereto and mixed. This mixture is then mixed at 100 ° C for 3
Upon heating for hours, a precipitated powder was obtained. This was left to stand for 1 hour to cool, the liquid was filtered at room temperature using a glass filter, washed with water of PH7, washed with acetone and dried.

The obtained copper powder is in the form of fine particles having a maximum particle size of 5 μm as shown in FIG. 1 and has a particle size larger than that of copper powder using copper carbonate, but has a particle size distribution width of 3 to 8 μm, which results in variation in particle size. Is small and homogeneous. Moreover, it was a spherical powder with small aggregation, good dispersibility, and high purity containing almost no impurities. This copper powder was also used as a copper paste or a fine powder additive to the paste in the same manner as described above, and the conductive coating baked on this had good solderability and adhesive strength.

〔The invention's effect〕

As is clear from the above description, according to the invention of claim 1, since copper powder is obtained by the wet reduction method using copper pyrophosphate and hydrazine or a hydrazine compound, copper carbonate is used. It is possible to easily obtain a spherical copper powder having small particles and good dispersibility as compared with the case.

Further, in the invention according to claim 2, since copper powder is obtained by a wet reduction method using copper formate and hydrazine or a hydrazine compound, the particle size is slightly larger than copper carbonate, but the particle size distribution width. It is possible to obtain a homogeneous copper powder having a small size.

[Brief description of drawings]

FIG. 1 is a particle size distribution chart of a copper powder using copper pyrophosphate and copper formate according to the present invention and a copper powder using conventional copper carbonate.

Claims (2)

[Claims] 1. A step of mixing a copper-containing solution containing copper pyrophosphate with hydrazine or a hydrazine compound; and a step of heating the mixed solution at 20 to 150 ° C. to reduce and precipitate copper powder. Powder manufacturing method. 2. A copper powder comprising: a step of mixing a copper-containing solution containing copper formate with hydrazine or a hydrazine compound; and a step of heating the mixed solution to 20 to 150 ° C. to reduce and precipitate the copper powder. Manufacturing method.