JPS6017432B2 - Manufacturing method of ultrafine gold-silica composite powder - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing ultrafine gold-silica composite powder.

Surface coating agents and surface coating agents made of composites containing gold powder, such as gold paste and gold powder, are widely used in the ceramics industry, electronics industry, etc., due to their excellent conductivity and corrosion resistance. It is expected to have a wide range of uses.

In particular, there is a strong desire to easily obtain fine gold particles for pastes used in fine printed wiring, which require stability over many years. In addition, when baking gold, a chloroauric acid solution is often applied together with a binder and phosphoroused in a reducing atmosphere. Application of paste is desired.

Conventionally, gold powder has been produced by a precipitation method in which a reducing agent is added to an aqueous solution of chloroauric acid, a thermal spraying method, a pulverization method, etc. However, in the precipitation method, the particle size is increased by 1 mm or more for grain growth. However, the latter physical and mechanical methods can only yield particles of 10 μm or more due to the malleability and surface tension of gold.

With gold paste using these gold particles, even if you try to obtain thin printed wiring with less than 20 threads, the lines will not be continuous, so the 10-3 to 10-
It was difficult to obtain a specific resistance of less than 50%. The present inventors have previously discovered that when so-called hydrophobized ultrafine silica particles are mixed with water, they form a free-flowing powder (referred to as dry water) that surrounds minute water droplets and contains water up to about one times its own weight. Focusing on the fact that silver nitrate aqueous solution was used instead of water, we obtained silver nitrate dry water powder, and by heating and reducing it, we discovered that ultrafine particle silver-silica composite powder could be obtained, and developed a method for its production. A patent application was filed (Samurai Gansho 55-1069029). As a result of further research, the present inventors completed the present invention by confirming that ultrafine gold-silica composite powder could be obtained by a similar method.

According to the present invention, hydrophobized ultrafine silica and a chloroauric acid aqueous solution are mixed, and the mixture is mixed with hydrogen-containing 100-1
Provided is a method for producing ultrafine gold-silica composite powder, which is characterized by placing the powder in a heated atmosphere at 000°C.

In the method of the present invention, the hydrophobized ultrafine silica refers to ultrafine silica obtained by hydrolyzing halogenated silane in an oxyhydrogen flame as disclosed in Japanese Patent Publication No. 36, General 53, Hakama Seki, 48-3579. Organic groups (alkyl groups) are bonded to the surface of the ultrafine powdered silica by treating silica with an organosilicon compound by the method disclosed in Hakamako Sho 41-17049 and Special Publication Sho 15799. .

In the method of the present invention, if the hydrogen reduction temperature is less than 100%, water volatilization will not be sufficient, and if it exceeds 1000%, the gold fine particles will phosphorize and grow.
A temperature range of qo is required.

The hydrogen concentration during hydrogen reduction does not need to be particularly specified, but usually 5% (by volume) or more is industrially significant, and the diluting gas is preferably an inert gas such as nitrogen, argon, or helium.

The concentration of the chloroauric acid aqueous solution can be freely selected depending on the expected gold content in the final product, but if it is less than 1% (by weight), the gold concentration in the final composite powder will be low. So I don't like it.

If it exceeds 10% (by weight), the fine gold powder will grow and coarse particles will be mixed in, so a range of 1 to 10% (by weight) is preferable.

Although the amount of free hydrochloric acid in the chloroauric acid aqueous solution is not specified, it is desirable that the amount is small. If the weight of the chloroauric acid aqueous solution is 0.1 weight per hydrophobized ultrafine silica, the proportion of ultrafine silica that does not contribute to inclusion of water droplets will increase, resulting in the final inclusion of fine gold particles in the silica. The amount will be small and it will be impractical.

Moreover, if it exceeds 10, the amount of silica will not be sufficient to enclose water droplets, and when the mixture is shaken and malted, it will become milky and cannot be handled as a powder, so it needs to be 10 or less. In order for the fired product of the ultrafine gold-silica composite powder, which is the product of the method of the present invention, to have a chamfer conductivity that can be used as wiring, the ratio of metallic gold to silica must be at least about 10% or more. Therefore, in the method of the present invention, the base content of chloroauric acid must be 15% (by weight) or more based on the hydrophobized ultrafine silica.

However, since the product of the method of the invention is not only used as a wiring material, the above conditions are not essential.

The ultrafine gold-silica composite powder obtained by the method of the present invention has a spherical shape of 1 m diameter when observed under a microscope, and a pattern of metallic gold crystals is observed by X-ray diffraction. Also X
Since the powder is such that gold and silica cannot be distinguished at all by line microanalyzer and Auger electron spectrometry, it is understood that it is a composite of fine gold particles and ultrafine silica. When this composite powder is made into a paste according to a conventional method and applied to a substrate, a uniform, corrosion-resistant, gold-colored coating is formed, exhibiting the desired fin-guiding properties. In this case, the coexisting ultrafine silica is one of the substances that can usually be added as a binder, and not only does it not impair the performance of the gold particles, but it also contributes to the bonding of the gold particles to the base material. . Examples of the present invention will be shown below. Example 1 100 parts of hydrophobized ultrafine silica (obtained by the method of Samurai Publication No. 41-1704) was mixed with 200 parts of an aqueous solution of chloroauric acid having a concentration of 9% (by weight), and the mixture was mixed with a shaker. It rang out beautifully.

The obtained fluid powder was placed in a tubular electric furnace and heated with 10% hydrogen.
When the powder was heated to 80 and 0 mm while passing through nitrogen gas containing 10 mm, an ultrafine gold-silica composite powder containing 15% gold (by weight) and having a specific surface area of 100 mm was obtained. It was done. (Refer to the attached drawing) After preparing a bait by mixing 13 parts of this powder, 13 parts of glycerin, 12 parts of low-melting glass powder, and 10 parts of benzyl alcohol, the smoothness of 2
I made a frame with cellophane tape on a glass plate and applied the paste with an applicator.

After preheating it to about 150℃ in a dryer, put it in a furnace for 5 minutes.
After standing next to each other for 60 minutes at 0 pm, the specific resistance of the resulting Akatsuki compact was 8 x 10-40. Example 2 Hydrophobized ultrafine silica (Special Publication No. 48-15799)
100 saw concentration 1.5% (obtained by the method of No.
800 g of an aqueous solution of chloroauric acid (weight) was mixed and the mixture was vigorously shaken using a shaker.

The obtained fluid powder was placed in a fluidized bed vertical tubular electric furnace.
When heated to 200qC while passing hydrogen, gold 1
An ultrafine gold-silica composite powder having a specific surface area of 120 m/m and containing 1% (by weight) was obtained.
65 parts of this powder, 13 parts of taglycerin, 12 parts of low melting point glass powder
After preparing a paste by mixing 10 parts of benzyl alcohol, the resistivity was measured under the same conditions as in Example 1 and found to be 1 x 10-30.

Example 3 Hydrophobized ultrafine silica (obtained by the method of Jiko Sho 41-17049) 100 saws, 6
% (by weight) of an aqueous solution of chloroauric acid was mixed and vigorously shaken in an Aya Liao machine.

The obtained fluid powder was placed in a fluidized bed vertical tubular electric furnace and heated to 40°C while hydrogen was passed through it.
．． An ultrafine gold-silica composite powder containing 2% (by weight), a specific surface area of 200 m/m, and a particle size of about 5 m was obtained. Example 4 Hydrophobized ultrafine silica (Hakama Koukai 48-15799
100 saws, 3% (by weight) obtained by the method of No.
200 g of an aqueous chloroauric acid solution was mixed and the mixture was vigorously shaken using a shaker.

The obtained fluid powder was placed in a tubular electric furnace and heated to 600°C while hydrogen was passed through it, resulting in approximately 5.7% gold content.
(weight), specific surface area is 150〆/unit, particle size is about 6
Ultrafine gold-silica composite powder was obtained. Brief Description of the Drawings The attached drawings are traces of the X-ray diffraction chart of the ultrafine gold-silica composite powder obtained in Example 1.

Claims (1)

[Claims] 1. An ultrafine gold-silica composite characterized by mixing hydrophobized ultrafine silica and an aqueous chloroauric acid solution and placing the mixture in a heated atmosphere containing hydrogen at 100 to 1000°C. Powder manufacturing method. 2. The method according to claim 1, which uses an aqueous chloroauric acid solution having a concentration of 1 to 10% (by weight). 3. The manufacturing method according to claim 1 or 2, wherein ultrafine silica and chloroauric acid aqueous solution are mixed in a ratio of 10:1.
A method of mixing at a weight ratio of ~1:10. 4. The method according to any one of claims 1 to 3, wherein the ratio of the amount of chloroauric acid to the amount of hydrophobized ultrafine silica is 15% or more by weight.