JPH0553873B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a metal plating method using a silver hydrosol, and more specifically, a metal plating method using a silver hydrosol to impart silver colloid to a plated object. rear,
The present invention relates to a metal plating method that makes it possible to form a uniform and strong metal plating film by chemical plating using applied silver colloid as a catalyst.

The main applications of the metal plating method according to the present invention are printed wiring boards, conductive materials, and the like.

[Conventional technology]

Fiber compositions such as paper and nonwoven fabrics, glass, ceramics, and plastics are originally insulators, but because they are lighter and cheaper than metal materials, they can be processed in various ways to add various metals. By doing so, it is possible to impart electrical properties such as conductivity.

Conventionally, methods described in US Pat. No. 2,702,253 and US Pat. No. 3,011,920 are known as methods for applying metal to these insulators.

The method described in U.S. Patent No. 2,702,253 involves immersing the plated object in a strongly acidic stannous chloride solution, washing it with water, and then immersing it in a strongly acidic palladium chloride solution. In this method, palladium is deposited on the surface of an object, and the object is further immersed in a chemical plating solution containing a raw metal salt and a reducing agent, thereby chemically plating the object using the palladium as a catalyst.

The method described in U.S. Patent No. 3,011,920 involves applying the colloid to the surface of the plated object by immersing the object in a strongly acidic palladium-tin colloid solution, and then treating the surface with acid or alkali. In this method, the catalytic activity is developed, and then chemical plating is carried out.

[Problem that the invention seeks to solve]

In the previously known chemical plating method mentioned above, palladium is used as a catalyst, but palladium is a fairly expensive metal and therefore accounts for a large portion of the manufacturing cost. Further, in the conventional method, in order to apply the catalyst, at least two stages of treatment are required, making the process extremely complicated. Furthermore, since the solution used is strongly acidic, there are other problems such as the coated object being easily damaged.

[Means for solving problems]

The present inventor conducted various studies in search of a method that uses a metal that is cheaper than palladium as a catalyst and also allows the application of the catalyst to be carried out in a single step in an almost neutral solution. The present invention was achieved by paying attention to the use of silver, which is a significantly inexpensive metal, as a catalyst.

One or two selected from cationic surfactants, anionic surfactants, nonionic surfactants, and water-soluble polymers are added to the plated material with 0.1 to 5 mmol/aqueous silver salt solution. After contacting a silver hydrosol obtained by reduction treatment with a reducing agent of 2 to 4 times the molar amount of the silver salt in a state containing 0.005 to 0.1% of the above to impart silver colloid, the activity of the silver colloid is A metal plating method characterized by immersion in a chemical plating solution of any one of a chemical copper plating solution, a chemical silver plating solution, and a chemical cobalt plating solution without performing a chemical treatment.

[Effect]

First, the most important point in the present invention is the use of silver colloid as a catalyst for chemical plating, and silver hydrosol is used to provide this.

In the present invention, the silver hydrosol used is neutral to weakly alkaline, and its dispersion state is stable and remains uniform for a long period of time, and the catalytic activity does not decrease. Furthermore, since the contained silver colloid is fine and uniform, silver colloid can be uniformly and firmly applied to the surface of the object to be plated with a single step of immersion in the silver hydrosol. It is capable of uniformly and strongly chemically plating the surface of a plated object.

Next, various conditions for implementing the method of the present invention will be described.

The silver hydrosol in the method of the present invention can be prepared by the following method.

In other words, a neutral to weakly alkaline silver hydrosol that is stable, maintains a uniform dispersion state over a long period of time, and does not reduce catalytic activity is produced by mixing an aqueous solution of a silver salt in the presence of a surfactant and/or a water-soluble polymer. It can be obtained by a method of reducing to (for example, JP-A-59-120249).

Examples of aqueous solutions of silver salts include aqueous solutions of silver () salts,
For example, an aqueous solution of silver nitrate () or silver cyanide () potassium is used, and the concentration in the aqueous solution is
Preferably 0.1 to 5 mmol/.

The reduction treatment can be carried out by a known method using a reducing agent.
In addition to alkali metal borohydride salts such as sodium borohydride and potassium borohydride, boron-based reducing agents such as dimethylamine borane, phosphorus-based reducing agents such as sodium hypophosphite, formaldehyde, hydrazine, and the like are used. The amount of the reducing agent is preferably at least equimolar to the raw material silver salt,
2 to 4 times the molar amount is used.

Examples of surfactants and water-soluble polymers include cationic surfactants such as stearyltrimethylammonium chloride, anionic surfactants such as sodium dodecylbenzenesulfonate, and polyethylene glycol mono-p-nonyl phenyl ether. Nonionic surfactants and water-soluble polymers such as polyvinyl alcohol and polyvinylpyrrolidone can be used. When used, these surfactants and water-soluble polymers can be used alone or in combination of two or more. The concentration of surfactant and water-soluble polymer used is in the range of 0.005 to 0.1.

Chemical plating in the present invention can be performed by a conventional method. That is, in a solution containing metal ions and a reducing agent, the metal ions are reduced in the silver colloid, thereby precipitating the metal.

The metal ion solution for chemical plating in the present invention includes neutral or weakly alkaline copper ions that are commonly used to impart electrical properties;
Solutions of silver or cobalt ions can be used.

As the reducing agent for chemical plating in the present invention, sodium hypophosphite, formaldehyde, etc. can be used.

The objects to be coated in the present invention include fiber molded articles such as paper and nonwoven fabrics, glass, ceramics, plastics, metals, and metal oxides.

The means for applying the silver colloid in the silver hydrosol to the plated object is the method usually used when applying a catalyst for metal plating, that is, the method of immersing the plated object in silver hydrosol, or the method of applying silver colloid to the plated object. A method is used in which the hydrosol is applied to the coated object and then dried.

〔Example〕

Next, the present invention will be explained by examples.

In addition, the surface resistance values in the examples are those of Mitsubishi Yuka Co., Ltd.
This was measured using a manufactured MCP-TESTER.

The adhesion of the plating was examined by strongly pasting Scotch Mending Tape (Sumitomo 3M Ltd.) onto the plated object and peeling it off one hour after the completion of plating.

Example 1 While vigorously stirring a solution of 50 μmol of silver nitrate () dissolved in 94 ml of pure water, 1 ml of an aqueous solution containing 10 mg of stearyltrimethylammonium chloride and 5 ml of an aqueous solution containing 200 μmol of sodium borohydride were sequentially poured into the solution. A homogeneous transparent silver hydrosol with a pH of 9.6 and a sudden change in color to yellowish brown.
100ml was obtained.

Next, a piece of paper (5 cm x 5 cm square, manufactured by Toyo Paper Co., Ltd., No. 5A) was immersed in the above silver hydrosol for 1 hour and then washed with water. At this time, the paper piece was colored yellow by the adsorbed silver colloid.

Separately, 170g of Lotusel salt, sodium hydroxide
50g, copper sulfate 35g, sodium carbonate 30g and
20 g of EDTA was dissolved in pure water to obtain a solution of 1, and 1/5 volume of a 37% formaldehyde aqueous solution was added and mixed with stirring to obtain a chemical copper plating solution.

The piece of paper coated with the silver colloid was immersed in this chemical copper plating solution for 5 minutes, washed with water, and dried to obtain a piece of paper with copper metallic luster. The weight of copper applied by plating was 24% relative to the starting paper strip.

When mending tape was strongly applied to this piece of paper and peeled off, the copper coating did not come off. Also, the surface resistance of a copper-plated piece of paper is 0.10Ω/
It was □.

Example 2 A homogeneous transparent silver hydrosol was prepared in the same manner as in Example 1, except that sodium dodecylbenzenesulfonate was used instead of the surfactant stearyltrimethylammonium chloride.

Next, a cotton cloth (4 cm x 4 cm square) was immersed in the above silver hydrosol for 1 hour and then washed with water. At this time, the cotton cloth was colored yellow by the adsorbed silver colloid.

Subsequently, the cotton cloth coated with silver colloid was immersed in the chemical copper plating solution obtained in Example 1 for 5 minutes, washed with water, and dried to obtain a cotton cloth with copper metallic luster. Obtained. The weight of copper applied by plating was 28% based on the starting cotton fabric.

When mending tape was strongly applied to this cotton cloth and peeled off, the copper coating did not come off. In addition, the surface resistance of copper-plated cotton cloth is 0.32Ω/
It was □.

Example 3 A homogeneous transparent silver hydrosol was prepared in the same manner as in Example 1, except that polyethylene glycol-p-nonylphenyl ether was used instead of the surfactant stearyltrimethylammonium chloride.

Next, limestone powder (manufactured by Diamond Catalyst Co., Ltd.)
100 to 200 mesh) was immersed in the above silver hydrosol for 1 hour and then washed with water. At this time, the limestone powder was colored yellow by the adsorbed silver colloid.

Subsequently, 50% of the limestone powder to which the silver colloid was added was added to the chemical copper plating solution obtained in Example 1.
After being immersed for a minute, it was washed with water and dried to obtain limestone powder with copper metallic luster.

Example 4 The same method as in Example 1 was used except that 1 ml of an aqueous solution containing 5 mg of sodium dodecylbenzenesulfonate and 5 mg of polyethylene glycol-p-nonylphenyl ether was used instead of the surfactant stearyltrimethylammonium chloride. A homogeneous transparent silver hydrosol was prepared.

Next, the above silver hydrosol was applied to a piece of paper (5 cm x 5 cm square, No. 5A manufactured by Toyo Paper Co., Ltd.) using a painter's brush.

Separately, 0.03 mol of cobalt sulfate () heptahydrate,
Dissolve 0.25 mol of sodium hypophosphite, 0.5 mol of sodium tartrate dihydrate, and 0.50 mol of boric acid in pure water to make 1, and add 3.3 mol/aqueous sodium hydroxide solution to make pH=9. It was prepared as a chemical cobalt plating solution.

The piece of paper to which the silver colloid was applied was immersed in this chemical cobalt plating solution for 20 minutes, washed with water, and dried to obtain a piece of paper with cobalt metallic luster.

When mending tape was strongly applied to this piece of paper and pulled off, the cobalt film did not peel off. The surface resistance of the cobalt-plated paper piece was 12Ω/□.

Example 5 A homogeneous transparent silver hydrosol was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone, a water-soluble polymer, was used instead of stearyltrimethylammonium chloride, a surfactant.

Next, a silk cloth (5 cm x 5 cm) was immersed in the above silver hydrosol for 1 hour and then washed with water. At this time, the silk cloth was colored yellow by the adsorbed silver colloid.

Separately, 28% ammonia water was added to an aqueous solution containing 20 g of silver nitrate () until the solution became colorless and transparent, and then pure water was added to make a silver aqueous solution of 1. Meanwhile, 100 g of potassium sodium tartrate tetrahydrate was added.
A reducing solution was prepared by dissolving it in 700 ml, and equal volumes of the silver aqueous solution and reducing solution were mixed to prepare a chemical silver plating solution.

The silk cloth coated with the silver colloid was immersed in this chemical silver plating solution for 60 minutes, washed with water, and dried to obtain a silk cloth with silver metallic luster.

The weight of silver applied by plating was 25% based on the starting silk fabric.

When mending tape was strongly applied to this silk cloth and peeled off, the silver coating did not come off. Also,
The surface resistance of the silver-plated silk cloth was 0.02Ω/□.

〔Effect of the invention〕

In the metal plating method according to the present invention, as shown in the above-mentioned examples, the silver hydrosol used is neutral or weakly alkaline, so even the object to be plated, which is sensitive to acids, will not be damaged. Moreover, since the silver colloid contained in the silver hydrosol is fine and uniform, the silver colloid serving as a catalyst can be firmly applied to the plated object, resulting in a metal plating film with good adhesion. It can be easily formed on the surface of a plated object.

Claims (1)

[Claims] 1. Apply 0.1 to 5 mmol of silver salt aqueous solution to the object to be coated with one or two selected from cationic surfactants, anionic surfactants, nonionic surfactants, and water-soluble polymers. After contacting a silver hydrosol obtained by reduction treatment with a reducing agent 2 to 4 times the molar amount of silver salt in a state containing 0.005 to 0.1% of silver salt or more to impart silver colloid, the activity of the silver is determined. A metal plating method characterized by immersion in a chemical plating solution of any one of a chemical copper plating solution, a chemical silver plating solution, and a chemical cobalt plating solution without performing a chemical treatment.