JPS60141875A - Sensitizing solution for electroless plating - Google Patents

Abstract

PURPOSE:To obtain a sensitizing soln. having superior stability by adding thiourea, pyrogallol or hydroquinone to an aqueous soln. contg. stannous chloride and hydrochloric acid as a sensitizing soln. for electroless plating. CONSTITUTION:This sensitizing soln. for electroless plating contains SnCl2 hydrochloric acid and one or more among thiourea, pyrogallol and hydroquinone or further contains metallic tin. The stability of the sensitizing soln. is improved by one or more among thiourea, pyrogallol and hydroquinone, and the stability is further improved by the reducing compounds combined with metallic tin. When powder or granules are sensitized with the sensitizing soln., the components in the soln. are not decomposed, and the sensitized powder or granules are easily separated from the soln. by filtration with a filter. The sensitized powder or granules are washed with water and separated from the water by filtration with a filter. At this time, the filter is not clogged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to sensitization, which is performed as a pretreatment for plating to adhere a catalytic substance to the surface of powder or granules when metal coating is performed by electroless plating.

This invention relates to improving the stability of a sensitizing solution during an activation process.

Conventionally, in electroless plating, the object to be plated is sensitized with an aqueous solution of stannous chloride and hydrochloric acid, washed with water, then activated with an aqueous solution of palladium chloride and hydrochloric acid, and washed with water. I have been doing electroless plating. However, when this method is applied to powder or granular materials, particularly fine powder (micron grade) or ultrafine powder (submicron grade), there are the following drawbacks.

(1) The stannous chloride in the sensitizing solution undergoes air oxidation, and the sensitizing solution ages, causing complete or partial non-deposition during electroless plating.

(2) When powder and granules are sensitized, the liquid decomposes during the treatment, and when the powder and granules are separated by filtration after treatment, the sifter is clogged with the decomposition products of the sensitized solution, and the sifter is separated by filtration. Separation becomes impossible.

(3) When the granular material is washed with water after sensitization treatment, the sensitizing treatment liquid adhering to the granular material decomposes and the filter is clogged by the decomposition products, resulting in separation of the granular material. cause trouble.

An object of the present invention is to provide a sensitizing treatment solution that eliminates these drawbacks and has excellent stability in pretreatment for electroless plating.

As a result of various studies on substances that improve the stability of sensitized solutions, we have found that the stability of sensitized solutions can be dramatically improved when certain reducing substances are added.

According to the invention, it contains stannous chloride and hydrochloric acid.

Further, there is provided a sensitizing treatment solution for electroless plating, which is characterized in that it contains one or more of thiourea, pyrogallol, and hydroquinone.

According to the invention, further comprising stannous chloride and hydrochloric acid,
Further, there is provided a sensitizing treatment solution for electroless plating, characterized in that it contains one or more of thiourea, pyrogallol, and hydroquinone, and gold tin.

The sensitization treatment solution of the present invention may be prepared by mixing the components at the time of use, but it can be sufficiently stored as a stock solution prepared in advance at various concentrations.

Ordinary tin chloride-hydrochloric acid sensitization treatment solution contains tin chloride from 0.1 to
Contains 10og7i and has a pH of 2 or less. For such a treatment solution, the total content of one or more of thiourea, pyrogallol and hydroquinone is O,OO1-5g/! It is added so that

When adding metallic tin, the tin is in the form of granules even if it is a lump.

It may be flaky. It is sufficient that it is present in an amount that does not dissolve during storage or use of the processing solution.

Table 1 shows the influence of various reducing substances on the stability of the sensitized treatment solution.

The sensitization treatment solution used was 8nC4109/l.

pH 1.05 (adjusted with HCI). Table 1 shows that the stability of the sensitized solution is improved by adding one or more of hydroquinone, pyrogallol, and thiourea. Furthermore, when these reducing substances and metallic tin coexist at the same time, the stability of the sensitization treatment solution is further improved. The preferable addition amount of the stabilizer is 0.001 to 5 g/l, and if it is less than 0.0011171, the effect is small (.5 g/1
This is because the stability of the sensitization treatment liquid tended to decrease in the above cases. In this way, the sensitized solution can be stored for a long period of time. Further, even in the sensitization treatment of powder and granular material using the sensitization treatment solution to which the above-mentioned stabilizer is added, there is no decomposition of the liquid components of the sensitization treatment solution.

It was confirmed that the powder and granules could be easily separated by filtration using the filter after treatment, and the filter was not clogged due to the decomposition of tin salts when the powder and granules were separated by filtration after washing with water following the sensitization treatment. This also solves the problem of .

The addition of a stabilizer to the sensitization treatment solution does not prevent the Sn2+ ions in the solution from adhering to the powder and granule, and the subsequent activation treatment with palladium salt provides sufficient catalyst on the surface of the granule. Activation is imparted, and a uniform metal coating without plating defects can be obtained by electroless plating.

Next, the present invention will be specifically explained using examples.

Examples and comparative examples were carried out using the steps shown below.

Sensitization treatment (5 minutes at room temperature) → Filtration → Water washing → Filtration → Activation treatment (pdclto, 2 g/l, HCI 2
．． 5m//1, room temperature, 5 minutes) → Filtration → Washing with water → Filtration → Electroless Ni plating (Nippon Kanigen Co., Ltd. 5B-55, 60°G,
1 minute) → Filtration → Water washing → Filtration → Dry powder is cubic boron nitride CBN (average powder diameter 6 μ) 1
．． ! I'wo is used for filtration, using a membrane filter (pore size 0).
．． 4 μm).

Example 1 A sensitization treatment solution containing sncMog/l, pyrogallol 0.05g/A', and a concentration of 1.05 (adjusted with HC/) was used. Separation of the CBN powder after sensitization treatment was easy, and a weight increase of 0.231 was obtained by electroless Ni plating, and the Ni plating was uniform.

Example 2 The sensitization treatment solution contained 8nC1*10 g/l, and a weight increase of 0.15 g was obtained due to thiourine Ni plating.
The plating was uniform.

Comparative Example 1゜The sensitization treatment solution contained 5nC1t 109/1! ,
A pH of 1.05 (adjusted with HO2) was used. It took three hours to separate the CBN powder by filtration after the sensitization treatment, and the subsequent washing with water also caused problems. CBN after electroless Ni plating
The weight of the powder was reduced compared to the time at the start of the test, and Ni precipitation was only slightly observed locally. The weight decrease in the weighing after electroless Ni plating was caused by the fact that CBN powder adhered to the tank wall in each step and less than 100% of it was recovered.

Claims (1)

[Claims] 1. A thiourea containing stannous chloride and hydrochloric acid. A sensitizing treatment solution for electroless plating, characterized in that it contains one or more of pyrogallol and hydroquinone. 2. The sensitizing solution for electroless plating according to claim 1, wherein the total amount of thiourea, pyrogallol or hydroquinone added is 0.001 to 5 fi/l. 3. Contains stannous chloride and hydrochloric acid, and thiourea. A sensitizing treatment solution for electroless plating, characterized in that it contains one or more of pyrogallol and hydroquinone, and Kinpeng tin. 4. The sensitizing treatment solution for electroless plating according to claim 6, in which the total amount of thiourea, pyrogallol or hydroquinone added is 0.001 to 5j; l/13
something that is.