JPS5980764A - Electroless plating bath for plating platinum or platinum-palladium alloy - Google Patents

Abstract

PURPOSE:To obtain the titled electroless plating bath having improved stability and increased utilization rates of Pt and Pd by adding Pt, or Pt together with Pd in the form of nitro or nitroammine complex salts and a hydroxylamine salt as a stabilizer and by specifying the pH. CONSTITUTION:This electroless plating bath for plating Pt or a Pt-Pd alloy has 10-13 pH and contains a nitro or nitroammine complex salt of Pt or the complex salt and a nitro or nitroammine complex salt of Pd (a), a hydroxylamine salt (b) as a stabilizer, and hydrazine (c). By the bath composition the stability of the soln. is improved, and deposition is carried out with increased selectivity. The plating bath is applicable to electronic parts made of Cu, Ni, Fe or an alloy thereof, an electrode material, plastic products, glass, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrazine type plating bath for electroless plating of platinum or platinum-palladium alloy onto metal or non-metallic surfaces, and in particular has excellent bath liquid stability.
This invention relates to a new plating bath that has a high palladium alloy utilization rate and a low operating temperature.

There are few known documents regarding electroless plating of platinum.

By analogy with commonly used electroless plating methods, a bath solution consisting of platinum salts and a reducing agent selected from hydrazine, borohydride salts, alkylamine borane, hypophosphite, formalin, etc. can be considered.

However, since the reduction of platinum ions proceeds relatively quickly compared to the case of other metals, the stability of the bath solution is poor.

For this reason, in any of the above combinations, it seems difficult to selectively grow a plating layer on the surface of the object to be plated.

For example, among the above-mentioned reducing agents, boron hydride has too strong a reducing power, so the reduction of platinum progresses too much and precipitates in the bath (i.e., self-decomposes). However, no suitable stabilizer has been found in this case. In addition, alkylaminoborane type bath liquids are certainly stable and have little self-decomposition, but the reduction temperature is high <7
It is carried out at 0-80°C. For this reason, the range of applicable plastics is narrow, and the amount of ammonia evaporated due to high temperatures is large, which is unfavorable from an operational standpoint. Furthermore, hypophosphite and formalin have weak reducing power, so it is necessary to carry out the process at high temperature, but when the temperature is high, self-decomposition is severe, and no stabilizer has been found to suppress this self-decomposition. However, when using hydrazine as a reducing agent, it is impossible to directly apply the bath solution conventionally used for plating other metals to platinum because the stability of the bath solution is extremely poor. It seems possible to improve the stability of the bath solution by selecting the ion form, stabilizer, etc.

In order to improve the stability of platinum hydrazine-type baths, the present inventor conducted research on various platinum ion particles and coexisting stabilizers. When a hydroxylamine salt is used as a curing agent, the stability of the bath solution is significantly improved, and in this case, the selective precipitation property is significantly improved.
The platinum utilization rate is over 95%, which is extremely high, and plating can be done at a low temperature of 60°C or less, and since it does not contain boron salt, the plating layer does not harden and has high adhesive strength. It was discovered that a platinum-palladium alloy can be plated in the same way when a nitro complex salt or a nitroammine complex salt of palladium is used at the same time.
The present invention has now been completed.

That is, the present invention provides (a) a nitro complex salt of platinum or (and) a nitro ammine complex salt, or a nitro complex salt or (and) a nitro ammine complex salt of platinum and (these), (
The present invention relates to an electroless plating bath for platinum or platinum-palladium alloy, which contains b) a hydroxylamine salt and (C) hydrazine, and has a pH of 10 to 1B.

Examples of platinum nitro complex salts or platinum nitroamine complex salts used in the present invention include 2 (Pt(NO2) 4),
Na2 [PtrNO2)4], (NHs)2Pt(N
Use crystals such as O2)z dissolved in ammonia water, or use a solution obtained by reacting a solution of platinum ammine complex salt or chloroammine complex salt with a salt such as an alkali metal salt of nitrous acid in ammonia water. do. However, coexisting ions in the bath solution often affect the plating conditions, so from the viewpoint of quality control of plating, it is preferable to use as pure a crystal as possible.

When using crystals, one type is usually used, but two or more types may be used.

When plating a platinum-palladium alloy, the above-mentioned platinum complex salt and palladium nitro complex salt or (and) crystals of palladium nitroammine complex salt are dissolved in aqueous ammonia, or the platinum ammine complex salt or chloroammine complex salt and palladium are used. A solution obtained by reacting a solution of ammine complex salt or chloroammine complex salt with nitrite in aqueous ammonia is used. Examples of the palladium complex salts include 2[Pd(NO2'4], Na21TPd(N
Examples include crystals such as O2)4], (NH3)2Pd(NOz)z, and the like. When using crystals, use at least one of these 1. When plating a platinum-palladium alloy, the molar ratio of platinum and palladium as metals is usually 0.1 to 1 mole of palladium to 1 mole of platinum. It is about .5 mol.

As the hydroxylamine salt used in the present invention, water-soluble salts such as hydrochloride, sulfate, nitrate, etc. are preferable.

As the hydrazine in the present invention, hydrazine that becomes hydrazine in an aqueous solution state, such as hydrazine hydrate, hydrochloride, sulfate, etc., can be suitably used.

The bath liquid composition of the present invention includes platinum or platinum-palladium A.
(7) Concentration force 5 X 10-'-5X 10-2M/1
(For white M(7), 0.1~I O?/e>favorable i):
t, < Ha2.5X10-3~2.5xlOM/l
(for platinum, o, 5-6y/l), hydroxylamine or 0.0014-0.7 M/l (for borate,
0.1-50 f'/l) Preferably 0.0014-
0.014M# (for hydrochloride, 0.1・-1f/l
l and hydrazine at o, o o a~1.5 M/l
(-0.15 to 76 y/l in case of hydrate) Preferably 0.008 = 0.8 h, Vl (-0.15 to -15 y/l in case of hydrate). In the present invention, the bath solution having the above composition is aqueous ammonia or alkaline H
Depending on the buffer, pH 10-18 preferably 11-12
Prepare and use within the following range.

When the pH is 18 or higher, the reduction rate becomes faster and self-decomposition becomes easier. Furthermore, if the pH is lower than 10, the reduction rate will be low and the plating time will be long. Hydroxylamine is 0.
If it is less than 0.015 M/l, the stability of the bath solution will deteriorate, and if it exceeds 0.7 M/A', the growth of the plating layer will be extremely suppressed, which is undesirable. When the object to be plated that has been previously activated is immersed, a reduction reaction proceeds catalytically at a temperature of room temperature to 60°C, preferably 80 to 60°C, and a high-quality platinum or platinum-palladium alloy plating layer grows. . If the plating temperature is lower than room temperature, plating will be difficult to proceed. ) Furthermore, when the plating temperature exceeds 60°C, self-decomposition begins to occur. Within the above temperature range, plating progresses well, and the reaction rate of platinum or platinum-palladium in the bath solution reaches 95-98%, and there is no self-decomposition in the bath solution or precipitation on the walls of the reaction vessel. It doesn't happen at all. The plating time is not constant as it depends on the shape of the object to be plated, but to give an example of obtaining a platinum plating layer of approximately 2 μm, it is 1
．． It is a short time of 6 to 2 hours.

In the plating bath of the present invention, the platinum complex salt itself is extremely stable (the same goes for the palladium complex salt), and when a hydroxylamine salt is added, an even more stable complex is formed, and self-decomposition is almost suppressed.

Therefore, the plating bath of the present invention has extremely excellent stability without self-decomposition over a long period of time when the object to be plated is not immersed.

Examples of objects to which the plating bath of the present invention can be applied include metals such as copper, nickel, iron, alloys thereof, electronic parts such as titanium and tantalum, and industrial materials such as electrode materials. In addition, synthetic resins such as acrylonitrile-butadiene-styrene coelectrolyte (ABS) resin, polyamide resin, carbonate resin, glass, ceramics, etc.
It can be applied to materials that can be electrolessly plated.

It can also be applied to the production of unit cells for hydrogen or oxygen producing water electrolyzers, which are used by bonding platinum to a cation exchange membrane. The plating bath of the present invention is superior to conventional alkylamine borane type plating baths in producing less gland contamination in the production of this type of bonded body.

In either case, it is preferable that the object to be plated be subjected to an activation treatment in advance.

In the case of metal, after surface cleaning, it is immersed in an aqueous salt solution such as palladium, platinum, rhodium, etc., and if necessary, it is subsequently immersed in an aqueous boron hydride salt solution, etc. for reduction treatment and activated, and then immersed in the plating bath of the present invention. .

Also in the case of polymeric materials, glasses, and ceramics, usually
These surfaces are subjected to surface hydrophilic treatment, sensitization treatment, and activation treatment that are used when chemically plating copper, nickel, etc., and then immersed in the plating bath of the present invention.

In addition, in the case of ion exchange membranes, after surface roughening and cleaning treatment, anionic or cationic platinum anchor ions are adsorbed depending on the polarity of the membrane, and then reduced to zero with sodium borohydride solution, etc. After bonding the first layer with a thickness of approximately 5 to 2 μm, the hardness is significantly lower because it does not contain boron, compared to platinum or platinum-palladium alloy deposited using the plating bath salt of the present invention, dimethylamine borane, etc. It is low, highly flexible, and has high bonding strength. Therefore, it is suitable for plating electrode materials, etc. It is also suitable for plating flexible substrates such as membrane-electrode assemblies.

The plating bath of the present invention can be used for plating platinum or platinum-palladium alloy as well as nitro-6, which is stable like platinum and palladium.
It can also be applied to plating metals such as iridium, rhodium, etc. alone or alloys with platinum, which produce 1 or nitroammine lead salts.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A perfluorocarbon sulfonic acid type cation exchange membrane [manufactured by DuPont, [Nafion 117J, 11fi thickness 7 mil (about 0.175 mm)] was used, and the diameter was about 39 mm.
Platinum was bonded to the circular part.

For pretreatment of the membrane, first, it was roughened by sandblasting, then boiled with 4N-HC to clean it, and then washed with hot water.

The treated membrane was placed in a plating cell, and a platinum ammine complex salt solution (obtained by boiling platinum tetrachloride in aqueous ammonia) was placed on both sides of the membrane.
Add platinum 50 Iny/l OOm, d) and leave at room temperature 2
Soaked for an hour. After washing with water, a 0.05% sulfur borohydride solution with a pH of 12 was added to the cell, and reduction was carried out at 40 to 60° C. for 2 hours to deposit a platinum layer with a thickness of about 1 μm on both surfaces of the membrane.

This activated film was immersed in a chemical plating bath having the following composition.

(l dinitrodiammine platinum 0.5y(
2) Ammonia water (28%) 50n+
6! (3) Water 25 Q ml (4)
Hydroxylamine tM! i2LM50% aqueous solution
IQnll (5) Hydrazine-hydrate (80% as hydrazine) 5 me (6)
Water Company-wide 400m1 (7
) pH 11.7 Bath solution is fl) (Dissolve 21+31 by heating to make a solution,
Then +4) (5) tel was added to prepare.

Plating was carried out at 40 to 50°C for 2 hours, and the amount of platinum deposited was 91.
The QI/C1n2 plating thickness was approximately 8 μm.

No precipitation occurred in this bath solution, and the utilization rate of platinum in the stock solution was about 98%.

Example 2 A composite membrane of sulfonic acid type and carboxylic acid type membranes (manufactured by DuPont, [Nafion 901 j]) was used, and platinum was bonded to the carboxylic acid membrane side.

In the same manner as in Example 1, the cell was sandwiched and immersed in a platinum ammine complex salt solution, and then reduced with a sodium borohydride solution of pH 12 to create a first reduction layer, and then immersed in a chemical plating bath with the following composition ( ,Ta.

(1) Potassium tetranitroplatinate 0.6y
(2) Ammonia water (28%) 20ml (
3) Water 100ml (4) Hydroxylamine hydrochloride 0°22
(5) Hydrazine-hydrate (80% as hydrazine) 9 ml (6)
Water Companywide 2
00ml (7) pH 11.8 Bath solution was fl) (2+ After heating and dissolving +31 to obtain an aqueous solution, it was prepared by adding (4), (5), and (6).

Plating was carried out at 40-45℃ for 2 hours, and the amount of platinum deposited was 3my.
/cm2, and the plating thickness was about 2.5 μm.

During this time, no precipitation occurred in the bath solution, and the utilization rate of platinum in the stock solution was 98%.

Example 3 A copper plate sample (2×40 m) was degreased and cleaned with a sodium cyanide solution, and then activated by immersing it in a 5% palladium chloride, 2N hydrochloric acid solution at room temperature for 80 seconds. After washing with water, add the following plating bath solution (prepared in the same manner as Example 2) to 40°C.
After soaking for 2 hours, a platinum-palladium alloy plating of approximately 2 μm (?) was obtained.

There was no decomposition in the bath liquid, and the metal utilization rate was 96% in all cases.

(1) Potassium tetranitroplatinate 0.05y
(2) Potassium tetranitropalladate 0.05y (3)
Ammonia ice 5 m1 (4)
Water 801M' (5) Hydroxylamine hydrochloride 0.1y
(6) Hydrazine-hydrate (80% as hydrazine) 1.51 nl (7
)Water total amount 40nld(s)
pH 11.8 Example 4 A nickel sample piece (1'2X4Cm) was degreased with alkali and treated with rhodium chloride A2y and hydrochloric acid 10ml. After activation by immersion in a solution of 100 md of water for 80 seconds, it was washed with water and plated at 40 to 50°C for 2 hours using a bath solution having the following composition.

(1) Dinitrodiammine platinum o, osy
(2) 7:/ Monia water (28%)
5111e (3) Water 20rr+1 (41hi I"mouth+sil y i 71M acid tji,
0.1p(6) Hydrazine-hydrate (80% as hydrazine) 1.5me(6)
Water 401n (71pll)
A platinum plating layer with a thickness of approximately 2 μm was obtained on the surface of the 11.5 nickel, and the utilization rate of platinum was 98%.

Example 5 Thickness of ABS resin (manufactured by Japan Synthetic Rubber Co., Ltd.) 2 m11
A plate-shaped sample (8×4 cm) of No. 1 was plated with platinum.

The pretreatment of the sample included activation using known chromic acid etching and catalyst activation bath.

The platinum plating bath used had the composition of Example 1.
After immersion at 0°C for 2 hours, a plating thickness of about 2 μl was obtained. During this period, no decomposition of the bath liquid was observed, and the utilization rate was 97%.

Claims (1)

[Claims] ■ Contains (a) a nitro complex salt or (and) a nitroammine complex salt of platinum, or a nitro complex salt or (and) a nitroammine complex salt of palladium, (1)) a hydroxylamine salt, and (C) hydrazine. 1. An electroless plating bath for platinum or platinum-palladium alloy, characterized in that the bath is HIO~1B.