Chemistry: electrical and wave energy – Processes and products
Patent
1986-01-17
1987-10-13
Tung, T.
Chemistry: electrical and wave energy
Processes and products
428670, C25D 356
Patent
active
046996974
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a high-purity palladium-nickel alloy plating, and particularly to a high-purity palladium-nickel alloy plating solution and process suitable for plating electronic parts, said plating solution and process producing a deposit having a low nickel content, an article plated with said alloy, and an article plated with said alloy and further with gold or a gold alloy.
BACKGROUND OF THE INVENTION
In general, a plating which contains palladium is known to have excellent electrical properties and be economical as compared to precious metal platings such as a gold plating. However, a pure palladium plating containing no other metal has such an intrinsic property that the deposit is liable to occlude hydrogen, leading to high internal stress and easy cracking. Therefore, a palladium-nickel alloy plating by co-depositing nickel has hitherto been widely used, as disclosed, for instance, in Japanese Patent Publication Nos. 46-25604 (1971), 47-33177 (1972) and 47-33178 (1972). The deposit obtained by the palladium-nickel alloy plating is glossy, occludes little hydrogen and is malleable, as contrasted to the pure palladium plating; therefore, a thick plating of the alloy can be obtained with extremely few cracks and favorable adhesion properties.
However, in the case of the conventional palladium-nickel alloy plating, the nickel content of the deposit is high (15% or more), so that the deposit is liable to be attacked by chemicals as nitric acid, and accordingly, such plating can hardly be utilized in the field where high-quality plating is required, for instance, electronic parts.
The present inventor, as a result of various experiments, has found that the abovementioned problems can be overcome if the nickel content of the deposit is not higher than 15%.
The present invention has been attained, based on the abovementioned finding, while paying attention to the prior art. Accordingly, an object of the present invention is to provide a plating solution and a plating process for a high-purity palladium-nickel plating by which a deposit comparable to a pure palladium plating in resistance to chemicals such as nitric acid can be obtained without sacrificing the intrinsic features of palladium-nickel alloy plating, an article plated with the palladium-nickel alloy and an article plated with the palladium-nickel alloy and further with gold or a gold alloy.
DISCLOSURE OF THE INVENTION
To attain the abovementioned object, the high-purity palladium nickel alloy plating solution and process, the article plated with the alloy and the article plated with the alloy and further with gold or a gold alloy according to the present invention are constituted as follows:
(1) A high-purity palladium-nickel alloy plating solution which is characterized in containing at least 5 g/l of palladium added in the form of palladous ammine chloride and 0.5 to 5 g/l of nickel.
(2) A process for plating with a high-purity palladium-nickel alloy which is characterized in comprising adjusting a high-purity palladium-nickel alloy plating solution containing at least 5 g/l of palladium added in the form of palladous ammine chloride and 0.5 to 5 g/l of nickel to a pH 6 to 8, and carrying out plating so that the nickel content of the deposit will be 1 to 15%.
(3) An article plated with a palladium-nickel alloy having a nickel content of 1 to 15%.
(4) An article plated with a palladium-nickle alloy having a nickel content of 1 to 15% and plated further with gold or a gold alloy.
If at least 5 g/l of palladium is not added as palladous ammine chloride, the so-called "burnt deposit" will be generated in the plating, thereby spoiling the intrinsic action of the palladium-nickel alloy plating, namely, the action of obtaining a glossy, malleable deposit which occludes little hydrogen and can have a large thickness with few cracks and favorable adhesion properties. Palladium can be used in any large amount not less than 5 g/l.
Like palladium, nickel is used in an amount of not less than 0.5 g/l, in ord
REFERENCES:
patent: 3580820 (1971-05-01), Yamamura et al.
patent: 3677909 (1972-07-01), Yamamura et al.
patent: 4428802 (1984-01-01), Kanai et al.
Abner Brenner, "Electrodeposition of Alloys", vol. I, p. 75, (1963).
Electroplating Engineers of Japan Limited
Tung T.
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