| 摘要 |
PROBLEM TO BE SOLVED: To surely make eutectic tin-bismuth in an electroless tin-bismuth alloy plating bath and to obtain a plating film having bonding strength and appearance comparable to those of a tin coating or the like. SOLUTION: The electroless tin-bismuth alloy plating bath contains a soluble stannous salt, a soluble bismuth salt, at least one of an org. acid such as an org. sulfonic acid or an aliphatic carboxylic acid and an inorg. acid such as hydroborofluoric acid, hydrosilicofluoric acid or sulfamic acid and a complexing agent comprising a thiourea deriv. or a mixture of a thiourea compd. (thiourea or its deriv.) and an amine compd. such as an aminocarboxylic acid compd., a polyamine or an amino-alcohol. Since the complexing agent is used, it is not necessary to reduce the concn. of the bismuth salt and the ratio of the bismuth salt to the stannous salt in the bath, tin and bismuth are smoothly coprecipitated from the bath and the objective tin-bismuth alloy plating film is formed.
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