| 摘要 |
PROBLEM TO BE SOLVED: To plate thin having high reflecting property on a substrate under fast electroplating conditions by incorporating stannous sulfonate and sulfonic acid to control the bath to specified pH, adding a specified concentration of a reaction product of polyalkylene glycol and phenolphthalein. SOLUTION: Sulfonic acid is mixed by about 10 to 30 g/l in an aq.soln. containing stannous sulfonate by preferably about 10 to 100 g/l concentration as metallic tin to control the pH of the liquid to about <1. As for the stannous sulfonate, either stannous alkylsulfonate or stannous alkoylsulfonate is used. The sulfonic acid is an alkylsulfonic acid or alkoylsulfonic acid. Further, one or more kinds of condensation reaction products of polyalkyleneglycol and phenolphthalein or phenol phthalein derivs. are added as an org. additive by about 0.2 to 2 g/l to the aforementioned soltion to obtain an electrolytic bath in which high-quality tin can be plated on a substrate by a fast electroplating method.
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