| 摘要 |
PROBLEM TO BE SOLVED: To use a Bi-Sn plating bath at a high cathode current density without eroding a material to be plated by incorporating two kinds of complexing agents different in complexing power from each other in the Bi-Sn plating bath and adjusting the pH of the bath to a specific range to improve the stability of the bath. SOLUTION: This Bi-Sn plating bath is formed by incorporating Bi3+, Sn2+ and the complexing agent I and the complexing agent II, which have different complexing power from each other, and adjusting to pH 2.0-9.0. The complexing agent I is selected from an aliphatic dicarboxylic acid having a 1-3C alkyl group, an aliphatic hydroxymonocarboxylic acid having a 1-3C alkyl group, an aliphatic hydroxypolycarboxylic acid having a 1-4C alkyl group, monosaccharide and polyhydroxycarboxylic acid obtained by oxidizing a part of the monosaccharide and the cyclic esterified compound and condensed phosphoric acid. The complexing agent II is selected from ethylenediaminetetraacetic acid, nitrotriacetic acid and trans-1,2-cyclohexanediaminetetraacetic acid.
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