| 摘要 |
PROBLEM TO BE SOLVED: To provide a tin or tin-alloy plating bath having greatly improved solderability, stannate and stannic acid or complexing-agent solutions for the preparation or maintenance/ supply of the plating bath, and electrical/electronic parts produced by using the plating bath. SOLUTION: The plating bath is a tin plating bath or a tin-alloy plating bath which consists of tin and one or more metals selected from the group (1) consisting of copper, zinc, silver, indium, gold, and bismuth. Further, this plating bath contains, as essential components, at least one or more kinds among the following components (A) to (D): (A) bivalent tin ions in an amount of 5-200 g/L; (B) one or more kinds among acids or complexing agents forming water-soluble salts or complexes together with the bivalent tin ions, in a total amount not smaller than the stoichiometrically equivalent weight based on the bivalent tin ions; (C) one or more metals selected from the group consisting of the group IB to VB elements in the fourth to sixth period of the periodic table, excluding tin, mercury, thallium and the elements contained in the above group (1), in a total amount of 20-2,000 ppm based on the amount of tin; and (D) one or more kinds among antioxidants in an amount of 1 mg/L to 10 g/L in total.
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