Sn-Cu alloy plating bath

摘要

An acidic Sn—Cu alloy plating bath composition comprising: (a) Sn^2+ ions and Cu^2+ ions, (b) at least one acid selected from the group consisting of alkane sulfonic acids, alkanol sulfonic acids, and sulfuric acid, and (c) a thiourea compound. The composition exhibits high current efficiency and does not cause Cu to deposit on the Sn anode, the Sn—Cu alloy plating bath is free from such problems as inadequate adhesion of the plating to substrate and covering of with copper deposit. Moreover, processing waste water from the Sn—Cu plating bath is easy because the composition does not contain a complexing agent. The Sn—Cu alloy plating bath of the present invention, therefore, can advantageously produce not only Sn—Cu alloy plating but also ternary alloy plating containing other metals in an industrial scale.