Aqueous solution for forming metal complexes, tin-silver alloy plating bath, and process for producing plated object using the plating bath

摘要

In the present invention, the tin-silver alloy plating solution comprising: a tin compound; a silver compound; and a complexing agent including a pyrophosphoric compound and an iodic compound. Therefore, the tin-silver alloy layer, whose composition can be optionally designed, can be formed, with high electric current efficiency, without using harmful compound: cyanide. The plating solution can resist to an air-stir; the plating solution is very stable; an external shape, adhesivility, solder-wettability of the tin-silver alloy layer are satisfactory; and the alloy is an advantageous alloy for solder plating.