AQUEOUS SOLUTION FOR FORMING METAL COMPLEXES, TIN-SILVER ALLOY PLATING BATH, AND PROCESS FOR PRODUCING PLATED OBJECT USING THE PLATING BATH

摘要

A tin-silver alloy plating bath characterized by comprising as the fundamental ingredients a tin compound, a silver compound, and complexing agents therefor consisting of a pyrophosphoric acid compound and an iodine compound. The bath is capable of depositing a tin-silver alloy coating having any desired composition at a high current efficiency without using any cyanide harmful to the human body. The plating bath is so stable as to withstand air agitation. The tin-silver alloy coating deposited from the plating bath is satisfactory in appearance, tight adhesion, and solder wettability, and is superior as a lead-free solder plating alloy.