Bright tin-silver alloy electrodeposition from an organic sulfonate bath containing pyrophosphate, iodide & triethanolamine as chelating agents

A new tin-silver alloy plating bath was investigated to obtain a lead-free solderable coating. Bright tin-silver electrodeposits having compositions close to eutectic were obtained from an organic sulfonate bath containing pyrophosphate, iodide and triethanolamine as chelating agents, and an amine-aldehyde reaction product as a brightener. A suitable bath composition was determined and the relationship between silver content in the deposit and bath composition and operating conditions were investigated. Properties of the deposits (i.e., solderability and whisker growth) were also investigated.