In view of possible environmental pollution associated with lead leached into ground water and the possibility of regulations against lead use in the future, research has been deveoted to the development of electrolytically deposited lead-free solders. Three systems that have been developed are Tin-Bismuth and Tin-Silver and Tin-Copper. Since all solutions are based on methanesulfonic acid solution (pH<1) they can be operated similarly to Tin-Lead alloys. In the case of Tin-Bismuth alloy plating, the deposits exhibit melting points between 140 and 220 deg C (60 - 10 wtpercentBi). In the case of Tin-Silver alloy plating, these deposits exhibit melting points between 220 and 300 deg C (3.5 - 10 wtpercent Ag). In the case of Tin-Copper alloy plating, these deposits exhibit melting points between 227 and 300 deg C (0.7 - 2.0 wt percent). All systems exhibit excellent solderability, mechanical strength, and prevention of whisker growth.
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