Lead-indium alloy solder joints

Soldered joints present their own characteristic corrosion problems usually in the form of dissimilar metal attack often aided by inadequate flux removal after soldering. Such joints have always been a source of concern to the electrical industry. Lead-containing solders must be used with caution for some types of electrical connection since PbfOHjj.PbCOj may be found as a corrosion product and can interrupt current flow. Indium has been found to be a useful addition to Sn-Pb solders to improve their corrosion resistanceHowever, in view of the toxicity of lead and its alloys, the use of lead solders, particularly in contact with potable waters and foodstuff s, is likely to decline. 

Figs. 69, 70, and 71 show that the use of lead-free solder (Sn-Ag-Bi-In) has not resulted in reliability problems. However, some joints have indicated a concern with the potential precipitation of bismuth from the alloy over time. Therefore the bismuth content of the solder used to assemble the MD player will be reduced from 2.5% bismuth to 0.5% bismuth with 6% indium. 

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