Impurities in Solder—Their Impact on Solderability and Corrosion

German silver was tinned at three temperatures with solder containing 17 different impurities at up to five different concentration levels. The tinning process was carried out in a wetting balance. After this, the samples were subjected to corrosion and tested in a wetting balance again. It was established that bismuth at high concentration levels has a corrosion resistant effect which gives superior solderability. Silver, aluminium, bismuth, cadmium and copper, in amounts accepted by specifications, make the tinned surface unsolderable after corrosion. Statistical evaluation of a large number of tests — 1755 tests with 21,060 evaluated points — gave valuable information on how a wetting balance curve should be evaluated and which criteria should be established for good soldering.