ELECTROCHEMICAL MIGRATION TESTS OF SOLDER ALLOYS IN PURE WATER

Electrochemical migration (ECM) tests on solder alloys were conducted by applying constant voltage with a power supply or sweeping the volta ge at a constant rate with a potentiostat. Distilled water was used as the test environment. Time to short and short voltage were the measur e of ECM susceptibility. Similar results were obtained in both test me thods. In Sn-Pb alloy system, pure lead showed the highest susceptibil ity. Alloys with 5-60%Sn showed similar high susceptibility. Further a ddition of tin lowered the susceptibility and pure tin had the lowest susceptibility. Dendrites grew from cathode and reached to the anode. The composition of dendrites of Sn-40Pb alloy was enriched in lead. So me tin base solder alloys without lead were more resistant to ECM than Sn-40Pb alloy. Pure indium, In-48Sn and In-50Pb alloys were found to be immune to ECM in pure water. Large anodic dissolution rate seems to be responsible to high ECM susceptibility. (C) 1997 Elsevier Science Ltd.