Abstract
The interfacial reactions of Sn-3.0Ag-0.5Cu solder jointed with electroless Ni-P/immersion Au (ENIG) and electroless Ni-P/electroless Pd/immersion Au (ENEPIG) were investigated. Cu 6 Sn 5 grew rather slower in ENEPIG samples among all aging conditions as compared with ENIG. Furthermore, the second phase, Ni 3 Sn 4 , started to form in the ENIG aged joints, but not in the ENEPIG aged joints. It was demonstrated that ENEPIG could inhibit the formation of Ni 3 Sn 4 , which further decreased the growth of columnar Kirkendall voids inside the Ni 3 P layer. With less voids formed in the Ni 3 P layer, it is expected that the reliability of ENEPIG joints would be superior to that of ENIG joints. Detailed mechanisms of Ni 3 Sn 4 suppression and void formation were discussed and proposed. © 2011 Elsevier B.V. All rights reserved.