Solder joint reliability with various silver finish on PCB

Abstract

Ag finish is a low cost and low resistant solution comparing with Au finish in electronic packaging. For the sake of application of Ag finish, the solder joint reliability with broad silver finish designs on PCB of packaging is studied. It is found that both finish structure and process affect the reliability. Electro-less Ni/Pd/immerging Ag (ENEPIS) has the best integrated solder joint performance in both thermal cycle test (TCT) and drop test. Immerging Ag finish has similar performance as OSP finish with good reliability in TCT and drop before aging. The TC reliability of electroplated Ag and drop reliability of electroplated Ni/Ag is poor because of voids associated with electroplating Ag process found at the interface of IMC and bulk solder. As for electro-less plated Ni/immerging silver (ENIS), the Ni-P layer is the weak point in drop test.