Weiqiang Wang a, Michael Ostermana, Diganta Dasa, and Michael Pechtb
a Center for Advanced Life Cycle Engineering (CALCE)
University of Maryland
College Park, MD 20742, U.S.A.
b Electronics Engineering City University of Hong Kong,
Phone: (301) 405-5323; FAX: (301) 314-9269
Tin-Bismuth (SnBi) is a lead-free alternative to pure Tin (Sn) lead frame finish. SnBi finish is considered by some to be a tin-whisker mitigation strategy. In selecting a SnBi finish, the interfacial strength and reliability of solder interconnects formed with select assembly solders must be considered. To characterize the solder interconnect reliability of SnBi finished parts, sets of test assemblies were created with Sn and SnBi finished thin-small-outline (TSOP) parts using SAC305 and SnPb solder. Test assemblies were subjected to temperature cycling and interconnect strength tests. It was found that SnBi finish caused thin-small-outline-package solder joints to have a shorter fatigue life than Sn finish under temperature cycling testing.
Key words: Reliability; Tin-bismuth; Solder joint; Temperature cycling; Shear test.
Complete article available to CALCE consortium members