The combined sequential reliability test of thermal cycling aging followed by board level drop test for lead-free SnAgCu soldered assemblies were investigated. Interfacial IMCs, Kirkendall voids formation and interconnect failure mode are studied subject to TC aging. Kirkendall voids were observed with Ar+ sputtering etching. The failure sites and mechanism were examined and correlated with IMC and void formation. Significant decrease of drop life was observed for both SAC/ENIG and SAC/Cu-OSP assemblies after thermal cycling aging. Growth of Kirkendall voids and IMC significantly weakened the solder joint interface during TC aging. Drop impact crack path changed from the IMC to the IMC/Cu interface.

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