Interfacial IMC and Kirkendall void on SAC solder joints subject to thermal cycling

The effect of thermal cycling on lead-free solder joints reliability was reported. The IMC compounds growth, Kirkendall voids formation and interconnect failure mode are characterized on SAC/Cu-OSP interface. The growth of interfacial CuSn IMC was observed after thermal cycling aging of 500, 1000 cycles, and faster IMC growth was found compared to isothermal aging with the proposed comparison criteria. Kirkendall voids were observed after Ar+ sputtering etching. Growth of Kirkendall void during TC aging was found in the Cu/sub 3/Sn layer or at Cu-Cu/sub 3/Sn interface. Coalesce of voids weakened the interface and decreased the drop reliability significantly.