Board-level reliability of conventional Sn-37Pb and Pb-free Sn-3.0Ag-0.5Cu solder joints
was evaluated using thermal shock testing. In the microstructural investigation of the solder joints,
the formation of Cu6Sn5 intermetallic compound (IMC) layer was observed between both solders and
Cu lead frame, but any crack or newly introduced defect cannot be found even after 2000 cycles of
thermal shocks. Shear test of the multi layer ceramic capacitor (MLCC) joints were also conducted to
investigate the effect of microstructural variations on the bonding strength of the solder joints. Shear
forces of the both solder joints decreased with increasing thermal shock cycles. The reason to the
decrease in shear force was discussed with fracture surfaces of the shear tested solder joints.
