Effects of surface finish conditions on interfacial reaction characteristics and mechanical reliability of novel Sn-1.2Ag-0.7Cu-0.4In solder bump

The effect of interfacial microstructures on the bonding strength of Sn-1.2Ag-0.7Cu-0.4In Pb-free solder bumps with respect to the loading speed, annealing time, and surface finish was investigated. The shear force increased and the ductility decreased with increasing shear speed, primarily because of the time-independent plastic hardening and time-dependent strain-rate sensitivity of the solder alloy. The shear force and shear energy decreased for each surface finish under the high-speed shear test of 1000 mm/s as a result of increasing intermetallic compound (IMC) growth and pad interface weakness associated with increased annealing time. The organic solderability preservative (OSP) finish showed lower shear force compared to the electroless nickel immersion gold (ENIG) finish. With increasing annealing time, the ENIG finish and OSP finishes exhibited the pad open fracture.