Interfacial reaction kinetics in Au stud/Sn bumps during annealing and current stressing

Annealing and current stressing were performed at 125∼160 °C with 5 × 104 A/cm2 conditions in order to investigate the interfacial reaction and growth kinetics of the Intermetallic Compound (IMC) in Au stud/Sn bumps. AuSn, AuSn2, and AuSn4 phases were formed at the interfaces between the Au studs and Sn after bonding. AuSn2 phases continued to grow with stressing time while the thickness of the AuSn4 phase decreased. The current stressing accelerated the interfacial IMC reaction. The apparent activation energies for the growth of the AuSn2 phase during the annealing and current stressing were 0.89 eV and 0.51 eV, respectively. The activation energies for current stressing were lower than that for annealing, which might be closely related to the acceleration of the interfacial reaction by electron wind force.