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

Abstract

Annealing and current stressing were performed at 125∼160 °C with 5 × 10 4 A/cm 2 conditions in order to investigate the interfacial reaction and growth kinetics of the Intermetallic Compound (IMC) in Au stud/Sn bumps. AuSn, AuSn 2, and AuSn 4 phases were formed at the interfaces between the Au studs and Sn after bonding. AuSn 2 phases continued to grow with stressing time while the thickness of the AuSn 4 phase decreased. The current stressing accelerated the interfacial IMC reaction. The apparent activation energies for the growth of the AuSn 2 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.