Effect of vacancy on the elements diffusion in Cu/Sn lead-free solder joints

The formation process of interface Kirkendall voids is accompanied by the formation and diffusion of vacancies, so the behavior can not be ignored during interfacial diffusion and void formation process. In this study, the diffusion process of Cu-Sn interface and the effect of vacancies on diffusion in Cu/Cu 3 interface were investigated using molecular dynamics simulation. Moreover, the diffusion behaviors of atoms were analyzed, while the vacancy formation energy, diffusion energy barrier and vacancy diffusion activation energy were obtained. By comparison, it was found that the models containing vacancies more easily formed diffusion than the models without vacancies. In addition, the formation energy of Cu vacancy in the Cu crystal was greater than that in Cu 3 Sn crystal. The formation energies of Cu 1 vacancy and Cu 2 vacancy were close to each other in Cu 3 Sn crystal, and they were both smaller than the formation energy of Sn vacancy. Furthermore, the vacancy diffusion barrier and vacancy diffusion activation energy of the Cu/Cu3Sn interface were calculated. The results showed that the vacancy diffusion activation energy of Sn was higher than that of Cu. © 2018, Editorial Board of Transactions of the China Welding Institution, Magazine Agency Welding. All right reserved.