Molecular Dynamics Simulation of the Interfacial Evolution and Whisker Growth of Copper-Tin Coating under Electrothermal Coupling

With the development of lead-free electronic devices, the failure caused by the growth of tin whiskers poses a potential threat to the reliability of electronic products. In this study, the modified embedded atomic potential proposed by Baskes was used to simulate the interfacial evolution and the whisker growth of copper and tin coatings under electrothermal coupling by using molecular dynamics. Numerical results show that the increase in electric field intensity and temperature can promote the diffusion of Cu atom to Sn atom, and the intermetallic compounds Cu6Sn5 and Cu3Sn are formed successively at the interface of the coating. Compression stress is formed in the coating, and the whisker is shaped at the weak part of the oxide film on the tin layer surface. The increase in electric field intensity and temperature can accelerate the growth of the whisker. This condition is because the increase in electric field intensity or temperature promotes the formation of intermetallic compounds, providing a greater driving force for the growth of tin whiskers. The results can provide a theoretical basis for the growth mechanism of tin whiskers.