Effect of bonding and aging temperatures on bond strengths of Cu with 75Sn25In solders

Abstract

In the present study, the interaction between thin film Cu and non-eutectic Sn-In is studied. The effects of the bonding and aging temperature on microstructure, IMC formation and also shear strength are investigated by SEM/EDX, XRD and shear testing. The bonding mechanism is proposed based on the obtained results. The bonding mechanism is proposed to occur over 2 stages: • An increase in bonding temperatures leads to an increase in the true contact area, and • The aging temperature leads to interdiffusion and assists formation of the IMC. The type of IMC that forms is η phase (Cu6(Sn,In)5) which is similar to the interaction between Cu and eutectic Sn-In. The shear strength increases with increasing the bonding temperature. On the other hand, the aging temperature does not have a significant impact on the shear strength. This indicates that the shear strength is mostly affected by the true contact area rather than the IMC formation.