Growth Behavior of IMCs and Fracture Forming Mechanism at Sn-Ag-Cu/Cu Interfaces under Thermal-Shearing Cycling Condition

In this paper, the atom diffusion and growth behavior of intermetallic compound (IMC) and fracture forming mechanism at Sn-Ag-Cu/Cu interfaces under thermal-shearing cycling were investigated. Shear-stress is beneficial to atoms´ diffusion and IMC growth, therefore, the results show that there is only one kind of IMC, Cu₆ Sn₅, forms at Sn-Ag-Cu/Cu interface after thermal-shearing cycling 720 cycles with 25degC~125degC, and which morphology changes from scallop-like microstructure to chunk-like one with the thermal-shearing cycling cycles increasing. There are microcrack formed and grown up between Cu₆Sn₅ and Cu interface due to atom transfer and IMC growth. As the thermal-shearing cycles increase, Ag₃Sn IMC forms uniform particles, congregates to grow up to planar-like in the solder