Finite element simulation of interfacial fracture and impact behavior at the interfaces of microscale Sn-Ag-Cu solder interconnects

Thus far, there is a severe lack of understanding about interfacial fracture and impact behavior of the microscale lead-free solder interconnects. In this study, the finite element simulation and analytical method were used to characterize the interfacial fracture and impact behavior at the interfaces of the microscale Sn-Ag-Cu solder joints. The intersection of a linear microcrack tip upon Sn-Ag-Cu solder/IMC interface was studied and the results reveal that the microcrack tends to debond rather than penetrate the interface with the impinging angle in the range of 20 to 90°, due to the fact that the solder provides 3 times more fracture energy than IMC to the crack propagation. Furthermore, in the interfacial impact between Cu and Sn-Ag-Cu solder, the maximum Von Mises stresses in Cu are obvious larger than that in Sn-Ag-Cu solder when the initial velocity is from 100 to 200 m/s. However, an inverse trend occurs, that is, the maximum Von Mises stresses in Sn-Ag-Cu becomes larger when the velocity increases from 500 to 1000 m/s. In addition, the simulation results show that rupture occurs more easily along Sn-Ag-Cu/Cu interface than along impact (or shock compression) direction when time is prolonging, owing to the effect of large shear stress caused by the effect of Poisson contraction of the visco-plastic Sn-Ag-Cu solder.