Phase field crystal simulation of morphological evolution and propagation of microcracks in the intermetallic compound layer of Sn/Cu solder interconnects

Abstract

The existence of microcracks in solder interconnects plays a key role in determining the performance and reliability of solder interconnects, in particular, may increase significantly the potential for brittle interfacial fracture of interconnects and reduce the thermal conductivity of the systems. Thus, characterization of the formation and propagation of microcracks is very important for evaluating the performance and reliability of solder interconnects. In this paper, a phase field crystal model is utilized to study the morphological evolution and propagation of microcracks in a typical solder joint consisting of the Sn-based solder and Cu substrate. The simulation results show that the initial crack notch configuration affects sigificantly the crack propagation. The length and area fraction of the crack gradually increase with the simulation time, while the crack propagation rate decreases initially and then becomes stabilized with the simulation time. The atomic density in the initial crack notch can also affect the crack propagation. The number and size of the crack branches increase with increasing both the atomic density in the initial crack notch and simulation time. When the atomic density in the initial crack notch is 0.9, new cracks form around the pre-existing cracks, and the propagation velocities of cracks along the x and y directions are the same. When the atomic density in the initial crack notch is 0.6, the cracks propagate faster along the y direction than the x direction.