The Influence of Chip Aspect Ratios on the Crack Evolution in the Die-attach Layer Simulated Using the Fracture Phase Field Method

This paper presents a simulation of the crack evolution in the die-attach layer of a 3D IGBT TO package model (Si chip-Pb92.5Sn5Ag2.5 solder-Cu substrate) under thermal cycles, considering different chip aspect ratios (1, 1.5, and 2) but with the same chip area (6.25mm
²
) using the fracture phase field method. The influence of three different chip aspect ratios on crack propagation was investigated and the interrelationship between the stress and the crack in the die-attach layer was discussed. The results reveal that the crack consistently initiates at the corner of the chip/solder interface and propagates to the center in an arc shape, irrespective of the chip aspect ratio. The crack initiation and propagation will be promoted by the increase of the chip diagonal asymmetry (i.e., the chip aspect ratio), and the crack propagation rates in the sections are faster when the section lengths are longer. Additionally, the crack propagation rates and maximum stress in the die-attach layer decrease in all three cases as the connecting area between the chip and the die-attach layer diminishes.