Numerical Study on Semi-elliptical Crack in Heavy Aluminum Bonding Wires for IGBT Module

During the manufacturing and service process of Al bonding wires of the IGBT module, the micro-cracks that lead to the failure of the bonding wires usually first initiate at the Al-Si interface and propagate along the interface, but the influence of micro-cracks on the reliability of the bonding wires is still unclear. In this paper, the fracture mechanics and finite element simulation are combined to calculate the energy release rate (ERR) of the semi-elliptical crack with different bond wire positions, different arc structure parameters, and different temperature cycle parameters, and explore the microcrack propagation mechanism. In the research on the competitive failure of microcracks in different Al bonding wires, it was found that the bonding wires located in the center of the chip were more prone to failure; in the investigation of the correlation between different wire arc structure parameters and cracks, it was found that the higher loop height and Bond wire cracks with larger wire diameter have lower ERR and higher reliability; in the simulation study of temperature cycling, it is found that higher Tavr and $\Delta \mathrm{T}$ will lead to larger bond wire crack ERR and lower reliability; The driving mechanism of crack propagation was studied, and it was found that the driving force for the initiation and propagation of the interface crack was the opening stress, but after a certain distance of expansion, the effect of the shear stress in the dominant driving force gradually increased. When the crack semi-major axis was 0.05mm, the tensile force was Open stress and shear stress are almost equal. As the shear stress in the driving stress gradually increases, the propagation of the interface crack will be unstable and eventually lead to the failure of the bond wire.