The sensitivity analysis of geometric parameters on the power cycling reliability of bond wires

Considering the reliability of the bond wire comes as the main factor determining the reliability of power devices at present, and the geometric parameters of the bond wire have an in-negligible effect. A Finite Element (FE) simulation model based on a discrete device with TO-247 package and a single bond wire is established in this paper, and the influences of the geometric parameters are analyzed, which include the joint length L, the diameter D, and the aspect ratio λ. Then to understand the influence degree of the parameter on the reliability, the sensitivity analysis of these geometric parameters is carried out based on the sobol' method, using the Monte Carlo method for estimating the sensitivity index. The results show that increasing the joint length L, the diameter D and the aspect ratio λ all have a negative impact on the bond wire reliability, while a positive influence is presented by increasing the aspect ratio λ in the case without epoxy mold compound (EMC). This is because of the EMC's protective effect which inhibits the bond wire's thermal expansion. The aspect ratio λ is the most sensitive parameter of the three geometric parameters since it has the largest total sensitive index.