On-time Dependency on the Power Cycling Capability of Al Bond Wires Measured by Shear Test

Inhalt:
In previous studies, several empirical models for standard power modules under power cycling tests (PC tests) have been proposed in order to predict the number of cycles to failure (Nf). However, the factors that influence the power cycling capability of Al bond wires still offer space for more investigations. In this paper, the power cycling tests for devices with 300 μm and 400 μm Al bond wires and Ag-sintered die attach have been carried out under different conditions of power on-times (ton) and junction temperature swings (ΔTj). Shear tests have been performed in parallel in order to monitor the degradation of bond stitches on the surface of the chips during the power cycling tests. A strong ton dependency on the shear strength degradation rate is demonstrated in this paper. Additionally, the ton dependency is affected by ΔTj. The bond wire diameter shows a significant influence on the temperature distribution and the shear strength degradation of the Al bond stitches.