Investigation of Ton Dependency of Al-Clad Cu Bond Wires Under Power Cycling Tests

Many research works have been conducted in order to improve the reliability performance of the interconnections in the power modules. Significant reliability improvements of power modules with standard chips bonded with Al-clad Cu wires under power cycling tests (PC tests) with different junction temperature swings (DeltaTj) were observed from the work of R. Schmidt et al. However, other factors that influence the power cycling capability of Al-clad Cu bond wires were not fully investigated. In this work, power cycling tests with different power on-time (ton) and varied current per bond stitch (I) were performed in parallel with measurements such as scanning acoustic microscopy (SAM), infrared camera (IR) and shear tests in order to monitor the degradation behavior of Al-clad Cu bond stitches. A significant improvement of the power cycling capability by using Al-clad Cu wires instead of standard Al bond wires were confirmed. A similar ton dependency of the Al-clad Cu bond wires on the power cycling tests compared to Al bond wires was observed. Furthermore, a basic lifetime model for Ag-sintered chips bonded with the Al-clad Cu bond wires was proposed in this work.