Experimental and analytical study of geometry effects on the fatigue life of Al bond wire interconnects

• Loop shape dependent fatigue life of Al wire bond frame connections was investigated.
• A fast optimization method for the fatigue life and ampacity of bond wires is purposed.
• Heel cracking was induced using an accelerated mechanical fatigue system at 500 Hz.
• An analytical model is presented for fast stress calculations of various loop shapes.
• The bond wire loop height and angle have the largest influence on the fatigue life.

The reliability of power electronic devices is mainly limited due to thermo-mechanical fatigue of the internal bond wire interconnections. The bond wire shape is already defined at the design stage of the device. Thus preliminary lifetime assessments become more and more important in order to satisfy the high quality demands and the short time to market of the devices. In this study a fast experimental test setup is used in order to determine the lifetime of a large number of wire bond shapes. Furthermore an analytical model is applied to calculate optimized wire bond shapes for a given set of parameters. The results of this investigation should help to optimize the shape parameters at an early stage of development using the presented analytical model in combination with the fatigue tests.