Interface Investigations and Modeling of Heavy Wire Bonds on Power Semiconductors for End of Life Determination

This paper investigates on refining lifetime models of power semiconductors. Especially the lifetime of heavy wire bonds is a weak spot and needs to be modeled in more detail. For a thorough understanding of the processes leading to a failed bond it is necessary to investigate more influencing factors than just the temperature excursion. Power cycling results for 125 ¿m wire revealed a much higher power cycling capability than it was originally expected. The analysis showed that temperature gradients on the chip surface lead to smaller temperature swings and therefore higher lifetimes. Countermeasures for future power cycling research have been evaluated. With the newly developed test equipment that is introduced in this paper it is possible in the future to conduct power cycling experiments for a wide variety of different influencing factors such as wire material, wire thickness and substrate properties, thus delivering valuable information for further simulation of e.g. crack propagation or for quality tests.