Design concept for wire-bonding reliability improvement by optimizing position in power devices

The most effective way to increase the reliability of wire bonds in IGBT modules is reduction of temperature difference between the aluminum wires and the device. However, this lowers the power handling capability of the modules. In this paper, we show that the configuration of aluminum wire bonds on power devices has a considerable effect on the temperature distribution of the device, and that the optimization of the layout by thermo-electric simulation can make the temperature distribution of the devices more uniform and consequently reduce the maximum junction temperature difference, ΔT_jmax. Tentative experiments showed that rearranging the bonding position resulted in reduction of ΔT_jmax by five to 8 °C, and that the chip temperature distribution estimated by the thermo-electric simulation was qualitatively similar to the actual measurement results. These results suggest that wire-bonding optimization by thermo-electric simulation can contribute not only to realizing more compact power modules but also to improving the module reliability.