Bond wire lift-off will cause an increase of remaining wires’ power dissipation, which usually is ignored for healthy modules. However, only partial wires’ power dissipation transfers through thermal path from junction to case, which will lead to overestimate the whole power dissipation from collector to emitter pole and underestimate the calculated thermal resistance using the proportion of temperature difference to power dissipation. A FEM model is established to show the change of heat flow after bond wires were removed, the temperature of bond wires increases, and the measured thermal resistance decrease after bond wires lift-off. It is validated by experimental results using open package Insulated Gate Bipolar Transistor (IGBT) modules under different current conditions. This conclusion might be helpful to indicate the bond wires lift-off and solder fatigue by comparing the change of measured thermal resistance. Using the Kelvin setup to measure thermal resistance will cause misjudgment of failure mode due to the ignoring of wires’ power dissipation. This paper proposed that the lift-off of bond wires will lead to underestimating the thermal resistance measurement, which will overestimate the lifetime of IGBT module and misjudge its state of health.

中文翻译：

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键合线剥离对IGBT热阻测量影响的研究

键合线剥离会导致剩余线的功耗增加，对于正常运行的模块通常不予考虑。但是，只有部分导线的功耗通过结点到外壳的热路径传递，这将导致高估从集电极到发射极的整个功耗，并使用温度差与功耗的比例低估计算出的热阻。建立了一个有限元模型，以显示移除键合线后热流的变化，键合线的温度升高以及键合线提离后测得的热阻降低。通过在不同电流条件下使用开放式封装的绝缘栅双极晶体管（IGBT）模块的实验结果验证了这一点。通过比较测得的热阻变化，该结论可能有助于指示键合线的剥离和焊料疲劳。使用开尔文设置来测量热阻会由于忽略电线的功耗而导致对故障模式的误判。本文提出，键合线的剥离会导致低估热阻测量值，这会高估IGBT模块的寿命，并会误判其健康状态。