Internal thermal resistance test and analysis of power device based on structure function

Five group thermal resistance test samples of the power devices were performed high temperature aging at 150°C for 0h, 24h, 48h, 72h, 96h respectively, then the maximum thermal test current without device self-heating temperature rise of 5mA was determined, and the transient thermal resistance test method was employed to obtain the heat transient response curves containing the thermal resistance and heat capacity parameters respectively. Numerical convolution method and structure function analysis techniques were used to acquire total junction-case thermal resistances of power devices, and the internal thermal resistance of each layer´s package structure of the chip, the adhesive and the case was separated from the total junction-case thermal resistances. Finally, the scanning acoustic test was performed on the five group samples to validate the package defect and the effect of typical package defect on internal thermal resistance of device was analyzed. The results show that the structure function analysis method can effectively separate the thermal resistance of internal each layer package structure. The excursion of structure function and die attachment delamination of tested sample were found after 96 hours aging. The excursion of structure function compared with the original curve can reflect the internal package quality of power device. Generally, the package defect, such as voids, delamination, etc. could induce the increase of internal thermal resistance. The structure function analysis method provides a favorable reference to thermal reliability design and analysis of power devices. Reducing the thermal resistance of the adhesive layer is the key to improving the overall heat dissipation of the device.