Development of thermal shock-resistant of GaN/DBC die-attached module by using Ag sinter paste and thermal stress relaxation structure

Abstract

GaN die-attach/DBC substrate joint structure bonded by Ag sinter paste/W thin film/Ag sinter paste sandwich die-attached layer was designed and its high-temperature reliability was investigated. GaN chips were bonded to DBC substrate using Ag sinter paste with thin W film at 220 °C and at 0.4 MPa for 60 min. The joints structure was subjected to thermal shock testing in temperature range of −50 to 250 °C for duration up to 1000 cycles. The initial average die shear strength of the GaN/DBC joint structure was about 30 MPa, and was maintained up to 1000 cycles. These results reveal that Ag sinter paste/W thin film/Ag sinter paste sandwich die-attached layer can provide a superior thermal shock resistant. The microstructure evolution of GaN/DBC joint structure during the thermal shock testing was observed by FE-SEM and EDX analysis. In addition, FEM numerical simulation has also been implemented in this study, which revealed that the GaN/DBC joint structure with the sandwich die-attached layer shows a stress-shielding effect from the external force, and thus achieves a reliable power module structure for wide-bandgap semiconductors for its application in high-temperatures.