Research on the Effects of Solder Layer THICKNESS on the Reliability of High Power IGBT Module

Solder layer in IGBT module not only plays the role of electrical and heat conduction, but also can absorb the stress and strain as interface materials protect DBC and chip from mechanical stress. Therefore, the solder layer quality is one of the important factors affecting the reliability of IGBT module. In this paper, the relationship between voids with solder area and thickness in the high power IGBT module are studied with the experimental method. The results show that when the size and thickness of the preformed solder are too small and too thin, the void rates significantly increase after soldering, which cause thermal resistance increases significantly and it is harmful to the reliability of the module. With the gradual increase of the solder thickness, the void ratio decreases significantly, but when the solder is further thickened, the bubble escape channel in the solder is not smooth, which causes the rise of void ratio again and solder accumulation will be formed at the outer edge of substrate, so this situation is also harmful to product reliability. Through a large number of comparative experiments, the results shows that 180 $\mu$ m-240 $\mu \mathrm{m}$ preformed solder thickness and $130\mu \mathrm{m}-170\mu \mathrm{m}$ solder layer thickness in the module is better for product reliability.