LAUSR

Ag sinter joining provides superior mechanical and thermal/electrical properties and is considered to become a leading next-generation wide band-gap (WBG) die-attach material. However, the microstructural evolution and mechanical characteristics of Ag sinter joining when subjected to high temperature have never been directly compared to those same characteristics of solder materials. In this study, we have evaluated the high-temperature and long-term reliability of a GaN/DBA die-attached module by pressure-less Ag sinter joining and Pb–5Sn solder in a harsh thermal aging test. Both the Ag sinter joining and Pb–5Sn solder were subjected to a thermal aging test of up to 1000 h at 250 °C. Initial shear strength of the Ag sinter joint exceeded 42 MPa, and increased stably up to 1000 h without any defects such as interface oxidation, diffusion, or mechanical deformation. The increase in shear strength of the Ag sinter joints was the result of necking growth of the sintered Ag during thermal aging. On the other hand, the shear strength of the Pb–5Sn joints exhibited substantially decreased shear strength (by 60%) after aging 250 h. Ni x Sn x intermetallic compounds (IMC) were also formed and serious interface degradation occurred during the aging process. These microstructure changes and mechanical characteristics have an important influence on mechanical reliability and, with that in mind, the tendency of fracture mechanism was investigated in detail by SEM–EDX. This study systematically examines the fracture mechanism on the microstructure of a DBA substrate and on high-temperature packaging during thermal aging tests for WBG semiconductor device applications.