Microstructural and mechanical reliability of a GaN/DBA die-attached module with Ag sinter joining in harsh thermal environments

This study was carried out to evaluate the high-temperature and long-term reliability of a GaN/DBA die-attached module with Ag sinter joining and with high temperature solder in a harsh thermal aging process. And its performance compared with high temperature Pb-5Sn solder. A GaN die was structurally sound bonded on a DBA substrate by using a micron/submicron Ag sinter paste and a high content lead solder, respectively. The assembled specimens were subjected to a thermal aging test up to 500 storage hours at 250 °C, then die-shear tested. The initial shear strength of the Ag sinter joint achieved above 42 MPa, the Pb-5Sn joint was above 37MPa. In case of the sintered Ag structure sustained durable die shear strength after 250 hours of the thermal aging. On the other hand, the Pb-5Sn joints exhibited significantly decreased shear strength after 250 and 500 hours of the thermal aging by 60%. Consequently, the Ag sinter joints strengthen during isothermal aging with a necking growth without any defects. Pb-5Sn solder joints formed the NixSnx IMCs by thermal aging. These microstructure characteristics have an important influence on the fracture mechanism, the tendency of fracture path was investigated by SEM-EDX. The thermal aging behavior of a GaN/DBA die-attached module will be addressed further in this paper.