Reliability of Cu Nanoparticles/Bi-Sn Solder Hybrid Bonding Under Cyclic Thermal Stresses

The influence of thermal cycle stress loading on hybrid bonding, which was formed by sintering a mixture of Cu nanoparticles and a eutectic Bi-Sn solder powder, has been investigated. A Si chip and a directly bonded aluminum (DBA) substrate were bonded using the hybrid bonding layer. The bonded sample was evaluated using a thermal cycle test (− 40°C and 250°C). The degradation process of the sample during the test was observed nondestructively using synchrotron radiation x-ray computed laminography. The thermal cycle stress loading had a minimal effect on the microstructure of the bonding layer, which has a high bonding strength owing to the liquid phase sintering and high decomposition melting temperature of the Cu-Sn compound formation. This property reduced the Al deformation of the DBA substrate caused by the thermal cycle loading, resulting in the suppression of the bonding layer degradation. Therefore, hybrid bonding can be instrumental in achieving the reliable operation of power modules at high temperatures.