Development of Silver Paste With High Sintering Driving Force for Reliable Packaging of Power Electronics

The spontaneous aggregation and weak stability of nanosilver particles largely overshadowed the application of nanosilver paste as die-attach materials in wide bandgap (WBG) devices. Taking advantage of the self-decomposition of silver-ammonia complexes to form silver particles, a novel particle-free silver paste was successfully developed to achieve higher sintering driving force as well as bonding quality. The proposed silver paste not only promotes the decomposition of silver complex but also reduces the oxygen requirement during the decomposition process, which significantly increases the shear strength from 23.8 to 59.4 MPa. The crystallization behavior and microstructure evolution confirm that the temperature required for the formation of silver particles in the proposed silver paste was reduced to 150 degree celsius. At the same time, the necking growth also occurred at the low temperature of 150 degree celsius, which is much lower than previous research and successfully confirms the higher sintering driving force of the proposed silver paste. More importantly, the proposed sintered silver paste exhibited high thermal stability, and the overall shear strength degradation was only 29.5% after 1000 cycles of thermal shock test (TST). The high sintering driving force combined with the high thermal reliability of the proposed silver-complex paste enables the development of high-performance WBG semiconductors with superior mechanical and electrical properties.