Grain refinement and pinning effect by SiC nanowires enhance the thermal reliability of sintered Ag joints for power electronics

The influence of 0.07 wt.% SiC nanowires (SiC NWs) addition on the microstructure, mechanical properties and crystallographic behaviors in sintered Ag joint during thermal aging at 300 °C for various durations has been investigated. The experimental results reveal that the shear strength of sintered Ag and Ag-0.07SiC joints both declines with prolonged aging time, while the composite joints consistently exhibit superior mechanical performance. After 1000 h, the Ag-0.07SiC joint retains a strength of 33.55 MPa, a 23.0% reduction, outperforming the pure Ag joint (28.62 MPa, 25.7% reduction). Hence, incorporating minor SiC NWs is able to prohibit the degradation of mechanical property of sintered joints. SiC NWs addition enhances the sintered silver density by filling in the pores and impeding the structure coarsening, thereby promoting the mechanical performance according to Gibson-Ashby model. EBSD analysis manifests that the grain size of sintered Ag reaches 2.32 μm after aging for 1000 h, approximately 14.3% larger than that of Ag-0.07SiC joints. SiC NWs as heterogeneous nucleation sites refine the grains during thermal service, which helps enhance the mechanical property in accordance with Hall-Petch relationship. Furthermore, the pinning effect that SiC NWs nailing at grain boundaries impedes the dislocation motion, also promotes the mechanical properties. Moreover, TEM observation illustrates that SiC NWs are wrapped in sintered Ag after1000 h of aging, with a solid interconnection, thus providing a superior mechanical performance of composite joints. Therefore, introducing SiC NWs can effectively facilitate the enhancement on the thermal stability and reliability of sintered joints for high-power electronics.