Achieving outstanding mechanical property after long-cycle thermal shock of reflow/ultrasonic-assisted Kovar/SnSb10 interfaces

The present study analyzed the microstructure evolution corresponding to the mechanical properties of reflow/ultrasonic-assisted Kovar/SnSb10/Fe joints after long-cycle thermal shock (TS). The results indicate that the thickness of interfacial intermetallic compounds (IMCs) at Kovar/SnSb interface with ultrasonication was less than 1 μm even after 2000 cycles, and almost no defects were detected, exhibiting superior microstructure stability. The ultimate shear strength with and without ultrasonication reached 58 MPa and 45 MPa, respectively. From TEM analysis, the nanoprecipitates inside Sn or IMC region primarily consisted of Ni₃Sn₄ and Ni₃Sn phases. The ultimate outstanding mechanical property after long-cycle TS was attributed to dispersed strengthening and dislocation strengthening. This work provides valuable insights into the stability and reliability of the Kovar/SnSb10 system.