Microstructure and mechanical properties of AlN/Cu joints brazed by Ag-Cu-Ti + Y₂O₃ composite brazing alloy

Copper-clad ceramic plate is an important heat dissipation component in an insulate-gate bipolar transistor (IGBT), which is composed of high thermal conductivity ceramic and pure copper connection. Active metal brazing is an important way to realize high-performance manufacturing of copper-clad plate. The low-expansion Y₂O₃ particles were used to enhance the Ag-Cu-Ti-based composite brazing alloy for connecting AlN and copper. The effect of brazing process (brazing temperature and holding time) and Y₂O₃ content in the brazing alloy on the microstructure and mechanical properties of the joint was systematically studied. The mechanism of joint formation was clarified, and the relationship between the microstructure and mechanical properties of the joint was established. The results show that increasing brazing temperature or extending holding time is beneficial to forming a uniform and dense brazing structure. Appropriate Y₂O₃ content (1%–3%) in the brazing alloy can refine the grain, alleviate the thermal mismatch of the joint, and improve the joint performance, but too much Y₂O₃ (4%–5%) will lead to particle agglomeration and welding defects. The shear strength of AlN/Cu joint obtained by Ag-Cu-Ti + 3% Y₂O₃ composite brazing alloy at 850 ℃/10 min is 275 MPa, which is the highest value reported in the literature. This study provides theoretical and technological guidance for high-performance manufacturing of an IGBT copper-clad ceramic plate.