Ag-CuO钎料空气反应钎焊AlN陶瓷接头组织及性能

Reactive air brazing of AlN ceramics is achieved using Ag-CuO brazes. The effects of CuO content, brazing temperature and pre-oxidation temperature on interface microstructure and mechanical properties are studied. The joining mechanism is analyzed. When the composition of brazes is Ag-6 mol% CuO, the highest shear strength about 13.9 MPa of the AlN/Ag-CuO/AlN joints is obtained under the brazing parameters of 1 000 ℃/5 min. The interface microstructure, fracture morphology and composition of the joints are analyzed by SEM, EDS and XRD. The typical joint interface microstructure is AlN/CuAl₂O₄/CuO/AlN+Ag+CuO/CuO/CuAl₂O₄/ AlN. However, a defect-free joint can not be obtained under this condition. In order to reduce the residual thermal stress and obtain a defect-free joint, a pre-oxidation treatment is applied to the AlN ceramic to form an Al₂O₃ layer on the surface of the AlN ceramic. When the pre-oxidation parameter is 1 000℃/5 h, the thickness of the Al₂O₃ layer on the surface of the AlN ceramic is about 10 μm. The pre-oxidized AlN ceramics are joined at a brazing temperature of 1 000 ℃/5 min using a brazing filler metal of Ag-6 mol%CuO to obtain a defect-free joint. The typical interfacial microstructure of the joint is AlN/Al₂O₃/CuAl₂O₄/CuO/Ag+Al₂O₃/CuO/CuAl₂O₄/ Al₂O₃/AlN. The joint has a shear strength of up to 22.6 MPa and an increase of 62.5% compared to the unoxidized AlN ceramic joint. When the joints are subjected to shear resistance test, the fracture sections mainly are observed in the AlN ceramic.