Relieving the residual stresses in diamond/copper combination using the Y2W3O12 NTE particles doped Ag-based filler alloys

Fabrication of the diamond microwave windows faced challenges due to the pernicious residual stresses within the diamond/copper brazing joint. In this work, the Y₂W₃O₁₂ (YWO) with negative coefficient of thermal expansion were introduced into AgCuSnTi filler to mitigate the residual stresses of the diamond/copper joint. The effect of the YWO content on the microstructure, shear strength, and the residual stresses of the joints were investigated. Furthermore, the joint formation mechanism and the reliving mechanism of the residual stresses was unveiled. The microstructure of the joints brazed with AgCuSnTi+1 vol% was mainly composed of Ag(s,s), Cu(s,s), CuSn₃Ti₅, CuTi, and YWO particles. The TiO₂+Ti₄Cu₂O double layers formed surrounding the YWO particles facilitated the bonding between the metallic filler and non-metallic YWO particles. The residual stresses detected are relieved by 15.8 %, and the corresponding shear strength of the joints reached 253.7 MPa. When increasing the content of YWO (3 and 5 vol%), the number of the CuSn₃Ti₅, and CuTi was reduced, however, the YWO aggregation defects formed wreaked the bonding strength of the joints severely. To conclude, a small amount of YWO addition could relive the residual stresses within the diamond/copper joints and provide guidance for fabrication of the diamond microwave windows.