Excellent mechanical properties obtained in Si3N4/Cu joint with a network structure via brazing with AgCuTi/porous Cu foam/AgCuTi sandwich composite filler

AgCuTi/porous Cu foam/AgCuTi sandwich composite filler was used as the interlayer to enhance the brazing strength of the Si ₃ N ₄ /Cu joints. The typical microstructure of the joint brazed with the sandwich composite filler at 880 ℃ was Si ₃ N ₄ /TiN/Ti ₅ Si ₃  + CuTi/Ag(s,s) + Cu(s,s)/Cu, where the Ag(s,s) + Cu(s,s) layer is an interpenetrating network structure. And the thickness of the TiN reaction layer increased from 0.58 µm to 1.28 µm when the thickness of the porous Cu foam layer increased from 100 µm to 300 µm. The Si ₃ N ₄ /Cu joint obtained with 300 µm porous Cu foam owned the highest shear strength of 121.7 MPa, which improved by 281% than that with the use of AgCuTi filler alone. Further EBSD analysis and finite element simulation revealed that the reduction in residual stress and the increase in plastic deformation effect induced by the Ag(s,s) + Cu(s,s) interpenetrating network structure are the key factor for the enhancement of the mechanical properties of this Si ₃ N ₄ /Cu joint brazed with AgCuTi/porous Cu foam/AgCuTi sandwich composite filler.