Effect of Ni foam on the microstructure and properties of AlN ceramic/Cu brazed joint

Aluminum nitride (AlN) ceramics and oxygen-free Cu were brazed with multilayer filler consisted of Ag-Cu-Ti +Ni foam. The microstructure and forming principle of AlN/Cu joints were studied and the influence of Ni foam on the joints was focused. The result shows that the composition of AlN/Cu joint was AlN/TiN/Ni3Ti+Cu(s,s)+CuTi+Ni foam+Ag(s,s)/Cu. The joint strength was only 66.7 +/- 3.7MPa with pure Ag-Cu-Ti solder and the fracture occurred inside AlN ceramics due to the residual stress. The foam nickel reacted with Ag-Cu-Ti filler metal to form Ni3Ti during brazing process. Ni foam still retained the basic skeleton structure during brazing, and the mechanical capacity of AlN/Cu joint was enhanced significantly. The maximum shear strength of the brazed joint can reach 89.6 +/- 4.5 MPa with .1 mm Ni foam, and the fracture position changed to the brazing filler. The result shows that nickel foam can reduce the residual thermal stress, and the mechanical properties of AlN/Cu joints were improved.