Study of a new technique for improving strength of brazing joint of sapphire microwave window

In order to improve the strength of brazing joint of sapphire microwave window with oxygen-free copper, a new technique is studied in this paper. The new technique consists of three parts: a) plating Ti film on sapphire surface, b) covering the surface with Ni film and pre-diffusing at high temperature, and c) brazing the surface with conventional AgCu filler metal. Using this technique, the shear strength of brazing joint specimens can reach up to 145 MPa. Further study shows that a continuous diffusion layer generated in the interface of sapphire plays a key role to improve the joint strength.