Brazing of Si{sub}3N{sub}4 ceramic to copper

摘要

Silicon nitride is one of the most promising structural ceramics for high temperature applications.There is an increasing demand for joining this ceramic to metal structures. Direct brazing using anactive filler metal has been found to be a reliable and simple technique, capable of producing strongand reliable joints. Several factors affecting the strength of such joints have been investigated and arereported in the literature. This preliminary study is directed mainly towards investigating the effect ofthe surface preparation of the base metal and of the load applied to the joint during brazing on thestrength of brazed joints. Experiments were conducted for brazing silicon nitride to copper using acommercial Ag-Cu-Ti active filler metal with and without applied load. The Si{sub}3N{sub}4/Cujoint shear strength and shear energy were determined for various brazing conditions. The initiationof the fracture was detected using acoustic emission sensing. The mechanism of bond formation isdescribed, with emphasis placed on the active metal reaction with the joint materials. Both theinterfacial adhesion and the microstructure were investigated. It was found that the smoother thesurface finish of the copper base metal, the higher the joint shear strength attained. The shear energyof the joints increased substantially as a result of applying a light load on the joints during brazing.