Interfacial microstructure and mechanical property of brazed copper/SiO2 ceramic joint

Vacuum brazing of copper to SiO2 electroceramics was carried out using commercially obtained Ag-Cu-Ti filler alloy. The effects of brazing temperature and bonding time on the interfacial microstructure and mechanical properties were investigated. The microstructure observation revealed that the typical interfacial structure could be expressed as SiO2 ceramic/Ti5Si3 + Ti4O7/Ti2Cu + Ti3Cu3O/Ag (s,s) + Cu (s,s)/Copper. The migration of Ti in brazing seam, which promoted the reaction of Ti with the SiO2 ceramic, was a positive factor on the interfacial microstructure and mechanical properties. With increased the brazing temperature or holding time, the thickness of Ti5Si3 + Ti4O7 reaction layer thickened, meanwhile, the amount of AgCu eutectic structure decreased. The shear strength firstly increased and then decreased with brazing temperature increasing or bonding time prolonging. The maximum shear strength of 22 MPa was obtained at 850 °C for 5 min. Its fracture occurred both along the ceramic substrate adjacent to the bonding interface and along the reaction layer, showing a mixture fracture mode.