Effects of Ti thickness on microstructure and mechanical properties of alumina–Kovar joints brazed with Ag–Pd/Ti filler

Alumina, metalized with Ti by magnetron sputtering, has been successfully bonded to a Kovar alloy using Ag–5 wt% Pd filler. The effects of Ti content on the interfacial microstructure and mechanical properties were investigated. The results showed that a reaction layer was formed at the alumina/filler interface. Microanalysis indentified the reaction products to be titanium oxide and Pd–Ti compounds. The thickness of the reaction layer and the residual filler layer played determinable roles on the joint strength. The maximum four-point flexural strength of the brazed joints at room temperature reached as high as 177.3 MPa when the thickness of Ti layer was 3 μm.