Brazing copper and alumina metallized with Ti-containing Sn0.3Ag0.7Cu metal powder

A Sn-based metallization layer was successfully prepared on the surface of alumina at 900 degrees C by using Ti-containing Sn03Ag0.7Cu (SAC, wt.%) metal powder. Reliable alumina/copper joints were obtained by brazing pre-metallized alumina and copper using SAC filler at 580-660 degrees C for 5 min. The typical interfacial microstructure of brazed joint was copper/Cu3Sn layer/Cu6Sn3 layer/beta-Sn layer containing Ti6Sn3 phase and Al2O3 particles/alumina. As brazing temperature increased, the Cu-Sn intermetallic layers thickened rapidly and the amount of beta-Sn phase reduced. When brazing temperature exceeded 640 degrees C, Kirkendall voids and microcracks formed at copper/Cu3Sn interface. The joints brazed at 580-620 degrees C possessed high shear strength and the highest average shear strength of 32 MPa was achieved when brazed at 620 degrees C. Fracture analyses indicated that the joints mainly fractured inside of the Cu6Sn5 layer and beta-Sn layer. The joints brazed above 620 degrees C demonstrated low shear strength due to the formation of Kirkendall voids which caused the joints fractured along the Cu/Cu3Sn interface. (C) 2015 Elsevier Ltd. All rights reserved.