Thermo-compression bonding of alumina ceramics to metal

Alumina ceramics and Kovar with aluminum interlayer are pressed together under vacuum at temperatures around 600°C for joining. This process produces mechanically strong ceramic to metal bonds in one step in an economic manner. In order to arrive at the optimum conditions for solid-state bonding, effects of bonding temperature, pressure and time on the bond strength have been studied. Bonding kinetics is also elucidated. Irradiation of 99% Al₂O₃ ceramics by 4–5 MV X-rays has been found to increase the bond-strength sharply from 33 to 60 MPa with a dose of 15 k Rads for bonding temperatures around 540°C. The apparent activation energy for the bonding process (Q _B) depends strongly on the type of alumina ceramics. Irradiation of alumina ceramics (99%), prior to joining with Kovar, accelerates the solid-state bonding by reducing (Q _B) from 209 to 76 kJ/mole.