Bonding Cu to Al2O3 with Bi-B-Zn Oxide Glass Via Oxidation–Reduction Reaction

Bonding Cu on Al 2 O 3 is a key and difficult technology applied in high-power semiconductor devices. A method proposed in this work investigates bonding with a kind of Bi-B-Zn oxide glass powder paste as a solder. Oxidation–reduction reactions between the Cu plate and the solder took place and generated Bi metal during the joining procedure. With an increase in the joining temperature, the tensile strength increased due to the increase of Bi metal formation. The Bi metal played an important role in joining Cu and Al 2 O 3 because of its much better wettability on Cu than that of the oxides. A compound ZnAl 2 O 4 was observed to form between the Al 2 O 3 ceramic and oxide layer, which strengthened the bond.