Bonding of Al to Al2O3 via Al–Cu eutectic method

Abstract The Al oxidation layer in the manufactures of direct aluminum bonded Al 2 O 3 substrates (DAB) has been a long-term trouble for industries. In this work we propose a new method for fabricating the DAB substrates with no requirement of high vacuum or active O 2 -getters. The new method comprises two stages: (i) Cu-film is bonded onto Al 2 O 3 ceramic surface via DBC method; (ii) Al foil is joined to the DBC substrate by Al–Cu eutectic method at 600 °C in pure N 2 atmosphere. KF–AlF 3 flux was used to disrupt the Al–oxide layer on the surface of Al foil. The wetting ability was significantly enhanced due to the diffusion of Cu into Al and the dissolving of Al. The final contact angle is achieved of 22.10°. Microstructure and composition of the interface between Al and Al 2 O 3 substrate were analyzed. The XRD, SEM and EDS results show that two new phases Al 2 Cu and CuAlO 2 were formed, leading to a strong bonding along the interface. The thermal cycling reliability and adhesion strength of DAB substrates were also evaluated. The results show that the DAB substrates can satisfy application requirements completely.