Analysis of interface structure and composition of Cu/Al2O3 for the high stability of DBC (direct bonded copper)

Copper and aluminum oxide have been bonded using two procedures; solid state bonding and liquid state bonding by the eutectic method. As a consequence of these treatments, the CuAlO2 and CuAl2O4 phases are formed at the interface. The phases transformations of delafossite CuAlO2 and spinel CuAl2O4 structures shows a particular orientation with respect to oxygen content during the joining process leading to improve the mechanical properties. In this study, eutectically bonded copper-aluminum oxide joints are subjected to oxygen potential. The interface phases are of important characteristics for manufacturing DBC substrates. Especially, the bonding strength is closely related to the different phases of eutectic conditions. One of these conditions, we used a copper powder in order to control the concentration of oxygen. The amount of copper powder to reduce the oxygen concentration increased, the bonding strength after firing increased due to the increase of CuAlO2 as well as CuAl2O4. In this paper, we identify the phase characteristics using electron backscatter diffraction (EBSD) for phase created by varying the components of the interface.