A new method for preparation of direct bonding copper substrate on Al2O3

The oxygen content is usually difficult to control in direct bonding copper process. In this study a new method for preparation of direct bonding copper on alumina ceramic substrates was realized. 96% Al2O3 ceramic substrates were first oxidized by pasting a thin layer of Cu2O and firing at 1150 degrees C in air. Then copper foil was bonded to the substrate by heating to 1070 degrees C in pure N-2 atmosphere. Microstructure and composition of the interface between the copper and Al2O3 ceramic were analyzed. The XRD and EDS results show that an interphase of CuAlO2 was formed and a eutectic transformation between oxygen and copper took place at the interface of the copper and the ceramic substrate. The interface was much thicker than the traditionally bonded substrates, which resulted in a better bonding strength. The directly bonded copper alumina substrate samples showed no evidence of de-bonding after 50 thermal cycles comprising quenching from 220 degrees C to room temperature. (c) 2007 Elsevier B.V. All rights reserved.