Microstructure–thermal properties of Cu/Al2O3 bilayer prepared by direct bonding

The thermal conductivity of Cu/Al2O3 bilayers prepared by a direct-bonding technique was determined. The direct-bonding process started with the pre-oxidation treatment of a Cu plate at a temperature less than 600 °C. Though a thin oxide layer was located on the surface of the plate after treatment, the oxygen solutes began to diffuse into the interior of Cu plate prior to bonding. Bonding occurred by a eutectic liquid formed at 1075 °C. No reaction interphase was observed at the Cu–Al2O3 interface. The thermal resistance of the Cu/Al2O3 interface is very low. The extremely low thermal resistance can be related to the clean interface between the two materials.