Thermal contact resistance and adhesion studies on thin copper films on alumina substrates

A new photothermal method for measuring the thermal contact resistance in the interfacial area is presented. Copper thin films were prepared on alumina substrates by physical vapour deposition. On the basis of a mathematical model developed here, thermal contact resistance was determined in samples of various thicknesses and processed under various argon pressures. The effects of these parameters on the films and interface properties are discussed. A correlation between the thermal contact resistance and the adhesion, as determined by the scratch test, is found. In order to understand the origin of the mean critical load and the thermal contact resistance evolution, observations were made by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results obtained have shown that the change in stress level in the copper film and the formation of a new compound in the interfacial area seem to be the main reasons for the enhancement of heat transfer.