THERMAL-DIFFUSIVITY MEASUREMENT OF A THIN-FILM IN THE DIRECTION ACROSS THE FILM BY AC CALORIMETRIC METHOD

A method utilizing ac calorimetry for measuring thermal diffusivity of a thin film in the direction across the film is proposed based on bot h theoretical analysis and experimental examination. The sample system is composed of three parts: a medium, a thin film sample and a second medium. For precise measurement, it is essential that one of the two media is made of the same material as the thin film sample. With this system, a thin polyimide film with thickness of 75 mum was experimenta lly examined in the frequency range from 4 to 140 Hz at room temperatu re. The standard deviation of the analyzed thermal diffusivity was les s than 0.2%. The value of the thermal diffusivity is consistent with t hat obtained with a laser flash method.