Thermal Diffusivity Measurement of a Thin Film in the Direction across the Film by AC Calorimetric Method

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Abstract
A method utilizing ac calorimetry for measuring thermal diffusivity of a thin film in the direction across the film is proposed based on both 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 µm was experimentally examined in the frequency range from 4 to 140 Hz at room temperature. The standard deviation of the analyzed thermal diffusivity was less than 0.2%. The value of the thermal diffusivity is consistent with that obtained with a laser flash method.