Thermal Diffusivity Measurement in Through-Thickness Direction of Dielectric Film With Metal Substrate

Thin polymer films are widely used as dielectrics in devices operating in the field of electrical engineering, and thermal diffusivity
${D}$
in through-thickness direction is one of their crucial thermophysical parameters concerned with heat dissipation within the involved devices. However, there exist some difficulties in precisely measuring the thermal diffusivity of micron-thick dielectric film. Considering that the measuring principle of thermal pulse method (TPM) for mapping space charge profile is strongly related to the thermal diffusivity of the film sample, a novel method is proposed to retrieve the coefficient based on the data analysis of the thermal response current of thin polymer dielectric film with a thermally conductive substrate. Experimental results of presentative polymer products biaxially oriented polypropylene (BOPP) and polyimide (PI) films with thickness of several micrometers show well consistency with the data in the literature, demonstrating the feasibility of the proposed method.