Measurement of the thermophysical properties of self-suspended thin films based on steady-state thermography

To measure the in-plane thermal conductivity and the infrared emissivity of thin films, a steady-state IR micro-thermography with simplified measurement procedure and new data processing method is presented in this paper. Thermal images at different optical heat intensities were collected by an IR camera. By subtracting two measurement results, the background thermal radiation was eliminated. Infrared emissivity, heat flux density and in-plane thermal conductivity were obtained by data fitting. The most important advantages of the proposed method were that the background thermal radiation was eliminated and the complicated optical absorption measurement was replaced by heat power measurement. We have performed measurements on self-suspended polyimide films with different thicknesses. For 504 nm thick film, the thermal conductivity and infrared emissivity in 7∼14 µm were 0.18 Wm⁻¹K⁻¹ and 0.07, respectively. The measurement uncertainty of the thermal conductivity and infrared emissivity were lower than 13% and 10%, respectively, which were much lower than the previous reported value (20%) from the steady-state method. Our measurement procedure was suitable for analyzing thin films with a wide range of thermal properties.