A Sensitivity Analysis of a Thin Film Conductivity Estimation Method

Abstract

An analysis method was developed for determining the thermal conductivity of a thin film on a substrate of known thermal properties using the flash diffusivity method. In order to determine the thermal conductivity of the film using this method, the volumetric heat capacity of the film must be known, as determined in a separate experiment. Additionally, the thermal properties of the substrate must be known, including conductivity and volumetric heat capacity. The ideal conditions for the experiment are a low conductivity film adhered to a higher conductivity substrate. As the film becomes thinner with respect to the substrate or, as the conductivity of the film approaches that of the substrate, the estimation of thermal conductivity of the film becomes more difficult. The present research examines the effect of inaccuracies in the known parameters on the estimation of the parameter of interest, the thermal conductivity of the film. As such, perturbations are introduced into the other parameters in the experiment, which are assumed to be known, to find the effect on the estimated thermal conductivity of the film. A baseline case is established with the following parameters: Substrate thermal conductivity 1.0 W/m-K Substrate volumetric heat capacity 106 J/m3-K Substrate thickness 0.8 mm Film thickness 0.2 mm Film volumetric heat capacity 106 J/m3-K Film thermal conductivity 0.01 W/m-K Convection coefficient 20 W/m2-K Magnitude of heat absorbed during the flash 1000 J/m2 Each of these parameters, with the exception of film thermal conductivity, the parameter of interest, is varied from its baseline value, in succession, and placed into a synthetic experimental data file. Each of these data files is individually analyzed by the program to determine the effect on the estimated film conductivity, thus quantifying the vulnerability of the method to measurement errors.