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.