Determination of the Thermal Conductance of Thermal Interface Materials as a Function of Pressure Loading

Abstract

This thesis presents an experimental apparatus and methodology for measuring the interface conductance of thermal interface materials (TIMs) as a function of clamping pressure. The experimental apparatus is a steady state characterization device based on the basic premise presented in ASTM D5470 – 06. The setup is designed to develop an approximately one dimensional heat transfer through a TIM sample which is held between two meter bars. The temperature is measured along the meter bars using resistance temperature detectors (RTDs) and the temperature drop across the interface is extrapolated from these measurements and then used to calculate the conductance of the interface. This setup and methodology was used to characterize six commercial TIMs at pressures ranging from 0.17-2.76 MPa (25-400 psi). These TIMs included: Tgrease 880, Tflex 720, Tmate 2905c, Tpcm HP105, Cho-Therm 1671, and Cho-Therm T500. The measured conductance values for the various tests ranged from 0.19 to 5.7 W/cm2K. A three dimensional FEA model of the experimental setup was created in COMSOL Multiphysics 4.2a. This model was compared to the experimental data for a single data point and showed good correlation with the measured temperatures and conductance value.