Effective Thermophysical Properties of Thermal Interface Materials: Part II — Experiments and Data

A new method for determining effective thermal conductivity and Young’s modulus in thermal interface materials is demonstrated. The method denoted as the Bulk Resistance Method (BRM) uses empircal thermal resistance data and analytical modeling to accurately predict thermophysical properties that account for insitu changes in material thickness due to external loading and thermal expansion. The BRM is demonstrated using commercially available sheets of Grafoil GTA. Tests were performed on thermal joints consisting of two Al 2024 machined surfaces with layers of Grafoil GTA in the interface. Test conditions included a vacuum environment, 0.2–6.5 MPa contact pressure, a nominal 50°C mean interface temperature and a continuous loading and unloading cycle. Test results indicated that the BRM consistently predicted thermal conductivity independent of the number of layers tested and that the predicted results were significantly lower than values reported using conventional ASTM test procedures.