Polyol-based phase-change thermal interface materials

Polyol-based phase-change thermal interface materials that exhibit high thermal contact conductance and thermal stability have been developed for microelectronic cooling. By using a diol (polycaprolactone or polyester diol in the form of 2-oxepanone) of molecular weight 1,000-2,000 amu, along with 4 vol.%-hexagonal boron nitride particles, this work attained thermal contact conductance (at 70 degrees C, across copper surfaces) that is higher than that attained by using paraffin wax, polyether glycol, polyethylene glycol, or tetradecanol (in place of the diol) and that attained by commercial phase-change thermal interface materials. The thermal stability of the diol is superior to the other phase change materials mentioned above, although the heat of fusion is lower. Boron nitride is more effective than carbon black (also 4 vol.%) for enhancing the conductance, but carbon black diminishes the heat of fusion less than does boron nitride.