Boron Nitride Particle Filled Paraffin Wax as a Phase-Change Thermal Interface Material

Wax (predominantly tricosane paraffin wax, with a melting temperature of $48°C$⁠) filled with hexagonal boron nitride (BN) particles $(5-11μm)$ was found to be an effective phase-change thermal interface material. The thermal contact conductance, as measured with the interface material between copper surfaces, decreased with increasing temperature from $22to48°C$⁠, but increased with increasing temperature from $48to55°C$⁠. The melting of the wax enhanced the conductance, due to increased conformability to the mating surfaces. For a given BN volume fraction and a given temperature, the thermal contact conductance increased with increasing contact pressure. However, a pressure above $0.30MPa$ resulted in no significant increase in the conductance. The conductance increased with BN content up to $6.2vol.%$⁠, but decreased upon further increase to $8.6vol.%$⁠. The highest conductance above the melting temperature was $18×104W∕m2.°C$⁠, as attained for a BN content of $4.0vol.%$ at $55°C$ and $0.30MPa$⁠. Below the melting temperature, the highest conductance was $19×104W∕m2.°C$⁠, as attained for a BN content of $6.2vol.%$ at $22°C$ and $0.30MPa$⁠.