Pyrolytic Graphite Heat Sinks: A Study of Circuit Board Applications

Pyrolytic graphite (PG) is of interest as a heat sink and heat exchanger material because it has a thermal conductivity greater than copper with a density less than aluminum. However, its anisotropic molecular structure creates a significant challenge to the realization of practical thermal performance benefits. The current computational study compares the performance of a high-thermal conductivity PG, Pyroid® HT, to aluminum over a design space that focuses on circuit board component cooling. The applications considered in this paper include flat-plate thermal spreaders and finned heat sinks. The results are presented in a form that can be used to provide material and geometry selection during preliminary design. The competition between the size of the heat source, the thickness of the spreader, its size, and the strength of the forced convection is quantitatively presented. In addition, the thicknesses that provide the optimal performance are determined and the performance is compared with a thickness that would be approximately cost neutral. A single isotropic analytical fin model is used to quantitatively establish the fin sizes and aspect ratios that would demonstrate the largest performance benefit if made from PG. Finally, the impact of Pyroid® on the size of finned heat sinks is examined.