Thermally anisotropic composite heat spreaders for enhanced thermal management of high-performance microprocessors

Numerically investigated is the performance of thermally anisotropic composite spreaders for enhanced thermal management of high performance microprocessors. The spreaders are comprised of two 0.5 mm-thick Copper (Cu) laments separated by a thin (δ = 0.25-1.0 mm) layer of thermally anisotropic material, such as graphite or highly oriented pyrolytic graphite (HOPG). The exposed rough surface (Ra = 1.79 μm) of the top Cu lament is cooled by saturation nucleate boiling of PF-5060 dielectric liquid. The performed 3-D numerical analyses quantify the effect of the Figure-of-Merit (FOM) of the thermally anisotropic layer, on the total thermal power removed, the spreader's total thermal resistance, and the maximum temperature of the underlying 20 × 20 mm chip. The spreaders suppress the propagation of the chip hot spots, and increase the total power removed. They remove 160-317 W of the thermal power dissipated by the underlying chip, at a chip maximum surface temperature of 80-120 °C. Developed empirical correlations estimate the total thermal power removed and the surface area of the composite spreaders. Increasing the FOM from 0 (all Cu spreader) to 400 (highly anisotropic spreader) increases the total thermal power removed from ∼88 to ∼450 W and the spreader dimensions from ∼25 × 25 to ∼69 × 69 mm. The total thermal resistance of the spreaders ranges from 0.16 to 0.4 °C/W.