Thermal conductivity and the cooling performance of Cu alloy-graphite composite heat spreaders fabricated by the powder metallurgy

Metal-graphite composites having two types of microstructure were fabricate d by powder metallurgical processing, and their thermal conductivities were measured to design heat spreaders. The microstructures and thermal conduct ivities of composites fabricated by a pressurized sintering were anisotropi c. The inplane thermal conductivity increased from 350 to 443 W/mK with inc reasing graphite content from 50 to 75 vol%, which was much higher than the through-plane value from 100 to 63 W/mK. The calculated thermal barrier co nductance h(c)) of the metal-graphite interface in the composites was 1.9 t o 2.1 x 10(7) W/m(2)K. On the other hand, a composite having a graphite con tent of 74.8 vol%, which was fabricated using a combinated technique of the cold isostatic pressing (CIP) and a infiltration method, had an isotropic thermal conductivity of 265 W/mK. Based on the above data, the cooling perf ormance of the anisotropic composite having a graphite content of 75 vol% a s heat spreaders for a microprocessor unit was calculated using three-dimen sional FEM. The calculation indicated that as the thickness of the composit e decreased, the cooling performance of the composite approached that of pu re Cu heat spreader having the same thickness.