Effects of Thin Film Heat Spreader on Hot Spots Mitigation in Heat Sinks

The effects of graphene platelets and diamond-based thin film heat spreaders on maximum temperature of integrated electronic circuits were investigated. A fully three-dimensional conjugate heat transfer analysis was performed to investigate the effects of thin film material and thickness on the temperature of a hot spot and temperature uniformity on the heated surface of the integrated circuit when subjected to forced convective cooling. Two different materials, diamond and graphene, were simulated as materials for thin films. The thin film heat spreaders were applied to the top wall of an array of micro pin fins having circular cross sections. The integrated circuit with a 4 x 3 mm footprint featured a 0.5 x 0.5 mm hot spot located on the top wall, which was also exposed to a uniform background heat flux of 500 W cm(-2). A hot spot uniform heat flux of magnitude 2000 W cm(-2) was centrally situated on the top surface over a small area of 0.5 x 0.5 mm. Both isotropic and anisotropic properties of the thin film heat spreaders made of graphene platelets and diamond were computationally analyzed. The conjugate heat transfer analysis also incorporated thermal contact resistance between the thin film and the silicon substrate. It was found that isotropic thin film heat spreaders significantly reduce the hot spot temperature and increase temperature uniformity, allowing for increased thermal loads. Furthermore, it was found that thickness of the thin film heat spreader does not have to be greater than a few tens of microns.