Fluid flow and heat transfer characteristics of liquid cooled foam heat sinks

In this paper, the fluid flow and heat transfer characteristics of liquid cooled foam heat sinks (FHSs) are investigated. Open-celled copper foam materials with two pore densities of 60 and 100 PPI (pore per inch) and four porosities varying from 0.6 to 0.9 were bonded onto copper base plates to form the FHSs. The FHSs were then assembled on flip chip BGA packages (FBGA) with thermal grease as the thermal interface material. A liquid cooling test loop was established to study the flow and heat transfer characteristics. Both pressure drops and thermal resistances were obtained through experiments. For the four 60 PPI FHSs, the one with the lowest porosity of 0.6 is found to possess the lowest thermal resistance level with the largest pressure drop. The FHSs with 100 PPI generally have slightly lower thermal resistances at the same flowrates but much larger pressure drops than the FHSs with 60 PPI. For overall performance assessment, the thermal resistances of the FHSs are plotted against the pressure drop and the pump power, together with a microchannel heat sink. At the given pressure drop and pump power, the thermal resistance of the FHS with a porosity of 0.8 and pore density of 60 PPI is the lowest among all the FHSs and is comparable to that of the microchannel heat sink. This study reveals that FHSs are a promising option in high performance electronics cooling.