Thermal Solution for Cooling of Electronic Equipment using Lotus-type Porous Copper Heat Sink

One issue for mounting next-generation power devices is to solve the hot spot problem. Therefore, a heat sink having a small volume and high heat transfer performance is required for mounting the power element, and research on using a porous metal as a heat sink has been widely conducted in recent years. Among the porous metals, lotus metal having unidirectional straight fine pores can increase the amount of heat transfer rate per unit volume with a small pressure loss by reducing the pore diameter and the fluid flow path length. By using lotus metal as a water-cooled heat sink, we obtained excellent cooling performance, that is 2 to 3 times higher cooling performance than that of a conventional grooved heat sink. For air-cooled heat sinks, we developed plane lotus heat sinks using lotus metals that conduct heat from the central base plate mounted by electronic element to surrounding fins in the same plane surface and dissipate heat through the fins. And we also developed lotus heat sinks combined with heat-pipes. It was shown that the thermal resistance per unit volume can be reduced by these lotus heat sinks compared to the grooved heat sink with fine gaps. As a comparing method of cooling performance of the various type of heat sinks, we introduced the method that compares the thermal conductance per volume and the thermal conductance per theoretical power of the heat sink. By this method, the relationship between the cooling performance per volume and the power required for cooling can be clarified. Thermal design can be advanced by using the above comparison method for evaluation of the heat sink under design for the development goal.