Feasibility study of fractal-fin heat sink for improving cooling performance of switching power converters

Recent progress of the semiconductor switching devices enabled the high-frequency design of the switching power converters, which successfully led to the miniaturization of the circuit elements. However, the heat sink has scarcely been miniaturized during past decades. Now, the heat sinks are one of the major obstacles that hinder further size reduction of the switching power converters. Conventionally, the heat sinks are designed to have a number of flat aluminum fins extending from the aluminum base. However, these flat fins tend to make the laminar airflow passing through the fins. This laminar airflow keeps the air contacting the fin surface to remain on the surface. As a result, the fin surface is covered with the air already heated in the upstream and the fresh open air is prevented from contacting with the fin surface, thus deteriorating the cooling performance of the heat sinks. To overcome this issue, this paper proposes a heat sink structure with a novel fin geometry. The proposed fin geometry incorporates two sizes of the louvers, which are disposed to form a fractal-like pattern. These louvers are intended to break the laminar flow on the fin surface, thus promoting the mixing of the air to improve the cooling performance. FEM simulation of the heat transfer was carried out to verify this concept. The result showed improvement in the heat transfer coefficient, implying the effectiveness of the proposed structure for miniaturization of the heat sink.