The thermal performance of a heat sink is analyzed according to the position of the partially heated surface. Numerical models for simulating forced convection were used to analyze the heat transfer between the heat sink and ambient air. The optimal partial heating position was discussed in terms of the effects of total heat transfer rate, air velocity, the ratio of total heat sink length to partially heated surface width, the thermal conductivity of the heat sink, and the thickness of the heat sink base. Finally, a correlation was suggested to determine the partial heating position that maximizes thermal performance by using the experimental design method. It was thus possible to reduce the thermal resistance of the heat sink by up to approximately 30% by finding the optimal partial heating position. (C) 2018 Elsevier Ltd. All rights reserved.