Heat transfer and pressure drop characteristics of micro pin fin arrays in a narrow rectangular channel with an air through flow are studied with different flow rates ranging from laminar to turbulent flow. Copper micro pin fins 150-400 mu m long and 75-700 mu m in diameter are fabricated by microfabrication techniques. Performance ratios that compare heat transfer to pressure drop characteristics are evaluated to investigate performance of the micro pin-fin surfaces when both heat transfer and pressure drop are important. The results indicate that fluid dynamic effects generated around micro pin fins take a more dominant role for heat transfer enhancement than the area increase due to micro pin fins. A maximum heat transfer enhancement of 79% over plain surface is achieved due to a micro pin-fin surface with a height of 250 mu m and a diameter of 400 mu m. It is expected that the micro pin-fin surfaces can be used for improving cooling performance of fan-assisted heat sinks for electronics thermal management. (C) 2015 Elsevier Ltd. All rights reserved.