The introduction of dimples to heat transfer surface can effectively improve the heat transfer performance of a microchannel heat sink with impinging jets (MU). MIjs with different dimple structures, including convex, concave, and mixed dimples, are compared with MUs without dimples by numerical simulation and the application of the field synergy principle. Results indicate that (1) MUs with convex dimples exhibited the best cooling performance, followed those without dimples, with mixed dimples, and with concave dimples; (2) the application of convex dimples could decrease flow resistance in MUs; and (3) among all tested cases, MUs with convex dimples exhibited the best overall performance, followed by MIJs without dimples, with mixed dimples, and with concave dimples. (C) 2017 Elsevier Ltd. All rights reserved.