The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks (MCHS) subjected to a uniform heat flux is investigated by means of numerical simulations. Various geometrical configurations are examined, particularly, the combinations of rectangular solid and perforated blocks, used to create a disturbance in the flow. The analysis focuses on several key aspects and related metrics, including the temperature distribution, the mean Fanning friction factor, the pressure drop, the Nusselt number, and the overall heat transfer coefficient across a range of Reynolds numbers (80–870). It is shown that the introduction of such blocks significantly enhances the heat transfer performances of the MCHS compared to the straight-through flow channel. Specifically, a case is found where the Nusselt number increases by 2.3 times relative to the reference case. The integration of perforated blocks facilitates the generation of vorticity within the channel, promoting the mixing of cold and hot fluids. Notably, MCHS incorporating perforated rectangular blocks exhibit more pronounced heat transfer benefits at Reynolds numbers smaller than 400.