An active array heat sink cooled by natural free convection is disclosed. A long extruded heat sink is partitioned into multiple, shorter zones separated by gaps having horizontal baffles. The gaps and baffles serve to act as air vents and air inlets for the convection currents. As such, the heat transfer for the overall heat sink is improved because hot convection currents are vented and replaced by cool ambient air along the length of the heat sink.