Abstract: A generally annular heat sink is adapted to be compressed and inserted within the cylindrical sleeve of a motor or the like, with the spring action of the heat sink being sufficient to hold it in place after it is released. Channels along the outer surface of the heat sink provide reservoirs for a potting compound to further fix the heat sink and improve the thermal conductivity between the heat sink and sleeve. A PC board is mounted to the heat sink only through the electrical leads of power transistors to provide a limited amount of flexure to accommodate insertion and removal of the heat sink. In a second embodiment, a generally rectangular heat sink is mounted in a conduit box by tabs which are deformed to fit within channels along opposite edges of the heat sink. An access hole in the side of the conduit box and aligned with the channel permits a pin to be inserted therethrough to push the tabs out of the channel and release the heat sink and PC board from the conduit box.