A heat transmitting slug is attached to a chip or other heat emitting electronic component by an adhesive. A heat sink is mounted on the slug by one or more screws or other fasteners, preferably with thermal grease between the bottom of the heat sink base and the top of the slug. The top of the slug is formed with a longitudinal tongue and the base of the heat sink with a mating groove. Preferably the base of the heat sink is offset upwardly above the groove to resist tendency to fracture under stress.