A dual base plate heatsink for use in dissipating heat for electronic devices with thermal contact between fins and the base plates and manufactured without welding. Separately extruded fins are connected to both base plates by placing the fins side by side in channels in both base plates. In order to couple the base plates and the fins, the base plates are maintained at a constant relative distance and a swaging tool is passed adjacent the fins and between the base plates in a direction parallel to the surface of the base plates. The swaging tool applies pressure to the base plates to thereby swage the base plates against the ends of the fins.