A thin layer of thermally conductive but electrically insulating dielectric is laminated between a metal base and a copper foil. The copper foil is etched into the desired circuit pattern and the metal base draws heat away from this circuit through the thin dielectric.
Benefits of Aluminum PCBs:
1. Heat dissipation is dramatically superior to standard FR-4 constructions.
2. The dielectrics used are typically 5 to 10 times as thermally conductive as conventional epoxy-glass and a tenth of the thickness
3. Thermal transfer exponentially more efficient than a conventional rigid PCB.
4. Lower copper weights than suggested by the IPC heat-rise charts can be used.