Aluminum base PCB’s are used when a good heat dissipation is needed. This technology was originally developed for the power-supply industry, however nowadays the LED lightning industry is the largest consumer of Aluminum boards.
The Aluminum base PCB use a very thin layer of thermally conductive but electrically insulating dielectric, which is laminated between the metal base and the copper layer. The metal base is designed to draw heat away from the circuit through the thin dielectric.
While the most common construction of Aluminum boards is a single-layer, multi-layer boards can also be made and are common in the high performance power supply applications.