Advantages of Aluminum PCBs:

Use of Aluminum PCBs offers several advantages over that of regular FR-4 PCBs. Compared to standard FR-4 constructions, the Aluminum PCBs offer a dramatically superior heat dissipation. Although only a tenth of the thickness of conventional epoxy-glass, the dielectrics in an Aluminum PCB can be 5 to 10 times more conductive thermally. This makes thermal management in Aluminum PCBs exponentially more efficient compared to that of a conventional rigid PCB. Therefore, designers can use lower copper weights in Aluminum PCBs than those suggested by IPC in their heat-rise charts.
 
Different Types of Aluminum PCBs
Manufacturers have been successful in innovating different types of Aluminum PCBs such as:
 
Flexible Aluminum PCBs: These use new flexible dielectrics featuring Polyimide resin systems with ceramic fillers for excellent electrical insulation, thermal conductivity, and flexibility. The metal base uses flexible Aluminum such as 5754 or similar. The combination produces a PCB that the user can bend into place, but not use for regular flexing.
 
Hybrid Aluminum PCBs: These use a non-thermal material as the sub-assembly, which the fabricator processes independently, and then bonds to the Aluminum base using thermal materials. For instance, a conventional 2- or 4-layer FR-4 PCB bonded to an Aluminum base helps to improve heat dissipation and mechanical rigidity.
 
Multi-Layer Aluminum PCBs: Fabricators make these from multiple layers of thermally conductive dielectrics. The designer can place one or more layers of circuits buried in the dielectrics, and use blind and buried vias. However, these PCBs are not so effective in transferring heat.
 
Through-Hole Aluminum PCBs: Prior to lamination, the fabricator must pre-drill the Aluminum base, and back-fill it with dielectric to form the core of a multi-layer PCB. This allows the fabricator to laminate both sides of the Aluminum base with thermal materials and PCB subassemblies. After lamination, the fabricator can drill the assembly like drilling a conventional multilayer PCB, with plated through holes passing through the clearances in the Aluminum. This is the most complex construction of an Aluminum PCB.