Usually PCB uses a fiberglass substrate (FR4 is the standard substrate used by PCB manufacturers), an aluminum entry sheet PCB consists of an aluminum substrate, a high thermal conductivity dielectric layer, and a standard circuit layer. The circuit layer is essentially a thin PCB that has been bonded together with an aluminum-based backing layer. In this way, the circuit layers can be as complex as those mounted on conventional fiberglass backings.
Although it is more common to see single-sided aluminum entry sheet PCB design, aluminum entry sheet PCB design can also be double-sided, with circuit layers connected to both sides of the aluminum base through a highly thermally conductive dielectric layer. These two side designs can then be connected via plated through holes. Regardless of the configuration, the aluminum base plate provides an excellent thermal path to the surrounding environment or any connected heat sinks. Again, improving the thermal conduction of power components is the best way to ensure design reliability, and aluminum PCBs provide an excellent solution to this problem.
As with traditional PCB design, the solder mask on the circuit portion of the board can be made in many different colors. That said, in LED designs, the solder mask is usually white. The white solder mask allows the associated LED array to produce higher levels of light reflection and result in a more efficient design. In power supply designs, the solder mask is also usually painted black to dissipate heat better.
Aluminum entry sheet PCB design is also highly mechanically stable and can be used in applications that require a high level of mechanical stability or are subject to significant mechanical stress. Also, they are less affected by thermal expansion than glass fiber-based structures.
Finally, aluminum is not a usable metal backing material. Copper and copper alloys are also used as backing materials, although less popular due to their generally higher cost. Copper and copper alloys offer higher performance than aluminum in terms of heat dissipation. Therefore, if a standard Aluminum entry sheet PCB design cannot meet the thermal requirements of the design, copper can be considered as the next step in solving the problem.
