About Aluminum Printed Circuit Boards
Most common among metal-core printed circuit boards is the aluminum PCB. This type of printed circuit board is built on top of an aluminum alloy base, instead of a fiberglass base. The alloy usually consists of a combination of magnesium, aluminum and silumin, altering the properties of the metal to best suit the needs of the application.
All aluminum PCBs consist of the following layers:
- The Base Layer: The base layer of the PCB is the aluminum alloy sheet upon which the rest of the PCB builds. This alloy is typically designed to provide maximum electrical insulation and thermal conductivity.
- The Thermal Insulation Layer: This layer is extremely important in the design of the PCB. Consisting of a ceramic polymer, this layer protects the PCB from mechanical or thermal damage by offering thermal resistance and viscoelastic properties. This works by absorbing the heat created as the current moves through the circuits and transferring it to the aluminum layer — there it disperses.
- The Circuit Layer: This layer contributes most to the end function of the board, containing the copper foil circuits needed for the PCB to function.
These layers occur in any number of variations, with one or several thermal and circuit layers depending on the particular application. The layers listed also lend a number of different benefits to aluminum PCBs, which can be of use to several key industries.
There are numerous ways the layers above can be altered to create new PCB designs. Each of these variations results in slightly different qualities of the PCB, making it more suitable for some industries and applications over others.
Some types of Aluminum PCBs include:
- Flexible Aluminum: This relatively new material uses ceramic fillers and polyimide resin to provide excellent insulation and flexibility, all while retaining the aluminum’s impressive thermal conductivity. These PCBs can be formed to connect directly where they are needed. This eliminates the need for cables, connectors and fixtures, which can add to the end cost of the product. Once they are bent, however, they are meant to stay there — these PCBs are not designed to flex constantly.
- Hybrid Aluminum: Just as it sounds, a non-thermal material fused to an aluminum base metal creates hybrid aluminum. Usually, the material is a circuit board made with conventional FR-4. By fusing these layers together, the circuit board can dissipate heat more effectively, as well as increase rigidity. These hybrids also tend to be less expensive than entirely aluminum products. The downside, however, is the loss of flexibility.
- Multilayer Aluminum: In high performance power-supply applications, multilayer aluminum PCBs are generally the best. These PCBs consist of layers of thermally conductive dielectrics. While this multilayer approach can handle high performance, they tend to be less efficient when it comes to transferring heat However, overall these PCBs tend to be effective for basic heat dissipation in more complex designs.
- Through-Hole Aluminum: For more complex constructions, the aluminum base of a PCB can be pre-drilled and back-filled with dielectric before being laminated with thermal materials. These are highly complex, and tend to be labor-intensive projects meant for particularly complicated or specific projects.