Introduction

Although Light Emitting Diodes (LEDs) operate at very high efficiencies, they do produce heat as a byproduct and this has to be removed if the LED is to operate continuously. As the heat generation in a semi-conductor, such as an LED, happens in the PN junction, the only way to remove it is via one of its leads. Manufacturers prepare special Printed Circuit Boards (PCB’s), which help in removing this heat by conducting it away from the lead and junction of the LED mounted on the PCB. IN this case, PCB’s are manufactured using a base of aluminum, and their names vary from aluminum PCB’s, insulated metal substrate (IMS), aluminum clad, metal clad (MCPCB), and thermally conductive PCB’s.

Mostly used as single-sided, aluminum based copper clad PCB’s have a copper foil bonded onto a thin thermally conductive but electrically insulating dielectric, which in turn is bonded onto a thick aluminum base. The copper layer is processed in the regular way to form the traces, while the profile is machined to the necessary size and shape. During the manufacturing process, the aluminum substrate needs protection from the etching chemicals.

Although this arrangement is specifically suited for population with surface mount devices (SMDs), through hole components are also used, in which case, the PCB’s are usually double-sided or hybrid types. Apart from LEDs and power converters, automotive and RF companies also take advantage of the thermally conducting properties of aluminum PCB’s in their applications.

Benefits of Aluminum PCB’s

• Dramatic increase in heat dissipation, as compared to conventional PCB’s using FR-4 material.
• The base of laminate is mechanically rigid.
• High reliability and MTBF, as thermal stresses on components are low.
• Improved heat transfer allows thinner tracks of lower width for high current designs.
• Smaller PCB’s on account of better thermal management, leading to higher component densities.
• Relatively lower cost compared to FR-4 PCB with heat sinks.

Types of Aluminum PCB’s

The single-sided aluminum based copper clad PCB is the most commonly used. However, other configurations are also available. Therefore, one can have hybrid aluminum PCB’s, flexible aluminum PCB’s, multilayer aluminum PCB’s, and Aluminum PCB’s for through-hole components.

Hybrid Aluminum PCB’s

These are usually conventional FR-4 or PTFE grade PCB’s of 2 or 4 layer construction, bonded on to an aluminum base with thermal materials. This assembly improves heat dissipation and rigidity, while acting as a shield.

Flexible Aluminum PCB’s

These are relatively new developments using IMS with flexible dielectrics. The dielectric material is mostly a polyimide resin system with ceramic fillers to improve the electrical insulation, flexibility, and thermal conductivity. This is applied to a flexible aluminum material that allows forming to different shapes and angles. However, this arrangement does not flex regularly.

Multilayer Aluminum PCB’s

High performance power supply designs commonly use this type of PCB’s. They are made of multiple layers of thermally conductive dielectrics combining layers of circuitry within them. Blind vias carry heat to the aluminum layer for dissipation, although the efficiency of heat transfer is not as good as that of single-layer boards.

Through-Hole Aluminum PCB’s

The Aluminum layer forms the core of the multilayer thermal construction. The aluminum layer is pre-drilled and back filled with dielectric. This is done before laminating it with thermal bonding materials on both sides. The completed assembly is then drilled through and plated. Clearances in the aluminum layer maintain electrical insulation.

Conclusion

At PCB Global, we commonly produce aluminum PCB’s and have the knowledge, experience and capability to advise our customers on the use of aluminum PCB’s and how this can be implemented in their specific design, for their intended application. For more information or any inquiries of aluminum PCB’s outside of our online capabilities, please proceed to contact us at sales@pcbglobal.com