PowerLink - PCB Technology
Selective Heavy Copper Printed Circuit Board Designs
"PowerLink" is simply defined as the use of 2 or more copper weights on the same layer in a circuit board. This has also been referred to as "selective plating". It should be noted that the process involved is only available on outer layers.
When Would PowerLink be Used?
PowerLink is an option when a printed circuit board has designated areas that need to carry current values larger than the standard 1 oz or 2 oz traces can handle within a reasonable trace width. Some other options for addressing this same concern are making parallel paths on other layers and connecting with vias, soldering a wire jumper to the affected areas or, in extreme cases, adding bus bar pieces to the board either by soldering or using threaded fasteners.
PCB Design Limitations With PowerLink
The standard or light copper circuits are typically anywhere from 1/2 oz to 6 oz copper. The areas designated for heavier copper can be anything greater than the base copper foil.
At Epec, we normally see heavier copper ranges from 4 oz up to 40oz and in some special applications we have built boards with designated areas of 100 oz copper. The heavier copper designated areas are created by plating up from the base copper.
PowerLink is also available in multiple steps. For example, the above sample was created to demonstrate multiple steps of 2 oz, 10 oz, 20 oz, and 30 oz areas. While 100 oz copper or more is possible, the practical limitation is determined more by economics. A relatively small differential from light to heavy copper sections (4 oz to 10 oz differential) can be built at a reasonable cost. As the amount of plating required increases so does the incremental cost. In this case we would recommend other options which can become more economical.
Advantages of Using PowerLink
The PowerLink approach has a number of advantages.
- For the signal portions of the circuit, PowerLink offers the fine lines and spaces capability of 5 mil (typical) and as fine as 2 mil for advanced designs.
- It keeps the high current path on one layer, eliminating the concerns with high temperature rises in the vias.
- With all the current on one layer there is no concern of an imbalance in current sharing and the hot spots that can occur due to the imbalance.
- With all the current on the outer layer, the traces are cooled more efficiently and can be easily monitored for temperatures excursions exceeding design limits. This is particularly valuable in prototyping.
- The PowerLink approach also allows for greater power density because the high current path doesn't have to be as wide, saving real estate on the circuit board.
- It also saves time and reduces the parts count during assembly compared to adding wire jumper or bus bar sections. Keeping the power and signal circuits all on one circuit board eliminates many "in" and "out" connections which results in an elegant solution with improved reliability and increased power density.
Disadvantages of Using PowerLink/Extreme Copper
The only disadvantage of using Extreme Copper in your design is it can cost significantly more than traditional printed circuit board technology. In many industries like aerospace and defense, the technology has received wide acceptance as the cost is secondary to the performance of the product. Using PowerLink can cost more than simply adding wire jumpers, depending on how many wire jumpers are needed and the complexity and length of the run.
However, it is important to be aware of the potential cost differentials before beginning a project with this technology as the engineering time and cost associated with these finished products is substantially higher than a typical printed circuit board.
While we are 100% confident that we can create a manufacturable design for any application, less than 10% of those designs are pursued do the fact that the end product from the design is much more costly than the customer can afford.
The best way to avoid this challenge is to let us know at the very beginning what the budget is for the product so we can design something with that in mind or quickly determine if the target price is not realistic.