Heavy Copper PCBs: Bridging the Gap Between Design and Fabrication, Part 1

Estimated reading time: 1 minute

They call me Sparky. This is due to my talent for getting shocked by a variety of voltages and because I cannot seem to keep my hands out of power control cabinets. While I do not have the time to throw the knife switch to the off position, that doesn’t stop me from sticking screwdrivers into the fuse boxes. In all honesty, I’m lucky to be alive. Fortunately, I also have a talent for building high-voltage heavy copper circuit boards. Since this is where I spend most of my time, I can guide you through some potential design for manufacturability (DFM) hazards you may encounter with heavy copper design.

I have always perceived the term “heavy copper” as a printed circuit board with layers containing at least three ounces of finished copper. Recently, I’ve noticed a peculiar trend. We see monikers being used to describe higher copper weights (think 10-ounce, 20-ounce) that are seemingly pulled right out of a ’90s-era Mountain Dew commercial: “extreme copper” or “super copper.” I’m trying to coin the term “stupid crazy copper,” but somehow, I don’t think it will stick.

These are all fabricated descriptions to highlight achievements in building PCBs beyond our industry’s standards. There is no standard definition for heavy copper from IPC, but that doesn’t mean we can’t have fun designing and building these beasts of the PCB world.

No matter what you call them or how you define them, we can all agree on why we use them. Heavy copper boards increase current carrying capacity and decrease circuit failures by reducing thermal resistance. To reduce layer count, some will contain more copper on the inner layers than the outer; moreover, some will even have different amounts of copper on the same layer. They can also function as a heat sink thanks to plated vias and their capacity to carry a higher current and heat through the board. Above all, they have eliminated the need for those complex wired buss configurations that C-3PO was forced to endure.

To read the rest of this article, which appeared in the March 2024 issue of Design07 Magazine, click here.