Issue link: https://iconnect007.uberflip.com/i/1540184
40 DESIGN007 MAGAZINE I OCTOBER 2025 Have you ever wondered why the PCB design seg- ment uses ounces to describe copper thickness? There's a story behind all of this—a story that's old, dusty, and more than a little absurd. (Note that I didn't add "Like many of us.") Legend has it that back in the days of copper tin- kers and roofing tradesmen, the standard was set when a craftsman hammered out a sheet of copper until it weighed one ounce, when its area conve- niently matched the square of the king's foot. Fast-forward a few hundred years, and somehow, this medieval measure wormed its way into mod- ern electronics. For too long, the PCB design world has clung to this outdated convention. Even today, TA RG E T C O N D I T I O N by Kelly Dack , CIT, CID+ Distribution of Power: Denounce the Ounce it's not uncommon to see PCB stackups simply call- ing out "1-ounce copper" or "2-ounce copper," as though the royal foot still governs our trace widths and current carrying capacities for our power distri- bution networks. Thankfully, the manufacturing industry has moved on. Now it's time for designers to do the same. The Legacy Lives On, but Should It? There's a debilitating loyalty lingering in the design community: Designers are still specifying copper using ounces per square foot (oz/ft²), a unit of mass per area, not thickness. That may be fine for order- ing roofing material, but it introduces real problems