Copper Weight

Copper weight specifies how thick the copper foil on a PCB layer is, expressed in ounces per square foot (oz/ft²). The unit is historical: it is the weight of copper that, spread uniformly over one square foot, yields a given thickness. One ounce of copper corresponds to roughly 1.4 mils, or about 35 microns, of thickness. Two-ounce copper is twice as thick — about 2.8 mils (70 microns) — three-ounce is around 105 microns, and anything at 3 oz or above is generally called heavy copper. On a fabrication drawing you will usually see copper weight called out per layer, because outer and inner layers of the same board frequently differ.

Why Thickness Matters

Thicker copper means greater cross-sectional area for every trace and plane, which raises current-carrying capacity and improves heat spreading. As a rough guide, a 10-mil-wide trace in 2 oz copper can carry roughly 2 A for a 10°C temperature rise, where the same trace in 1 oz copper carries noticeably less; the IPC-2152 charts that underpin trace current capacity calculations all take copper weight as a primary input. Heavier copper also lowers DC resistance, reducing voltage drop on power-delivery paths — critical when a rail runs at high current and low voltage, where every milliohm shows up as lost watts and extra heat. The trade-offs are cost and resolution: thicker foil is harder to etch finely, so very fine traces and tight spacing are easier to achieve in 0.5 oz or 1 oz copper. Designers often mix weights across the stackup, keeping signal layers thin and dedicating heavy layers to power.

Copper Weight on Mining Hashboards

A modern hashboard is one of the more demanding power-delivery designs a hobbyist will ever probe. The board must move kilowatts from the input connector through buck converters and along the series chain of hash domains, where dozens of ASICs share supply rails at low voltage and very high current — and voltage regulation there is per-domain, with groups of chips sharing each converter stage. That is exactly the regime where heavy outer copper and thick internal power planes earn their cost: they keep resistive losses down, spread heat away from the converter stages, and hold the domain voltages stable under load. Large copper pours around power components double as heatsinking, which is why hashboards feel like solid slabs of metal compared with ordinary logic boards.

What It Means at the Repair Bench

Copper weight changes how a board behaves under the iron. Heavy copper is an enormous heat sink, so desoldering a connector or power component on a hashboard usually demands a preheater and a high-mass tip — the same joint that flows instantly on a 1 oz signal board will drink heat for many seconds on a 3 oz power layer. When repairing a damaged trace, sizing a replacement jumper starts with knowing the original copper weight, since it sets the baseline cross-section you must match; undersizing a jumper on a domain rail creates a hot spot that fails again. Lifted pads are also more consequential on heavy copper, because the currents involved leave no forgiveness for a marginal repair. If a power-path burn looks beyond a clean bridge, that is the point to hand the board to a bench equipped for it — our repair service sees this failure class weekly.

In short: 1 oz copper is the default for general logic, and heavier weights are chosen wherever current and heat dominate — which on mining hardware is almost everywhere that matters. Read the copper weight off the fab notes before you judge a trace, plan a jumper, or set your iron's temperature, because the number quietly governs all three.