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What does 2 oz copper change in a PCB?

A 2 oz copper PCB uses about 70 碌m, or 0.070 mm, of copper as a nominal planning convention on the specified layers. Compared with 35 碌m copper at the same finished width, length and conductor temperature, its rectangular cross-section is twice as large and its ideal DC resistance is half as much. That useful result does not mean twice the allowable current or half the temperature rise.

The important decision is whether heavier copper addresses the limiting requirement of your circuit. A voltage-drop problem, a narrow package escape, a thermal problem and an impedance constraint require different checks. Increasing copper globally can add manufacturing consequences without resolving the local cause. Start with the actual path and compare alternatives against the same operating condition.

Use this page for the 1 oz versus 2 oz design decision. For the baseline specification and a single-trace voltage budget, see the 1 oz copper PCB page. For higher copper classes and different manufacturing routes, use the heavy copper PCB guide. The terms 鈥渟tandard鈥� and 鈥渉eavy鈥� vary across suppliers; the finished dimensions matter more than the label.

Compare 1 oz and 2 oz under the same assumptions

Keep length, current and conductor temperature fixed when isolating the effect of thickness. Also state whether widths are identical. If the 2 oz option uses a narrower path, it may give back some or all of the expected resistance reduction. A fair comparison uses finished conductor geometry rather than an ounce label in one column and a measured minimum in the other.

The equal-area example is particularly useful during layout discussions. A 2 mm wide, 35 碌m thick trace and a 1 mm wide, 70 碌m thick trace each have 0.070 mm虏 cross-section. Their same-temperature DC resistance is equal at equal length. Their surface area, etched profile, neighboring clearance and impedance need not be equal. Do not convert this identity into permission to halve every trace width.

Try a same-temperature DC comparison

Enter the finished width and thickness of each candidate, shared path length, current and conductor temperature. The worksheet reports resistance, voltage drop, loss and the mathematical width needed for equal resistance. The two thickness fields remain editable so you can use supplier-agreed minimums rather than a rounded nominal label.

For the example, compare a 100 mm long and 2 mm wide route at 75掳C and 5 A. Option A uses 35 碌m; option B uses 70 碌m. With the stated approximate copper model, A is about 29.02 m惟 and B about 14.51 m惟. Drops are approximately 145.11 and 72.55 mV, while copper losses are about 0.726 and 0.363 W.

These results use R = 蟻L/A and a temperature correction referenced to 25掳C, with 蟻 = 17 脳 10鈦烩伓 惟路mm and 伪 = 0.0039/掳C. The calculation approach is documented in (the guide uses 16.8 脳 10鈦烩伖 惟路m; this worksheet rounds resistivity to 17 脳 10鈦烩伖 惟路m). It is deliberately an electrical comparison: temperature is supplied by you, not solved by the worksheet. The model excludes irregular pours, contacts, vias and AC effects.

Try reducing option B to 1 mm width. Its resistance returns to the baseline value. That exercise helps separate the benefit of more copper from the benefit of retaining routing area. If you change both geometry and operating temperature, describe those changes explicitly rather than attributing the whole difference to copper weight.

Choose thickness, width or architecture for the actual limit

When voltage drop dominates, shortening the route or increasing its cross-section can help. When the restriction is an IC pad escape, a terminal or a layer transition, the broad middle section may already be sufficient. Review the complete loop, including the return conductor. A supply path with low calculated loss can still have an unacceptable connector drop.

When temperature dominates, include component heating, nearby copper, stackup, mounting and airflow. The IPC technical paper explains why conductor temperature depends on the board and environment. A resistance ratio is therefore not a temperature-rise ratio. If the operating condition is uncertain, retain that uncertainty instead of hiding it behind a precise current number.

For a switching converter, thicker copper may reduce part of the conduction loss while the layout still needs a compact high-frequency current loop. Moving components closer or improving the return path can address a different loss or interference mechanism. Use the power PCB design route when the question concerns the complete power stage rather than one conductor.

What must be reviewed when changing to 2 oz?

Confirm whether 2 oz means starting foil or finished copper. The process may use different base materials and added deposits to achieve the final requirement. Inner and outer layers should be listed separately. Hole-wall copper remains its own requirement and should not be inferred from the surface label.

Review the smallest line and space, not just the power polygon width. A copper change can affect the etch and compensation strategy, especially near dense signal routing. Ask the fabricator to evaluate the complete combination of geometry, copper and stackup. A published minimum for another copper class is not an automatic acceptance of this build.

For controlled impedance, maintain a revised stackup and finished geometry record. More copper can require a different line width or spacing to preserve the target. Link the copper change to the PCB impedance review rather than assuming a previously approved routing width remains correct. Where only selected layers need heavier copper, a mixed construction may be worth discussing.

This catalog photograph is a real product example, but it does not resolve the electrical or manufacturing choices for another board. Use the layout file, layer schedule and measurable acceptance requirements to compare builds. A successful order requires those records to refer to the same revision.

Check soldering and mechanical consequences

More copper can change local heat flow during assembly. A large connected region may draw heat from a joint, while a fine-pitch area on the same board follows a different thermal response. Discuss soldering access and the intended process when reviewing pad connections. Thermal reliefs are design features with both electrical and assembly consequences, not a universal setting to switch on or off.

If the board includes press-fit terminals, large connectors or mechanical fasteners, provide their drawings and requirements. Copper thickness alone does not establish insertion force, hole tolerance, pad integrity or acceptable board deflection. Keep the relevant mechanical interface in the quotation and verification plan, especially when it connects to a high-current path.

An early prototype should answer specific questions: whether the revised path meets its voltage budget, whether joints assemble consistently and whether the installed thermal behavior matches the design assumptions. Merely proving that the board powers up does not verify those objectives. Record the test condition and retain the files associated with the result.

How much more does 2 oz copper cost?

There is no dependable universal percentage. The answer depends on which layers change, the panel and order quantity, the plating and etching route, material availability, geometry and verification scope. Compare dated supplier quotations for equivalent designs. If board size or layer count changes between options, show those differences rather than describing the result as a copper-only premium.

A useful comparison asks for a baseline and one or two defined alternatives. One option might keep 1 oz copper and widen the critical path; another may keep the outline and increase only named layers. Include any layout rework, assembly or qualification consequence when evaluating the system decision. The cheapest bare board is not always the cheapest approved product change.

The optional budget brief uses entered allowances and clearly records the layer scope. It can also generate an enquiry without cost values. It does not claim current market prices or a calibrated 2 oz manufacturing rate. Attach the brief and fabrication files manually for a firm quotation; using either worksheet is optional.

Questions about 2 oz copper PCB design