Heavy Copper PCB
Specify the finished copper and compare DC loss before choosing a copper weight.
Heavy copper PCB designs commonly use 3 oz/ft² (about 105 µm nominal copper) or more on selected layers. The term is not a complete specification: the finished thickness, layer location, conductor geometry and interconnections determine what the board can do.
Original 5 oz product photo. The visible board edge helps explain the construction; copper thickness must be verified against the fabrication requirement.
5 oz design considerations →Why use a heavy copper PCB?
Increasing conductor cross-section reduces DC resistance for the same path length and temperature. That can reduce voltage drop and I²R loss without widening the board. It also changes etching, lamination, soldering and thermal behavior, so more copper is not a free improvement.
| Application | What thick copper can help with | What still needs design work |
|---|---|---|
| Power conversion and motor drives | Low-resistance paths between switching devices, capacitors and terminals. | Switching-loop geometry, thermal paths, isolation and terminal bottlenecks. |
| Battery and power distribution | Reduced drop along sustained-current distribution paths. | Protection, current sharing, fault behavior and connection ratings. |
| Industrial power supplies and inverters | Power routing where width or allowable loss constrains the design. | Cooling, assembly heat demand and the complete duty cycle. |
| Planar magnetics | Defined winding resistance and copper cross-section. | Frequency-dependent loss, skin/proximity effects and insulation; DC calculations alone are insufficient. |
High current and high voltage are different design problems. Thick copper does not establish safe creepage, clearance or insulation. A thicker conductor can carry less current than expected if a via, neck-down or terminal is the limiting element.
Review the connections as well as the board conductors: terminal interfaces can constrain the current path.
Compare winding DC loss, then evaluate switching-frequency effects and insulation separately.
Copper thickness, voltage drop and loss planner
Convert oz/ft², µm, mm and mil; then compare conductor resistance using the actual path dimensions. Enter a known minimum finished thickness when you have it. Nominal oz conversion is not a copper-thickness acceptance limit.
Heavy Copper Thickness & DC Loss Planner
A worked example you can check
For a uniform conductor, R = ρL / A, voltage drop = IR, and DC loss = I²R. Use length in meters and cross-section in m² with resistivity in Ω·m; the calculator converts the entered dimensions.
For a 100 mm long, 10 mm wide path with 105 µm copper at 20°C, the idealized cross-section is 1.05 mm². Using ρ = 1.724 × 10⁻⁸ Ω·m gives R ≈ 1.642 mΩ. At 20 A DC, the drop is approximately 32.84 mV and the loss 0.657 W.
This does not predict the resulting conductor temperature. The entered temperature is an assumption. Real current capability depends on the board construction, nearby copper, heat removal, environment and allowable temperature rise. Use appropriate thermal analysis and validation for the actual assembly.
Heavy copper PCB cost: what changes the quotation?
Raw copper is only one part of the price. Thick features can affect processing time, resin needs, mask coverage, drilling, panel yield and inspection. A simple “heavy copper costs 2–5×” rule cannot quote a particular board.
Heavy Copper PCB Budget Planner
The copper/geometry planner and budget planner use separate inputs. A DC comparison does not approve the construction or automatically populate a quotation.
Copper weight to thickness: 0.5 oz through 20 oz
Use these nominal equivalents for comparison: 1 oz/ft² ≈ 35 µm ≈ 0.035 mm ≈ 1.38 mil. Starting foil, added plating and the minimum finished copper requirement are different specifications. Request the actual finished requirement in the fabrication notes.
| Copper weight | Nominal thickness | Design focus |
|---|---|---|
| 0.5 oz copper PCB | 17.5 µm | Standard copper reference: compare geometry and finished thickness. |
| 1 oz copper PCB | 35 µm | Standard copper reference: compare geometry and finished thickness. |
| 2 oz copper PCB | 70 µm | Standard copper reference: compare geometry and finished thickness. |
| 3 oz copper PCB | 105 µm | Compare 3 oz with a wider 2 oz path using a voltage-drop and DC-loss example. |
| 4 oz copper PCB | 140 µm | Review finished trace cross-section, gaps and solderable pad connections. |
| 5 oz copper PCB | 175 µm | Heavy copper: review features, resin fill and the full current path. |
| 6 oz copper PCB | 210 µm | Budget copper and dielectric thickness in a mixed 6 oz stackup. |
| 8 oz copper PCB | 280 µm | Heavy copper: review features, resin fill and the full current path. |
| 9 oz copper PCB | 315 µm | Heavy copper: review features, resin fill and the full current path. |
| 10 oz copper PCB | 350 µm | Compare the main conductor with separately specified hole walls and connections. |
| 12 oz copper PCB | 420 µm | Separate copper temperature, material Tg and pulse-duty loss. |
| 20 oz copper PCB | 700 µm | Compare thick PCB conductors with a separate copper path, including joints. |
0.5, 1 and 2 oz pages are standard-copper references in this comparison. For extreme copper weights, start with a fabrication review; a nominal conversion does not demonstrate that a particular multilayer stackup can be built.
Read copper weight separately from board thickness
Standard copper references
A standard-copper reference from the product library; not classified here as heavy copper.
1 oz copper guide →
Use the same geometry and operating assumptions when comparing with a heavier copper option.
2 oz copper guide →Design decisions that change heavy copper manufacturability
| Design item | Why it matters | What to specify or review |
|---|---|---|
| Base versus finished copper | Outer copper can receive additional plating; inner copper and finished minimums need explicit requirements. | Copper requirement for each layer, with tolerance/acceptance conditions. |
| Trace width and spacing | Etching a thick conductor changes its sidewall profile and the practical feature window. | Critical finished width and spacing with the fabricator; do not reuse thin-copper minima. |
| Dielectric and resin fill | Tall copper features need suitable resin coverage and dielectric separation. | Material system, copper distribution and cured dielectric requirements. |
| Copper balance | Unequal thickness or coverage can change laminate stress and processing. | Review the complete stackup and panel, not only one mirrored copper pair. |
| Vias and transitions | Planar copper weight does not equal hole-wall plating thickness or via current capacity. | Finished holes, barrel copper, aspect ratio, via/terminal layout and current sharing. |
| Mask and assembly | Copper topography and thermal mass affect mask coverage and soldering. | Mask openings, component attachment, thermal relief choices and assembly profile. |
| High-voltage spacing | Conductor thickness does not replace an insulation design. | Working/transient voltage, pollution/environment and applicable product standards. |
For combined signal and power layers, see multilayer PCB stackup planning. HDI geometry and heavy copper can place competing demands on fine features; do not assume the two maximum capabilities are available simultaneously.
Structure reference: the photo does not establish a heavy-copper specification.
Review HDI geometry →Power routing and fine features need a joint review
A broad power conductor and a fine-pitch escape region impose different geometry requirements. Identify which layers need thick copper and where thin-copper signal routing can remain.
Review the finished feature sizes and the complete layer construction before combining HDI with heavy copper. A photograph cannot confirm that a specific copper weight and fine feature are available together.
What changes in heavy copper production?
- Engineering review. Confirm layer-specific copper, actual finished features, dielectric separation and the current path. Identify extreme or mixed constructions early.
- Patterning and copper processing. Select a suitable process for the required copper profile; account for etching and any additional plating. Not every build follows one identical recipe.
- Lamination and interconnections. Review resin fill and copper balance. Drill and plate the selected structure; verify the hole requirements separately from plane thickness.
- Mask, finish and verification. Check coverage around the copper topography, critical dimensions, continuity/isolation and specified copper or section measurements. Agree which reports accompany the order.
Review rigid PCB capability requirements and quality evidence alongside the proposed construction.
Thick copper, metal core or a busbar?
| Option | Primary task | Key distinction |
|---|---|---|
| Heavy copper circuit layers | Reduce resistance and distribute current in routed conductors. | Heat still needs a path into the surroundings or cooling system. |
| Metal-core construction | Provide a thermal path through a defined dielectric to a metal base. | Metal base thickness is not circuit copper thickness; isolation and thermal resistance matter. |
| Ceramic substrate | Address substrate thermal, dielectric or packaging requirements. | Material and metallization choices require a separate process review. |
| Busbar or copper insert | Carry concentrated current or bridge a power connection. | Mechanical attachment, insulation, assembly and current sharing become part of the system design. |
A thicker board trace is not always the lowest-cost or best-performing answer. Compare alternatives at the same voltage-drop, thermal and mechanical requirements.
Heavy copper PCB product examples
Open an individual photo for a closer view. Copper-weight names below follow the original product identifications; they are not measurements inferred from the photos.
Compare finished copper, feature sizes and inspection requirements for your board.
Open the copper-weight guide →
Compare finished copper, feature sizes and inspection requirements for your board.
Open the copper-weight guide →
Compare finished copper, feature sizes and inspection requirements for your board.
Open the copper-weight guide →
Compare finished copper, feature sizes and inspection requirements for your board.
Open the copper-weight guide →
Compare finished copper, feature sizes and inspection requirements for your board.
Open the copper-weight guide →Special constructions: specify copper by layer
These product photos illustrate construction families. Confirm copper weight, bend requirements and feature sizes for the actual build; the photo alone does not establish a combined-process capability.
Review the full material and copper stackup.
Multilayer planning →
Identify bending zones and copper requirements separately.
Multilayer flex guide →
Specify rigid-zone and flex-zone requirements separately.
Rigid-flex design →
Confirm the copper and fine-feature combination during engineering review.
HDI design and fabrication →Agree how the finished copper will be verified
For critical power paths, define the measurement location and minimum finished requirement. A nominal foil weight, surface finish thickness and plated hole-wall copper are different specifications.
- Layer requirement: identify which layers need heavy copper and whether the drawing states nominal or minimum finished thickness.
- Cross-section scope: request the coupon or board locations, sampling plan and report needed for your order.
- Electrical scope: agree continuity/isolation testing separately from any application-specific load or thermal validation.
- Traceability: connect material, inspection and shipment records to the released drawing revision and lot.
Confirm available records during quotation. Review quality assurance and PCB manufacturing equipment as part of supplier evaluation.
Send a copper specification, not just “high current”
For an exact quotation
- PCB fabrication data, drill files, outline and quantity.
- Layer-by-layer copper: starting foil or minimum finished requirement.
- Board thickness, dielectric and material requirements.
- Critical widths, gaps, holes and terminal interfaces.
- Current waveform, duty cycle and design environment where relevant.
- Finish, assembly needs and required inspection records.
If you are still evaluating the copper weight
Include the current-path drawing and your allowable voltage drop or loss. Tell us which dimensions can change. The planner summary helps explain assumptions; it is not a release drawing.
Send files for a heavy copper quoteHeavy copper PCB questions
What copper thickness counts as heavy copper?
3 oz/ft² and above is a common industry description, but definitions vary. Always specify the actual copper thickness and layer location.
How much current can a 4 oz PCB carry?
Copper weight alone cannot answer that. Trace width and length, cooling, construction, temperature limits, vias and connections all matter. The planner calculates DC resistance and loss, not allowable current.
Is the copper weight the starting foil or the finished copper?
It may be used either way unless the requirement is explicit. State minimum finished copper where needed and agree how it will be verified.
Can I mix heavy power layers with thinner signal layers?
Yes, as a construction concept. The complete stackup needs review for resin fill, balance, feature sizes and interconnections; it is not an automatic price or capability approval.
Does thicker copper solve high-voltage isolation?
No. Creepage, clearance, dielectric insulation and product-level requirements must be assessed independently.
Can I use a simple IPC-2221 calculator for 20 oz copper?
Do not treat extrapolated historical curve-fit results as a safe-current rating. IPC-2152 addresses conductor current-carrying design; apply a suitable model and validate the actual thermal construction.
Does heavy copper always run cooler?
At equal current and geometry, lower resistance reduces conductor loss. The final temperature also depends on all heat sources and cooling; copper thickness alone does not predict it.
Why might thicker copper increase assembly cost?
Thermal mass, attachment geometry and support can affect soldering and test/inspection work. Request a quotation for the full assembly scope, not only the bare board.
Engineering references
- IPC-2152 — scope of current-carrying capacity in printed-board design (public table of contents; not the full standard).
- NIST — Copper Wire Tables, reference copper resistivity and temperature dependence.
- Isola — material and stackup planning.
The DC planner uses a simplified uniform conductor and stated material constants. It does not implement IPC-2152 charts or certify compliance.