Heavy Copper PCB
Manufacturing
Thicker conductors. A more deliberate power design.
Bring your copper targets, stackup and operating conditions to GlobalWellPCB. Start with a project-specific manufacturing review for power conversion, motor drives and energy-storage electronics.
Copper weight alone is not a current rating. Define the complete current path, cooling conditions and allowable temperature rise.
What is a heavy copper PCB?
A heavy copper PCB uses thicker copper conductors to increase the cross-section available for power routing. It is also called a thick copper PCB.
Epec uses a 4–20 oz/ft² range for heavy copper. For purchasing, specify the copper weight and required finished thickness on each layer rather than relying on the label alone.
Specify the copper you need at the end of fabrication.
State the layer, nominal copper weight and any minimum finished thickness in micrometres. Keep base foil, finished conductor copper and plated-hole copper as separate requirements.
More conductor cross-section
For the same trace length, width and temperature, increasing copper thickness reduces DC resistance. Current limits still depend on the resulting heat and the full connection path.
Better lateral heat spreading
Thicker copper planes can spread heat across the board. Vias, interfaces, heat sinks and airflow determine how effectively that heat leaves the assembly.
Power and control, planned together
A reviewed stackup can combine different copper weights on different layers. Fine-pitch signal routing and heavy-current areas need compatible fabrication rules.
Heavy copper PCB thickness, at a glance.
PCB copper weight is mass per unit area. The common rounded convention is 1 oz/ft² ≈ 35 µm. The table scales that convention; actual finished copper depends on foil tolerance, processing and plating.
| Copper weight | Nominal thickness | In millimetres |
|---|---|---|
| 1 oz/ft² | ≈ 35 µm | ≈ 0.035 mm |
| 2 oz/ft² | ≈ 70 µm | ≈ 0.070 mm |
| 3 oz/ft² | ≈ 105 µm | ≈ 0.105 mm |
| 4 oz/ft² | ≈ 140 µm | ≈ 0.140 mm |
| 6 oz/ft² | ≈ 210 µm | ≈ 0.210 mm |
| 8 oz/ft² | ≈ 280 µm | ≈ 0.280 mm |
| 10 oz/ft² | ≈ 350 µm | ≈ 0.350 mm |
| 12 oz/ft² | ≈ 420 µm | ≈ 0.420 mm |
On narrow screens, scroll the table horizontally to view all columns.
A better drawing note: identify the relevant layer and required minimum finished copper explicitly. Agree the measurement method and tolerance before treating a nominal “4 oz” label as an acceptance criterion.
Design the whole current path—not just a thicker trace.
Use an early DFM review to resolve geometry, construction and assembly questions before freezing the layout. The checklist below is a starting point for that discussion.
Trace width and spacing
Do not reuse light-copper routing limits unchanged. Ask for layer-specific rules based on the base foil, finished target and etching or plating route. Check the narrowest part of the actual conductor profile.
Vias and current transitions
Review via arrays, plated barrels, pads, thermal spokes and connector neck-downs as part of the same current path. Specifying heavy surface copper does not define the copper in a hole barrel.
Stackup, resin fill and copper balance
Ask the fabricator to review prepreg selection, resin fill between tall conductors, dielectric thickness and copper distribution. Include the layer map in the design package rather than leaving the construction implicit.
Solder mask and surface finish
Identify copper steps, mask coverage needs, openings and exposed conductors. Select the finish with the assembly process and contact requirements in mind; agree any special acceptance checks.
Assembly and thermal reliefs
Large copper areas draw heat away from pads during soldering. Review the soldering profile and any thermal-relief pattern together, so a solderability improvement does not create an unreviewed current bottleneck.
Material and electrical insulation
Specify the material grade, assembly exposure and service environment. Review dielectric thickness, spacing and insulation requirements against the working voltage and applicable product rules—not copper weight alone.
What should a current-capacity review include?
- Continuous current, peak current, pulse duration and duty cycle.
- Trace geometry, finished copper and layer location.
- Ambient temperature, allowable rise and nearby heat sources.
- Vias, terminals, copper planes, enclosure and cooling conditions.
IPC-2152 addresses current-carrying capacity in printed-board design. Use a suitable engineering method, then validate the relevant load cases on the finished assembly.
Heavy copper is not the same as a copper-base PCB.
Heavy copper describes the circuit conductors. Metal-core or insulated metal substrate (IMS) describes a construction with a metal backing and an insulating layer beneath the circuitry. A copper base is not a substitute for specifying conductor copper.
Choose the architecture around the current route and the heat-removal path. Ask whether a conventional laminate, an IMS construction or another thermal solution best fits the project before finalizing the specification.
Heavy copper PCB manufacturing requirements
A quotation should identify the copper, construction and verification scope together. Use this checklist to make your enquiry actionable.
| Item | Provide with your enquiry | Confirm before release |
|---|---|---|
| Copper by layer | Base and finished copper targets; minimum finished thickness where required. | Per-layer copper map, tolerance and agreed measurement basis. |
| Stackup & board thickness | Layer count, stackup, overall thickness, dielectric spacing and tolerances. | Material construction, lamination feasibility and copper balance. |
| Critical conductors | Minimum line/space, power nets, neck-downs and controlled-impedance features. | Copper-dependent design rules and any changes needing approval. |
| Holes & vias | Finished hole sizes, PTH/NPTH identification, via type and barrel requirements. | Drill/plating route, annular rings, filling requirements and inspection scope. |
| Material & finish | Named laminate or performance requirement; solder mask and surface finish. | Availability, approved alternatives and assembly compatibility. |
| Electrical & thermal inputs | Current profile, voltage, ambient conditions, cooling and allowed temperature rise. | Required engineering review and prototype or qualification load cases. |
| Acceptance & documentation | Applicable IPC documents, class/revision, electrical test and report requirements. | Sampling, evidence, acceptance criteria and traceability scope. |
| Quantity & delivery | Prototype/production quantities, drawing revision, destination and required date. | Quoted scope, tooling, procurement and agreed delivery schedule. |
On narrow screens, scroll the table horizontally to view all columns.
One approved specification, across all documents.
Keep the fabrication drawing, stackup, Gerber notes and purchase order consistent. Do not leave one document calling for base copper while another assumes the same number means minimum finished copper.
Where heavy copper deserves a closer look
High-current power electronics are a common setting for heavy copper. Use the application to define the design inputs—not to assume a universal copper weight or current rating.
Power conversion & motor drives
Identify the switching stage, DC-link paths and power terminals. Review concentrated heat sources along with the board’s electrical connections.
EV charging & energy storage
Bring the charger or battery-system operating profile, peak loads and insulation requirements. Agree application-specific validation separately.
Renewable-energy power systems
For inverter and conversion projects, define thermal cycles, duty profile and enclosure cooling before comparing copper constructions.
Industrial power distribution
Map high-current routes, connector interfaces and installation constraints. Evaluate heavy copper against the needs of the complete system.
Agree how the construction will be verified.
Fabrication acceptance and application validation answer different questions. Establish both before the board enters production.
- 01 / Project review
Review inputs
Provide the design files, layer copper targets and operating profile. Identify any missing or conflicting requirements.
- 02 / Project review
Agree the build
Resolve stackup, materials, geometry changes and the required inspection scope before accepting a quotation.
- 03 / Project review
Define the evidence
Request the drawings, coupons, measurements and reports needed for the project’s acceptance criteria.
- 04 / Project review
Validate & release
Review prototype results against the relevant load cases. Control later material, copper and process changes.
Ask for evidence that matches the requirement.
- Conductor and plated-hole measurements
- Microsections can reveal copper thickness and the internal construction at the sampled location. Agree coupon selection, measurement locations and acceptance criteria.
- Dimensional, visual and electrical checks
- Specify critical dimensions, continuity/isolation testing and required workmanship criteria. IPC-6012 addresses qualification and performance requirements for rigid printed boards; state the applicable class and revision.
- Loaded thermal validation
- Define the assembled-board test conditions, instrumentation and pass/fail limits. A copper-thickness result does not, on its own, validate operation under the intended load.
Agree the inspection methods, sampling and reports required for your copper structure and current-carrying design.
Compare complete builds, not just ounces.
Request a project-specific price and delivery schedule. A meaningful comparison keeps quantity, design revision and acceptance scope consistent.
Material & copper route
Identify the laminate, layer copper targets, allowed alternatives and any unusual procurement requirements.
Construction & geometry
Include stackup complexity, critical spacing, hole structures, panel requirements and the approved drawing revision.
Quantity & evidence
State the build quantity, required reports, qualification work, destination and requested date in the same enquiry.
Heavy copper PCB questions, answered.
Key distinctions for design notes, sourcing discussions and quotation requests.
Does heavy copper start at 3 oz or 4 oz?
Epec describes 4–20 oz/ft² as heavy copper. Specify the copper weight and required finished thickness on each layer instead of relying on the name.
How thick is 4 oz copper?
Using the common rounded convention of 35 µm per oz/ft², 4 oz corresponds to about 140 µm, or 0.140 mm. This nominal conversion does not establish the minimum finished thickness after processing.
How many amps can a heavy copper PCB carry?
There is no single current rating for a copper weight. The assessment needs the conductor geometry, layer location, temperature-rise limit, thermal surroundings and connection details. Review the actual design rather than using a universal amps-per-ounce figure.
Can different layers use different copper weights?
Different layer weights can be considered within a reviewed stackup. Specify each layer separately. Local thick and thin features on the same layer are a separate, process-specific question and should not be assumed from a mixed-weight stackup.
Can a heavy copper PCB use FR-4?
An FR-4 construction can be considered, but the exact grade and stackup must suit the project. Include assembly exposure, service conditions and electrical requirements in the material review. Request approval of the named material rather than specifying “FR-4” alone.
Is heavy copper the same as metal core or copper base?
No. Heavy copper refers to conductor thickness; an insulated metal substrate describes a metal-backed construction. The conductor requirement and the substrate architecture need separate specifications.
Can I keep the same fine-pitch layout when copper gets thicker?
Do not assume so. Thicker base copper generally calls for wider routing features, and the appropriate rules depend on the process. Review the critical footprints, neck-downs and clearances before changing copper weight.
What should I send for a heavy copper PCB quote?
Prepare Gerber or ODB++ data, drill files, a fabrication drawing, stackup and revision identifier. Add copper requirements by layer, quantities, operating conditions and acceptance criteria. For assembly, include the BOM and placement data. Agree a secure file-transfer route before sharing confidential designs.
Technical references & scope
Manufacturer and standards-body references support the engineering discussion. Their processes, capacity, certifications and delivery terms are not presented as GlobalWellPCB capabilities. All project limits and acceptance criteria require written agreement.
- Multi Circuit Boards — Thermal management for Printed Circuit BoardsTerminology and application context; supplier-specific capabilities are not adopted.
- Epec — Heavy copper PCB designAlternative terminology, current paths, mixed copper and fabrication concepts.
- Würth Elektronik — BASIC Design Rules (PDF)Copper-weight conversion and the distinction between base and finished copper.
- IPC — Design standards directoryIPC-2152, IPC-2221 and IPC-2222; agree the applicable document and revision.
- Würth Elektronik WEdirekt — Design Guide for PCBs from the online shop (PDF)Why base copper thickness affects routing rules; no generic minimum is copied.
- Epec — Heavy and extreme copper: holes, traces and spacingProcess-dependent geometry. Extreme-copper examples are not standard heavy-copper limits.
- Texas Instruments — Thermal design for power-tool motor drivesHeat spreading, thermal vias, heat sinks and airflow; application-specific figures are not generalized.
- Würth Elektronik — Technical Delivery Specification for PCBs (PDF)Construction and copper-thickness inspection methods, not a GlobalWellPCB test commitment.
- PCB Elegance — Thermal reliefThe solderability trade-off when pads connect to large copper areas.
- IPC — IPC-6012F qualification and performance scopeRigid-board qualification and performance scope; this does not assert that F is the latest revision.
Sources reviewed on 14 September 2026. Nominal conversions are for reference. Check the applicable controlled documentation for the build; references to IPC documents do not constitute certification or a claim that a named revision is the newest.