Heavy Copper PCB
(High-Current)
From 3oz power distribution layers to 20oz+ busbar-replacement designs — boards engineered to carry current, not just signals, without exceeding your thermal rise budget.
Copper as a power conductor, not just a signal trace
A heavy copper PCB uses copper weights of 3oz (105 µm) or greater on one or more layers — well above the 1oz–2oz standard used for signal routing. The added copper cross-section carries higher current with lower resistive voltage drop and lower I²R heating, replacing what would otherwise require external bus bars or cabling.
Heavy copper is not simply 'thicker plating.' Etching heavy copper without undercutting fine features, plating uniformly into deep etched channels, and maintaining registration through lamination all require process control that differs materially from standard 1oz fabrication.
Many designs mix heavy copper power planes with standard or fine-pitch copper for control and signal circuitry on the same layer — a differential copper / step-stencil construction that must be planned into the stackup and etch process from the start, not added as an afterthought.
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Three specification decisions that determine heavy copper reliability
Current-carrying boards fail differently than signal boards — these are the variables that matter most.
Current-Carrying Capacity Is Calculated, Not Assumed
Trace width and copper weight together determine current-carrying capacity and temperature rise, per IPC-2152. A trace sized by rule-of-thumb rather than calculation either wastes board area with unnecessary copper or under-sizes the trace and creates a hot spot. We size every heavy copper power trace against your target current and allowable temperature rise before fabrication, not after a thermal failure in test.
IPC-2152 current rating · temperature rise calculation · trace width sizingDifferential Copper Weight Enables Power and Signal on One Layer
Step-stencil (differential etch) construction allows heavy copper power traces and fine-pitch signal traces to coexist on the same layer, each etched to a different effective thickness. This requires a two-stage etch process with tight control of resist and etch depth — done incorrectly, it undercuts fine-pitch features or leaves heavy traces under-etched with shorts between adjacent conductors.
step-stencil etch · differential copper · fine-pitch + power on one layerEtch Factor Widens the Practical Minimum Trace/Space
At heavy copper weights, the etchant attacks the sides of the trace as well as the top, undercutting the resist and narrowing the base of the trace relative to its top width (etch factor). This means minimum achievable trace/space widens as copper weight increases — a 10oz layer cannot hit the same trace/space as a 1oz layer. Reviewing this against your layout during DFM avoids a redesign cycle after tooling.
etch factor · trace/space vs copper weight · plating uniformity in deep channelsFull heavy copper PCB fabrication specification
Current-carrying capacity calculated per IPC-2152 and confirmed by resistance measurement on every production lot.
Fabrication Parameters
| Copper Weight Range | 3oz – 20oz standard · 30oz+ specialty |
| Layer Count | 2 – 16 layers |
| Min. Trace / Space (Heavy Cu) | 8 / 8 mil at 6oz · widens with weight |
| Construction | Standard heavy copper · differential (step-stencil) |
| Board Thickness | 0.8 mm – 6.4 mm |
Performance & Standards
| Current Rating Method | IPC-2152 calculated |
| Thermal Management Options | Embedded copper coin / copper inlay |
| Surface Finish | HASL · ENIG · Immersion Ag · Selective gold |
| IPC Build Standard | Class 2 default · Class 3 on request |
| Prototype Turnaround | 5 days express · 8 days standard |
How heavy copper PCB is manufactured
Extended etch and plating cycles compared to standard copper — each step calibrated to the target copper weight.
Base Copper Selection & Imaging
Heavy-gauge copper-clad laminate is selected to match target weight, then imaged with extended-thickness photoresist to withstand the longer etch cycle.
Controlled Deep Etch
Extended etch time removes copper to the final circuit pattern, with etch factor compensation applied to hold trace geometry at the specified copper weight.
Drilling & Heavy Copper Plating
Through-holes are drilled and plated with extended electrolytic copper cycles to achieve uniform via wall thickness despite the thick outer copper layers.
Solder Mask, Finish & Resistance Test
Solder mask is applied over stepped copper contours, surface finish is added, and 100% resistance/continuity test confirms current-carrying integrity.
Where heavy copper PCB is the right choice
Any design that would otherwise need external bus bars, cabling or heatsinked power modules is a candidate for heavy copper.
Power Distribution / Busbar Replacement
6oz–20oz copper planes replacing discrete bus bars for DC power distribution within an enclosure.
Welding Equipment
Heavy copper boards carrying high pulsed currents in resistance and inverter welding power supplies.
EV Power Modules & Inverters
Differential copper boards combining heavy-current traction power traces with fine-pitch gate-drive signal routing.
Solar Inverters
Heavy copper power stages for string and central solar inverters handling high DC-link current.
Wind Turbine Controllers
Heavy copper control and power boards rated for high-current pitch and yaw motor drive circuits.
Industrial Motor Drives
Copper-coin-embedded heavy copper boards for VFD and servo drive power stages with concentrated heat sources.
Power Supplies
High-current secondary-side boards in switch-mode power supplies requiring low resistive voltage drop.
Battery Management Systems
Heavy copper current-sense and balancing boards for high-capacity battery pack BMS designs.
Heavy copper quality — from current-rating calculation to resistance test.
Quality on a heavy copper board starts with a current-carrying capacity calculation against your design load. Our DFM review checks etch factor impact on your layout before tooling. Post-fab, 100% resistance test confirms the as-built copper cross-section meets rating.
- ISO 9001 : 2015Third-party audited quality management
- IPC-6012Rigid PCB qualification & performance
- IPC-2152Current-carrying capacity calculation standard
- IPC-A-600 Class 2 / 3Acceptability criteria
- RoHS / REACHEU hazardous substance compliance
Inspection & Testing Methods
- 100% Electrical Test — Flying Probe / FixtureOpen / short on all nets
- 100% Resistance / Continuity TestConfirms current path integrity per net
- Microsection & Cross-section AnalysisCopper thickness verification per layer
- Plating Thickness DistributionDeep-channel and via wall uniformity check
- Peel Strength — Heavy CopperAdhesion per IPC-TM-650 2.4.8
- Bow and TwistIPC-TM-650 2.4.22
- Thermal Cycling / Temperature Rise VerificationAgainst IPC-2152 calculated rating
- Solder Mask Step CoverageOver stepped heavy copper contours
Heavy copper boards we have built
Real high-current fabrication challenges — solved.
150A EV Onboard Charger Busbar Replacement
10oz differential copper board replacing three discrete bus bars in a 150A onboard charger, integrating power and gate-drive signal routing on one 8-layer stackup.
Eliminated 3 discrete bus bars and associated fasteners, reducing assembly time by 40% and cutting resistive voltage drop by 15% versus the cabled design.
String Solar Inverter Heavy Copper Power Stage
6oz heavy copper power board with embedded copper coin under the switching MOSFETs to manage concentrated switching losses in a compact string inverter.
MOSFET case temperature reduced by 12°C at full load, allowing a smaller heatsink and a 9% reduction in overall enclosure footprint.
Inverter Welder 20oz Power Board
20oz single-layer power board for a resistance welding inverter, replacing a copper bar assembly and reducing manufacturing lead time from custom fabrication.
Reduced power stage manufacturing cost by 35% versus custom copper bar fabrication while meeting the same current and thermal rise targets.
Common questions about Heavy Copper PCB
Technical questions about heavy copper fabrication, current rating and layout.
Our standard heavy copper range is 3oz to 20oz per layer. Specialty constructions above 20oz, up to 30oz or more, are available on a project basis — these typically require extended etch and plating cycles and a dedicated DFM review to confirm achievable trace/space at the requested weight. Contact our engineering team with your target current and layout constraints for a feasibility check.
Yes, using a differential copper (step-stencil) construction, where two etch stages produce heavy copper in the power regions and standard or fine copper in the signal regions of the same layer. This is common in EV power modules and motor drive boards that need both high-current power delivery and fine-pitch gate-drive or control signal routing. It requires more careful process control than uniform copper weight boards and is reviewed in detail during DFM.
Current-carrying capacity is calculated per IPC-2152, which accounts for trace width, copper weight/thickness, allowable temperature rise, and whether the trace is on an internal or external layer (internal layers have less convective cooling and lower rated capacity for the same geometry). We provide a current-capacity calculation for your critical power traces as part of the DFM review before fabrication.
Etching heavy copper removes material from the sides of the trace as well as the top, an effect called etch factor. The thicker the copper, the more lateral etching occurs relative to trace height, which narrows the trace base and widens the practical minimum trace/space compared to standard 1oz copper. At 6oz, minimum trace/space is typically around 8/8 mil; heavier weights require progressively wider geometry, which we confirm during DFM against your specific stackup.
Copper coin (or copper inlay) is a solid block of copper embedded into the board directly beneath a high-power component, providing a low-resistance vertical thermal path to a heatsink or chassis that heavy copper planes alone cannot match. It's typically specified under power MOSFETs, IGBTs or other concentrated heat sources in motor drive, inverter and welding equipment power stages where localized thermal rise, not overall board current capacity, is the limiting factor.
We fabricate heavy copper multilayer boards from 2 up to 16 layers. Higher layer counts with heavy copper require careful lamination planning, since heavy copper layers create larger resin flow gaps that must be filled uniformly during press to avoid voids. Mixed stackups — heavy copper power layers combined with standard-weight signal layers — are common and are planned into the press cycle during engineering review.
Get your heavy copper design reviewed — today.
Send your Gerber and target current requirements. Our engineers review copper weight, trace sizing and etch factor within 8 hours.
- DFM & current-capacity review included with every enquiry
- NDA signed on request — standard practice
- Response within 8 working hours
- 5-day express prototype available
- No commitment required to get a quote
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