A 4 oz Heavy Copper PCB features a finished copper weight of 140 um (4 oz/sq ft) on outer and/or inner layers. Built for high-current distribution and thermal dissipation, this architecture prevents localized overheating and trace burnout. Typical stack-ups combine heavy copper planes with standard signal layers for mixed-signal power electronics.

Technical Specifications

Parameter	Specification Range
Finished Copper Weight	4 oz (140 um) nominal (Outer/Inner)
Layer Count	1 to 24 layers (Hybrid heavy/signal stack-ups available)
Board Thickness	0.8 mm to 4.0 mm
Min. Trace Width / Spacing	5 mil / 5 mil (depending on copper thickness and etching parameters)
Max. Board Size	600 mm x 500 mm
Surface Finishes	ENIG, Immersion Silver, OSP, HASL (Lead-Free), Galvanic Gold (selective)
Solder Mask	High-temperature liquid photoimageable (LPI), thick-film clearance capabilities
Base Materials	FR-4 (Tg >= 170°C), Polyimide, Ceramic-filled high-frequency laminates

Key Features

High Current Density: Accommodates continuous currents up to 50 A+ per trace depending on trace width and allowable temperature rise (30°C delta).

Thermal Management: Dissipates heat away from high-power components (MOSFETs, IGBTs) directly into internal copper planes, reducing dependence on external heat sinks.

Mechanical Strength: Withstands high mechanical vibration and thermal cycling without trace cracking or pad lifting at mounting holes.

Planar Transformer Integration: Supports embedded planar magnetics and high-frequency inductive components directly within the PCB layout.

Applications

Renewable Energy

Solar string inverters, wind turbine pitch controllers, and energy storage system (ESS) battery management units.

Electric Vehicles

On-board chargers (OBC), DC-DC converters, and motor drive inverters.

Industrial Automation

High-power variable frequency drives (VFD), servo controllers, and industrial power supplies.

Grid Infrastructure

Smart grid distribution switches and high-voltage protection relays.

Customization

Hybrid Stack-ups: Combine 4 oz power/ground planes with 1 oz or 2 oz signal layers to balance high-current capability and fine-pitch routing.

Thermal Vias: Filled and capped via-in-pad arrays under high-dissipation power packages (TO-220, D2PAK).

Controlled Depth Routing: Partial cavity milling for busbar integration or direct component seating.

Specialized Dielectrics: High-Tg (>180°C) and high-CTI (>600V) laminates for high-voltage isolation.

Quality Control

Etching Verification: Automated Optical Inspection (AOI) calibrated for thick copper edge profiles to control undercut and maintain nominal trace geometries.

X-Ray Inspection: Non-destructive testing for multi-layer inner-layer alignment and barrel crack detection in plated through-holes (PTH).

Electrical Testing: 100% flying probe or fixture test (Hi-Pot test up to 2000V DC based on insulation spacing).

In-House Testing Equipment: AOI systems, micro-section analysis labs, thermal stress testing baths, and ionic contamination testers.

Manufacturing & Certifications

Production Facility

Fully automated heavy copper etching lines, pulse plating rectifiers for uniform copper distribution, and vacuum lamination presses.

Standards Compliance

Manufactured in accordance with IPC-A-600 (Class 2/3) and IPC-6012.

Certifications

ISO 9001:2015, IATF 16949 (Automotive), ISO 13485 (Medical), and UL certified (E-file available upon request).

Packaging & Delivery

Packaging: Vacuum-sealed anti-static moisture barrier bags with desiccant and humidity indicator cards; double-walled corrugated cartons with edge protection for transit security.

Lead Time:

Prototypes (1-4 layers): 5 to 7 working days.
Batch Production: 12 to 18 working days depending on volume and stack-up complexity.
Logistics: Direct air/ocean freight options via trusted international couriers (DHL, FedEx, UPS).

FAQ

Q: How do you prevent excessive copper undercut during the 4 oz etching process?

A: We utilize specialized differential etching parameters, pulse-reverse plating to optimize copper crystal grain structure, and compensation factors built into our CAM engineering step to maintain edge wall verticality within +/-15% of copper thickness.

Q: Can 4 oz copper layers be combined with fine-pitch signal layers in the same stack-up?

A: Yes. Hybrid stack-ups use 4 oz foil for dedicated power/ground planes and 1 oz or 2 oz foil for outer and inner signal layers, allowing fine-pitch routing (down to 4 mil line/space) on designated layers.

Q: What is the maximum current capacity for a 4 oz copper trace?

A: Current capacity depends on allowed temperature rise, trace width, and inner/outer layer location. According to IPC-2152 standards, a 100-mil wide outer trace in 4 oz copper typically handles roughly 15 A to 20 A for a 30°C temperature rise. Exact calculations require thermal-electrical simulation based on specific layout geometries.

Q: How do you ensure uniform copper plating inside plated through-holes (PTH)?

A: We apply DC/pulse periodic reverse (PR) electroplating combined with periodic bath agitation and chemistry monitoring. This prevents barrel thinning and ensures a minimum average copper wall thickness of 25 um inside the holes.

Q: What documentation is required to initiate an RFQ for a 4 oz heavy copper PCB?

A: Submit Gerber files (RS-274X or ODB++ format), an IPC-compliant fabrication drawing specifying finished copper weights per layer, stack-up requirements, surface finish preferences, and estimated annual usage or batch quantities.

Q: Do you perform micro-section analysis reports for heavy copper shipments?

A: Yes. Micro-section reports detailing copper plating thickness, solder mask thickness over heavy copper, and dielectric spacing are available upon request as part of our outgoing quality inspection protocol.