Heavy Copper PCBs: Manufacturers, Applications, and Key Industries

Heavy copper PCBs—defined by copper thicknesses of 3oz (105μm) or more—are the backbone of high-power electronics, enabling the efficient distribution of large currents in applications ranging from electric vehicles (EVs) to industrial machinery. Unlike standard PCBs (1–2oz copper), heavy copper designs deliver superior thermal conductivity, current-carrying capacity, and mechanical strength, making them indispensable for systems that demand reliability under extreme conditions.

This guide explores the unique properties of heavy copper PCBs, their manufacturing challenges, top manufacturers, and real-world applications across industries. Whether you’re designing a 500A EV battery management system or a high-power industrial inverter, understanding heavy copper technology will help you select the right solution for your high-current needs.

Key Takeaways
 1.Heavy copper PCBs use 3oz (105μm) to 20oz (700μm) copper, supporting currents up to 500A—10x more than standard 1oz PCBs.
 2.They dissipate heat 3x faster than standard PCBs, reducing component temperatures by 20–30°C in high-power applications.
 3.Critical manufacturing techniques include controlled etching, press-fit technology, and thermal management features like copper-filled vias.
 4.Leading manufacturers (e.g., LT CIRCUIT, Sanmina) specialize in heavy copper PCBs, offering tolerances as tight as ±5% for trace widths.
 5.Key industries include EVs, renewable energy, industrial automation, and aerospace—where high current and durability are non-negotiable.

What Are Heavy Copper PCBs?
Heavy copper PCBs are circuit boards with thick copper layers (3oz+) on power planes and traces, designed to carry large currents and dissipate heat efficiently. The copper thickness is measured in ounces per square foot (oz/ft²), where 1oz equals 35μm. Heavy copper designs typically range from 3oz (105μm) to 20oz (700μm), though custom applications can use even thicker layers.

How Heavy Copper PCBs Work
The thick copper layers serve two primary functions:

 1.High Current Handling: Wider, thicker traces reduce resistance (Ohm’s Law), allowing more current to flow without overheating. A 10mm-wide, 4oz copper trace can carry 50A—5x more than a 1oz trace of the same width.
 2.Thermal Dissipation: Copper’s high thermal conductivity (401 W/m·K) spreads heat from components like MOSFETs and transformers, preventing hotspots that degrade performance.

Heavy Copper vs. Standard Copper PCBs

Key Properties of Heavy Copper PCBs
Heavy copper PCBs offer a unique set of characteristics that make them ideal for high-power applications:

1. High Current-Carrying Capacity
The most critical advantage of heavy copper is its ability to handle large currents. This is governed by the ampacity (current-carrying capacity) of the copper traces, which increases with thickness and width:

Note: Higher ambient temperatures reduce ampacity, as heat dissipation becomes less efficient.

2. Superior Thermal Management
Thick copper layers act as built-in heat sinks, spreading heat away from components:

 a.A 4oz copper plane reduces component temperature by 25°C compared to a 1oz plane in a 100W power supply.
 b.Copper-filled thermal vias (0.3–0.5mm diameter) transfer heat from surface-mounted components to inner layers, further improving dissipation.

Testing Data: An EV inverter using 4oz heavy copper PCBs operated at 85°C under full load, vs. 110°C for a 2oz design—extending semiconductor lifespan by 2x.

3. Mechanical Durability
Heavy copper traces and planes are more resistant to physical stress:

 a.Withstand vibration (20–2,000Hz) in automotive and industrial environments (MIL-STD-883H compliant).
 b.Resist fatigue from thermal cycling (-40°C to 125°C), reducing solder joint failures by 50% compared to standard PCBs.

Manufacturing Heavy Copper PCBs: Challenges and Solutions
Producing heavy copper PCBs requires specialized processes to handle thick copper while maintaining precision:

1. Controlled Etching
Etching thick copper (3oz+) without undercutting (excessive removal of trace sides) is challenging. Manufacturers use:

 a.Acid Copper Sulfate Etching: Slower etching rates (1–2μm/min) with precise temperature control (45–50°C) to maintain trace accuracy.
 b.Step Etching: Multiple passes with reduced etchant concentration to minimize undercut, achieving trace tolerances of ±5%.

Result: A 4oz copper trace with a target width of 10mm maintains 9.5–10.5mm dimensions, ensuring consistent current flow.

2. Lamination and Bonding
Thick copper layers require stronger adhesion to the substrate (e.g., FR4, ceramic) to prevent delamination:

 a.High-Pressure Lamination: 400–500 psi pressure at 180°C ensures proper bonding between copper and substrate.
 b.Adhesive-Free Processes: Direct bonding (e.g., DBC for ceramic substrates) eliminates epoxy layers, improving thermal conductivity.

3. Thermal Vias and Heat Management Features
Heavy copper PCBs often include additional thermal features:

 a.Copper-Filled Vias: Plated with 20–30μm copper to enhance heat transfer between layers.
 b.Integrated Heat Sinks: Thick copper planes (10–20oz) bonded to aluminum cores for extreme thermal loads (e.g., 500A EV systems).

Top Heavy Copper PCB Manufacturers
Choosing the right manufacturer is critical for ensuring quality and performance. Leading providers include:
1. LT CIRCUIT
Capabilities: 3–20oz copper, 4–20 layer PCBs, tight tolerances (±5% trace width).
Specialties: EV battery management systems, industrial inverters, and renewable energy PCBs.
Certifications: IATF 16949 (automotive), ISO 9001, UL 94 V-0.

2. Sanmina
Capabilities: 3–12oz copper, large-format PCBs (up to 600mm×1200mm).
Specialties: Aerospace and defense, medical imaging equipment.
Certifications: AS9100, ISO 13485.

3. TTM Technologies
Capabilities: 3–20oz copper, hybrid PCBs (heavy copper + HDI).
Specialties: Data center power supplies, EV traction inverters.
Certifications: ISO 9001, IATF 16949.

4. Multek
Capabilities: 3–10oz copper, high-volume production (10k+ units/week).
Specialties: Consumer electronics (high-power chargers), industrial motors.
Certifications: ISO 9001, UL certified.

Applications of Heavy Copper PCBs
Heavy copper PCBs are used across industries where high current and durability are critical:

1. Electric Vehicles (EVs) and Hybrid EVs
 a.Battery Management Systems (BMS): 4–10oz copper traces monitor and balance 800V battery packs, handling 200–500A during charging/discharging.
 b.Traction Inverters: Convert DC from the battery to AC for the motor, using 6–12oz copper to manage 300–600A currents.
 c.On-Board Chargers (OBC): 3–6oz copper PCBs handle 10–40A AC-to-DC conversion, with thermal vias to dissipate heat.

2. Renewable Energy
 a.Solar Inverters: 4–8oz copper PCBs convert DC from solar panels to AC, withstanding 50–100A currents in outdoor environments.
 b.Wind Turbine Controllers: 6–10oz copper manages power from turbines, resisting vibration and temperature swings (-40°C to 85°C).

3. Industrial Automation
 a.Motor Drives: 3–6oz copper PCBs control industrial motors (10–50HP), handling 50–200A in variable frequency drives (VFDs).
 b.Welding Equipment: 10–20oz copper carries 100–500A currents in arc welders, with thick planes to dissipate heat from high-power arcs.

4. Aerospace and Defense
 a.Aircraft Power Distribution: 6–12oz copper PCBs manage 28V DC systems in planes, withstanding altitude-related temperature changes.
 b.Military Vehicles: 10–15oz copper PCBs power radar and communication systems, resisting shock and vibration in combat environments.

5. Medical Devices
 a.Imaging Equipment (CT, MRI): 3–6oz copper PCBs handle high currents in power supplies, ensuring stable operation for precise imaging.
 b.Laser Therapy Systems: 4–8oz copper dissipates heat from 50–100W lasers, maintaining consistent performance during treatments.

FAQs About Heavy Copper PCBs
Q1: What is the minimum trace width for heavy copper PCBs?
A: For 3oz copper, the minimum trace width is 0.5mm (20mil) to avoid etching issues. Thicker copper (10oz+) requires wider traces (≥1mm) to maintain tolerances.

Q2: Can heavy copper PCBs be used with high-frequency signals?
A: Yes, but thick copper can cause signal loss at >1GHz. Manufacturers mitigate this by using hybrid designs: heavy copper for power layers and standard copper (1oz) for high-frequency signal layers.

Q3: How do heavy copper PCBs reduce system costs?
A: By eliminating the need for external heat sinks and busbars, heavy copper PCBs reduce component count and assembly time. For example, an EV inverter using 4oz copper saves $15–$20 per unit by replacing a 1oz PCB + heat sink.

Q4: What substrates are used with heavy copper?
A: FR4 (high-Tg, Tg≥170°C) is standard for most applications. Ceramic substrates (alumina, AlN) are used for extreme thermal loads (e.g., 500A systems).

Q5: Are heavy copper PCBs RoHS compliant?
A: Yes—manufacturers use lead-free copper and substrates, ensuring compliance with RoHS, REACH, and IATF 16949 (automotive) standards.

Conclusion
Heavy copper PCBs are essential for high-power electronics, enabling the efficient handling of large currents in EVs, renewable energy systems, and industrial machinery. Their ability to combine high current capacity, thermal dissipation, and mechanical durability makes them irreplaceable in applications where standard PCBs fail.

While heavy copper PCBs cost more upfront, their ability to reduce system complexity (e.g., eliminating heat sinks) and extend component lifespan results in lower total costs over time. By partnering with experienced manufacturers like LT CIRCUIT or TTM Technologies, engineers can leverage heavy copper technology to build reliable, high-performance systems that meet the demands of tomorrow’s power-hungry electronics.

As industries like EVs and renewable energy continue to grow, heavy copper PCBs will play an increasingly critical role in enabling efficient, sustainable power distribution—proving that when it comes to high current, thicker copper is always better.