Heavy Copper PCB for power supplies with high current resistance

1.Structure

The structure is similar to a standard PCB but involves a specialized plating and etching process.
◈ Copper layer: The "veins" of the board are much taller and wider. The thickness of the copper varies from 3 Oz to 20 Oz in some special cases. The maximum inner layer copper thickness is 10 OZ whereas the outer layer thickness can be up to 20 OZ.
◈ Base material: The heavy copper PCB construction is purely dependent on base materials like FR4 or Halogen free or Rogers or Aluminium or in some cases, hybrid base materials are used. Normally FR4 will be Middle Tg and High Tg material. 
◈ Number of Layers: The number of heavy copper PCBs layer is from 2 to 20 layers depending on the manufacturing.
◈ Board thickness:  The thickness of the board is from 1.6mm to 5.0mm. 
◈ Heavy Plated-Through Holes (PTH): The holes connecting different layers are reinforced with thick copper to carry high current without overheating.Normally it is required 25um min hole copper thickness, even to 38um or 50um hole plated copper thickness to ensure performance. 
◈ Core: Often uses high-temp FR-4 or metal-core materials to support the added weight and heat. Normally it is middle TG and high TG material. 
◈ Dielectric layer: Minium 2 pieces prepreg for heavy copper PCB, if have required high current, it needs 3 pieces prepreg. 
◈ Surface Finish: PCB surface finish will be OSP, HASL, HASL Lead-Free (HASL LF/ ROHS), Tin, Immersion gold (Au), Immersion Silver (Ag), ENIG, ENPIG as per standards,  and few boards are also used Golden finger + HASL, ENIG + OSP, OSP + Golden finger for better conductivity on the surface as huge current has to make contact with the external component’s terminal. 

2.Key Advantages

Heavy copper offers three primary "superpowers" for electronics:

3.Production Technology requirement

Manufacturing a Heavy Copper PCB is significantly more challenging than standard boards. Because the copper is "thick," traditional chemical processes can easily ruin the traces.
Here are the key production technology requirements and techniques: 
◈ 3.1 Lamination & Resin Filling
1)Because the copper traces are so thicker,  the "valleys" (copper tooth) between them are deep.
2)High Resin Flow: Specialized "Prepreg" (bonding layers) with high resin content is required to fill these gaps completely.
3)Void Prevention: If the resin doesn't fill every gap, air bubbles (voids) formed. Under high power, these bubbles can expand and cause the board to explode or delaminate.
4)Higher Pressure/Temperature: The lamination press must operate at higher parameters settings to ensure the thick copper "sinks" into the substrate evenly.
◈ 3.2 Specialized Drilling
Drilling through a standard PCB is like drilling through plastic; drilling a Heavy Copper board is like drilling through a metal plate.
1)Drill Bit Life: Copper is soft and "gummy." It generates immense heat, which dulls drill bits quickly. Manufacturers must replace bits much more frequently (e.g., every 10-20 holes vs. hundreds).
2)Peck Drilling: Large holes often require "pecking"—drilling a little, retracting to clear the copper "chips," and drilling again to prevent the bit from snapping.
◈ 3.3 Advanced Etching & Plating
Standard etching is like spray-painting a stencil; for thick copper, it’s more like carving a deep canyon.
1)Differential Etching & Step Plating: Instead of one long chemical bath, manufacturers use multiple cycles of plating and etching. This prevents undercutting (where the chemicals eat away the bottom of a trace, making it unstable).
2)Trace Profile Control: To achieve straight sidewalls, high-speed etching systems are used to ensure the final trace is rectangular rather than a "trapezoid" or "mushroom" shape.
◈ 3.4 Solder Mask Application
A standard single coat of solder mask is too thin to cover the "cliffs" of a heavy copper trace.
1)Multiple Coatings: Usually requires 2 to 3 layers of solder mask.
2)Electrostatic Spraying: This method is often preferred over silk-screening because it ensures the ink wraps around the sharp vertical edges of the thick copper traces.
◈ 3.5 Design for Manufacturing (DFM) Rules
To ensure the factory can actually build the board, designers must follow stricter rules:

4.Application Fields

You will find Heavy Copper PCBs in environments where "failure is not an option" and power demands are high:
◈ Power Electronics: Inverters, converters, and power supplies.Planar Transformers, Amplification Systems
◈ Automotive: Electric vehicle (EV) charging systems and power distribution modules.
◈ Renewable Energy: Solar panel controllers and wind turbine power systems.
◈ Industrial: Welding equipment, heavy machinery controllers, and trans
◈ Medical Electronics: Special medical equipment like laser operation or robotic machines, imaging devices like scan machines, X-ray, etc
◈ Military & Aerospace: wireless, satellite communication devices, and radar appliance
◈ Industrial Equipment: Industrial equipment uses heavy copper PCB which can be used in harsh environments as it is corrosion resistant to many chemicals. 

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