High TG Thick Copper PCB for Energy Storage

Heavy Copper PCB

Heavy Copper PCBs are specialized circuit boards designed for high levels of power and heat during working. While a standard PCB typically uses 1 OZ-2OZ copper, a Heavy Copper PCB uses 3 oz to 20 oz (or more). The thicker copper layers allow the board to conduct higher currents and high voltage. The boards will be well and no damage for long time working with high thermal.

Their type is such as winding board, BMP products, AC-DC boards and so on.

Normally it is used for high power (electric current) electronics like power supply or some power circuit or high requirement on Thermal in industry. It can be designed in inner layer or outer layer. In PCB production process, it is more difficult than traditional circuits with 2OZ copper foil.

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 FR-4 with Middle TG or high TG material or metal-core materials to support the added weight and heat.

• Dielectric layer: Minimum 2 pieces prepreg for heavy copper PCB, if have required high current and voltage, it needs 3 pieces prepreg in core.

• 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 advantages for electronics product:

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

Because the copper traces are so thicker, the copper tooth between them are deeper.

• High Resin Flow: Specialized "Prepreg" (bonding layers) with high resin content is required to fill these gaps completely.
• 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.
• 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.

• 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).
• 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.

• 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).
• Trac e 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.

• Multiple Coatings: Usually requires twice of solder mask to ensure thicker soldermask cover board surface to ensure performance.
• 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.