Heavy Copper PCB Design

Heavy Copper PCB Overview

A heavy copper PCB is a board that has a heavy copper circuit. This kind of PCB is subjected to specialized plating and etching techniques such as step plating and differential etching. It is also referred to as a thick copper PCB. After all, copper weights range from 4 oz/ft2 to 20 oz/ft2.

As a result, there is no need to create high-current/high-power circuits and control circuits on separate boards with the thick copper board. In addition, the thick copper plating comes with a simple board design and is highly dense.

The construction of a heavy copper circuit endows a board with benefits such as:

  • Increased endurance to thermal strains.
  • Increased current carrying capacity.
  • Increased mechanical strength at connector sites and in PTH holes.
  • Use of exotic materials to their full potential (i.e., high temperature) without circuit failure.
  • Reduced product size by incorporating multiple copper weights on the same layer of circuitry .
  • Heavy copper plated vias carry higher current through the board and help to transfer heat to an external heatsink.
  • On-board heatsinks directly plated onto the board surface using up to 120-oz copper planes.
  • On-board high-power-density planar transformers

How is Heavy Copper PCB Fabricated?

Plating or etching is commonly utilized in the production of extreme copper PCBs. The primary goal is to increase the copper thickness of sidewalls and plated holes. However, normal etching processes result in unevenly etched margins and edge lines. Therefore, specific etching and plating processes are required to achieve the additional thickness of copper on heavy copper PCBs.

Heavy copper PCBs are electroplated throughout the PCB manufacturing process. This will assist in thickening the PTH barriers on the PCB. As a result, the layer count is reduced, and the impedance distribution is narrowed with this method. However, when PCBs are driven to several cycles throughout the manufacturing process, the plated holes might become fragile.

Methods for Fabricating Heavy PCBs

Blue Bar Method: The Blue Bar Method is used to create automobile PCBs. It entails inserting thick copper bars onto PCBs to transmit the additional current.  Because just a few lines are needed to carry more significant current in high-power circuits. This approach saves both time and money by reducing the weight of the PCB. On the other hand, fabricators of multi-layer PCBs must pay close attention to the copper fill level between inner layers in order to prevent additional delamination.

Embedded Copper Method: Using this approach, a thick copper PCB with a heavy copper and flat surface incorporated within the prepreg resin is created. The resin thickness determines the thickness of the heavy copper that must be used.

Difference between a Thick Copper PCB and Standard PCB

The thickness of the copper deposition on the board is the significant difference between regular PCB and thick copper PCB.

The copper layer on a standard PCB weighs one ounce or 35 micrometers, but the copper layer on a thick copper PCB weighs four ounces or 140 micrometers.

Standard PCB cannot conduct large current values; however, extreme copper PCB can perform significant current levels.

Furthermore, standard PCBs do not sustain mechanical stress to enhance heat conductivity.

On the other hand, thick copper PCBs are recognized for enhancing heat conductivity while preserving mechanical stress.

Heavy Copper PCB Capabilities

When employing heavy copper PCB for various applications, it’s vital to evaluate its capabilities. Based on its specifications, this sort of PCB is more expensive to build.

Below mentioned capabilities should be available on a heavy copper PCB:

  • A maximum board size of 457mm x 610mm and a minimum board size of 6mm x 6mm is required.
  • Copper thickness per square foot is more than 3oz.
  • Green, black, blue, red, white, purple, or yellow solder masks are recommended.
  • The color of the silkscreen is either white, yellow, or black.
  • A board with a thickness of 0.6mm to 6mm
  • The maximum copper weight for the exterior layer should be 15 ounces.
  • Immersion Gold, HASL, and OSP should be used for surface finishing.
  • The final thickness ranges from 0.020 to 0.275 inches.

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