While there is no standard definition of Heavy Copper, it is generally accepted that if 3 ounces (oz) of copper or more is used on the internal and external layers of a printed circuit board, it is called a heavy copper PCB. Any circuit with a copper thickness of more than 4 oz per square foot (ft2) is also categorized as a heavy copper PCB. Extreme copper means 20 oz per ft2 to 200 oz per ft2.
A heavy copper PCB is identified as a PCB with a copper thickness 3 oz per ft2 to 10 oz per ft2 in the outer and inner layers. A heavy copper PCB is produced with copper weights ranging from 4 oz per ft2 to 20 oz per ft2. The improved copper weight, along with a thicker plating and appropriate substrate in the through-holes can change a weak board into a long-lasting and dependable wiring platform. Heavy copper conductors can increase the entire PCB thickness considerably. The copper thickness should always be considered during the circuit design stage. The current-carrying capacity is determined from the width and thickness of heavy copper.
The primary benefit of heavy copper circuit boards is their capability to survive frequent exposure to excessive current, elevated temperatures and recurring thermal cycling, which can destroy a regular circuit board in seconds. The heavy copper board has a high tolerance capacity, which makes it compatible with applications in rough situations such as, defense and aerospace industry products. Some of the added advantages of heavy copper circuit boards are:
Compact product size due to several copper weights on the same layer of circuitry
Heavy copper-plated vias pass the elevated current through the PCB and assist in transferring the heat to an outer heat sink
Onboard high-power-density planar transformers
Heavy copper PCBs are used for multiple purposes such as in planar transformers, heat dissipation, high power distribution, power converters, etc. There is an increased demand for heavy copper-clad boards in computer, automotive, military, and industrial controls. Heavy copper printed circuit boards are also used in:
Power supplies, power converters
Solar panel manufacturers, etc.
Depending upon the design requirement, heavy copper PCBs are more expensive to produce than regular PCBs. Hence, the more complicated the design, the more it will cost to produce a heavy copper PCB.