For many reasons, there are many different types of PCB manufacturing projects that require specific copper weights. We receive questions from customers who are not familiar with the concept of copper weight from time to time, so this article aims to solve these problems. In addition, the following includes information about the impact of different copper weights on the PCB assembly process, and we hope that this information will be useful even for customers who are already familiar with the concept. A deep understanding of our process can enable you to better plan the manufacturing schedule and overall cost.

You can think of the weight of copper as the thickness or height of the copper trace, which is the third dimension that the copper layer data of the Gerber file does not consider. The unit of measurement is ounces per square foot (oz / ft2), where 1.0 oz of copper is converted to a thickness of 140 mils (35 μm).

Heavy copper PCBs are usually used in power electronic equipment or any equipment that may suffer from harsh environments. Thicker traces can provide greater durability, and can also enable the trace to carry more current without increasing the length or width of the trace to an absurd level. At the other end of the equation, lighter copper weights are sometimes specified to achieve a specific trace impedance without the need for extremely small trace lengths or widths. Therefore, when calculating the trace width, “copper weight” is a required field.

The most commonly used copper weight value is 1.0 ounce. Complete, suitable for most projects. In this article, it refers to plating the initial copper weight to a higher value during the PCB manufacturing process. When specifying the required copper weight quotation to our sales team, please indicate the final (plated) value of the required copper weight.

Thick copper PCBs are considered to be PCBs with outer and inner copper thicknesses ranging from 3 oz/ft2 to 10 oz/ft2. The copper weight of the heavy copper PCB produced ranges from 4 ounces per square foot to 20 ounces per square foot. The improved copper weight, coupled with a thicker plating layer and a suitable substrate in the through hole, can turn a weak circuit board into a durable and reliable wiring platform. Heavy copper conductors will greatly increase the thickness of the entire PCB. The thickness of copper should always be considered during the circuit design stage. The current carrying capacity is determined by the width and thickness of heavy copper.

A higher copper weight value will not only increase the copper itself, but also cause additional shipping weight and time required for labor, process engineering, and quality assurance, leading to increased costs and increased delivery time. First, these additional measures must be taken, because the additional copper coating on the laminate requires more etching time and must comply with specific DFM guidelines. The copper weight of the circuit board also affects its thermal performance, causing the circuit board to absorb heat faster during the reflow soldering stage of PCB assembly.

Although there is no standard definition of heavy copper, it is generally accepted that if 3 ounces (oz) or more of copper 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 exceeding 4 ounces per square foot (ft2) is also classified as a heavy copper PCB. Extreme copper means 20 to 200 ounces per square foot.

The main benefit of heavy copper circuit boards is their ability to withstand frequent exposure to excessive currents, high temperatures and repeated thermal cycles, which can destroy conventional circuit boards within a few seconds. The heavier copper plate has a high bearing capacity, which makes it compatible with applications under harsh conditions, such as defense and aerospace industry products. Some other advantages of heavy copper circuit boards include:

Due to the multiple copper weights on the same circuit layer, the product size is compact
Heavy copper plated through holes pass the elevated current through the PCB and help transfer heat to the external heat sink
Airborne high power density planar transformer

Heavy copper printed circuit boards can be used for many purposes, such as planar transformers, heat dissipation, high power distribution, power converters, etc. The demand for heavy copper coated boards in computers, automobiles, military, and industrial control continues to grow. Heavy copper printed circuit boards are also used for:

Power supply
Electricity deployment
Welding equipment
Automobile industry
Solar panel manufacturers, etc.

According to design requirements, the production cost of heavy copper PCB is higher than that of ordinary PCB. Therefore, the more complex the design, the higher the cost of producing heavy copper PCBs.