There are many different types of PCB Fabrication projects that require specific copper weights for a variety of reasons. At Gold Phoenix, we offer a generous selection of copper weights to suit your specific needs. From time to time, we receive questions from clients who are unfamiliar with the concept of copper weight, so this article is intended to address those concerns. Additionally, information about the effects of different copper weights on the PCB Assembly Process is included below, which we hope will be useful even to those clients who are already familiar with the concept; a firm understanding of our processes allows you to better plan for the manufacturing schedule and overall cost.

You can think of copper weight as the thickness or height of your copper traces, the third dimension that is not taken into account by the copper layers data of your Gerber Files. The measurement is given in ounces per square foot (oz / ft2), WHERE 1.0 oz copper translates to 1.4 mil (35 μm) thickness.

Heavy Copper PCBs are commonly used for power electronics devices, or any device that might be subjected to harsh environments. The thicker traces allow for greater durability, and also allow the traces to carry a larger amount of current without trace length or width being increased to absurd levels. On the other end of the equation, lighter copper weights are sometimes specified to achieve a specific trace impedance without requiring an extremely small trace length or width. As such, Copper Weight is a required field when calculate trace width.

The most commonly used copper weight value is 1.0 oz. finished, which is suitable for the majority of projects. “Finished” in this context, refers to the fact that the initial copper weight will be plated up to a higher value during the PCB Fabrication process. When specifying your desired copper weight to our sales team for quotation, please indicate the finished (plated) value of copper weight that you require.

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.

Higher copper weight values introduce additional cost and lead time not only due to the additional copper itself, but also for additional shipping weight, as well as time required for labor, process engineering, and Quality Assurance. These additional measures are necessary first of all because the additional copper cladding on the laminate will require more time for etching, and must observe specific DFM Guidelines. The copper weight of your board will also affect its thermal profile, causing your board to absorb heat significantly more quickly during the Reflow Soldering stage of PCB Assembly.

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.

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: