Printed circuit boards (PCBs) are among some of the most complicated components of any electrical device.
Many small things come together to create a properly functioning PCB. PCB copper weight is one of these many things that need to be completely understood and micromanaged when manufacturing PCBs.
Because it is such a strong conductor, copper is one of the most significant components of a PCB. If you don't calculate and apply the weight of copper correctly, many things will go wrong.
It can be very complicated to measure and calculate PCB copper weight. There is also a lot of information about the PCB copper weight available. This article will put all this information together.
1、What is the PCB Copper Weight?
As mentioned earlier, copper is a massive conductor. It is a major building block of any PCB. It is nearly impossible to create an effective PCB that works consistently without properly measuring copper weight.
It brings up the question: What exactly is PCB copper weight?
A specific set of calculations determines copper weight. It is then applied to the rest of the PCB and connected to everything else around it. When the calculations are performed correctly, the PCB is ready to be manufactured.
It sounds simple enough, but there are specific things that need to know about copper that contribute to copper weight calculations.
Image 1: PCB Copper Weight
Copper is an alloy
Like any metal, copper is an alloy. It is what makes it a conductor. Alloys come in many forms, but copper is the most common when it comes to the construction of PCBs.
Alloys come in many forms, whether it is a bar, a sheet, or a tube. It is the first thing to consider before determining the weight of the PCB copper.
Knowing the grade and what form the copper takes are only two of several things that go into calculating the PCB copper weight itself. The rest pertains to physical measurements involving the copper itself.
One thing that needs to be mentioned is that these calculations and measurements must be perfect. Failing to do this will not cause any major problems, but going back and remeasuring things will take a long time and can be troublesome.
The worst case scenario is applying the copper to the circuit board after making incorrect calculations. In this case, it would be extremely difficult to undo what has been done, if not impossible.
2、Design Considerations With Heavy Copper
In the previous section, we learned about the weight of PCB copper. This section will explore how heavy copper can be used to enhance the design of a PCB.
Copper thickness in ounces. Heavy copper can be as thick as 19 ounces per square foot. It makes it a popular option for many PCBs since most of today's electronics are much smaller than electronics in the past. While other sizes of copper are still useable, heavy copper has become the most common and most popular.
Heavy copper allows for a lot more options in designing a PCB. Experts in the field of PCB production and design have discovered ways to improve how a PCB looks because heavy copper is very versatile in PCB production.
Image 2: PCB Copper Weight
Another reason is that in PCB production, copper only accounts for a small amount of space on an actual circuit board. Because of this, they are using the standard green rectangular board outline not necessary.
From this, it is now possible to create PCBs that not only function well, but also look a little more desirable than they used to.
Because of this, it is now possible to create artwork out of PCBs such as this:
Doing this is not as difficult as you would think. All it takes is a good knowledge of copper weights, how to measure and weigh copper, and basic soldering techniques.
3、PCB Copper Weight Specifications
The previous section was about how heavy copper can be used to improve the aesthetics of a PCB. This section will describe the three specifications of copper weight.
There are three "weight classes" of copper. Each of these has its use in PCB manufacturing.
Copper thickness is measured in ounces per square foot. It makes sure that other calculations are accurate. Because copper is such a strong conductor that yields predictable rates of amps and mils, it is not necessary to measure it per square inch.
Any form of copper plating that is ¼ of an ounce per square foot to 4 ounces per square foot is considered standard. For a long time, this was the de facto industry standard when it came to building almost any given PCB, as there was a very low risk of failure when using it to plate a PCB.
Still using standard copper today, and in many cases, if a particular size of copper is not specified, many distributors of materials will assume that the manufacturer desires copper plating of 1.2 ounces per square foot.
Copper that is 5 to 19 ounces per square foot is considered heavy copper. Over the years, testers and designers have been using heavy copper to experiment with their designs. As mentioned earlier, it is now possible to create a PCB with a heavy copper, and in many cases, it is superior to standard copper.
For years, this was considered risky, as most believed that copper was too strong a conductor to be plated onto a circuit board without very bad things happening.
Recently, this proved to be wrong, as it is still possible to lessen the amp value of the charge produced from heavy copper by exposing the copper before plating it onto a surface. What results is the ability to create customizable designs of copper plating onto a PCB.
It was not enough for some testers, as they decided to go one further. What if it were possible to possess copper that was even thicker than heavy copper, but could create lasting and powerful charges?
EXTREME copper is the result of this. Copper that is 20 to 200 ounces per square foot is considered EXTREME copper, and naysayers over the years have considered this unthinkable to plate into any PCB.
After all, even PCBs that were placed inside of even the largest electronics only needed to possess heavy copper plates at most.
It was the case until the 2010s, when testers discovered that it was possible to use EXTREME copper in a PCB, provided the charges they yielded were somewhat restricted.
These restrictions are made possible by performing something called a “Powerlink,” which is achieved by placing at least two copper weights on the same layer of a PCB. While this is only possible to do on the outer layers, it did prove that it was possible to plate EXTREME copper onto a PCB.
Now we know three kinds of copper weight classification. The next chapter will be about the copper plating process.
4、PCB Base Weight vs. Copper Plating Thickness
On its own, copper does not achieve anything as a conductor. It needs to be heated or cooled to certain levels for it to carry a charge in any PCB. The classification of PCB copper weights above describes base copper weights that are completely unaltered.
Plating thickness is determined when copper is heated or cooled to certain levels. This chart shows a clear relationship between the unaltered copper weight, trace width, which pertains to a cross-section of copper, usually measured in millimeters (or “mils” for short), and current carrying capacity.
A mistake that some manufacturers make is that they do not take into account both temperatures and trace when determining plating thickness. They will consider one thing but not the other.
This mistake occurs because unlike many other operations that entail determining PCB copper weight, knowing trace width and temperatures are generally not part of calculations when finalizing PCB copper weight.
We explored the copper plating process. The calculation method of copper weight will be accurately displayed below.
5、How is the Weight of the PCB Copper Finalized? - The Copper Weight Calculator
Recall that copper is an alloy that requires a set of calculations to determine its final weight. Some of these methods were mentioned earlier, but all of these calculations will be explored now.
Before starting any copper weight calculation, you should know the difference between copper and copper alloy. While pure copper is an alloy in and of itself, there are some cases where pure copper is combined with another alloy, such as nickel, to form what is called a “copper alloy.”
These have different grades than pure copper.
Both pure copper and copper alloy have a grade. The grade of pure copper starts with a “C” followed by a number. There do exist other grade families of copper, but when it comes to determining a PCB copper weight, pure copper and copper alloy are the most common forms of copper that are used. Both of these have their specific grades.
The grade of pure copper or copper alloy is something that you should know before ordering it, as the grade is usually listed on any given order form. Different grades of copper used for different purposes, but C110 is the grade of copper that is used the most among PCB manufacturers.
The next thing that needs to be determined is the shape of the copper. Most manufacturers will use sheet copper or a flat bar of copper, but other shapes of copper can also be melted down and used for plating. For example, it is much easier to create copper wires using round bars of copper, since they already possess the cylinder type shape that makes it easier to cut into wires.
After determining whether you are using pure copper or a copper alloy and knowing the grade of whichever one you are using, it is time to make some measurements. These measurements must be 100% accurate.
They need to be perfectly accurate because working with PCBs usually entails micromanaging small spaces that yield a sizeable charge. If there is a problem, the charge will not exist, or the power will be too high, and the PCB will not function.
6、Heavy Copper and EXTREME Copper in PCB Design
Image 3: PCB Copper Weight
The final section describes the process of calculating copper weight. This section is about the role that heavy and EXTREME copper play in PCB design.
As mentioned earlier, heavy copper and EXTREME copper are considered more than ever because of testing that revealed that they could be soldered into a PCB without anything detrimental happening to the PCB itself.
It revealed a couple of things. First, it revealed that the larger thickness of heavy and EXTREME copper made most PCBs last a lot longer than if they were built with standard copper.
The other thing is that not only is placing heavy and EXTREME copper in the right areas on a PCB improves longevity. It also improves the design by replacing the smaller standard copper weights. It makes the design of PCBs a lot less complicated.
6.1 How copper weight impacts PCB manufacturing
The reason why copper weight is so important in PCB manufacturing is due to a couple of major factors that affect how the PCB will carry a charge: Current, which is measured in amps, and impedance, which is measured in ohms.
When it comes to standard copper, it is easy to detect current and impedance. It becomes a little more complicated when working with heavy and EXTREME copper. True to their names, heavy and EXTREME copper is a lot thicker than standard copper and is much stronger conductors.
Because of this, the current and impedance of heavy and EXTREME copper have different rates that are much stronger. While this will last much longer than the charges that standard copper yield, it also means that different things must be done to maintain their proper weights on a PCB.
While standard copper can be placed on all layers of a PCB, heavy and EXTREME copper can only be placed on the outer layers. It creates what is called a "Powerlink.” This Powerlink can eliminate the need to have multiple standard copper plates on a PCB by instead just placing a smaller number of heavy or EXTREME copper plates on them.
It may take a lot more time and effort to create and manufacture PCBs using heavy and EXTREME copper at first. But it is well worth it, as the PCB itself will look much better and will be every bit as efficient as PCBs using standard copper, if not more. Once creating Powerlink becomes routine, you will not look back.
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