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What Is Heavy Copper PCB?
Regarding the definition of heavy copper PCB, I believe many people can say off the top of their heads, “As the name implies, heavy copper PCB is the PCB with thicker copper than normal PCB, right?” Of course, you are right. In normal products, the copper thickness is around 0.5 to 2 ounces, which is 17.5 to 70um. So when the finished thickness of copper foil on the copper layer is more than 2 ounces (70um), we call it heavy copper PCB, also extreme copper PCB.
With the development of science and technology, the application of thick copper is more and more. Many people may wonder, “Can thick copper PCB be used in products that require high current and high reliability?” The answer must be “yes”. It exists in all aspects of our life, from industrial equipment to automotive, to white goods, to the electricity industry, or even to the military industry, etc. According to the different thicknesses of copper, the product application is also very different.
Most heavy copper PCBs are made of FR4 material, but can also be made by polyimide which is called heavy copper flex PCB. Besides, aluminum-based and copper-based materials are also used.
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Why Design Heavy Copper PCB (extreme copper PCB)?
There is a growing demand for heavy copper PCBs for electronic products with high performance, multiple functions, small size, ability to carry high currents, and good heat dissipation. Heavy copper PCBs have the characteristics of carrying high currents, reducing thermal strain, and good heat dissipation.
Why Is Heavy Copper PCB Used?
Heavy copper is chosen by engineers because it has any characteristic that less copper thickness cannot achieve. Let’s take a glimpse at the characteristics of heavy copper PCB or extreme copper PCB. Firstly, it can do well in volume simplification and can withstand large currents and voltage. Secondly, its extensibility and heat dissipation rate are much stronger than that of ordinary PCB. In addition, it is not sensitive to high temperatures and low temperatures and has strong corrosion resistance. Many people thus make the observation, “Does this mean that the life of heavy copper PCBs is usually much longer than that of ordinary PCBs?” Yes, what a correct conclusion!
Especially with the rapid development of science and technology, electronic products have higher and higher requirements in various aspects, high current and voltage requirements, small volume requirements, extremely high-reliability requirements, anti-interference, thermal conductivity, and electrical conductivity requirements, very extreme use environment, etc., heavy copper PCB can fully meet these stringent requirements.
Applications of Heavy Copper PCB
Here are some applications for heavy copper PCBs:
- Solar converters
- Rail traction systems
- Nuclear power industry
- Automotive industry
- UPS systems
- Protective Relays
- Torque control
- Safety and signaling systems
- Welding equipment
- Power line motors
- Military equipment
Common Usage of a Heavy Copper Printed Circuit Board
The common usage of a heavy copper PCB includes cell phones, microwaves, aerospace, satellite communications, network base stations, hybrid integrated circuits, power supply high-power circuits, and other high-tech fields, as well as a variety of home appliances, medical, and other electronic equipment.
Our Heavy Copper PCB Capability
| Items | Capabilities |
|---|---|
Copper thickness | 2oz to 40oz |
Layers | 1-12 layers |
Max. PCB size | 24×48’’ |
Material | FR4, polyimide, aluminum base, copper base |
Technologies | Countersink, the cavity structure |
Material thickness | 0.5-10.0mm |
Outline method | Routing with mouse bite, v-cut, punching |
Blind/buried vias | yes |
Min trace width/space | 6mil (0.15mm) |
Min drill size | 8mil (0.2mm) |
Surface treatment | HAL, ENIG, immersion silver, immersion tin, ENEPIG, OSP |
Lead time | 1-4 weeks |
The Advantages and Disadvantages of Heavy Copper PCB
Everything has its advantages and disadvantages, and it is the same for heavy copper PCBs. The following analysis is about the advantages and disadvantages of heavy copper PCBs.
The main advantages of heavy copper PCB
Needless to say, heavy copper PCB can do better in many application areas which need High reliability, long life circle, high currency or voltage, high thermal conductivity, or extreme environments, because its higher thick copper is much more robust. There are 4 main advantages as below:
The disadvantages of heavy copper PCB
Next comes the analysis of the disadvantages of heavy copper PCB. Please refer to the following disadvantage of heavy copper PCB:
Heavy Copper Printed Circuit Board Design Guidelines
How is Heavy Copper PCB Fabricated & The Main Differences in Heavy Copper PCB Production Process
Generally speaking, the production processes of heavy copper are more or less the same as FR4 PCB production: Base material cut into the smaller panel →Drilling → Copper plating →Out layer dry film →Etching → AOI inspection →Solder mask →Silkscreen →Surface finishes →Outline profiling → E-testing →Visual inspection →Packaging. But there are also some main differences as follows:
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Three Common Functional Failures in Heavy Copper PCB
With the continuous development and progress of social science and technology, the electronic products in our lives have higher and higher requirements in all aspects: smaller size, more functions, longer usage life, high reliability, high currency and voltage, extreme usage environment, high thermal conductivity etc. And only heavy copper can meet some of these requirements. So we can foresee that copper PCB will be used more and more in difference industrial area, such as industry equipment, automotive, medical, aerospace, military etc. But all these application need very reliable PCBs and can hardly bear any failure at all. But we all know problems will happen any how. Here we would like to share some common problems in heavy copper PCB manufacturing and what we have done in Viasion to avid them happens in production.
We may see different kinds of problems in extreme copper PCB, but here we just want to focus on 3 main functional failures, rather visual problems such as solder mask or silkscreen defects. As a heavy copper PCB manufacturer, the following 3 points are the functional problems we may often encounter in heavy copper PCBs.
If the surface of the heavy copper circuit PCB is not flat, it will cause problems in PCB assembly or final usage. The reason is: usually, during lamination, the part with a high residual copper rate will be thicker than the low part, which will lead to an uneven surface, and finally affect the operation of the final SMT assembly or even problems for final product assembly.
Some people may point out like that, ”Are heavy copper PCBs always used to meet the dedicated requirements from the designer and the end user, such as high voltage and high currency, high reliability, thermal conductivity, electrical conductivity, anti-interference, extreme usage environment, etc?” Of course, we can think of it this way. Some people want to know, “If there are production defects or base material defects as such, will the finished heavy copper PCB not fully meet the customer’s requirements?” The answer is already clear in our minds: such a situation does occur.
How to Avoid Failures in Heavy Copper PCB Production
As summarized above, although heavy copper PCB has many advantages, due to the thickness of copper, it also leads to many problems and difficulties in processing, such as uneven PCBs surface after finished, deformation or delamination in PCB assembly, difficulty in etching, insufficient resin filling, drill to be damaged and affects the drilling quality, PCBs cannot meet the requirements from the designer and so on. But thanks to our experienced team and new technology, here in Viasion we can solve all these problems. To ensure product quality and production stability, the following summarizes some points that need to be paid special attention to by heavy copper PCB manufacturers. Please refer to our advice for a few points below:
Try to solve problems in the design stage
Charge large copper areas into copper spots
Try to change a large area of copper into copper spots in heavy copper PCBs design, add some copper to the copper-free area of the inner layer, and then design the PCB traces and subdivisions to achieve balance and symmetry. In this way, the above problems can be solved in advance mostly, to avoid the low quality of the product after the production is completed.
Keep proper residual copper
In heavy copper circuit production, after the copper thickness is increased, if the residual copper rate is too low, then a lot of work needs to be done to make up for the problem of insufficient resin. If the overall filling of the resin is not enough, it will also cause a series of problems, so it is necessary to keep as much residual copper as possible. Since the increase in the residual copper rate, the above series of problems may be avoided.
Increase trace width and spacing
There are many advantages to further increasing the line width and line spacing. The most important point is that the line width and line spacing are improved, so the pressure on the resin filling will be much smaller, not only, but also in the subsequent etching stage. The difficulty can be greatly reduced. But anyhow, trace width and spacing need to meet the copper wire connections and functions first in heavy copper PCBs manufacturing and design.
Optimize the pad design of the inner layer
Things need to pay attention to in the production process
Whatever we have done in the design stage, there will be problems in production anyhow. Here are some things we need to pay attention to in heavy copper PCB production processes.
Regarding etching, the increase in copper thickness, according to Viasion’s many years of production experience in heavy copper PCBs fabrication, will also lead to more difficulty in chemical exchange in the etching and plating processes. To solve this problem, we have better perform multiple etchings and multiple copper plating to solve it.
We need to increase the period of high temperature during lamination to ensure the curing effect of the cured sheet. Because the copper thickness increases and the board thickness also increases, heavy copper PCB will absorb more heat during lamination, which will lead to the overall when the temperature rises slowly, the stability of the cured sheet will be greatly affected, so we need to increase the high temperature during lamination to stabilize the curing effect.
Regarding the difficulty of stack-up, as mentioned above, due to the relatively large thickness of copper, in the case of a low residual copper rate, a large amount of resin needs to be filled, which is very difficult, and a cured film is also used to carry out, so the first point is to carry out preparatory copper plating in areas without copper in advance in the design stage, etc., to avoid subsequent problems.
Regarding the difficulty of drilling, As mentioned earlier, the copper thickness and plate thickness will further increase the worn of the drill bit, so to ensure the high quality of the final hole, we need to make some changes to the drill, such as reducing the service life of the drill. Drill bit works on heavy copper PCB will be worn quickly, and will be more easily damaged, which will lead to the substandard quality of the subsequent holes, therefore, we should reduce the life expectancy of the drill and replace it earlier. In addition, sub-drilling is carried out to reduce the worn of the drill.
A second copper plating is always needed in heavy copper heavy copper PCBs manufacturing, the hole size of the finished product needs to be compensated after completion. Before and after the secondary copper plating, the pin holes need to be strictly recorded and controlled in detail, and a series of compensation and optimization measures should be taken after the completion of the finished products. For example, the accuracy of the outer layer alignment should be guaranteed first, and the pin holes for the primary alignment should be designed, with a size of about 0.3175 cm. As I wrote in the previous article, after the secondary copper, the size of the hole will become smaller, which is inevitable, and it is also based on VIASION’s experience. Therefore, subsequent compensation is required, otherwise, the final quality of the product and the accuracy of PCBA will be affected.
Solder mask printing is very important in heavy copper printed circuit board production. The purpose of strengthening the control of the solder mask is to ensure that the ink filling of the finished product is good and complete and to ensure that the ink and copper surface of the finished product is flat so that the appearance is beautiful and the work stability of the PCB can be guaranteed.
As mentioned earlier, to ensure that the height difference between the final solder mask and the copper surface is the same, the ink amount should be controlled. Try to choose 36T mesh as the basic material, so the effect is the best. It should not be too much or too little. If too much, it will overflow, and if too little, it cannot keep the height level. Also, note the viscosity of the solder mask.
To avoid baking the solder mask twice, it should be printed on both sides at the same time. This has the advantage of saving the time and cost of manpower and machines. It is not only more efficient but also avoids the baking time of the solder mask long, resulting in quality problems and being unusable. After pre-baking, lay the PCB flat and check whether the solder mask layer is abnormal, for example, whether there are bubbles, and then leave it for 1-3 hours to allow it to cool and set.
For the secondary copper plating to increase the copper thickness, to ensure that the copper can be evenly laid on the plane, the copper face should be treated first, mainly roughening treatment. In addition, it is not a rubber slag removal cylinder, and the original copper plating time needs to be extended. The increase is about five minutes, which is about five minutes longer than the original copper plating time. Finally, to prevent the copper sheet on the base material from wrinkling, it is OK to dry it.
Regarding the second outer layer, our main purpose is to make the copper layer area that mainly needs to be plated. To achieve the purpose, the first thing we need to do is to perform acid after the first outer layer and turn off the grinding brush. Immediately after acid treatment, it can effectively prevent wrinkles. Another purpose of this is to avoid electroplating and plating caused by wrinkles on the copper surface and to make the alignment more accurate.
Advanced material for heavy copper PCB can be used
Besides design and production, advanced materials are also helpful to reduce the problem in heavy copper printed circuit board manufacturing. And the more important thing is these materials can be helpful to get better performances and achieve customers’ requirements, here are a few which should be helpful.
RTF copper foil is usually the first choice material for heavy copper PCB manufacturers, mainly to meet the requirement of good heat resistance, good corrosion resistance, and can carry larger current and voltage. Why not choose standard copper? Because the Ra value of RTF (Reverse Treated Foils) is smaller than standard copper, which is more suitable. To withstand high pressure, in addition, extreme copper PCB usually uses two or more pieces of material, which has many advantages. The probability of being punctured and thus the stability of the product is higher. In addition, if there is a problem with a certain part of the material, it can be made up, but if the whole material has a problem, it cannot be made up. Copper is characterized by good extensibility, which can meet various processability requirements.
When the inner layer copper thickness is greater than 4 ounces, according to past production experience, usually, everyone solves the high copper thickness filling solution by filling PP powder or resin, but the shortcomings of this are also obvious. Firstly, it is difficult to control the thickness, and the process is complicated and long as well. Therefore, with the advancement of technology, many manufacturers including Viasion, will now use the latest material for filling in heavy copper printed circuit board fabrication. First of all the PCB surface is flatter after lamination. Besides, the resin has better heat resistance, lower expansion coefficient, and high resin content will make the filling effect better, complement each other, and the special structure will further improve reliability.
Some people will make the argument, “Will it be possible to form a PCB with strong heat dissipation to meet the growing demand in technology If the copper thickness of the substrate with high thermal conductivity is higher?” Yes, it will. Its thermal conductivity and heating rate of the finished product will be greatly improved. Compared with ordinary PCB, its heating rate can be reduced by about 10°. For PCB aspect is a huge improvement. There will be more and more research in this area in the future, and now most manufacturers are working hard in this area to seize the opportunity.
To sum up, heavy copper PCB will be used more and more widely in the future, and Viasion and other manufacturers will continue to work hard in this field to seek better and stronger production solutions and more advanced materials, to produce the best quality heavy copper PCB for our customers. Besides heavy copper F4 PCB, we can also supply heavy copper flex PCB, heavy copper rigid-flex PCB, heavy copper aluminum PCB, and copper based PCB. Please send us your files to quote if you have demands for such special projects. And we are looking forward to serving you in the future.
Why Choose Viasion for Heavy Copper PCB
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Frequently Asked Questions
Heavy copper PCBs are ideal for high-power equipment, automotive, defence and military applications, medical devices, and many other areas.
According to the different uses of the PCB, the required copper thickness is different. Like PCBs for general consumer and communication products, copper thicknesses of 0.5oz, 1oz, and 2oz are needed; for electronic products carrying high current, such as high-voltage products, power supply boards, and other products, PCBs generally need more than 3oz of thick copper. In short, choose the appropriate copper thickness according to the requirements of the product.
There is one layer of copper in a single-sided PCB. There are two layers of copper in a double-sided PCB. There are more than two layers of copper in a multi-layer PCB. For example, there are four layers of copper in a 4-layer PCB.
There is no difference between these two terms, all means printed circuit boards with 3oz or thicker copper thickness. Thick copper PCB or heavy copper boards are widely used in higher power electronic boards.
The typical copper weight for heavy copper PCBs is more than 2 ounces (70um). But we can also produce higher copper thickness such as 4 oz copper PCB, 10 oz copper PCB and upto 20 oz copper PCB.
RTF copper should be used.
Better filling material in lamination
High thermal conductivity substrates
Charge large copper area into copper spots
Keep proper residual copper
Increase trace width and spacing
Optimize the pad design of the inner layer
Withstand more currents and higher voltages
High reliability
More resistant to heat, cold, and corrosion
Long life circle
In Viasion, printed circuit boards with 0.33oz, 0.5oz, 1oz and 2oz are normal copper thickness. So we think 2oz PCB is not heavy copper circuit board, and we regard PCBs with 3oz or above copper thickness as heavy copper boards.