In high-power electronics, it’s usually not enough to use circuit boards with wider traces. Instead, manufacturers thicken the conductive layers to create heavy copper PCB boards. If your project involves controlling, converting, or distributing vast amounts of current, you want to learn more about this PCB type. If so, you’ll find the guide helpful.
What is Heavy Copper PCB?
A heavy copper PCB is a printed circuit board with over 3 oz. of copper per square foot. This feature applies to the inner and outer layers. You can also call it a thick copper PCB board. Note that 3 oz. is about 4 mil or 100 microns.
Using more copper improves the board’s current carrying capacity, allowing application in heavy-duty circuits, such as industrial electronics and automotive systems. It also enhances the board’s thermal performance.
In most cases, the amount of copper varies between 4 to 20 ounces. However, the mass can increase to 200-ounce copper in higher current applications. In comparison, standard PCB copper thickness is usually less than 3 oz. / f².
Heavy Copper PCB Specifications
Heavy copper circuit boards are application-specific. They come with features to enable them to fit your product or electronic system, usually based on the amount of current. The table below is a sample of typical specifications.
Material Options | FR4 Teflon, Polyimide, Metal Core, Ceramics |
Number of Layers | 1-32 (or higher in special stack-ups) |
Copper Mass | 3 to 20 ounces (and higher for custom quotes) |
Minimum Drill Size | 0.012″ |
Maximum Hole Aspect Ratio | 30:1 |
Controlled Impedance | +or- 10% |
Surface Finish | HASL, OSP, Immersion Gold, Immersion Silver |
Solder Mask Options | Green, Blue, Black, White, Red, Purple, Yellow |
Silkscreen Color | White, Yellow, Black |
Final Thickness | 0.020″–0.275″ |
The above specifications vary widely depending on whether you ordered a standard or custom board. A manufacturer may also only fabricate circuit boards with specific features.
Resource: https://hackaday.com
What are the Benefits of Heavy Copper PCB?
A conductor’s resistivity (and power loss) is directly related to its cross-sectional area. Therefore, you want it to be thick when dealing with higher currents. In light of that, using a circuit board with thicker conductive layers than standard practice has these benefits.
High Current Carrying Capacity
The traces and vias have higher conductivity. Improved conductivity means lower losses due to heating, enabling the circuit board to handle higher currents without overheating and causing component failure.
Superior Heat Dissipation
Copper has a high thermal conductivity of 401 W/mK. It quickly loses heat to the surroundings, allowing the board to run cooler in high-current applications. Besides thick traces and vias or through holes, these boards also have bare sections copper-plated to improve heat loss.
High Reliability
The increased copper thickness reduces resistive heating and voltage drop. It makes the board withstand thermal strain at higher loads. As a result, you can use the board to control, convert, or distribute power more reliably and efficiently.
Increased Mechanical Strength
Despite the increased copper weight, thick layers improve the board’s mechanical strength, allowing stronger connections and rigidity in other areas, such as the plated-through holes (PTH). The increased strength enhances the board’s lifespan.
Resource: https://www.youtube.com/watch?v=WdlN8bHw-w0
How Are Heavy Copper Circuit Boards Manufactured?
Heavy copper circuit boards are more challenging to make. The process starts with copper-clad laminates of 0.5 – 2.0 ounces of copper. The laminations are etched to create the desired circuitry and then plated to increase trace thickness. The vias or through holes also receive plating to increase their strength and ampacity.
After fabrication, the fabricator coats the board with a protective layer and any other layer, just like a standard PCB. When making multilayer boards, the stack-up process is similar to regular boards, using pre-preg between sheets.
Traditionally, fabricating the boards involved etching to remove material and achieve the desired thickness. This method has limitations. It creates uneven sidewalls due to excessive side-etching or undercuts.
Today, PCB manufacturers increase the thickness of layers by adding material in an additive process called plating. Plating offers various benefits, such as straighter sidewalls.
In some instances, bars are physically inserted into the layers to make embedded circuit boards. Below, we explain more about this board type and when to consider its fabrication method rather than etching and plating.
Embedded Heavy Copper PCB
When the conductors are needed thicker, embedding them can be more economical. Instead of etching or plating, the board has rolled bars directly attached or embedded in the layers.
This fabrication method saves material and reduces the overall copper weight, lowering production costs. It also allows the fabricator to use thick traces only where necessary.
Manufacturers also employ the embedding method to enhance heat dissipation in high-current circuit boards. They place the metal between layers to remove heat using its higher conductivity rate.
Resource: https://youtu.be/ucvms2xljw8?
Heavy Copper PCB Design Considerations
Proper design is critical to ensuring the reliable performance of thick copper printed circuit boards, given the higher loads they must handle and the extreme conditions that characterize their use. These guidelines apply when creating these PCB types.
Substrate Material
The substrate must withstand heat, with a Tg above 130. Options include high-performance FFR4, ceramics, metallic core, and Teflon or polyimide. In higher current ratings, metal cores can help enhance thermal conductivity and prevent heating issues better than FR4.
Copper Thickness and Width
The amount of copper per square foot should match the desired current capacity level and expected heat rise. The designer also ensures adequate spacing. Trace width calculators can help determine this value. The IPC 2152 and IPC 2221 standards also define these boards’ minimum trace width and spacing.
Layer Configuration
The core material’s coefficient of thermal expansion should not cause the traces to crack due to unequal expansion. Proper symmetry is also necessary, considering that pre-preg resin flow can cause inner layers to shift and lead to registration problems.
Another crucial consideration when creating a multilayer board is properly utilizing thermal and plated vias. They improve conductivity and effectively manage heat in the stack up when correctly placed.
Electrical and Thermal Considerations
Thermal management is an essential feature in high-power electronics and a critical consideration in the design stage. As current flows in the traces, losses generate heat. This heat must dissipate, or it will cause components and circuits to fail.
In addition to loss through conduction and convention, the designer conveniently places heat sinks to absorb and radiate heat to the environment. The heat sinks include embedded and external types. Thermal vias placed underneath high-load components can also help.
Resource: https://www.researchgate.net
Applications of Heavy Copper PCB
Due to their high current capacity and heat dispersion capabilities, these PCB types suit applications with high current levels and (most often voltage). These are products and systems conducting up to several hundred amperes. They include the following.
High Power Electronics
Power units rely on these PCBs to control, convert, or distribute current. Devices that require them include DC and AC converters or rectifiers, amplifiers, and voltage regulators.
Automotive Industry
In the automotive industry, the boards are a part of charging systems and inverters of electric vehicles or the motor drives of the propulsion systems. Other uses include rail power systems that carry enormous amounts of current.
LED Lighting
They are crucial parts of LED lighting power supply and control circuits. In this application, the boards effectively manage power and efficiently carry away heat, dissipating it to the environment. Specific applications include LED street lights and industrial lighting systems.
Industrial Electronics
Industrial applications running high currents use these circuit boards in their electronic systems. Examples include automation equipment, the drives of large motors, welding machines, and other heavy-duty circuits.
Renewable Energy
In renewable power, thick copper boards manage the current flow from the generation phase to conversion and distribution or use. They are the backbone of transformer circuits, converters, battery charging systems, and high-energy inverters.
Military and Aerospace
The range of applications also includes their usefulness in military and aerospace systems. They operate the power systems of spacecraft, weaponry, and any electronic system that carries higher loads than standard circuits.
Conclusion
In the PCB world, manufacturers improve the load-carrying capacities of circuit boards by increasing the thickness of traces, vias, or through holes and other conductive elements. A thick copper PCB offers remarkable performance in higher currents, ensuring circuit efficiency and reliability. Its use cuts across industries, from automotive circuits to lighting and renewable power systems.
