Heavy copper PCB products are used extensively in power electronic devices and power supply systems. A growing trend in the PCB industry, this unique type of heavy copper PCB features a finished copper weight of more than 4oz (140μm), compared to the 1oz (35μm) or 2oz (0μm) copper weight generally found in those with a standard PCB copper thickness.
The additional copper PCB thickness enables the board to conduct a higher current, achieve good thermal distribution and implement complex switches in a limited space. Other advantages include increased mechanical strength at connector sites, the ability to create a smaller product size by incorporating multiple weights on the same layer of circuitry and the ability to use exotic materials to their maximum capacity with minimal risk of circuit failure.
Strong and simple structure:
PCBs integrated with high current circuits, allowing designers to achieve high density and reduce the layers count. This can also keep the structures of the PCB relatively strong but uncomplicated.
Reduces failure rates:
Complex PCBs with higher current requirements generate high heat. Copper PCB has high heat-conducting abilities and can help to conduct heat away from vital temperature-sensitive components.
Lowers production costs:
Normally Copper is very expensive, rather than using copper cables, using PCBs with heavy copper can lower the production costs.
Heavy Copper Circuit Construction
Standard printed circuit boards, whether double-sided or multilayer, are manufactured using a combination of copper etching and plating processes. Circuit layers start as thin sheets of copper foil (generally 0.5 oz/ft2 to 2 oz/ft2) that are etched to remove unwanted copper, and plated to add copper thickness to planes, traces, pads and plated-through-holes. All of the circuit layers are laminated into a complete package using an epoxy-based substrate, such as FR4 or polyimide.
Boards incorporating heavy copper circuits are produced in exactly the same way, albeit with specialized etching and plating techniques, such as high-speed/step plating and differential etching. Historically, heavy copper features were formed entirely by etching thick copper-clad laminated board material, causing uneven trace sidewalls and unacceptable undercutting. Advances in plating technology have allowed heavy copper features to be formed with a combination of plating and etching, resulting in straight sidewalls and negligible undercut.
Plating of a heavy copper circuit enables the board fabricator to increase the amount of copper thickness in plated holes and via sidewalls. It’s now possible to mix heavy copper with standard features on a single board, also known as PowerLink. Advantages include reduced layer count, low impedance power distribution, smaller footprints and potential cost savings. Normally, high-current/high-power circuits and their control circuits were produced separately on separate boards. Heavy copper plating makes it possible to integrate high-current circuits and control circuits to realize a highly dense yet simple board structure.
The heavy copper features can be seamlessly connected to standard circuits. Heavy copper and standard features can be placed with minimal restriction provided the designer and fabricator discuss manufacturing tolerances and abilities prior to final design.
Circuit Board Strength and Survivability
Circuit board manufacturers and designers can choose from a variety of dielectric materials, from standard FR4 (operating temp. 130°C) to high-temperature polyimide (operating temp. 250°C). A high-temperature or extreme environment situation may call for an exotic material, but if the circuit traces and plated vias are standard 1 oz/ft2, will they survive the extreme conditions? The circuit board industry has developed a test method for determining the thermal integrity of a finished circuit product. Thermal strains come from various board fabrication, assembly, and repair processes, where the differences between the coefficient of thermal expansion (CTE) of Cu and the PWB laminate provide the driving force for crack nucleation and growth to failure of the circuit. Thermal cycle testing (TCT) checks for an increase in resistance of a circuit as it undergoes air-to-air thermal cycling from 25°C to 260°C.
An increase in resistance indicates a breakdown in electrical integrity via cracks in the copper circuit. A standard coupon design for this test utilizes a chain of 32 plated through holes, which has long been considered to be the weakest point in a circuit when subjected to thermal stress.
Applications of Heavy Copper PCBs
Heavy Copper-Clad circuits demand is growing very fast in automotive, computer, industrial controls, and the military. Most of the existing PCB manufacturers are very limited or not capable to produce reliable heavy copper printed circuit boards. Here are some applications:
- Overload relays
- Power converters for railway systems
- Power line monitors
- Traction converters for rail applications
- Excitation systems for power regulators
- Position control systems
- Power grid switching systems
- HVAC systems
- Solar power converters
- Safety and signal systems
- Renewable energies and storage pumping plants
- Torque controls
- Welding Equipment
- Weapons control systems
- Radar systems
- High power rectifiers
- Energy storage and power grid back up
- Nuclear power applications
- UPS systems
- Electric vehicle charging (commercial and industrial)
- Protection relays
- Line reactors
- Hydro-electric plants
- Surge protectors
- Fuse blocks
Top Advantages of Heavy Copper PCBs
- It can help in the dispersion of the heat and lowering its core temperature. This application is keeping the device safe and sound by itself from any kind of damage. It can transfer the heat of the component at a faster rate.
- Heavy Copper PCBs are high-frequency PCBs. These are limited to only those which cannot cool by using the regular fan-cooling system. These boards scatter, laminate and eliminate heat by making the device much cooler. Therefore, device performances improve.
- These PCBs are made of a mix containing various alloys. Also, these PCBs are 8 to 9 times faster than the other regular PCBs.
- These PCBs can save the performance of LED devices. It is advisable to use high-density Heavy Copper PCB while using LED devices.
With the increase in demand for heavy copper PCBs, fabricators are developing newer methods of incorporating heavy copper with standard features on the same PCB.
This is helping to lower the layers count, offering the effective resistance of an electric circuit for distributing power, enabling small footprints and saving costs.
Electroplating is helping to integrate heavy copper for high current circuits and standard copper for control circuits allowing researchers and designers high density but simple board structures.