Since each day we experience technological changes, manufacturers ensure that every design or rather product that leaves their company is of high speed and great power current. The design process of every PCB is quite challenging, so it is very important to take proper and necessary precautions to get a proper circuit operation, mostly when dealing with high-power printed circuit boards. Electronic devices on the other hand are becoming smaller each day, this has enabled designers and manufacturers to become keen on every design aspect like power supply and thermal management.
In this article, we are going to present some of the guidelines for the design of high-power printed circuit boards, advantages, disadvantages, applications, and design processes.
High Current PCB
Generally, a high-power printed circuit board is a PCB that uses a thicker copper core thus reducing the track width for the same current. Hence, reducing the space occupied by the traces on the printed circuit board. The need for high current PCB was brought into existence because devices required a printed circuit board that could carry higher than usual current, which could move large currents on the board. Companies also realized there was a need to produce high-quality products. This of course was to be achieved in a record time where the designers could follow safety principles hence keeping the process more secure. As stated earlier, while executing a high current printed circuit board design, it is very key and most important to consider the necessary precautions to make sure there is no thermal sparkling event experienced during the design process. Therefore, below are some of the practices that one needs to follow and them at the back of their mind while formulating the printed circuit design that carries high currents or power.
Designing a High Current PCB
The Width of the Track
This is among the primary factor that determines how much current a trace can carry, hence its width. According to some principles, the lengthy the track, the higher its resistance and the quantity of heat to be dissipated. The goal is always the need for minimization of power, hence ensuring high reliability and durability of the circuit. Thus it is recommended that the traces that conduct the most currents be kept as short as possible. Designers are also encouraged to use an online calculator or the IPC-2221, to calculate the width of the track if they know the maximum current that can pass through the track.
The Copper Thickness
This is the real or actual thickness of the traces found on a printed circuit board. The typical standard thickness of copper is normally 17.5 microns for the internal layers and 35 microns for the external layers and also the ground planes. High-Power PCB usually uses a thick copper to reduce trace width for the same current. The outer layers having a high number of microns, make a less wide trace that will carry the same current. The high copper thickness will come with an additional cost but will always save the board’s space this is because, with high viscosity, the width of the trace required is much less. The thickness of the thicker copper ranges from 35 microns to 105 microns, these are typically used for currents of more than 10 A.
When doing the design of the board, ensure that you position the flow of the current in the right way. If in your design you are using components that consume high currents you need to introduce some large thermal columns. It is very necessary to note that the large power-consuming parts should never be placed at the edges of your PCB because they accumulate heat and this will increase the board temperatures by a reasonable difference. When you ensure that the microcontroller is placed at the center centerboard will make sure that the heat that it generates is dispersed from one edge of your PCB to the next end.
The electrical energy we get via power terminals should be transformed to heat energy form. Thermal energy is dissipated to any area of the PCB or environment. The circuit boards carry a bigger amount of heat column energy. Designers and manufacturers must understand that some components like the amplifiers, voltage reference, converters, regulators, including other transmitters can be responsive to movement in their surroundings.
Two main methods are used in improving high-current PCB thermal management. The two techniques include;
- Creation of big ground planes: This allows one to raise the area available on the printed circuit board for maximum heat dissipation. More often, the planes are connected to the upper or lower layer of the circuit board to increase the heat exchange with the environment surrounding the PCB, though the inner layers can also be used to extract part of the power dissipated by the components on the printed circuit board.
- Inserting thermal Vias: These are used to transfer heat across all the layers on the same board. However, their function is to control heat from the hottest spots on the board to the other layers.
Solder Mask Removal
The high current printed circuit boards require the board to be receiving connection. A single method guarantees that the track transports a bigger amount of current on the circuit board by eliminating the solder mask. If eliminated this will expose the copper matter. If a soldier mask is added it can aid raise the copper thickness. Hence, this will lower the overall resistance of the current movement to the printed circuit board. Later, the PCB will adapt to a big volume of current. However, this will not raise the track width.
These have a role to play, they are capable of increasing the PCB’s current transmitting ability. This will help in the process of heat separation of responsive board parts. One can also add polygon pours related to several tracks below some chips.
High-Current Printed Circuit Board Design
This part must be considered and taken seriously in every stage of the printed circuit design development. There is an important rule that applies to every high-power printed circuit board, which is to determine the path that the power of current will follow. Location and quantity of current flowing through a circuit board are also important factors that evaluate the amount of heat that a printed circuit board needs to dissipate.
However, there are main factors that affect the layout of a high-current printed circuit board. These factors include;
- Level of power flowing through the circuit
- Ambient temperature where the board operates
- Quantity of airflow that affects the board
- Types of materials used to manufacture the printed circuit board
- The density of components that are loaded on the circuit board
However, the need is less urgent with modern technology and machinery, while with the change of direction it is advisable one avoids right angles but instead use angles like 450 angles, or curved lines.
Placement of Components
- It is of vital importance that one first establishes the position on the circuit board for the high-power component. Such components include voltage converters and power transistors, these are responsible for the generation of a large amount of heat.
- The components for high-power PCB should not be mounted near the edges of the board. This will prevent causing heat build-up and a significant temperature rise. Integrated digital parts like the microcontrollers, processors, and FPGAs, must be positioned at the center of the PCB, this will allow uniform heat diffusion across the board and will bring a decrease in temperature. The power components in any case should never be concentrated in the same area because this will help avoid the formation of hot spots; rather than a linear type arrangement is preferable. The image below shows a PCB with thermal analysis. Areas with the highest concentration of heat are marked red.
Placement of components should begin from power devices, that have traces kept as short as possible and are wide enough to eliminate noise generation and unplanned ground loops. Below are some of the rules that should apply during placement:
- One should identify and minimize current loops, more so high-current paths
- Ensure there is the minimization of resistive voltage drops and other parasitic phenomena in between the components
- Ensure high-current circuits are placed away from sensitive circuits
- Ensure they have taken good grounding measures.
For most cases, it might be preferable for one to place components on several separate boards, as long as the form factor of the device allows to do it.
Materials Used in High-current PCB
All through we have been referring to this printed circuit board as a high current PCB. Therefore a high current PCB can reach into the kV range that is either in direct current or alternating current. There exist several properties of the materials in datasheets that can help one determine the type of laminate that is best for their PCBs and will ensure high reliability at high voltage and current. Some of the substrate materials that are used in high-current PCBs include;
- Phenolic-cured rigid laminates
- High voltage Teflon (HVPF)
- BT epoxy
Advantages of High Current Printed Circuit Board
- Thermal strains endurance is increased
The heavy copper used in the high current PCB offers it the ability to endure thermal strains that it is exposed to. Electronic devices made using high current PCB are therefore in the position to oppose thermal fluctuations hence making them reliable. That’s why they are suitable for military applications.
- Reduction of size
The high current printed circuit board design also helps in the reduction in the size of products. This has been ably made possible through the incorporation of multiple copper weights on the same layer of the circuitry. Still, this reason makes these boards suitable for military applications since they have to be portable.
- Heat transmission to the external heat sink
The heavy copper-plated Vias make it possible for high current transfer through the board, which helps in the transfer of heat to the external heat sinks. This advantage makes high-current PCBs the most effective board for applications that require high power, voltage, and current to function effectively. Heat sinks in the high current PCB design can also be directly mounted on the board. Hence the reason they are used in industrial sectors.
- High current carrying capacity
The heavy copper gives high current PCBs the capacity to conduct high currents without much tension. With lighter copper, malfunctioning and failure will be experienced in case high currents are passed through them. Devices like transformers being exposed to high voltage use high currents printed circuit boards. That’s why there are no failures and disasters experienced on transformers.
- Raised Mechanical strength
The amount of copper used in the manufacture of high current PCBs is heavy and this gives the PCBs their mechanical strength. This makes it important in supporting the components that are placed on the board. Connector sites are stronger in high current PCBs which extend to the through-holes that are also strengthened by copper.
High-Current Printed Circuit Board challenges
Although High Current printed circuit boards are accompanied with very important advantages that other types of printed circuit boards lack, they are also accompanied by different types of challenges such as the durability challenge, the thermal and temperature management challenge ad the incorporation of the failsafe challenges.
- Durability: this type of printed circuit board should have the ability to withstand heavier loads and this is a very big challenge practically. The copper tracks are heavier as compared to other types of PCBs.
- Incorporating fail-safes: For one to mitigate the designs that might go wrong, one can incorporate fail-safe protection. Some of the fail-safes include;
- Fuses;- This alleviates the short circuits
- Thermal or temperature sensors; – This fail-safe monitors hotspots and other important parts and components. They also help a PCB adjust to the hotspot, thus making them a reliable way to monitor the pulse of the circuit board.
- Temperature management: PCBs are designed to only be able to handle a specific amount of thermal temperature which is always determined by the type of materials that have been used in the design process. If a given PCB can overcome at least a temperature of 150 degrees Celcius then it is classified as a high current PCB.
Capabilities for High Current Printed Circuit Board
Here we are going to focus on one company, however, there are many companies out there that manufacture high-current PCBs. So, one of the companies responsible for the manufacture of high current PCBs is Millennium Circuits Limited whose PCBs have their capabilities.
- The thick copper traces used by this company, allow for more thermal resistance and can manage higher current rates. Their solutions can withstand high temperatures for extended periods for stronger connection points. Having a heavy copper printed circuit board, one can opt for single-sided or even double-sided solutions or multiple layers for their PCBs.
- Single-sided and double-sided solutions have simple configuration design options, but with the multi-layered board, it is more complex. This is because they can relay high and heavy current loads while at the same time handling multiple functions. Traces of copper like these support industries that require high processes and performance levels.
- The weight of copper produced by Millennium Circuits Limited is a heavy one that ranges from 3 microns to 10 microns. But in case someone wants a copper trace of more than 10 microns, still it can be produced.
Applications of High-Current Printed Circuit Board
Due to the high-current printed circuit board being able to conduct huge rates of currents and able to accommodate fluctuating temperatures, they have so many applications. Below are some of the areas where these high-current PCBs are applicable.
Solar Power Distribution
The types of solar power distribution boards rely heavily on high current printed circuit boards for efficiency. The boards in solar power distribution transmit both high currents and high voltage. They rely on high current PCB to enable them to transmit currents effectively.
Most applications in the military need high currents and also get exposed to fluctuating and extreme temperatures. Hence there is a need to use PCBs that can handle the features of heat, and the features are only found in high current PCBs. Therefore, military applications like communication devices, satellites, and radar rely on high current PCBs for efficiency. Normally, they are also used in armored military vehicles and jets used in military operations.
Generally, all the airplanes and spacecraft are subjected and subjected to high fluctuating temperatures, therefore they rely on high currents and voltage to perform effectively and safely. If there is a failure in selecting a suitable board it can result in accidents and fatalities. For instance, the flow of current during the launching of an aircraft, and can never be handled with any other printed circuit board knowing there are high currents involved. The communication devices and other electronic components used in this industry mostly rely on high current PCBs, since they get exposed to the diverse and harsh environment, and also it’s the same case in the radar used by the control tower.
Industrial sectors experience heavy reliance on high currents and voltage, this is the reason why high current PCBs are applicable in this sector. Within the industries there are power transformers that use high current PCBs, this enables them to transmit currents effectively for the performance of industrial machines and electronics.
Since are highly exposed to fluctuating temperatures, they rely on high current printed circuit boards for them to perform effectively. Though other PCBs can sustain these factors, high current printed circuit boards are most preferred in this sector.
Most electronic devices emit more heat and are exposed to a lot of heat. This makes the motherboard sometimes overheat. Therefore, high current PCB is a vital technology in the current generation of technology, since it helps reduce the heat on the circuit boards.