A common staple in science fiction movies and television shows is the portrayal of high-powered circuits. From Star Trek to Jurassic Park, someone somewhere is usually pushing or pulling a huge lever on a panel that is clearly labeled; “Danger – High Voltage.” This effort is usually rewarded by either the restoration of normal operating conditions or a huge shower of sparks and smoke along with screaming alarms. And though these scenarios are usually pretty unrealistic, they can be a lot of fun to watch – until the dinosaurs show up.
What is much more realistic in our world is working with circuit boards that conduct high current. You usually won’t find a lot of Hollywood drama here, but there is still the chance that you might see some sparks and smoke if the boards aren’t designed correctly. Working with high power circuits does involve some different PCB design techniques, such as the width and weight of the copper that is used on the board. Let’s take a look here at some of the most important high current PCB design tips that you should know about to avoid any unnecessary drama.
Some of the Problems that Can Happen on High Current Printed Circuit Boards
Circuit boards that aren’t designed correctly for the amount of current that they are conducting will be prone to failures. Those failures can usually be characterized by overheating, or functionality and reliability:
- Overheating: If the board’s metal traces and planes are not sufficiently wide enough for the current that is being conducted through them, the board will end up with areas that run hotter than they should. This can affect how steady the current is being distributed throughout the board, which in turn could force other components to operate outside of their specified temperature ranges. As more and more components operate at higher than expected temperatures, the greater the chance is for a board failure.
- Functionality & reliability:Not only will increased operating temperatures affect the proper functioning of the board, but other mechanical problems could manifest themselves as well. In some cases, the high currents could lead to the board deteriorating if it isn’t designed correctly for the levels of current that it is operating at. For instance, board materials could end up melting, or thin metal traces might burn through like a blown fuse.
The important thing is to design your circuit board for the currents that it will be operating at, and for you to understand what the power path of your design is when laying the PCB out. Here are some recommendations that can help.
The Top Five High Current PCB Design Tips You Need to Know
1. Component Placement
In order to create the best power integrity for your design, it is important to start first with the component placement of your high-power parts. They need to be placed close to their accompanying parts so as to have the shortest high-current paths as possible. They also need to have some distance from sensitive high-speed circuitry in order to reduce the chance of interference, and they need to be well-grounded to their own isolated ground nets.
2. Metal Conductors
With a good tight placement of your power components, you will already have a straight shot at making your connections short. You also will want to route these connections with wide traces, and when possible, increased copper weight in the board construction. For traces used in routing power connections, the more metal the better. It is also better to use a full plane for routing ground as opposed to ground traces. This will also help improve the power integrity of the board.
3. Heat Dissipation
Using wider traces with a greater copper weight is the first action that you should take in combating the heat of a high-current design, but there are other techniques that you should consider as well. Power components that run hot should not only be isolated from sensitive circuits, they should also be placed towards the center of the board for better heat dispersion as well as being separated from other hot components. Hot running components should also be placed so as to leverage any natural airflow across the board. Additionally, cooling fans, heat sinks, and thermal relief vias should be considered as well. It may also be appropriate to use a thicker board width or different board materials, both of which can withstand and dissipate more heat.
4. PCB Holes
Using larger holes in the board is preferred for conducting high currents as they are also better at conducting heat. At the same time, using multiple holes instead of a single hole is also a good idea for high current circuits. The greater the board width, the larger the annular ring on drilled holes should be as well. This gives more room for the drill bit to drill through the thicker board materials.
5. Industry Standards
Don’t guess when it comes to designing circuit boards with high current circuitry. There are different online current calculators available to use, as well as industry standards. The IPC-2152 standard serves as a general guide on the relationship between current, conductor size, and temperature. It can be used for determining the appropriate trace size to use on your high current PCB design. And in addition to those resources, there’s one other resource that can also offer a lot of help.
How Your PCB Contract Manufacturer Can Help
Your local PCB Contract manufacturer has had years of experience building high current circuit boards and understands what is required for their best performance. They will be able to evaluate your design according to a number of different design and manufacturing criteria, including power integrity and high current specifications. Not only can they guide you in any corrections that might need to be made before your board is produced, but they are also available for consultation before you start laying out the board.
At VSE, we have been helping our customers with high current designs for more than 35 years. When we first meet with you for our initial design kick-off meeting, we will be glad to help you with any questions or concerns that you might have regarding your high current PCB design.