It was a wonderful day pulling teenagers on water skis, wakeboards, and tubes, but we were in a different river than normal, and I wasn’t familiar with it. At one point, I got preoccupied retrieving an upended skier and didn’t notice how fast the current was pulling us toward some anchored yachts. Fortunately, we didn’t drift into anyone, but some fishing lines were hastily retracted, and some rather rude comments were left in their place. I learned just how powerful the current could be on that day.
Current is a vital part of the operation of any circuit board, but as with the current in a fast-moving river, it can also be unforgiving if not treated with the care it deserves. When you are working with high-current applications, you need to exercise an even greater amount of caution in your design. Let’s take a look at some via stitching guidelines and other tactics that are helpful in designing high-current printed circuit boards.
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Via Stitching Guidelines and High Current PCB Design Tactics
One of the essential keys to successfully routing high-current circuits is to use a lot of metal in the form of wider traces, copper pours, and stitching vias. Stitching vias are used to join the routing of high-current circuits on multiple circuit board layers. If a trace on one layer is insufficient to carry the needed current, then the trace can be routed on multiple layers and stitched together with vias. Routing a high-current circuit on two different PCB layers connected with stitching vias will double the current carrying capacity of the circuit. This routing strategy will help keep the board size smaller instead of increasing the trace width on a single layer.
Stitching vias do have some concerns to be aware of, though. The first is that the high current traces will also be conducting heat. The stitching vias will absorb this heat, but the heat still needs to be dissipated through a thermal via to an external layer of the board for cooling. The stitching vias don’t have to be large, but there must be enough of them to conduct all the current and heat without overloading. You must also ensure there is adequate room for your current return paths in the design. In some cases, multiple traces and stitching vias take the place needed for a current return path and create a current loop instead.
Some other effective methods of conducting high currents are wider traces and copper pours. If the traces aren’t wide enough to carry the current, they could create areas of high heat, which could affect the board’s ability to provide the steady-state current requirements for the rest of the circuitry. These areas of heat can impact the performance of other components as they push their maximum temperature constraints, and the entire board may fail to perform as intended.
Many different tactics can be used when planning for high currents in your PCB design, and your PCB contract manufacturer can help you work through the various options.
Get Your PCB Contract Manufacturer Involved Early in Your Design
The PCB CM you are working with will have a lot of experience in building high-current circuit boards and can offer advice on what will work best for your design. Here are some of the areas they will focus on:
- Fabrication: Depending on how much current your design will handle, your CM can recommend different materials for fabricating the board designed for high currents and temperatures. The CM can also help you develop the layer stackup that will work the best for your needs and recommend copper pour patterns that will help the board to not twist and bow during fabrication.
- Assembly: While high currents usually dictate the use of more metal in the connections of the board, you still will need to exercise caution to ensure that the manufacturer can successfully assemble the board. Large metal areas can cause thermal imbalances, affecting the soldering of components, such as smaller discrete parts that could tombstone during solder reflow. The use of thermal relief pads in these connections will help during assembly, and your CM can recommend their proper size and placement.
- Layout: The proper component placement and trace routing of high-current circuits is also important for the best performance of the board. The PCB CM can give you different layout recommendations and work with you on current capacity calculations for trace widths, high current routing, and stitching vias.
With their experience, your contract manufacturer can help you avoid manufacturing problems and achieve the performance goals you are looking for in your design. The important thing is to choose a PCB CM with the expertise you are looking for.
High Current PCB Expertise at VSE
At VSE, we have been working with engineering clients like you for over 30 years. We have a deep level of experience with via stitching for high-current circuits, as well as many other printed circuit board technologies. We can help you fine-tune your design’s high-current circuitry, including your power routing and stitching vias so that it can be built and operated as intended.
