In a recent post, we discussed the importance of stackups in multi-layer PCB design. However, another crucial factor to consider when designing both single-layer and multi-layer PCBs is trace width. Trace width requirements impact the size and layout of your printed circuit board, and failing to consider it can lead to suboptimal performance.
Trace width is important because it directly impacts the effectiveness and functionality of the trace, whether it’s for power or signal. When designing a PCB, there are several considerations to keep in mind when determining the optimal trace width.
Firstly, you must determine the purpose of the trace, whether it’s for power or signal. Secondly, you need to take into account the current flowing through the trace. This is often referred to as amperage. The location of the trace is also important, as the heat generated may not escape as quickly on inner layers as it would on outer layers. The thickness of the copper on the layer is another factor to consider, as well as the length of the trace.
When it comes to the width of the trace, generally, traces used for signals can be thinner than traces used for carrying current. A trace optimized for current may range from 0.010 inches for 0.3 amps up to 0.150 inches for 6.0 amps.
The shape of the trace is also important. A trace can be laid out horizontally, vertically, or at a 45-degree angle. It’s not recommended to use right or acute angle turns for trace widths of 0.012 inches or less. You should try to keep the traces as short and direct as possible. If you’re using a trace along the edge of a layer, make sure there’s enough space between the trace and the edge of the layer, usually around 10 to 15 mils.
Spacing is also an important factor. Traces that are too close to each other or other components could potentially short the board during operation. While the minimum spacing between traces is typically 0.003 inches, recommended spacing for most trace widths should be at least 0.010 inches. If you’re dealing with higher voltage traces, then the spacing should be larger.
Most design tools offer basic trace width checking functionality, but we also recommend using our free, fully-automated, web-based tool, InstantDFM, to verify that your trace widths are optimal for your PCB design.