What should be considered when designing a PCB for high-current applications?

When a PCB needs to carry significantly higher current, simply increasing the trace width is not always enough. There are several factors that need to be considered during the PCB design stage to make sure the board can handle the electrical and thermal requirements.

Copper thickness is one of the first things I would evaluate. A high-current design may require thicker copper depending on the expected current and allowable temperature rise. Trace width, copper pours, and the overall current path are also important because resistance in the PCB can result in voltage drop and heat generation.

Thermal management is another consideration. Components such as MOSFETs, regulators, connectors, and power devices can generate significant heat, so the PCB layout needs to provide suitable copper area and thermal paths. Vias can also be useful for transferring heat and connecting copper between layers.

The return-current path is just as important as the power path. Poorly planned ground connections can increase impedance and create unwanted voltage differences or noise, particularly when high-current switching circuits are involved.

I also think the PCB manufacturer should be considered early in the design. Copper thickness, layer stackup, minimum trace/spacing, via capabilities, and manufacturing tolerances can affect what is practical to fabricate.

I recently came across PCBCool while looking at PCB manufacturing and production considerations, and their PCB manufacturing capabilities are relevant when evaluating these requirements.

For engineers who have designed high-current PCBs:

What has been the most important factor in your experience — copper thickness, trace width, thermal management, layer stackup, or something else?