Bad EMC Advice Recently Spotted on the Internet
The internet is convenient way to find information on EMC and signal integrity. Unfortunately, much (perhaps most) of the information related to EMC design is either not helpful or just plain wrong. Here are recent sightings of bad EMC design advice from a variety of internet sources.
Claim: Circuit boards with RF traces should have a ground pour on the top layer.
Sighted: PCB Supplier on social media site (June 6, 2026)
Why this is bad advice: Ground pour on the outer layers of a multi-layer circuit board is generally not recommended unless it is for the purposes of heat dissipation and/or copper balancing. Microstrip RF traces routed 0.25 mm or less above a return plane have a relatively stable impedance and do not generally benefit from a copper pour. In fact, any copper pour that comes too close to the RF trace can introduce EMC and signal integrity problems.
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Reason often cited for using a ground pour include:
Ability to achieve a lower characteristic impedance with a thinner trace. But no space is saved, because maintaining a uniform ground pour on both sides of a trace requires even more space than a wide trace.
Reduced crosstalk to nearby traces. But copper pours are not a particularly effective or reliable way to reduce crosstalk when the return plane is 0.25 mm or less below the signal traces. Proper lateral spacing of the signal traces achieves the same isolation with no danger of introducing unwanted resonances or coupling signal power to nearby structures through the plane structure.
Claim: Circuit boards with RF traces should have a ground pour on the top layer.
Sighted: PCB Supplier on social media site (June 6, 2026)
Why this is bad advice: Ground pour on the outer layers of a multi-layer circuit board is generally not recommended unless it is for the purposes of heat dissipation and/or copper balancing. Microstrip RF traces routed 0.25 mm or less above a return plane have a relatively stable impedance and do not generally benefit from a copper pour. In fact, any copper pour that comes too close to the RF trace can introduce EMC and signal integrity problems.
more ...
Reason often cited for using a ground pour include:
Ability to achieve a lower characteristic impedance with a thinner trace. But no space is saved, because maintaining a uniform ground pour on both sides of a trace requires even more space than a wide trace.
Reduced crosstalk to nearby traces. But copper pours are not a particularly effective or reliable way to reduce crosstalk when the return plane is 0.25 mm or less below the signal traces. Proper lateral spacing of the signal traces achieves the same isolation with no danger of introducing unwanted resonances or coupling signal power to nearby structures through the plane structure.
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