Guard fences around PCBs

Thread Starter

electrosn

Joined Jun 9, 2022
14
Hi,

I occasionally see some PCBs with exposed copper around their edge, sometimes with many vias. Some of these designs are seen in equipment for high-temperature operations.

As far as I know, the reason is regarding radiated EM emissions. Are there any guidelines on how to do that appropriately (if the fence should be connected to the ground, if using via is a good idea, etc.)? I found this document by Nasa that briefly mentions this: https://ntrs.nasa.gov/citations/20120009353.

Are there other uses for such a design?
 

Ya’akov

Joined Jan 27, 2019
9,264
Welcome to AAC.

The paper you linked is very clear about the nature and purpose of the guard fence. It cites these things:

The fence should be exposed.
It should be grounded
It should be split at each side to avoiding becoming a loop antenna
It should be accompanied by a .5” keep out zone where nothing should be routed.

The only purpose cited is as a path for ESD, particularly in handling.
 
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