Vent holes and EMI

[Pack34]

I can't seem to remember the rule of thumb for the acceptable diameter for vent holes for immunity. I could have sworn it was something like the diameter of the vent has to be less than 1/2 of the maximum wavelength, but that seems large.

[OwO]

Depends on how much isolation you need. I recall it's more like 1/20th of the wavelength for good isolation (>50dB). The amount and density of the holes are also important, as well as how close the holes are to your circuitry.

[coppercone2]

There are example radiation graphs to give you an idea. Rf honeycomb is an option.

[Tomorokoshi]

The other suggestions are correct. For more details, see "Noise Reduction Techniques in Electronic Systems" by Henry W. Ott.

Key takeaway: watch out for slot antennas. These are very easy to accidentally design in, particularly if penny-pinching mechanical engineers are involved.