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Placing ground vias all over the PCB (stiching) to improve the EMI.

  • Have all ground vias to be spaced the same distance? Or may they be separated different distances if it is under lambda/8?

I mean, I have to place ground vias all over the PCB edge to reduce EMI. The space between these ground vias are below lambda/20, around the edge. But the doubt comes from the ground vias which are not at the edge.

  • Have these ground vias to maintain the same distance between them? How can I calculate the maximum number of them?
  • Is there any rule of thumb to do it manually?
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  • \$\begingroup\$ If it's EMI you're worried about, it's certainly not narrow band. Which lambda will you use? Vias might help as part of a coordinated strategy, they might also make it worse. \$\endgroup\$ – tomnexus Apr 21 '15 at 16:36
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Step one: Show one solid proof that this helps in a predictable way. Not just some textbook, but real solid proof. And I can tell you: If that works and really does something measurably good in a predictable way, there will be plenty of solid science to back it.

Step two: Realize that it may not be worth your time.

PS: A good low impedance PDN (power distribution network) works in a predictable and measurable way. And so does other things like shielding. If done right.

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