ENGINEERING ANSWER
Via fences can help control fields and ground continuity, but spacing is a design variable tied to guided wavelength, geometry and mode behavior. Wavelength fractions are preliminary layout heuristics rather than universal design rules.
What to decide before release
Use the wavelength tool to understand electrical scale. Then evaluate spacing, distance from the signal, via inductance and enclosure effects in an electromagnetic model. Manufacturing hole and annular-ring limits still apply.
Checks to put in your design brief
- Calculate using effective permittivity
- Review the highest relevant frequency
- Validate the actual fence geometry
Important distinction
A λ/20 number is not a guarantee of shielding, mode suppression or isolation.
Sources & basis
Material facts follow the cited source. Design checks are preliminary guidance, not supplier process instructions.