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Printed Circuit Board Design and Layout Questions

2. How important are the apertures in a shielded enclosure?

For a shielded enclosure with no significant leakage due to seams or wire penetrations, the effect of apertures on the shielding effectiveness is given by [1],

Shielding Effectiveness Equation

where N is the number of apertures, L is the maximum length of each aperture, alpha is the ratio of aperture length to width, and f is the frequency.

In most cases, where the aperture size is reasonably controlled, leakage at seams and wire penetrations is much more significant than leakage through the apertures.

Apertures are rarely significant in electric-field and magnetic-field shields, which do not need to enclose the object of the shielding completely.