EMC screening options for plastic enclosures

To provide screening, Vero Technologies offers three alternative internal coatings that provide varying levels of attenuation at different price points to suit more than 95% of possible applications; for highly specialised applications, other coatings are available. For less demanding commercial applications, the lowest cost 50-micron nickel coating provides attenuation of 50dB at 1GHz. The default coating is a 10- or 20-micron silver-coated copper particle coating, which typically attenuates by 78dB at 10 GHz. The highest attenuation is achieved using a 22.5-micron silver coating, which gives in excess of 80dB at 1.5GHz. It provides an effective shield against RFI and EMI and can act as a ground plane to protect against electrostatic discharge (ESD).

The design of the enclosure is important. A tongue and groove structure between the mating halves of an enclosure forms an effective complex path, improving the attenuation performance. Removable end panels are secured into an interference fit slot or, if fixings are used, a conductive gasket should be fitted to the mating surface. The rear face of plastic panels will have to be conductively coated, or if aluminium panels are used, the front surface will normally be anodised and the rear left with a natural finish or iridised, a RoHS-complaint conductive finish.