EMC and electronic enclosure design: Page 2 of 4

May 16, 2019 //By Kemtron
EMC and electronic enclosure design
RFIEMI screening is a discipline that is of interest to both the electronic engineer and the enclosure design engineer. The electronic engineer must take EMC into account when designing PC boards by careful component and circuit layout, using PCB shielding cans as small Faraday cages over problem components, paying attention to wiring runs, use of filters and ferrites etc.

Screened enclosures are rarely a simple case of a closed box design and may have openings for optical displays, ventilation and cable entry. All these areas may have to be screened:

  • Optical displays with the use of a screened optical window which can be made by using fine wire meshes laminated in glass or clear plastic such as acrylic or polycarbonate or conductive clear coatings on the substrate such as indium tin oxide.
  • Enclosure ventilation can be screened using simple pierced or expanded metal in low performance applications or with the use of honeycomb ventilation panels made of aluminium or steel in higher performance applications.   
  • Cable entry into a screened enclosure needs to have the cable screening bonded to the conductive surface of the enclosure through a screened cable entry gland or screened connector.

 

Flange/gasket design and considerations

The design requirements for a gasket joint in a screened enclosure are primarily that there must be good electrical conductivity between opposing flanges through the gasket. Poor conductivity or high resistance between the flange and the gasket will result in poor shielding and if in areas there is no contact with the gasket this can result in a gap which could possibly act as a slot antenna making things worse, it is therefore important to consider fixing pitch and gasket compression forces to ensure an good continuous seal.

Design category: 

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