TOP TIPS FOR RFI/EMI SHIELDING
IN THE AEROSPACE INDUSTRY
The Aerospace & Defence industry have always been the main drivers for RFI/EMI shielding design andproducts. Achieving EMC (electromagnetic compatibility) in this sector is safety critical, whereas ineveryday life it can just be a frustrating nuisance. David Wall, Chairman, Kemtron Ltd looks at some ofthe design challenges aerospace engineers face and talks about the best shielding options available.

Conductive elastomers

Aircraft can get struck by lightning with regular occurrence
which will cause an electromagnetic pulse or EMP. EMP will
have a devastating effect on electronic circuitry, so it isimportant that the aircraft has a path for the lightning tocontinue without causing damage. Space is another matter;satellites are in a very hostile electromagnetic environment
with solar flares that can emit a coronal mass ejection. We areprotected on earth by the magnetosphere, but satellites don’t
have that advantage, so shielding is paramount to ensure thesafety of the satellite and its systems.
Greater integration of electronics mean electromagnetic
compatibility between systems is of upmost importance toensure they work in harmony and not interfere witheach other. Aircraft are more fly by wire than mechanicalsystems, with complex software operating computerised
systems. Sensors measuring the aircraft environment,
flight data etc. all need to communicate with each other,
operate independently and provide back up for system
failure or malfunction.

‘O’ rings

RFI/EMI shielding is a mechanical fix for an electrical problem
and the enclosure design engineer should be aware of thetypes of gaskets available and their different attributes andensure there is enough land area on the enclosure seams, doors
etc. to fit the gasket. In aerospace, weight and size of equipment
and systems is important so miniaturisation where possible
is used. This means that the shielding options available to thedesign engineers must also be small and offer good shielding.
Electrically conductive elastomers are the best option foraerospace as the material can be moulded, extruded or
fabricated into very small components or deposited directly tohardware. Many electrically conductive fillers are available
to suit shielding requirements and a fluorosilicone base meetsthe needs of resistance to fuel oils etc.
The aim is to always design for the worstcase scenario andconsider shielding early in the design process as it is very
difficult, if not impossible, to retrofit shielding to an enclosurethat doesn’t have the space or facility to a shielding gasket
or component.

Electronics engineers are very familiar with this and will consider
in their design good board layout, filtering, grounding, signal
integrity etc. to try resolving EMI at its source. However,shielding of the enclosure is just as important and solves theproblem of radiated emissions and susceptibility. Mating
surfaces on an enclosure can look very flat and you think
there is full metal to metal contact but, in a mass production
process nothing can be that flat and gaps will exist.
These gaps are slots and can become radiating antennas.
This joint unevenness can be addressed by using an electricalgasket and or adding more fixings to get good contact
between the mating surfaces.

About the author:
David Wall is Chairmanof Kemtron Ltdte.comTE Connectivity, TE Connectivity (logo) and Every Connection Counts are trademarks. All other logos, products and/or company names referred to herein might be trademarksof their respective owners.
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06/22

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PERFORMANCE MATERIALS / TOP TIPS FOR RFI/EMI SHIELDING IN THE AEROSPACE INDUSTRY