The basic principle of woven and expanded wire in elastomer is based on moulding (encapsulating), either woven wire mesh or expanded mesh into an elastomer sheet. The resultant gasket material in each case has the combined properties of excellent low contact resistance and a high level of environmental sealing afforded by the elastomer carrier.
Weaveshield Elastomer filled woven aluminium mesh
Commonly known as ‘Weaveshield’, this is an effective thin (typically 0.5mm) EMI gasket material comprising of a woven aluminium cloth infilled or ‘over’ moulded with elastomer. The elastomers used are silicone, fluorosilicone or synthetic type (similar to neoprene). It can provide a watertight or pressure seal where sealing faces have a flatness tolerance of >0.05mm.
A high level of EMI shielding performance is reliably achieved by virtue of the array of aluminium mesh contact points exposed at the surface. This material also has the advantage that the woven mesh layer acts as an internal compression limit allowing small cross-sectional area gaskets to be designed in without the requirement for additional mechanical compression stops.
Monoshield Elastomer filled expanded metal foil
Monoshield is similar to the above material with the same elastomer options but instead of incorporating a woven aluminium mesh expanded metal foils are used instead. These expanded metal foils can provide improved contact, and therefore improved shielding performance, along with slightly more compliance than woven aluminium in some applications.
Materials based on monel, aluminium, copper and stainless steel expanded foils are available. The expand foil is available unfilled for use as a gasket material where there is no requirement for environmental sealing.
The main elastomer types available are:
Silicone ZZ-R-765 2B 50 – a high specification silicone
Silicone AMS 3302D – a more general purpose silicone
Low out-gassing silicone ASTM 595-84 – a silicone elastomer with very low levels of condensable and non condensable volatiles
Fluorosilicone Mil-R-25988 – a fuel and oil resistant version of silicone
Synthetic elastomer AMS3222C – a high performance synthetic elastomer resistant to fuels and hot oil
This material is available 15 meter rolls up to approximately 600mm in width (usually 300mm)
This material is ideally suited to connector gaskets because of the way in which it ‘self limits’ compression negating the need for additional compression control features. In order to achieve reliable environmental sealing gasket mating surfaces should be machined (flat)
This material cannot be joined, therefore gaskets are die cut as a single piece
We recommend Electromagnetic Testing Services Ltd to test EMI shielding products in your application.
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