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EMI shielding gaskets for all occasions

23 November 2015

Examining the market requirements for EMI shielding gaskets leads to one overriding conclusion: there is huge demand for gaskets that can fulfil not just some but all of industry’s common application criteria. Tim Kearvell explains more.

For instance, in modern applications, high EMI shielding performance needs to be matched with a host of additional criteria, such as stable performance in uncontrolled environments (indoor or outdoor), device life expectancy in years, compatibility with aluminum housings and narrow flange requirements (no room for dual seals).

However, few EMI shielding gaskets, if any, are able to match this list of demands, which is why Chomerics, a division of Parker Hannifin, set about developing its latest generation of nickel-plated, aluminium filled (Ni/Al) silicone elastomer EMI shielding gaskets. Here, nickel is plated on to nodule-shaped aluminium particles and dispersed into silicone, fluorosilicone & EPDM polymers.

The high performance of these advanced gaskets can be corroborated in trials. For instance, in tests on Cr3+ and Cr6+ Class 1A and Class 3 treated aluminium, Ni/Al gaskets show circa 50 percent less galvanic corrosion in comparison with Ag/Al alternatives at 500 or 1000 hours in non-SO2 salt fog. What’s more, the gaskets demonstrate 20dB higher shielding effectiveness (SE) in the range from 30MHz to 18GHz, as well as more stable SE in extended (1,000 hour) temperature and humidity tests. SE is the ratio of the RF energy on side of the shield to the RF energy on the other side of the shield expressed in decibels.

Tests also show that Ni/Al gaskets retain strong mechanical performance after life testing. Not only will the elastomer retain its environmental and physical EMI seal, but fluorosilicone has excellent resistance to fluid swell.

The benefits for end users are extensive. For instance, downtime and field service costs will be reduced considerably, around 50 percent in many cases, through fewer equipment inspections and reduced requirements to replace gaskets or repair flanges. In addition, Ni/Al gaskets support field equipment deployment in uncontrolled environments without the need for secondary enclosures. As a result, installation costs are lower, typically to the tune of 20-30 percent, while greater flexibility in location (portable, vehicular, airborne or fixed) is another advantage. 

For non-marine or aerospace applications, Ni/Al gaskets make it possible to eliminate dual seals, metallic plated flanges, flange paint schemes and the use of Class 1A Cr to improve housing durability – all of which present considerable cost savings to the end user. The use of narrow gaskets with high SE also makes for a smaller overall package design. This is important as the trend is very much towards smaller and faster electronic devices.

In marine and aerospace environments, Ni/Al gaskets are intrinsically less active, providing longer life and more insurance against shielding decay and flange corrosion, regardless of design. Field repair costs will be reduced or eliminated, and total cost of ownership (TCO) minimised.

In short, the industry now has an EMI shielding gasket solution to suit all of the market’s key application requirements. 

Tim Kearvell is with Chomerics Division Europe

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