EMI shielding gasket for defence and commercial use

The Chomerics Division of Parker Hannifin Corporation has released a new low-durometer EMI shielding gasket for use in defence and commercial electronics applications. CHO-SEAL 1299 offers a lower hardness (only 45 Shore A, typical) compared to many conventional conductive elastomer gaskets, while still delivering highly effective shielding and corrosion resistance against aluminium.

The device is an electrically conductive EMI shielding elastomer gasket comprising passivated silver-plated aluminium particles in a fluorosilicone binder. The new material offers a higher temperature limit than most conductive fluorosilicones (up to 200C continuous use) and is resistant to harsh chemicals, such as machining coolants, hydraulic fluids, mineral oils, and various fuels.

While the legacy CHO-SEAL 1298 is among the company’s most trusted products, the material requires more force to compress than certain applications can provide. It developed CHO-SEAL 1299 to provide customers with the same performance they could trust in a softer form.

At only 45 Shore A hardness (35% softer than CHO-SEAL 1298), the low compression force of the new product makes it an excellent choice for EMI shielding applications, including military communication modules, UAVs, naval and shipboard electronics, portable electronics, and robotics equipment.

Protecting against the ingress of dust, moisture and more, the new RoHS-compliant material is groundbreaking for the many electronic device applications that require design flexibility without compromising EMI shielding effectiveness.

One common use case is connector interface seals. In smaller connectors, it can be especially challenging to compress a conductive elastomer material by even small amounts due to the high force required. Access to a softer material will benefit customers who have experienced a similar challenge.

As an electrically conductive fluorosilicone elastomer, the new product provides great EMI shielding across a wide frequency spectrum. For example, according to the MIL-DTL-83528 test method (para 4.5.12), the new EMI gasket material delivers a minimum shielding effectiveness of: 128dB at 100MHz (E field); 102dB at 500MHz (E field); 110 at 2GHz (plane wave); 122dB at 10GHz (plane wave); and 94dB at 18GHz (plane wave).

While the legacy version provides an elongation of 60%, the new product can provide 100% according to the ASTM D412 test method. Superior elongation supports greater flexibility and ductility, enabling the new material to conform to irregular surfaces and resist deformation without fracturing. This capability is crucial for maintaining an effective seal and shielding against EMI and makes the gasket easier to install.

CHO-SEAL 1299 is available in moulded format, including O-rings, D-rings or custom-moulded shapes. The company also provides the new material in sheet format for cut gaskets. Sheet stock can be die-cut using a steel rule, X-Y knife cut or water-jet cut (non-abrasive) to make precision parts in large quantities. If required, sheet stock can be supplied with an electrically conductive, pressure-sensitive acrylic adhesive (PSA) to aid the assembly process. In addition, CHO-SEAL 1299 will soon be available in extruded profiles.