Electromagnetic Shielding: Enclosure Performance Depends on Seams, Apertures and Penetrations

Electromagnetic radiations emanating from your television, radio or microwave travel through the air. They intervene with the functioning of different kinds of devices and equipment. This is where the importance of EMI shielding comes into the picture. You must design an electrical circuit to reduce the level of electromagnetic interference that it causes. The use […]

Electromagnetic Shielding: Enclosure Performance Depends on Seams, Apertures and Penetrations

Electromagnetic radiations emanating from your television, radio or microwave travel through the air. They intervene with the functioning of different kinds of devices and equipment. This is where the importance of EMI shielding comes into the picture. You must design an electrical circuit to reduce the level of electromagnetic interference that it causes. The use of proper EMI shielding materials can obstruct the radiations and let your electronic devices and appliances operate normally. Electromagnetic shielding does not only block the emissions that the devices release, but also obstructs the radiations that affect the equipment.

Although a metal box or enclosure controls RF interference, the effectiveness of the circuit would be limited if you are not able to penetrate the metal box. This is where the problem arises when RF enters the apertures, penetrations (wires and cables) and seams. Read on to learn more.

Seams and Apertures

You can find seams on enclosures where a metal meets another metal. Make sure the bonding between the components is fine. Else, it would produce a voltage over the seam, and once that happens, the RF will penetrate the seam. The ideal way to deal with this problem is to create a short circuit. Make sure that there is a steady contact between the metals. Use uniform surfaces with tight spacing of screws. You can consider large spacing and choose stiffer or thicker materials that will not bend or curve. It will help to prevent any loose contact between the screws. Use quality gasket material like finger stocks to ensure there is contact between the metal parts. Avoid using anti-corrosion coatings because they are non-conductive and lead to shielding problems. When it comes to shielding effectiveness, metal plating is a better option than iridite or alodine.

As far as apertures are concerned, keep them small. They should be a fraction of the smallest wavelength of the frequencies that are causing trouble. Generally, it will be one-twentieth of the wavelength of the maximum frequency.

Penetrations

You know that every wire has a voltage, and when voltage is present, you’ll find an electrical field. The cables and wires have the ability to move the circuit-produced electromagnetic radiation out of the metal box or enclosure. This is the onset of problems, but there are ways to get rid of this RF energy conduction. Use shielded cables with the shields closed to the metal enclosures for better shielding performance. You can establish the perfect connection through an EMI type connector, which closes the electromagnetic shield at an angle of 360 degrees at the connector backshell.

You can also consider using a fiberoptic cable for electromagnetic shield penetration. Use these bulkhead type connections in enclosures to prevent any radio frequency from entering or leaving it.

For effective EMI shielding and optimum enclosure performance, make sure that the designs addresses the apertures, seams and penetrations the right way. Get in touch with a reliable EMI/RFI shielding partner to help you choose the best material.

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