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Cable Assemblies: The Importance of EMI/RFI Shielding

Posted by Evan Freemon on March 06, 2017 | Updated on January 2, 2020

EMI/RFI shielding reduces electronic malfunction vulnerability by blocking unwanted external electromagnetic waves or preventing internal electromagnetic waves from emitting and interfering with other circuits or devices. This is achieved by using a metallic screen to absorb the electromagnetic interference that is being transmitted through the air. Not having EMI/RFI shielding can be a potential problem in any industry.

Wireless technologies like Wi-Fi, Bluetooth and cell phone signals are crowding our airwaves, crossing over one another and creating a lot of electrical “noise.” Cable assemblies are similar to antennas that draw in (or emit) external signals, making them a hot target for attracting this noise. The resulting phenomenon is what we call electromagnetic interference (EMI) or radio frequency interference (RFI).

When cable assemblies are affected by electromagnetic interference (EMI) or radio frequency interference (RFI), they may experience poor signal quality, loss of data or complete disruption of the function of electronic equipment and other nearby components. For example, an incoming call on a cell phone can interfere with a microphone and cause audio equipment to give off a buzzing sound. Apply this scenario to life-sustaining medical equipment, transit signaling systems, high-voltage contact switches or nuclear operations, and the gravity of this problem is evident — EMI/RFI interference can be disastrous. Luckily, some regulations mandate EMI testing to ensure that:

A) The product doesn’t generate EMI/RFI disturbances that could impact other electrical circuits.

B) The product performs in electromagnetic environments without being affected by interferences.

The Solution: EMI/RFI Shielding

 EMI/RFI shielding encases the cable assembly conductor to protect the assembly from electrical noise. EMI/RFI shielding works in two ways: It deflects electromagnetic energy or it picks up electromagnetic energy and grounds it. But as technology continues to advance, so do the issues of blocking EMI/RFI.

EMI/RFI radiates from an electronic source in a wave-like pattern. In addition to the increasing number of “sources” creating signals, smaller and faster electronic devices create smaller and faster waves, making them increasingly difficult to block. This is why off-the-shelf cable assemblies don’t always represent a wise investment.

Your best bet is to team up with an engineered interconnect solutions partner with specialized expertise on cable assemblies, including EMI/RFI shielding. The two main types of shielding are foil and braid. Foil shielding products cover the entire conductor and are generally less expensive than braided shielding. Braided shielding products weave copper into mesh material that surrounds the conductor. An interconnection solutions partner will help you decide which shielding is best given the nature of your product and the environment in which it will operate.

Interested in learning more about shielded cables and connectors? Download our free whitepaper, Maintaining EMI/RFI Shielding in Electrical Connectors.

EMI/RFI Shielding White Paper

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