Common EMI/RFI shielding techniques

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By Steve Baker | Dec 03, 2020
Metal cans used for shielding

Minimizing electrical interference is critical to a product’s performance, especially in highly regulated industries where excess interference from components can be disastrous or life-threatening. Excess electrostatic, radiofrequency, or electromagnetic signals can affect sensitive components, causing a multitude of issues or possible failure. Fortunately, there are several ways to mitigate the input and output of undesired electronic signals.

What is shielding?

Shielding is the process of preventing both the input and output of radiofrequency interference (RFI), electrostatic interference (ESD), or electromagnetic interference (EMI) from impacting the proper functioning of electronics. It is typically done by the addition of a sprayed, adhered, or molded metal to help absorb the interference. The metal is connected to the ground plane, where any excess inbound or outbound electronic signals are pulled to ground to avoid damaging sensitive internal components.

Below, we’ll be going over common types of shielding for electronic components.

Common EMI/RFI shielding methods:

  1. Metal cans: One of the most frequently used shielding methods, formed aluminum cans or covers are added over computer chips on the circuit board. Each can contains small extensions at the bottom which go through the board and connect to the ground plane. Given aluminum’s excellent conductivity and the ease of adding metal cans after production, this is an effective option for covering any hotspots that may have been missed and emanate interference.
  2. Aluminized mylar: Typically one of the least expensive options, aluminized mylar consists of a thin sheet of mylar coated with aluminum. The sheet is die-cut and adhered to the inside of an enclosure using an adhesive. The mylar is connected to the chassis ground to effectively absorb and dissipate electronic interference.
  3. Screen-printed conductive ink: For a wide variety of substrates, a popular option is to use screen-printed conductive ink. The ink is printed around the perimeter of an enclosure to absorb excess interference. The ink is then connected to the chassis ground where any absorbed EMI, RFI, or ESD signals are pulled to ground. For substrates where screen printing may be difficult, the ink can also be applied via spraying or pad printing.
  4. Vacuum deposition: As an alternative to pre-formed aluminized mylar or screen-printed inks, vacuum deposition can be used to coat the inside of an enclosure, creating a thin layer of metal on the substrate. This layer of highly conductive metal blocks EMI, ESD, and RFI signals, pulling them to ground. This shielding method is typically used for plastic enclosures or irregularly shaped enclosures where it may not be ideal to print conductive ink.
  5. ITO films and mesh: Indium tin oxide (ITO) films and meshes are frequently used to provide shielding on displays. Applied directly to the glass or plastic, ITO films are almost see-through. The high level of transparency and conductivity allows displays and touchscreens to maintain functionality while mitigating outbound and inbound electrical interference.

How to determine the right type of EMI/RFI shielding?

When it comes to finding the right type of shielding, there are several important questions to ask. Is the product for use in a highly regulated industry such as military or medical, where EMI or RFI could be detrimental? Does the product need to adhere to specific industry standards to meet an acceptable threshold of incoming or outgoing signals? Is there a specific substrate where certain shielding methods may be ineffective?

Ultimately, substrate selection, part size, and even cosmetic requirements can be important factors in selecting a suitable shielding method. Different types of shielding are often mixed and matched to find the perfect solution.

To find out which shielding option is right for your next project, schedule a consultation with our experts.