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3m emi absorbers
Lee K. HouseJan 29, 20252 min read

How Do EMI Absorbers Work and What Are They Made of?

How do you protect delicate technology from the sea of signals surrounding us at any given moment? 

If electromagnetic signals are like a torrential downpour, an EMI absorber is the thick, London-proofed umbrella that protects your device from getting soaked. 

Strouse’s engineers have helped design and build hundreds of EMI shielding products, and EMI absorbers are no exception. 

This article will explain how absorbers function, helping you build a solution to prevent EMI from harming your electronic devices. 

What is an EMI Absorber?

EMI or RFI absorbers are layered pieces of metal or magnetic materials that repel unwanted signals to eliminate noise and stray frequencies. They can be built in sheeted or roll form. The pre-cut sheets, known as EMI absorber sheets, often have an adhesive film on one side, allowing for rapid device application and assembly. 

Common EMI absorber uses include:

  • Cable wrapping
  • Metal surface attachment
  • Semiconductor chips or microprocessors
  • Near-field communication
  • Insertions between modules

HOW DO EMI ABSORBERS FUNCTION?

The absorber layer of an EMI absorber acts as a magnetic deterrent for interference, interacting with the electromagnetic (EM) field to help reduce unwanted signals. It suppresses EMI noise at different frequencies to protect electronics in close proximity.

Magnetic materials can repel or absorb unwanted EMI signals due to the concept of “permeability” in electromagnetism, which dictates how well a material can attract and conduct magnetic fields. Materials with higher magnetic permeability will create a stronger shield against electromagnetic interference or absorb them more effectively.

Types of EMI Absorbing Materials

The material you choose for an EMI absorbing application will depend on the required level of signal protection and the substrates being used

Examples of EMI absorbing or deflecting materials include: 

  • Soft magnetic materials
  • Rubber with magnetic powder 
  • Ferrite-loaded elastomers
  • Conductive foils, fabrics, tapes, and adhesives

Soft magnetic materials, such as polymer or ferrite sheets, are commonly used in flexible EMI noise suppression. These materials may contain mixtures of ceramic, iron, nickel, or zinc oxides which help them serve as effective EMI-blocking solutions. 

Conductive foils, such as aluminum, copper, and stainless steel tape, are also used in electromagnetic and radio frequency shielding and are especially useful in thin applications. 

As you develop your design, you should also consider the type of adhesive and/or liners you plan on using. 

EMI ABSORBING ADHESIVES AND LINERS

Many manufacturers use acrylic, non-conductive pressure-sensitive adhesives (PSAs) in their absorber applications due to their powerful bonding properties. Film liners, often PET film release liners, are also a common choice for additional covering protection.

Ultimately, both the adhesive and liner you use will depend on the substrates you’re working with and your chosen absorber stack-up materials

Where Can I Find EMI Absorbers? 

There are many different places where one can find EMI absorbers, but your sourcing will ultimately depend on the quantity and complexity of your desired parts

If you’re looking for standard EMI absorbers, suppliers such as 3M, have product lines you can purchase right off the shelf. However, for more complex designs, you’ll want to find an adhesive converter.

Adhesive converters can laminate and die cut custom designs for mass production. If you’re building product components with unique EMI shielding requirements, contact a converter who will help you start the process. 

If you’re looking for more resources on EMI shielding, visit our Learning Center for more information and use cases. 

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Lee K. House

Content Marketing Manager at Strouse. Lee is a lifelong reader with a penchant for breaking down scientific and engineering concepts for those who don't spend all day clicking between fancy-looking graphs and a blank word document.

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