What is EMI Shielding and Why Does it Matter?

EMI shielding is one of the methods that engineers use to protect electrical and electronic systems from EM interference. But how does it work and when do you need it? This guide aims to provide an overview of how shielding EMI ensures electronic systems and products are operating as they should.

Table of Contents

What is EMI?

First, what is EMI? EMI stands for electromagnetic interference, a type of electrical noise that can disrupt the normal operations of electrical or electronic components. It generally appears as a radiated or conducted waveform.

EMI is mostly caused by manmade sources such as power lines, cellular towers, or even equipment using higher voltage such as motors. It can also emanate from natural sources like lightning, solar flares, and other natural phenomena.

As we have seen, EMI can affect disrupt and degrade the performance of electrical systems such as medical and communication equipment or navigation systems. To prevent its effects, engineers use various EMI protection methods.

These methods include EMI shielding, filtering, and grounding. Shielding is a type of passive technique that physically blocks the radiation from reaching sensitive components or systems. It’s one of the most commonly used methods for reducing EMI in modern electronics. Learn more about it below.

EMI Shielding

EMI shielding is one of the most used—and effective—techniques for reducing EMI effects. Engineers use it to protect various electrical and electronic components, from mobile phones to medical equipment and communication systems. Here’s what it means:

EMI Shielding Meaning

EMI shielding means using a physical barrier (shield), to keep internal EMI inside, confined, or external EMI out. The EMI shield is placed around the components or systems that need to be protected, blocking any radiation from entering or leaving.

There are several types of EMI shielding materials and designs available, depending on your needs. These include metal enclosure shields, EMI foils, conductive foam, braided mesh, fabric, or even spray paints and coatings.

For effective EMI shielding solutions, it’s always required to ensure the shielding material is tightly fitted against the component or system, and that no gaps or holes are left for radiation to leak through. In such situations, shielding gaskets are normally used.

Why is EMI Shielding Important?

Electromagnetic shielding creates a barrier between the EMI source and the sensitive component or system. This barrier is usually made of conductive materials such as copper, aluminum, and steel, sometimes also a non-conductive material that’s been filled with conductive particles.

EMI interference shielding offers many benefits: it helps reduce the effects of EMI on operational parts, improving their reliability or performance. Without an EMI shield, vulnerable systems can be disrupted by external interference, leading to one of these problems:

  • Electrical noise
  • Data errors
  • Interference with power supply
  • Incorrect operation of a system
  • False triggering of control systems
  • Electrical short circuits

In most cases, EMI shielding is required by law or industry standards. This is called EMC (electromagnetic compatibility). EMC is an important compliance requirement for many products, especially those that use radio frequencies or are intended for environments with high levels of EMI.

How Shielding Works

This is how EMI shielding works: The EMI shielding material, usually metal or some other type of conductive material is placed around the components that need protection. It then acts as a Faraday cage, forming a barrier between the EMI source and the vulnerable parts. The shield will then either absorb or reflect the electromagnetic waves.

EMI Absorption

EMI absorption is when the shield absorbs the magnetic component of the electromagnetic wave, which reduces the strength of the wave. This can be achieved by using an EMI shielding material with a high magnetic permeability.

An electromagnetic wave contains two components; electric and magnetic fields. The electric field is reduced by the shield’s conductivity, while the magnetic field is reduced by the shield’s permeability.

An EMI absorption material will typically use the principle of eddy currents to weaken the EMI signal. Eddy currents are created when an alternating current passes through a conductive material, causing it to act like a solenoid and generate its own magnetic field. This field then opposes the incoming EMI field.

EMI Reflection

EMI reflection is the most common type of shielding for electronic systems, where the shield will reflect the electromagnetic wave. This reduces the amount of energy that reaches the components/systems in need of protection, effectively protecting them from interference. 

Unlike absorption, EMI reflection involves the electric field components of the wave. An EMI shield with high electrical conductivity is needed to reflect these fields. Metals such as copper, aluminum, and steel are the most used materials for this purpose, as they have high conductivity. 

In some cases, a combination of EMI absorption and reflection may be necessary. This type of shielding provides more effective protection against EMI interference since it utilizes both materials properties to reduce the strength of the wave.

EMI Shielding Applications

EMI shielding applications cut across all industries, and can be found in a variety of products. These include the PCBs and other components in computers, smartphones, tablets, and other mobile devices. It also applies to military equipment, medical systems, aircraft, automotive, industrial automation systems, and more.

  • One of the most common EMI shielding applications today is seen in mobile communication devices such as such as smartphones and tablets. These use RF circuitsthat must be shielded from both internal and external EMI.
  • In computers, EMI shielding enclosures and gaskets are used to prevent electromagnetic waves from interfering with components and processes. These often come in the form of metal shields on the motherboard and other components.
  • In today’s use of EMI shielding, automotive applications take a huge part in the industry. Car manufacturers often use EMI shielding to protect onboard systems from interfering with each other as well as from external
  • EMI shielding in the healthcare industry is also paramount, as medical devices must function properly in high EMI environments. Some, like the MRI machine, must be completely shielded and isolated from other electrical devices.
  • In military applications, EMI shielding is used to protect sensitive electronics from both external and internal sources of interference. This includes shielding for communications systems, navigation equipment, and other mission-critical components.

Overall, EMI interference shielding is a critical factor in ensuring that electronic systems are protected from unwanted electromagnetic interference. Without proper shielding, these systems could malfunction or suffer damage due to the high levels of electromagnetic radiation.


EMI shielding is an effective technique for protecting electronic components and systems from electromagnetic interference. It involves using a physical shield to block the radiation before it reaches sensitive components, ensuring that their normal operations are not disrupted. With proper design, engineers can ensure a system operates as intended, without any EMI-related issues.

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