EMI Shielding
Electromagnetic interference (EMI) shielding technologies are essential to the reliable function of many devices we use every day, including computers, cell phones, and a wide range of electronics. To choose how to meet your EMI enclosure needs, you need a basic understanding of what electromagnetic interference blockers are, how they work and how they’re used.
What is EMI Shielding?
EMI shielding refers to using specific materials to reduce the electromagnetic field within a space. In the context of electrical engineering, you achieve this protection by blocking the electromagnetic waves using magnetic or conductive materials.
What Is Electromagnetism and Why Does It Need to Be Shielded?
Electricity comes from the movement of electrons between atoms. As the electrons move, they can ignite lights, power handheld devices and computers, run motors and so on. When electrons are in motion, they create an electromagnetic field. Often, this is a good thing. For instance, electromagnetic fields are:
• Generated by the earth’s core and form a kind of force field around the planet, protecting humans from harmful radiation flowing through space
• tuned to form radio waves, which transmit your AM and FM and cell phone signals
• What microwaves use to heat up food
• Used by X-ray machines because these frequencies can pass through the human body
However, electromagnetic fields can also interfere with the operation of devices and systems people need on a day-to-day basis. This is because an electromagnetic field can’t be stopped unless another conductor or magnet gets in the way. Otherwise, it can interfere with other electromagnetic fields.
In addition, some devices depend on electromagnetic waves of a certain frequency, including radios, cell phones, televisions and wireless speakers. If an electromagnetic field is introduced that has one of the frequencies these devices are looking for, the sound or image you expected can include what amounts to electromagnetic pollution: bleeps, blips, screeches and the like.
Why Is EMI Shielding Necessary?
EMI enclosures are necessary to ensure critical devices work as expected and if this doesn’t happen, there may be significant functionality or even safety issues. Our devices and bodies are constantly receiving electromagnetic waves nearly 24/7 but most of the time, the amplitude and frequencies aren’t a problem. For example, a cell phone produces electromagnetic waves similar in frequency to what some microwave ovens produce, but they aren’t significant enough to present any danger.
On the other hand, because there is so much EMI inhabiting so many frequencies, the interference can sometimes pose a serious problem. Take, for example, the use of mobile phones. Some countries make it illegal for mobile phone manufacturers to build phones that use certain electromagnetic frequencies. When companies obey, people can use these phones near electronic devices without any problem because the phones use safe frequencies. This ensures the safe operation of everything from car radios to pacemakers. However, some manufacturers don’t obey the rules. Also, because the rules are different from country to country, some devices are produced legally in one jurisdiction, but when they cross into another region, they can interfere with devices in that country.
If you don’t have EMI enclosures protecting the electrical components crucial to the operation of your products, you’re susceptible to these kinds of illegal or under-engineered devices. For instance, a company that makes fake or illegal cell phones can produce devices that interfere with sound systems. While this is, in most situations, merely a nuisance, the problem gets more severe with other kinds of devices.
For instance, an illegal or fake mobile device charger can explode or cause a fire, which could endanger the lives of users and innocent bystanders.
A more common issue arises when a device emits EMI that can interfere with business- or mission-critical components. This is why airplanes don’t allow cellphone use during certain stages of the flight—the airplane guidance systems depend on uninterrupted radio waves that use the same frequencies as some cell phones.
Legal Requirements for EMI Shielding
In addition to the many safety and operational considerations, EMI shielding is necessary because of national regulations. For example, in the United States, the Federal Communications Commission mandates that all devices capable of mass communication be equipped with EMI shielding. The same holds true of military equipment. The circuits inside have to be shielded from external radiation that could harm their operation. Some circuits also need EMI enclosures because they may emit a frequency that disturbs the operation of another electronic component on the battlefield.
How does EMI Shielding Work?
EMI shielding may not always be able to completely block waves, but it can reduce their amplitude enough to make them harmless. Amplitude refers to how “strong” the wave is, not its frequency. For example, a sound wave as represented by a jagged line with peaks and valleys in recording software is louder when the waves are bigger. That’s the amplitude. Similar to how ear plugs can reduce the amplitude—or loudness—of sound waves, EMI shielding decreases the severity of electromagnetic waves.
RF Shielding
RF shielding blocks the radio frequencies caused by electromagnetic radiation. This is accomplished by using conductive compounds that pull the signal into the material, preventing it from passing through at high enough amplitudes to cause a problem.
Magnetic Shielding
Magnetic shielding works by positioning a magnet between two other magnets that you don’t want to interfere with each other. The magnet in the middle sends what would have been interference back at the magnet that initiated it.
These two methods are often combined to provide more comprehensive protection or to suit specific parameters required to safeguard a component or signal.
The Three Basic Types of EMI Shielding
EMI shielding happens in three ways, reflection, absorption, or multiple reflections. Here’s how they work in simple terms:
• Reflection. Material on the outside of the shield reflects the radiation as it hits it.
• Absorption. With absorption, the signal enters the EMI shield and a combination of magnetism and conductivity prevent it from impacting a sensitive mechanism.
• Multiple reflections. Multiple reflections involve having a reflective surface on either side of the shield, which allows it to trap the radiation, bouncing it back and forth inside.
Common Applications for EMI Shielding
Virtually any device that sends or receives an electromagnetic signal can benefit from EMI shielding. In addition, anything that transmits an electrical signal, whether it’s to power a device or deliver data, needs EMI shielding. Some examples include:
Personal Computers (PCs)
Because PCs both generate and receive electromagnetic radiation, you need shielding to limit the interference received and leaked. This is particularly true if the PC uses a digital data link, such as a broadband Wi-Fi signal.
Cell Phones
The inner components of a phone are dependent on uninterrupted electrical and magnetic signals. Interference in any of these processes could significantly impact the phone’s function.
Computer Peripherals
While some computer peripherals, like keyboards and mice, are merely used to send low-level electronic pulses to a card that interprets the signal, others can generate significant EMI. Some devices such as musical keyboards, printers, and audio devices can easily generate enough EMI to interrupt workflows.
Mobile Devices
Mobile devices, similar to cell phones, depend on digital chips that perform essential functions. Without EMI enclosures, users can suffer from several kinds of issues. Some of these include:
• Wireless local area network (LAN) malfunctions. The device may not be able to maintain a consistent connection with a router or other devices on your LAN, such as wireless printers
• Radio frequency issues. A mobile device can produce frequency conflicts with devices around it—or receive interference from other components—rendering it or the equipment nearby unreliable.
• Bluetooth. Bluetooth devices, just like cell phones, use radio waves. The only difference is their frequencies are typically much higher, which is part of the reason why Bluetooth devices can only work over short distances. As a result, electromagnetic interference can interrupt Bluetooth performance.
Internet of Things (IoT) devices
Internet of Things (IoT) devices are becoming an increasingly important part of the modern business and leisure landscape, so it’s especially important to ensure they don’t create or receive EMI. An IoT device used on a factory floor, for example, may get exposed to several different kinds of devices, machinery, and computers. Both these and the IoT device itself need adequate EMI shielding to avoid performance issues.
Benefits of Laird Performance Material’s EMI Shielding Enclosure Solutions
Laird Performance Material’s EMI shielding enclosure solutions provide you with the protection you need to ensure the safety and functionality of your components and those within their electromagnetic fields. Some of the benefits include:
• Your offending circuits are adequately isolated, preventing them from interfering with other systems or devices
• You can make your devices immune to external radiation
• Your components can be engineered to meet all immunity requirements
• With Laird Performance Materials you can customize your EMI needs, ensuring your components perform as required without interfering with others
Laird Performance Materials dedicates knowledgeable engineers to every project, taking personal ownership over the success of your solution. As you progress from one phase of design to the next, our team of engineers will ensure you have the highest quality products for precisely what you need for peak performance and compliance. Find the solution for your components today!