Hold out your hand. Wave it. You felt nothing more than the slight movement of the air, right? You may not realize it, but you very likely just waved your hand through electromagnetic and radio frequency disturbances. If you were an unprotected electronic device, you would have felt it.
Our world is filled with invisible signals flying through the air and moving along conductive surfaces. As we create more electronic devices, we generate more of these signals. And electromagnetic interference (EMI) and radio frequency interference (RFI) become even more common.
The problem? EMI and RFI can interfere with electronic devices, disrupting their functions or leaving them useless. Fortunately, this is a problem we can solve. The solution is EMI/RFI shielding.
Modus Advanced didn’t write the book on EMI/RFI shielding, but we did write the definitive guide. Check it out.
Read the Complete EMI Shielding Guide
Electromagnetic Interference (EMI) / Radio Frequency Interference (RFI) Shielding Definition
Let’s begin with a simple definition:
That’s the simplified answer, but there’s a lot more to know about this concept. Read on.
EMI/RFI Shielding FAQs
Over the years, the Modus team has received a lot of questions from customers about EMI/RFI shielding. These questions tend to go a lot further than the simple, “What is EMI/RFI shielding?” There’s plenty to ask, and we have plenty of answers. We’ve answered a few of the most common questions below.
What is the Difference Between EMI and RFI?
You may see the terms EMI and RFI used interchangeably, but that’s not entirely accurate. Think of the difference between EMI and RFI like the difference between dogs and golden retrievers.
All golden retrievers are dogs, but not all dogs are golden retrievers. Similarly, all RFI is EMI, but not all EMI is RFI. The distinction here is about the frequency of the interfering signal. Any frequency that can cause electrical interference is EMI, but RFI refers only to signals that fall into the frequency range used for radio transmissions — usually somewhere between a few kilohertz and 30 megahertz.
What Kinds of Materials Act as EMI/RFI Shields?
Any material that attenuates a disruptive electromagnetic signal can be considered an EMI/RFI shield, but the shielding materials used in electronic devices are typically some kind of metal. In EMI/RFI shielding gaskets, the most common shielding materials are as follows:
- Silver
- Silver aluminum
- Silver nickel
- Silver copper
- Nickel graphite
In gaskets, these materials are usually a “filler” inside a base material, which is typically made from silicone or fluorosilicone. When electromagnetic emissions reach the gaskets that contain these filler materials, the signals are reflected or absorbed.
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How Does Shielding from EMI and RFI Protect Electronic Devices?
By attenuating electromagnetic signals before they reach critical components of electronic devices, EMI/RFI shields can prevent everything from minor crackling in telecommunications broadcasts to deadly malfunctions in aircraft safety equipment. When left unmitigated, external electromagnetic signals can disrupt the essential functions of electronic devices.
For example, medical equipment that monitors patients may have its monitoring capabilities disrupted by an errant signal. Electromagnetic signals can also erase or damage data in all kinds of electronic equipment. Even satellites in space need to be shielded from EMI/RFI in order to function properly.
Visit our complete EMI shielding resource center.
What Are Some Common Sources of EMI/RFI?
What is EMI/RFI shielding protecting devices from, exactly? In the modern world, the answer is almost everything.
Cell phones, microwaves, cell networks, ignitions, power lines, and computer circuits are just a few examples of human-caused EMI and RFI. But then, you have to consider the natural causes of these disruptive signals, with auroras, solar flares and lightning being some of the most common examples.
In Which Industries is EMI/RFI Shielding Important?
Nearly any industry that uses or produces electronic devices that are susceptible to electromagnetic interference can benefit from EMI/RFI shielding. The following are some of the industries that rely on EMI/RFI shielding most heavily:
- Military and defense
- Aerospace
- Satellites and telecommunications
- Medical technology
- Electric vehicles
- Rail and other mass transit
Each of the above industries has a direct interest in reducing interference from external signals, with the potential complications ranging from low-quality audio transmissions to total failure of a rail control system.
How Do I Determine the Right Level of Shielding Effectiveness for My Application?
Selecting the appropriate level of shielding effectiveness depends on several factors including the sensitivity of your components, the strength of potential interference sources, and regulatory requirements for your industry.
For aerospace and defense applications, MIL-STD-461 often dictates minimum shielding effectiveness requirements. Medical devices typically follow IEC 60601-1-2 standards. We recommend starting with a comprehensive EMI/RFI assessment of your device to identify susceptible components and potential interference sources before determining shielding requirements.
What's the Difference Between EMI/RFI Shields and Absorbers?
While both serve to protect devices from electromagnetic interference, shields and absorbers work in fundamentally different ways.
EMI/RFI shields primarily reflect and redirect electromagnetic energy away from sensitive components. They're typically constructed from conductive materials that create a barrier against electromagnetic fields.
EMI/RFI absorbers, on the other hand, convert electromagnetic energy into heat through loss mechanisms. Absorbers are particularly useful in applications where reflected energy could cause secondary interference problems within the device or system.
How Does Temperature Affect EMI/RFI Gasket Performance?
Temperature fluctuations can significantly impact the performance of EMI/RFI gaskets, particularly those with elastomer base materials.
At high temperatures, silicone-based gaskets may experience decreased compression set resistance and accelerated aging. At low temperatures, gaskets can harden and lose flexibility, potentially creating gaps in the shielding.
When designing for environments with extreme temperature ranges—like aerospace applications that might experience both the heat of desert operations and the cold of high altitudes—it's crucial to select gasket materials with appropriate temperature ratings and to account for thermal expansion and contraction in your design.
Read our Custom Gasket Production Guide
What Manufacturing Considerations Should I Keep in Mind for EMI/RFI Shield Design?
When designing EMI/RFI shields, consider factors like:
- Gasket compression requirements and available compression force
- Minimum flange width for proper gasket mounting
- Electrical continuity across seams and joints
- Accessibility for installation and maintenance
- Potential for galvanic corrosion between dissimilar metals
- Form-in-place (FIP) gasket dispensing constraints if applicable
Early collaboration with a manufacturing partner familiar with EMI/RFI shielding can help identify potential manufacturability issues before they become costly design changes.
How Can I Test the Effectiveness of My EMI/RFI Shielding Solution?
Testing shielding effectiveness typically involves measuring the attenuation of electromagnetic signals across a range of frequencies. Common test methods include:
- MIL-STD-285 or IEEE 299 for shielding effectiveness of enclosures
- ASTM D4935 for planar materials
- MIL-DTL-83528 for conductive elastomer gaskets
For complete systems, you may need to conduct compliance testing according to industry-specific standards like MIL-STD-461 or CISPR requirements. We recommend developing a comprehensive test plan early in the design process to ensure your shielding solution meets all performance requirements.
High-Tech, High-Quality EMI/RFI Shielding
Shielding devices from EMI and RFI is only going to become more important with time. Designing effective EMI/RFI gaskets and other parts is already an enormous consideration for any device, and it’s going to stay that way.
At Modus Advanced, we’re prepared for that. Our team of manufacturing experts and engineers is dedicated to supporting you throughout the design process — from idea to ignition — to make sure your device meets every last specification, effective shielding included.
What is EMI/RFI shielding? It’s an important part of what our team can help you with as you bring your design from concept to concrete. Interested in working with us? Reach out. Give Modus Advanced a call at (925) 960-8700 or contact us online today.
