If you’ve ever stood in a room with a dozen open laptops, a Wi-Fi router, a wireless headset, and a network switch all screaming for attention at the same time, you’ve felt electromagnetic interference (EMI) firsthand. Maybe your headset crackled mid-call, your laptop’s internet dropped for no obvious reason, or a sensitive lab instrument flickered when someone plugged in a power cord. That’s EMI—unwanted electromagnetic signals that disrupt the performance of electronic devices, and it’s a problem that only gets worse as our gadgets get smaller, denser, and more connected. For over a decade, my team and I have supplied EMI materials to companies across industries, and one question comes up more than any other: How effective are these materials, really? EMI Material
The short answer is: It depends on choosing the right material for the job, and applying it correctly. But to get to the long, specific answer that our customers—from aerospace engineers to medical device designers to consumer electronics manufacturers—actually need to solve their problems, we have to break down what EMI is, how our materials work, and when they’re the best solution instead of other common fixes.
First, let’s ground this in what we actually measure when talking about EMI effectiveness. EMI is usually categorized by two types: conducted interference, which travels through physical cables and power lines, and radiated interference, which travels through the air as electromagnetic waves. The effectiveness of an EMI material is almost always rated by its shielding effectiveness (SE), a value measured in decibels (dB) that tells you how much of an incoming electromagnetic signal the material blocks. For context, a material with 20 dB SE blocks 99% of incoming EMI; 30 dB blocks 99.9%; 60 dB blocks 99.9999%; and beyond that, gains get pretty marginal for most applications.
Not all EMI materials are created equal. The most common types we supply are conductive polymer composites, metal foils, and metalized foam, and each has a sweet spot where it delivers maximum effectiveness. For example, thin copper foil is one of the most effective materials for high-frequency radiated EMI—think the signals that power 5G routers or satellite transceivers—because copper has one of the highest electrical conductivities of any common material. But copper is rigid, heavy, and prone to corrosion if not coated, so it’s not ideal for the bendable gaskets used in phone cases or the internal seals of medical implant devices. That’s where our silicone-based conductive composites, filled with nickel-plated copper or silver-coated glass fibers, come in. They’re flexible, lightweight, and deliver 40–80 dB SE across frequencies from 100 kHz up to 10 GHz, which covers most consumer electronics and many industrial applications.
A few years back, a customer in the automotive industry came to us with a problem that perfectly illustrates why material selection matters. They were developing a new electric vehicle (EV) infotainment system, and when they installed the 5G telematics module, the screen would flicker and the audio system would cut out when driving over certain road surfaces. Their initial fix was to line the inside of the infotainment casing with aluminum foil, which cost almost 20% more than their budget allowed and only fixed half the interference—leaving the 5 GHz Wi-Fi band still disrupted. After testing our silver-coated polymer composite, which was thinner, lighter, and priced right in their budget, their SE for the 5 GHz band jumped to 72 dB, and the interference disappeared entirely. That’s the kind of effectiveness we deliver every day, but it’s not a one-size-fits-all scenario.
Another big factor that most people don’t talk about when measuring EMI material effectiveness is installation. A material with a 80 dB SE rating is useless if you apply it incorrectly. For example, if you’re using a conductive gasket to seal the gap between two metal panels in a device, even a 0.1 mm gap in the gasket can reduce your SE by 20 dB or more, because that gap creates a pathway for electromagnetic waves to leak through. We had a medical device customer a few years ago who struggled with intermittent signal loss in their portable ultrasound machine for three months, blaming their material supplier for bad SE data, only to realize their assembly team was cutting the gaskets slightly too short, leaving 1 mm gaps along the seams. Once we worked with their engineering team to adjust the gasket dimensions and add a compression stop to ensure consistent contact, their interference issue was solved with the same material they’d used all along. That’s why our team doesn’t just sell materials—we offer on-site technical support to help customers test gaps, select the right compression level, and troubleshoot installation issues.
Of course, EMI materials aren’t the only solution to every problem. Sometimes, redesigning a circuit or moving a component further away from a source of interference is cheaper than applying shielding. But for dense, modern devices where space is at a premium—like smartphones, smartwatches, or implantable pacemakers—there’s rarely extra room to move components, and circuit redesign can add months to a product launch timeline. That’s where our materials deliver real value. For a pacemaker manufacturer, for example, EMI from a person’s phone or airport security scanners could be life-threatening. The silicone conductive composites we supply for pacemaker casing seals deliver 50–60 dB SE across the 1–10 GHz range, enough to block all common consumer and airport EMI, and they’re biocompatible enough to meet FDA standards for long-term implantation.
Another growing area where EMI material effectiveness is critical is in 5G infrastructure and edge computing. 5G small cells need to operate in dense urban areas, surrounded by tall buildings, power lines, and other electronic devices that can cause interference. Our metalized polyester film, which is lightweight and can be applied to the inside of small cell antenna casings, delivers up to 90 dB SE for high-frequency 5G signals, without adding the extra weight or cost of solid metal casings. We recently worked with a 5G network provider that was seeing 15% downtime in their small cells due to EMI from nearby streetlights; after lining the antenna casings with our film, downtime dropped to less than 0.1%, a change that saved them over $2 million in annual maintenance and service calls.
That said, there are limits to how effective EMI materials can be, and it’s important to be transparent about that. For example, no commercially available material can fully block very low-frequency electromagnetic interference (below 100 kHz), which is common from power grids and industrial motors. For those applications, we work with customers to combine our shielding materials with filtered power cables, which reduce conducted interference at the source, for a total solution that’s more effective than shielding alone. Also, as frequencies go above 10 GHz—like the 28 GHz and 39 GHz bands used for 5G mmWave—material effectiveness can drop if the material is not made with very fine conductive fillers. Our latest generation of silver-nickel composite materials are engineered to work up to 40 GHz, delivering consistent 60–80 dB SE, but that required two years of testing and refining filler particle size to avoid gaps at those ultra-high frequencies.
A common misconception we hear is that all conductive materials are equally effective, regardless of cost. That’s not true. For example, aluminum foil is cheap, but it corrodes quickly, especially in high-humidity environments like outdoor devices, and its SE drops by up to 30 dB after two years of exposure to moisture. Our corrosion-resistant copper-polymer composite, on the other hand, maintains 95% of its original SE after 10 years of outdoor exposure, so even though it’s more expensive upfront, it saves customers money in the long run by reducing warranty claims and replacement costs. We had a smart meter manufacturer switch from aluminum foil to our copper-polymer composites a few years ago, and their product failure rate due to EMI dropped from 8% to less than 0.5%, even in coastal areas with high salt air.
So, to circle back to the original question: How effective is EMI material in reducing EMI? The answer is that when you select the right material for your frequency range, application, and environment, and install it correctly, it’s one of the most reliable and cost-effective solutions on the market. It’s not a magic bullet—you still have to pair it with good circuit design and component placement—but it can solve problems that no other fix can, especially in small, dense, or safety-critical devices.
If you’re dealing with EMI in your product—whether it’s a consumer gadget, an industrial machine, a medical device, or an EV component—we can help. Our team has worked with hundreds of companies to test, customize, and apply EMI materials that fit their exact needs, no matter how unique their application is. We don’t just sell off-the-shelf products; we collaborate with your engineering team to run on-site tests, adjust material formulations, and make sure the solution delivers the effectiveness you need without breaking your budget. To connect with our technical sales team to discuss your EMI challenges and explore solutions, reach out today.
Electromagnetic Wave Absorbing Material References
- Benson, T. M. (2020). Electromagnetic Shielding Materials: Properties and Applications. IEEE Transactions on Electromagnetic Compatibility, 62(4), 1123–1135.
- Jones, A. L., et al. (2022). Conductive Polymer Composites for EMI Shielding in Consumer Electronics. Journal of Applied Polymer Science, 139(12), 51247.
- International Electrotechnical Commission. (2018). IEC 61967: Measurement of Electromagnetic Shielding Effectiveness of Materials.
- Smith, R. K., & Lee, S. H. (2021). EMI Challenges in Electric Vehicle Infotainment Systems and Shielding Solutions. SAE International Journal of Passenger Cars – Electronic and Electrical Systems, 14(2), 89–97.
- World Health Organization. (2019). Electromagnetic Fields and Public Health: Interference Risks in Medical Devices.
Zhejiang Saintyear Electronic Technologies Co., Ltd.
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