Blocking and controlling radio frequency and electromagnetic interference (EMI) is an enormous concern in almost every industry that produces electronic devices. But for defense contractors and others creating devices for the military, that concern goes double.
That’s because engineers and designers in the defense and military space are obligated to uphold extremely strict EMI shielding standards. If your device does not resist interference up to the levels described in U.S. Military specifications (MIL-SPEC), it’s never going to be built.
In particular, the MIL-G-83528/MIL-DTL-83528 specification governs EMI shielding materials for use in gaskets and similar parts. But what kinds of materials are up to this standard? And how do you choose? That’s exactly what we explore in this post. Read on to learn more.
Modus Advanced is a leader in defense manufacturing, serving as manufacturing partner and guide to countless customers in the defense, aerospace and military industries. That means we know MIL-SPEC EMI shielding materials inside and out. You can benefit from our expertise by working with us. Contact us to learn more.
Read our full guide on EMI Shielding
About MIL-DTL-83528/MIL-G-83528
The U.S. Military has laid out dozens of specifications for materials and parts used in defense devices, from vehicles and weapons to satellites and wiring. One of those specifications is MIL-DTL-83528/MIL-G-83528.
This specification governs the requirements for electrically conductive gaskets that are meant to shield devices from EMI and radiofrequency interference (RFI). It lays out requirements for both base and conductive filler materials, durometer and other material characteristics.
If a gasket material is labeled with MIL-DTL-83528/MIL-G-83528, that means that the material meets this standard. Defense contractors must always use gasket materials within this spec or risk having their devices rejected.
Types of MIL-SPEC EMI Shielding Materials
Only one MIL-SPEC governs EMI shielding gasket materials, but there are multiple ways to create an EMI shielding material that will satisfy MIL-DTL-83528’s requirements. That means there are several MIL-SPEC EMI shielding materials to choose from. Below, we have broken them down by the types specified in MIL-DTL-83528.
Comparison of MIL-DTL-83528 EMI Shielding Material Types
When selecting EMI shielding materials for defense applications, understanding the specific characteristics of each MIL-DTL-83528 type is crucial for design success. Each material type offers different performance characteristics based on its composition, filler material, and physical properties. The table below provides a comprehensive comparison of the seven material types specified in MIL-DTL-83528, allowing engineers to quickly evaluate which options might best suit their particular application requirements.
| Type | Base Material | Conductive Filler | Temperature Resistance | Shielding Effectiveness (10 GHz) | Typical Durometer |
|---|---|---|---|---|---|
| A | Silicone | Silver-Coated Copper | -55°C to 125°C | 110 dB | 65-75 Shore A |
| B | Silicone | Silver-Coated Aluminum | -55°C to 160°C | 100 dB | 65-75 Shore A |
| D | Fluorosilicone | Silver-Coated Aluminum | -55°C to 160°C | 90 dB | 65-75 Shore A |
| E | Silicone | Pure Silver | -45°C to 125°C | 110 dB | 65-75 Shore A |
| K | Silicone | Silver-Coated Copper | -55°C to 125°C | 110 dB | 85 Shore A |
| L | Silicone | Silver-Coated Nickel | -55°C to 125°C | 100 dB | 65-75 Shore A |
| M | Silicone | Silver-Coated Glass | -55°C to 160°C | 100 dB | 65-75 Shore A |
As this comparison shows, while all types meet military specifications, they offer different performance profiles. The selection of base material (silicone vs. fluorosilicone) and conductive filler directly impacts temperature resistance and shielding effectiveness. Type K stands out with its significantly higher durometer rating, making it suitable for applications requiring greater firmness and compression resistance.
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How to Choose the Right EMI Shielding Material
As you can see, various EMI shielding gasket materials live up to the standards set by MIL-DTL-83528/MIL-G-83528. That means you have multiple material options to choose from as you design your EMI gasket.
How do you choose? By considering the following factors:
- Cost. What is the budget for your project? If you’re operating within a narrow budget, you may need to consider a lower-cost material, such as one filled with nickel coated graphite. If cost is less of a concern but you need high EMI resistance, more expensive silver filler may be the way to go.
- Durometer. The hardness of gasket materials is measured with durometer, and this metric can be a determining factor as you choose an EMI gasket material that meets military specifications. If, for example, your gasket must resist a lot of force, high-durometer materials, like type K, may be best for your application.
- EMI resistance. Resistance to EMI is the main point behind an EMI shielding gasket, and not all MIL-SPEC EMI gasket materials provide the same level of resistance. Ask yourself how sensitive to EMI your device will be, and choose a gasket material that provides a sufficient level of EMI resistance to protect it.
- Environmental sealing. Not all electrically conductive shielding gaskets provide an effective environmental seal, but some designs need them to. Each material will vary in its ability to protect against high or low temperatures, moisture, corrosion and other environmental threats.
Each MIL-DTL-83528 EMI gasket material will come with information about these and other factors. If you need help, you can always reach out to your manufacturing partner for guidance.
Selection Factors for MIL-DTL-83528 EMI Shielding Materials
Beyond the basic specifications, selecting the optimal EMI shielding material involves considering several critical performance factors that directly impact your application's success. Factors such as corrosion resistance, galvanic compatibility with housing materials, and environmental sealing capabilities can significantly influence long-term performance and reliability in the field. The decision matrix below provides guidance on these additional selection factors to help engineers make informed choices when specifying materials for mission-critical defense applications.
| Type | Corrosion Resistance | Galvanic Compatibility | Environmental Sealing | Relative Cost | Best Suited For |
|---|---|---|---|---|---|
| A | Good | Best with copper alloys | Good | Moderate | General purpose applications with copper housings |
| B | Excellent | Good with aluminum alloys | Good | Moderate | Aerospace applications with aluminum housings |
| D | Excellent | Good with aluminum alloys | Excellent for fuel/solvent exposure | High | Applications with exposure to fuels, oils, and solvents |
| E | Superior | Compatible with most metals | Good | High | Applications requiring maximum shielding effectiveness |
| K | Good | Best with copper alloys | Good | Moderate | High-compression applications requiring firm gaskets |
| L | Excellent | Compatible with most metals | Good | Moderate to High | Applications where corrosion resistance is critical |
| M | Excellent | Compatible with most metals | Good | High | Applications requiring high temperature resistance |
When reviewing these selection factors, consider your application's specific environmental conditions, mounting surface materials, and performance requirements. Each type offers unique advantages that make it particularly well-suited for certain applications. The Modus engineering team can provide additional guidance on material selection to ensure your EMI shielding solution meets both the required specifications and the practical demands of your defense application.
Modus: Military-Grade Gaskets, Always in Spec
Selecting a MIL-SPEC EMI shielding material that will work for your design isn’t easy, but it’s also just step one. After that, you have to actually complete the design, make sure it’s manufacturable, prototype it and get it into full production. That’s a lot of work — we would know because the Modus team has helped countless customers complete that exact process.
We’re here to help you, too. From guidance on EMI shielding materials to design help and manufacturing, we are your go-to, stress-free partner. Want to learn more? Give our expert team a call at (925) 960-8700 or contact us online today. Visit our Glossary for more definitions of key manufacturing terms.
