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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.
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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.
Type A
Type A EMI shielding gasket materials consist of a silicone base material filled with copper that is coated in silver. These materials can resist temperatures between -55 degrees Celsius (C) and 125 degrees C, and their shielding effectiveness is 110 decibels (dB) at 10 gigahertz (GHz).
Type B
MIL-G-83528 Type B calls for a silicone gasket material filled with silver-coated aluminum. Materials must have a shielding effectiveness of 100dB at 10 GHz and resist temperatures between -55 degrees C and 160 degrees C.
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Type D
If an EMI gasket material meets MIL-G-83528 Type D, it has a base of fluorosilicone that is filled with aluminum that has been coated in silver. It must meet a shielding effectiveness requirement of 90 dB at 10 GHz and resist temperatures between -55 degrees C and 160 degrees C.
Type E
Resistant to EMI at 110 dB at 10 GHz and temperatures between -45 degrees C and 125 degrees C, MIL-DTL-83528C Type E consist of a silicone base filled with pure silver particles.
Type K
Type K EMI gasket materials are made of silicone that is filled with silver coated copper. The temperature resistance range of these materials is between -55 degrees C and 125 degrees C, and they can provide effective EMI shielding up to 110 dB at 10 GHz. This product is similar to the Type A call out, however it calls out a very high durometer of 85 shore A.
Type L
MIL-G-83528 Type L calls for a silicone base filled with silver coated nickel. The material must have a shielding effectiveness of 100 dB at 10 GHz, and it must resist temperatures between -55 degrees C and 125 degrees C.
Type M
If an EMI shielding gasket material meets the MIL-DTL-83528 Type M Spec, it is filled with silver-coated glass with a base of silicone. It will resist temperatures between -55 degrees C and 160 degrees C. It must also have a shielding effectiveness of 100 dB at 10 GHz.
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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.
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.
