conductive emi o-rings

EMI O-Rings: Standard, Custom& M83528 Slash Sizes

SSP fabricates EMI O-Rings from the EMI shielding elastomers that we make.

As a vertically integrated manufacturer, we also make the tools that are needed so you don’t have to wait.

Whether you need standard or custom EMI O-Rings, SSP has faster turnaround time and lower MOQs than the competition.

Compare our materials to Parker Chomerics CHO-SEAL and GORE EMI shielding, and then ask us for a quote.

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What are EMI O-Rings?

EMI O-rings are donut-shaped gaskets that combine environmental sealing with shielding against electromagnetic interference (EMI). These EMI gaskets are designed to fit a groove and are crushed into place during installation. Products can be molded as a single piece, or bonded from cut lengths of extrusions. The quantity to produce determines which fabrication method is most cost-effective. 

EMI O-rings are electrically conductive because they are they are made of particle-filled elastomers such as silicones and fluorosilicones. Elastomers are electrically insulating, but compounding them with metal, bimetallic, or metal-coated particles imparts electrical conductivity. This is why EMI O-Rings are also called conductive O-rings.

Product specifications for EMI O-rings include material type and cross-sectional size and shape. Conductive O-rings made from MIL-DTL-83528 (M83528) materials are available in what are known as slash sizes. Both standard and custom products are available.

  • M83528/002 (Standard)
  • M83528/005 (Non-Standard)
  • M83528/013 (D-shaped cross-section)

EMI O-Ring Materials

SSP makes nickel-aluminum silicone and fluorosilicone, nickel-graphite silicone and flurosilicone, silver-aluminum silicone and fluorosilicone, and silver copper silicone. The main difference between silicone and fluorosilicone is that the latter provides enhanced chemical, fuel and oil resistance. Fluorosilicones also resist extreme temperatures and have broader temperature resistance.

CHO-SEAL EMI O-Rings: SSP's Alternatives

SSP makes EMI shielding elastomers that provide cost-effective alternatives to CHO-SEAL EMI shielding materials from Parker Chomerics.  


CHOMERICS® and CHO-SEAL® are registered trademarks of Parker Hannifin Corporation. SSP is not a Parker Chomerics CHO-SEAL distributor.

GORE EMI O-Rings: SSP's Alternatives

SSP also makes alternatives to discontinued UL 94 V0 flame-resistant EMI shielding materials from Gore. 

Gore® is a registered trademark of W.L. Gore & Associates, Inc. SSP is not a Gore distributor.Gore® is a registered trademark of W.L. Gore & Associates, Inc. SSP is not a Gore distributor.

Two Types of EMI O-Rings

SSP can compression mold EMI O-rings as single pieces or bond them from cut lengths of EMI extrusions. 

  • Molded EMI O-rings are cost-effective for higher-volume manufacturing, or for when a design is fully mature and tooling changes are unlikely. SSP molds EMI O-rings from the compounds that we make and molds that we fabricate in-house. 
  • Bonded EMI O-rings are good choice for for prototyping and lower-volume applications, especially when there are potential design changes or dimensional issues. SSP bonds EMI O-rings from the EMI extrusions that we make and using tooling we fabricate in-house.

Molded EMI O-Rings

When are molded EMI O-rings the right choice? Consider the example of a designer who orders prototypes of molded EMI O-rings with a 0.93 in. cross-section and a 4.7-in. diameter.

The cost is $2500 for a small, one-cavity mold and the lead time is 8 weeks. Fit testing reveals an issue with the enclosure’s dimensions, and the designer needs EMI O-rings with a diameter of 4.9 in. instead. New tooling for another $2500 is ordered, and the lead time is another eight weeks. By the time fit testing is successfully completed, the designer has paid $5000 for tooling alone and waited 16 weeks just to confirm the prototype gasket works.    

If the designer had ordered hot-spliced EMI O-rings instead, the savings in time and money would have been significant. Instead of larger and smaller molds, a single hot-splice tool could have been used. The designer could have received samples in both 4.7 and 4.9 in. as well O-rings in an intermediate diameter of 4.8 in. If the designer discovered that the EMI O-ring diameter of 4.7 in. was too small, no additional tooling would have been needed. Production for 4.9-in. diameter O-rings could then have begun using the same hot-splicing tool. 

Bonded EMI O-Rings

There are three ways to bond EMI O-Rings. SSP uses the third method: hot splicing (vulcanizing) with a conductive silicone adhesive.

  • Cold Bonding with a Non-Conductive RTV Silicone Adhesive: The first way to bond EMI O-rings is with a non-conductive, room-temperature vulcanizing (RTV) silicone adhesive that lacks an EMI filler. This type of adhesive is less expensive, but signals can penetrate the joint and result in EMI.
  • Cold Bonding with Non-Conductive Acrylic Glue: The second method uses a non-silicone, non-conductive acrylic glue. This adhesive leaves a “hard spot” in the gasket, and acrylic adhesives can’t match the temperature range of the EMI cord stock itself.       
  • Hot Splicing with Electrically-Conductive Silicone Adhesive (The SSP Method): The third way applies heat and pressure to a conductive silicone with a durometer that is similar to the EMI cord itself. This reduces the risk of a “hard spot” and EMI leakage.

M83528/002 Standard EMI O-Rings

SSP makes EMI O-rings in M83528/002 sizes. Additional sizes are available upon request.

MIL-DTL-83528
Part Number

Dimension B

Dimension C

Cross section area

M83528/002X007

.070

(1.78)

.145

(3.68)

.025

M83528/002X011

.070

(1.78)

.301

(7.65)

.025

M83528/002X012

.070

(1.78)

.364

(9.25)

.025

M83528/002X013

.070

(1.78)

.426

(10.82)

.025

M83528/002X014

.070

(1.78)

.489

(12.42)

.025

M83528/002X015

.070

(1.78)

.551

(13.99)

.025

M83528/002X017

.070

(1.78)

.676

(17.17)

.025

M83528/002X018

.070

(1.78)

.739

(18.77)

.025

M83528/002X019

.070

(1.78)

.801

(20.34)

.025

M83528/002X020

.070

(1.78)

.864

(21.94)

.025

M83528/002X021

.070

(1.78)

.926

(23.52)

.025

M83528/002X022

.070

(1.78)

.989

(25.12)

.025

M83528/002X024

.070

(1.78)

1.114

(28.30)

.025

M83528/002X026

.070

(1.78)

1.239

(31.47)

.025

M83528/002X028

.070

(1.78)

1.364

(34.65)

.025

M83528/002X114

.103

(2.62)

.612

(15.54)

.054

M83528/002X115

.103

(2.62)

.676

(17.17)

.054

M83528/002X117

.103

(2.62)

.799

(20.29)

.054

M83528/002X126

.103

(2.62)

1.362

(34.59)

.054

M83528/002X128

.103

(2.62)

1.487

(37.77)

.054

M83528/002X132

.103

(2.62)

1.737

(44.12)

.054

M83528/002X134

.103

(2.62)

1.862

(47.30)

.054

M83528/002X142

.103

(2.62)

2.362

(59.99)

.054

M83528/002X145

.103

(2.62)

2.550

(64.77)

.054

M83528/002X155

.103

(2.62)

3.987

(101.27)

.054

M83528/005 Non-Standard EMI O-Rings

SSP makes EMI O-rings with round cross-sectdions in M83528/005 sizes. Additional sizes are available upon request.

MIL-DTL-83528 Part Number

Dimension B 

Dimension C 

M83528/005X001

.030

.76

.442

11.23

M83528/005X002

.030

.76

.577

14.66

M83528/005X003

.030

.76

.692

17.58

M83528/005X004

.030

.76

.817

20.75

M83528/005X005

.039

.99

.425

10.80

M83528/005X006

.048

1.22

.295

7.49

M83528/005X007

.050

1.27

.533

13.54

M83528/005X008

.051

1.30

.446

11.33

M83528/005X009

.057

1.45

.415

10.54

M83528/005X010

.063

1.60

.541

13.74

M83528/005X011

.063

1.60

.648

16.46

M83528/005X012

.068

1.73

.847

21.51

M83528/005X013

.068

1.73

1.182

30.02

M83528/005X014

.068

1.73

3.165

80.39

M83528/005X015

.070

1.78

.495

12.57

M83528/005X016

.070

1.78

.610

15.49

M83528/005X017

.070

1.78

.635

16.13

M83528/005X018

.070

1.78

.667

16.94

M83528/005X019

.070

1.78

.860

21.84

M83528/005X020

.070

1.78

1.230

31.24

M83528/005X021

.103

2.62

1.040

26.42

M83528/005X022

.103

2.62

1.612

40.94

M83528/005X023

.103

2.62

1.790

45.47

M83528/013 EMI O-Rings

SSP makes EMI O-rings with D-shaped cross-sections in M83528/013 sizes. Additional sizes are available upon request.

 

MIL-DTL-83528 Part Number

Dimensions

A

B

D (ID)

T

M83528/013X002

.056

1.42

.041

1.04

.410

10.41

.082

2.08

M83528/013X004

.048

1.22

.039

0.99

.587

14.91

.078

1.98

M83528/013X006

.125

3.18

.078

1.98

.885

22.48

.155

3.94

M83528/013X008

.065

1.65

.049

1.24

1.122

28.50

.099

2.51

M83528/013X011

.088

2.24

.048

1.22

1.340

34.04

.095

2.41

M83528/013X012

.077

1.96

.058

1.47

1.310

33.27

.115

2.92

M83528/013X014

.085

2.16

.048

1.22

1.392

35.36

.095

2.41

M83528/013X017

.078

2.16

.053

1.35

1.550

39.37

.105

2.67

M83528/013X036

.188

4.78

.120

3.05

3.910 ± .026

99.31 .66

.240

6.10

EMI O-Ring Applications

EMI O-ring applications span multiple industries. Here are some examples.

Electronics & Enclosures

  • Shielded electronic enclosures

  • Rack-mounted equipment

  • PCB enclosures

  • Control panels

  • Sensor housings

Aerospace & Defense

  • Avionics compartments

  • Military communication devices

  • Satellite systems

  • Missile guidance systems

  • Radar enclosures

Automotive

  • Electric vehicle battery housings

  • Infotainment systems

  • Advanced driver-assistance systems (ADAS)

  • Under-the-hood electronics

Medical Devices

  • Diagnostic equipment

  • MRI and imaging systems

  • Patient monitoring devices

Industrial

  • Control cabinets in high-noise environments

  • Robotics

  • Factory automation systems

  • EMI-sensitive test equipment

Telecommunications

  • Cell towers and 5G equipment

  • Base station enclosures

  • Satellite communication gear

Space Applications

  • Spacecraft electronics

  • Satellite shielding

  • Launch system controls

Security & Surveillance

  • EMI-shielded camera enclosures

  • Sensitive listening or scanning equipment