Conductive Elastomers are fully cured silicone, flourosilicone or EPDM available in sheet form and many different extrusion profiles. These elastomers are loaded with electrically conductive particles to give excellent EMI shielding performance along with environmental sealing. The conductive particle filler is available in various materials depending on your substrate and environmental conditions.
Conductive Elastomer Material Construction Matrix
Select the product name to access its datasheet.
Please see Parker Chomerics' Conductive Elastomer Engineering Handbook for more detailed information.
Conductive elastomer gaskets are typically used to achieve a Faraday effect in an electronic enclosure/device and with our conductive elastomer range we can offer superior corrosion resistance, environmental sealing and cost-effective EMI shielding. These come in the form of sheet stock, die-cut to your drawings and extrusion offered as cord stock at length or spliced/fused to form a continuous seal.
Frequently Asked Questions
Custom extrude profiles
Is it important to consider the environment the equipment/seal will operate in?
Yes. Harsher environments require higher specification conductive materials. For example, if salt water is present, Cho-Seal 1298 is needed to prevent galvanic corrosion.
What are the advantages of using a spliced o-ring?
Spliced o-rings have quick turn around, no tooling costs, lower MOQ's, and there are hollow profile gaskets available. Also, MIL SPEC of the material is carried over to the spliced gasket that is made at HITEK.
What are the advantages of using moulded o-rings?
Moulded o-rings have tighter tolerances, shape retention (prevents o-rings from jumping out of the groove), are cost effective when taken in volume and have smaller sizes available (<10mm I/D).
Do I need PSA (Pressure Sensitive Adhesive) backing on my gasket?
PSA is recommended where a ‘3rd hand’ is needed. It is designed to hold the gasket in place during assembly. Please note all adhesive backed conductive silicones have a reduced shelf life of 12 months. Please consider this if stocking of parts is needed.
How do I decide on the correct size of profile for the groove in my product to give optimum shielding performance?
Ideally, you need to have 10-20% deflection of the profile to achieve a good environmental and EMI shield. For assistance on selecting the right profile, please email firstname.lastname@example.org, contact us on our live chat or call us on +44 (0)1724 851678.
Why are some gaskets so expensive?
The materials used within the gaskets have highly conductive particles and make up to 70% (by weight) of the product. These particles are high grade materials such as copper, aluminium and silver. Shielding gaskets should not be compared to non-conductive rubber gaskets for cost purposes.
Is there a recommend flange width for a U channel groove?
No there isn't, though start with something close to 10mm wide flange, and see what you can accommodate. Please note greater surface area is one of the key attributes in achieving good EMI/RF screening.
In terms of EMC shielding effectiveness it is relative, as reflection is independent to thickness of the material, but the solid profile would offer better absorption properties. Hollow profiles handle compression better under compression load force than a solid profile, if you want to minimise the gap between the lid/cover and box flange consider a hollow profile. If your bolt gap spacing is resulting in the lid/cover bowing when the gasket is in the groove, consider a hollow profile. Primarily, it is regarding the deflection load of the lid and the bolt spacing for securing. The lower closure forces seen with a hollow profile will assist in reducing lid bowing (especially on thinner lids). Solid profiles require a higher deflection load but offer a superior environmental seal as well as absorption properties.
Why do I need hard stops or compression stops when using a flat die-cut gasket?
Firstly, die-cut gaskets offer ease of assembly and greater surface area contact on the flange areas. Compression stops are advisable to avoid and prevent one time use of flat die-cut gaskets. The main reason is to resolve over torquing, over deflecting the gasket and resolving any movement/vibration challenges.
What do I need to take into consideration when choosing an EMC gasket for an application?
There are three main attributes to be taken into consideration when selecting an EMC gasket for application. 1. What frequency do you want to shield? Up to 1Ghz: typically wire mesh gasket or 10Ghz and above: typically metal loaded elastomer gaskets. 2. What is the environment: land, sea or air? 3. Mating part materials - to avoid galvanic corrosion.
1.35mm OD x 0.51mm ID, part number: 10-04-21120-XXXX.
How do you work out the o-ring developed length?
The formula to work out developed length of an o-ring gasket is: DL = ID + cross section x 3.142. Please note, from the centreline, the developed length can be reduced to 2.5mm to 3mm (max).
Do you have an extrusion selector guide to review what profiles are available?
Please see Parker Chomerics' Extruded EMI Gaskets Products & Custom Solutions Catalog and Conductive Elastomer Engineering Handbook for more information.
What is the recommended gap between bolts\screws?
20mm (min) to 50mm (max); if you need to have a gap between bolts/screw above 50mm, please consider reviewing your lid/cover thickness. Please note, you should try to have as many bolts/screws as you can (within reason) to aid EMC shielding effectiveness and environmental protection.
What is the overall groove fill for a solid and hollow profile gasket?
For a solid profile: 90% to 95% max overall groove fill and for a hollow profile: approx. 100% to 105% max overall groove fill. Please note, you need to avoid 100% overall groove fill, as this will result in deforming the gasket and accelerated compression set. The elastomer gasket needs space in the groove to contract outwards such as in the temperature changes/cycles phase.
How can I check how my o-ring gasket behaves in the U channel groove?
Use a clear lid/cover (Perspex or similar) with bolt holes and bolt down this lid/cover to visually check the o-ring gasket in the groove.
How do I handle tolerance stack when choosing an o-ring gasket?
Tolerances play a greater influence on smaller o-ring gaskets. For example, 1mm OD cross section o-ring (manufacturing tolerance +/-0.13mm) taking into consideration tolerance on the metalwork, resulting in a greater chance of damaging the o-ring gasket, larger o-ring profiles such as 3.18mm can handle tolerance stacks better. The larger the profile size, the better in handling tolerance stacks. Handle the worse tolerance case and work backwards.
What information do you have on general tolerances?
Please see our General Tolerances information.
What file formats can you accept for a gasket drawing?
Please send your drawings to email@example.com in a DXF, DWG or STP file.
How can I achieve a possible IP rated (water tight) seal?
Tight tolerances on the metalwork are required (no gaps), which aids and assists the EMC gasket to provide an IP seal. The surface finish should be close to 32 micro-inches. Our standard finish recommendation is 32-64 micro-inches. In particularly severe applications, better than 32 micro-inches would be necessary. Close pitched bolts/fixings: the closer the better, such as 20mm gap between bolts. Use a minimum of a 3.18mm solid O if possible. Conduct the environmental and EMC tests in parallel but in separate tests.
Do your EMC elastomer materials or EMC shielding materials meet NASA outgassing?
Please see Parker Chomerics' NASA Outgassing information pack.