Directed threads in silicone

Conductive silicone wires

Embedded wires in silicone are an effective solution when a design needs to combine EMI shielding, electrical continuity and environmental sealing in a single gasket. By embedding a large number of conductive metal wires throughout the thickness of the silicone, electrical contact is established between two joined metallic surfaces, whilst the silicone provides a seal against, for example, moisture, dust and other external influences.

Swelex offers silicone with reinforced fibres for demanding electronic and industrial applications where a standard elastomer seal is not sufficient. We also assist in selecting the material, fibre type, dimensions and design based on the application’s requirements for EMI shielding, environmental conditions, mechanical specifications and installation.

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What are targeted threads in silicone?

Oriented wire silicone, also known as oriented wire silicone, consists of silicone or fluorosilicone with thin conductive metal wires oriented through the thickness of the material. When the gasket is compressed between two electrically conductive surfaces, the wires create a large number of contact points between the surfaces.

The result is a gasket that fulfils two functions at the same time:

  1. Electrical connection between the joined surfaces for EMI, RFI and, in certain designs, EMP shielding
  2. Elastic seal against the surrounding environment

Unlike a conventional silicone material, it is therefore not the silicone itself that needs to be electrically conductive. Instead, the conductive silicone filaments create a defined conductive path through the gasket.

Depending on the design, the wires may, for example, be made of Monel, aluminium or phosphor bronze. The choice of material must take into account factors such as the surfaces with which it comes into contact, the risk of corrosion and the environment in which the product is to be used. Commercially available materials feature around 100 contact points per cm², and certain designs can have up to approximately 140 wires per cm².

Tufted wires can be combined with materials such as solid silicone, silicone foam and fluorosilicone. This makes it possible to tailor the solution to factors such as compressive force, temperature, chemical exposure and environmental requirements.

This technique is suitable for rigid gaskets where there are high demands for long service life and sealing performance. As the material normally requires a defined compression and a relatively stable clamping force, it is often used between flanges or panels that are secured with screws spaced at appropriate intervals.

Applications for silicone with oriented fibres

Silicone with oriented fibres is primarily used where a joint, hatch, panel or other opening in a conductive enclosure needs to maintain both a seal and electrical continuity.

Some typical areas of application are:

  • Electronics cabinets and equipment cabinets
  • Electronic enclosures and chassis
  • Access panels and bolted hatches
  • Seals around connectors
  • Telecoms and communications equipment
  • Industrial electronics and control systems
  • Defence and aviation applications
  • Transport and railway electronics
  • Medical devices
  • Energy and power-related electronics

For hatches that are opened and closed very frequently, other EMI gaskets may be more suitable, particularly if low closing force is important. However, a softer variant made from silicone foam may be an alternative, depending on the design.

When is silicone with directional fibres suitable?

It is often a good option when the design requires:

  • High shielding performance
    The closely spaced metal wires provide numerous electrical contact points between the surfaces of the enclosure.
  • EMI protection and sealing in a single component
    The silicone material provides elasticity and environmental sealing, whilst the wires provide the electrical connection.
  • Reliable performance over the long term
    The material principle is well suited to solid gaskets in demanding applications.
  • Customised packaging formats
    The material can be supplied in forms such as sheets, strips or pre-cut gaskets, depending on the application and material variant.
  • Chemically demanding environments
    Where resistance to, for example, oils, fuels or certain solvents is important, fluorosilicone may be a suitable alternative to standard silicone.

Shielding attenuation and specifications

The level of shielding attenuation provided by a gasket cannot be assessed solely on the basis of the material’s name. The result is influenced by, amongst other things:

  • Frequency range
  • Electric or magnetic field
  • Choice of wire material
  • Wire density
  • Dimensions of the packing
  • Degree of compression
  • Contact pressure
  • Surface treatment of the casing
  • Bolt spacing and flange design
  • Any breaks in the screen’s electrical continuity

For certain commercially available oriented-wire materials, shielding values are specified ranging from approximately 55 dB at low frequencies to over 100 dB in parts of the MHz range, whilst performance varies again at higher frequencies. The values should therefore be regarded as material-specific test values and not as a general guarantee for every finished design.

It is also important that the bedding is properly compacted. For certain materials, a compression of around 15 per cent of the unloaded height is recommended, and mechanical compression stops can be used to prevent over-compaction.

The contact surfaces are also crucial. Paint, anodising, oxidation or other non-conductive layers between the wires and the housing can impair electrical continuity. The design must therefore be regarded as a complete EMI system – not merely as a choice of sealing material.

Examples of technical parameters

Depending on the product range and manufacturer, silicone-coated wires may be available with, for example:

Parameter Examples of alternatives
Elastomer Solid silicone, soft silicone, silicone foam, fluorosilicone
Guide wire Monel, aluminium, phosphor bronze
Wire density Approximately 100–140 wires/contact points per cm², depending on the design
Format Sheet, strip or pre-cut gasket
Assembly Compression between conductive surfaces, with or without a self-adhesive mounting aid
Temperature range Depends on the material; certain product ranges are specified for temperatures as low as approximately –55 °C and as high as approximately +250 °C
Adaptation The dimensions, gasket geometry, wire material and material type are selected according to the application


Specific values must be checked against the technical data sheet for the relevant material variant. For example, Nolato specifies a temperature range of –55 to +250 °C for one of its product families, whilst other manufacturers and elastomer variants may have different limits.

To achieve the correct result, it is not enough simply to choose a gasket with a high specified shielding attenuation. The design around the gasket must also be correctly dimensioned.

We recommend that the following be defined at an early stage:

  • desired frequency range and shielding attenuation requirements
  • materials and surface finish of the casing
  • environmental requirements and any IP rating
  • temperature range
  • any exposure to fuel, oils or chemicals
  • available closing and clamping force
  • the dimensions and geometry of the gasket
  • number of opening cycles
  • desired lifespan

Galvanic compatibility is also important. The combination of wire material and enclosure material should be selected so as to minimise the risk of galvanic corrosion in the environment in which the assembly is to be used.

Comparison with other elastomeric seals

There are several ways to combine sealing and EMI shielding. The best solution depends on the design.

Directed threads in silicone 

Suitable for: for solid gaskets where high shielding performance, environmental sealing and a long service life are priorities. The wires provide numerous defined conductive paths directly through the gasket. 

Suitable for: you want to combine a robust seal with high electrical continuity in a permanently mounted assembly. 

 

Particle-filled conductive silicone 

Here, electrically conductive particles are mixed directly into the elastomer. The material becomes electrically conductive throughout its entire volume and can be manufactured in a variety of shapes and profiles. 

Suitable for: A fully continuous conductive elastomer and flexible geometry are desirable. 

 

Conductive fabric over foam 

A soft foam core is encased in a metallised, electrically conductive fabric. This solution can provide very low compression force and is therefore well suited to designs featuring delicate or thin panels. 

Suitable for: at Low closing force and high flexibility are more important than maximum robustness in demanding environments. 

 

Wire mesh gaskets 

Metal wire mesh provides effective electrical contact and EMI shielding, but does not automatically offer the same environmental sealing as an elastomer. In some designs, wire mesh is therefore combined with a separate sealing element. 

Suitable for: Electrical screening is prioritised, and environmental sealing can be dealt with separately. 

Frequently Asked Questions (FAQ) about silicone-coated wires 

  • What are targeted threads in silicone? 

  • Reinforced silicone is an elastomeric material in which a large number of thin metal wires run through the thickness of the silicone. When the material is compressed between two conductive surfaces, the wires make contact with both sides, creating electrical continuity across the joint. At the same time, the silicone provides elasticity and environmental sealing.

  • When should I choose threaded fittings rather than another type of seal? 

  • Targeted threads are particularly useful when you need both Effective EMI protection and environmental sealing in a single gasket and is designed in such a way that the seal can be maintained under controlled compression. 

    If very low closing force, an extremely high number of opening cycles or a complex profile are the most important factors, a different type of EMI gasket may be more suitable. 

  • What level of shielding attenuation do directional silicone wires provide? 

  • This depends on the material, wire type, frequency, packing geometry, compression and the final enclosure design. For certain material ranges, shielding levels of around 80–120 dB are reported within parts of the frequency range, but this is not a universal value for all oriented-wire gaskets or installations. 

    Contact Swelex Based on your technical requirements, we can help you identify the right materials and relevant performance data. 

  • What types of wire are available? 

  • Common options include Monel and aluminium, and some product ranges are also available in phosphor bronze. The right choice depends, amongst other things, on the enclosure material, electrical requirements and the risk of galvanic corrosion. 

  • Is the material available in fluorosilicone? 

  • Yes. Braided hoses are also available in fluorosilicone for applications where greater resistance to, for example, fuels, oils and certain solvents is required.

  • Can the gasket be adapted to our design? 

  • Yes. Depending on the product range, silicone-coated wires can be supplied as sheets or strips and processed into gaskets to the required geometry. Dimensions, material, wire type, a self-adhesive backing (if required) and other properties can be selected to suit the design. 

    For bespoke solutions, it would be helpful if you could send us a drawing along with the key technical requirements.

Contact Swelex

Choosing the right EMI shielding made from wire-reinforced silicone involves more than simply finding a gasket of the correct dimensions. The material, wire type, compression, contact surfaces and enclosure design all need to work together optimally.

Swelex helps you find the right solution based on the application’s requirements. We can assist with product selection, technical queries, material options and bespoke solutions, and, where necessary, supplement these with other components to form a complete system.

Do you already have a specification or drawing? Send it to us and our technical sales team will help you identify the right solution.

Are you unsure which material you need? Please contact us with details of the application, frequency range, temperature, enclosure material, environmental requirements and desired dimensions. We will then be able to advise you further.

Please contact Swelex for technical advice or a quotation for silicone with embedded fibres.

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