Car under bonnetAs automotive electronic applications continue grow in number and complexity the demands made upon them for increased performance and reliability present many design challenges.  By nature the environmental conditions under which these units have to work are very harsh. Temperatures under the bonnet are increasing and geographical locations can also produce extremes in the other direction, these extreme thermal cycles induce stress and the possibility of component failure.  Another source of mechanical stress is a direct result of vibration derived from the engine and road conditions.  Chemical and oil attack are also common in and around the engine compartment with water and humidity a constant threat. All these factors make component protection a high priority for any electronic design engineer working within the automotive industry.

The sealing of the powertrain, water and fuel systems require strong, flexible, temperature and fuel resistant sealants.  In many cases traditional pre-cut gaskets have been replaced using FIPG (formed in place gaskets) which offer overall cost reductions during the manufacturing process.

Silicone Gels

Silicone gels are formulated to form a very soft cured elastomer they can provide the very best environmental protection and are able to absorb potentially damaging vibration.  If harder, high modulus elastomers are used the extreme thermal cycles within the engine compartment will stress the sensitive electrical connections and cause component failure.  This risk is either completely eliminated or greatly reduced when a silicone gel is used.

The ionic purity of the material has a direct bearing on electrical performance and integrity, materials with a high ionic content will cause unwanted electrical tracking.  Silicone gel can be formulated with very low ionic content, thereby ensuring minimal interference with the sensitive electronics protected within the encapsulant.

For engine efficiency and control there are a number of gas sensors located in and around the engine, these sensors can also be sensitive to volatile materials escaping from encapsulants.  Careful selection of polymers and good formulation techniques has enabled the production of silicone gels with very low volatile content to avoid this problem.

Hybrid silicone gels have been produced to incorporate a degree of thermal conductivity.  The combined advantages of a silicone gel and thermal conductivity is particularly useful when there is a requirement for heat to be dissipated away from the component to a suitable heat sink.  With other gels ACC has managed to incorporate a degree of flame retardancy into the gel.

Automotive lighting is now utilising LED technology in almost all applications.  Optically clear silicone gels are extensively used within the manufacture of LED modules to offer protection and improve light output and efficiency.  The refractive index of the gel can be adjusted to between 1.40 and 1.49 allowing design flexibility in the module and at the diode level.

Additional benefits of using a soft silicone gel; include the ability to remove the gel without damaging the PCB or electronics, particularly useful for reworking very expensive components and low viscosities and simple to use mix ratios, ensure fast, efficient and  error free production.

Applications for gels include:

  • Encapsulating and sealing sensors
  • Encapsulating electronic control units
  • LED encapsulation
  • General potting

For more infomation on see our silicone gels product page 

Silicone Adhesive Sealants

Used extensively for sealing applications particularly under the bonnet where the high temperatures benefit most from the use of a silicone material. 

ACC Silicones 1800 series Acetone cure RTV's benefit from a neutral cure system for safe use on sensitive electronics with a high degree of resistance to diesel fuel.  Within this range ACC also have thermally conductive sealants up to 2.3 W/mk. These new sealants are ideal for use in the sealing of the powertrain either by wet application or FIPG.

 Successful applications include;

  • Sealing fuel flow control units
  • Anti-vibration control of large electronic components
  • Heat dissipation
  • FIPG applications
  • Sealing electronic enclosures
  • Sealing LED electronics

For more infomation see our silicone adhesive product page

Silicone Encapsulants & Coatings

Used for the protection of electronic components ACC have an extensive range of encapsulants offering varied physical properties and cure speeds. High performance PCB's can be conformal coated for extra protection in the harsh operating conditions found in automotive electronics. The use of a thermally conductive encapsulant will help maintain performance and extend product life.

For more infomation see our silicone encapsulants page


ACC Silicones Ltd, Amber House, Showground Rd, Bridgwater, TA6 6AJ
Tel: +44 (0) 1278 411400 Fax: +44 (0) 1278 411444