Silicones and LEDs - removing heat and enhancing light

Optics and packaging are playing an ever more important role when designing LED-based products which are both efficient and maintain performance over long periods of time. Silicone elastomers have proven themselves to be versatile in solving a variety of design and production issues. Our sales partner, ACC Silicones, have published a guide to products and applications in this growing field.

These include Optically Clear Encapsulants, a range of gels with differing cure cycles and physical properties. Together with harder silicone elastomers we can offer a product for most LED potting applications which require optical clarity. In particular, we can offer refractive index from 1.40 to 1.49, with an exciting new product available at 1.53.

Dissipating unwanted heat away from the diode to a suitable heat sink is essential for overall performance and can easily be achieved by selecting a thermally conductive silicone encapsulant. When selecting a thermally conductive encapsulant there is always a trade off between flexibility and thermal conductivity, due to the nature of the fillers used - as you raise the conductivity you will also see a rise in hardness. ACC Q-Sil 553 has been proven to provide a good balance offering reasonable conductivity whilst retaining a low modulus and hardness, thus reducing stress during the thermal cycle.

Not just flying high, cooking too

Part of our range of silicone adhesive/sealants from ACC, the Silcoset range has a long-established reputation. They are approved for use by the MOD and Rolls Royce in aerospace and other critical applications.

With high temperature resistance and good adhesion, you would expect there to be other, perhaps more conventional, applications as well. You would be correct. Silcoset 158 is the product of choice for fixing glass panels onto doors and hinges in domestic ovens.

Single part, solvent free silicone conformal coating

ACC 14 is a new silicone conformal coating which is single part, 100% solids and solvent free. The RTV (ambient temperature curing) coating has been formulated to provide protection for high specification printed circuit boards.

Key features:

• 1-part, no mixing


• Clear


• Ambient temperature cure - touch dry in 15 minutes


• Wide service temperature range (-50°C to +200°C)


• Low viscosity


• Excellent adhesion


• Excellent resistance to solvents, humidity and mould


• Solvent free, 100% solids content


• No shadowing effect

It can be applied by dip, spray coating, selective spray applicators, and flooding. No solvent dilution is required to achieve application viscosity. And, it's pretty safe to use! No flash-proof equipment needed, and there are no risk or safety phrases associated with it.

Let us know if you need it!

Good conductivity

We have just updated the website with a Technical Bulletin describing the case for silicone conductive compounds, and why they have so many applications.

One product fairly new to the range is ACC AS1806, which is a single part thermally conductive silicone adhesive. It is a black paste, with a fast, neutral cure and good adhesion. It has an excellent thermal conductivity of 1.55 W/m·K.

It is used for electronics applications in aerospace, under bonnet automotive, consumer products and LED applications. Because of its neutral cure and the absence of any harmful by-products, ACC AS1806 is a perfect replacement for conventional oxime based silicone adhesives. A self-levelling version, ACC AS1803, is also available.

Silicone in a bag

To complement our successful range of silicone encapsulants and potting compounds, we have introduced these new, easy to use, twinpack sachets.

The small pack size (250g) makes this the affordable solution for users who want to avoid the use of scales and mixing equipment.

Simply remove the clip, mix and pour. Standard products include ACC Q-Gel 310, ACC Q-Gel 301, ACC Q-Sil 550, ACC Q-Sil 553 and ACC Q-Sil 216.

• Clean & Simple to use


• Minimum wastage


• No external mixing equipment needed


• Guaranteed correct mix ratio