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.

Latest brochure for electronics assembly adhesives

Download the complete DYMAX Electronics Adhesives, Coatings & Encapsulants Selector Guide (548Kb pdf).

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.