31 October 2013

Use silicone for best heat conduction from the LED

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LEDs have really developed by leaps and bounds: a few years ago it was practically impossible to produce LEDs powerful enough to be used as headlights, but nowadays LED headlights are everywhere. The highly efficient LEDs have a very long life and enable great freedom for the designer.

High-power LEDs in the headlights of an Audi A6.
Image borrowed from www.audi.se
Click on the image to go to Audi's film about LED headlights.

But the diodes' large heat radiation still causes problems for the designers. The reasons are several:

• LED generates at best approx. 34 % light of input energy, while 65 % radiates as heat.

• The heat causes both the light effect and the service life to deteriorate.

• The high temperature also shifts the dominant the wavelength of the light, which leads to color shifts.

An excellent way to keep the heat in check is to use silicone to conduct heat away, for example to a heatsink.

Silicone-based materials for heat dissipation have a wide range of technical advantages, including:

• They withstand high heat really well, even for a long time. 200°C is no problem.

• They have very low surface tension, which gives the best possible surface contact to the LED chip and to the heatsink. This maximizes the heat energy transferred.

• It is easy to automate a production line with a silicone adhesive or grease. Fast production can be easily fixed.

The picture below shows the dramatic effect the right heat conduction can have on the temperature of an LED. The more yellow and red the image shows, the higher the temperature right there. The picture on the right shows an LED unit with a significantly lower temperature and more symmetrical heat distribution.

Pictures taken with a thermal camera - before and after adding heat conduction silicone under the LED chip
Pictures taken with a thermal camera - before and after adding heat conduction silicone under the LED chip

Tribotec can currently offer more than 20 different silicone materials for heat conduction. We have several products designed for gluing and/or embedding. With an adhesive, no additional attachment of the heatsink is needed, but there is also grease if you want to be able to disassemble the parts easily. A grease will always remain soft and unhardened. At the same time, a fat can be made very heat conductive. The latest products are also optimized to minimize so-called bleeding of oil even at high temperature and for a long time.

Please read about the technical data in Momentive's brochure which shows a selection for heat conduction (in English called Thermal Interface Management, TIM), and contact us and we will help you find the right product for the right area of use.