Thursday, June 9, 2011

A Simple Low Cost Solution to Improve Life time of your HP LED (High Power Light Emitting Diode)

The Temperature of the LED junction is related to the life and reliability performance of a LED, especially Hi Power LED which runs at Hi current at High Power.
A reduction of LED junction temperature for 1 degree C would increase the life time for more than 1,000 hours. If we can reduce the Junction temperature of the LED from 135 deg C down to 120 Degrees, it could possible increase the life time of 19000 hours.
Refer to Lumileds LUXEON Rebel Automotive Specification Datasheet DS58 (09/12/18) 8
Automotive White Short-Term Maximum Rating Estimated Lifetime
350 mA, Tc ~120°C, Tj ~135°C 50,000 hours
350 mA, Tc ~135°C, Tj ~150°C 31,000 hours
There are a few points that we should design for a long reliable LED life time.
The life time is inversely proportional to the operative temperature. The Die bonding process should not create any hot spot, such as undesired void between the die and the substrates.
The using of highly conductive Hi Silver Content Silver epoxy would help to conduct as much as it could heat from the Chip on to the substrates. The Selection of Substrates, ceramic Substrates or copper base leadframe material could be possible the best conduction for heat transfer from the chip passing through onto the substrate then through the heat sink into the external world. But the CTE must be matched… for best matching CTE with the LED, ceramic Substrates may be a good way for silver epoxy process or Directly Eutectic process for better reliability.
How to conduct the heat from the substrates into the other bigger heat sink!? OR how to conduct the heat energy form the HP LED to an external heat sink.

Yes, we have such solution ,,, Metafoam, a new solution to conduct heat energy form a LED to a heat sink. The solution developed by Metafoam significantly improves the heat management performance of heat pipes by providing a substitute to the currently used wick structures, especially the sintered copper powder.
By providing an open-cell copper foam wick structure instead of a simple copper powder wick, Metafoam allows for much improved material characteristics as much as 76% more , especially higher permeability which results with faster working fluid pumping speed in the heat pipe which result in faster thermal cycle within the heat pipe, thus enhanced heat load capacity.
How does it work!?
There is a micron porous whole material which was made from Copper, a very good heat conductor that fill up the copper pipe, a few drop of water that run and carries the heat from one end into other efficiently.
This can be used as the heat sink for the high beam head lamp for the Audi A8, that is a way to conduct the heat energy from the substrate of the HP LED into the main chassis of the Lamp cover. Cooling the LED bar of Back Light Unit of LCD TV. The heat Sink for those HP LEDs in the Street Lamp.
This kind of heat sink is being intensively tested with heat pipe manufacturers and major computer brands. Proven to be a reliable solution for cooling the CPU.
And that ensures the operation of the CPU would be trouble free! Price is reasonably low.
Visit at Metaform website for more.

HK Snob

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