LEDs are Hot Stuff
October 31st, 2007I attended the Intertech-Pira conference on High-Brightness LEDs in San Diego last week. Two things to take-away from the conference were LEDs were hot stuff - in a good way and a bad way.
Matt Brennesholtz
Insight Media Analyst
In the good sense, the HB-LED industry sees a wide variety of markets in front of it. Speakers at the conference focused on markets as diverse as projection and direct view displays, street lighting, interior lighting, emergency lighting and such specialized markets as marine and aviation warning and interior lights, product testing, decorative use, etc.
Jagdish Rebello of iSuppli broke the market down into segments in his talk, as shown in the figure. He said the HB-LED market, which represents 57% of the total market for LEDs by value, had grown 9% in 2006 and the ultra-high brightness LED (UHB-LED) market had grown at a remarkable 67%. He expects the 2007 growth rate to return to the double-digit values seen in the past. The slower growth in 2005 and 2006 was due to declining ASPs, not slowing unit sales. Note that according to this graph, LCD and handset backlighting represents more than half of the market and projection is not mentioned at all.
HB- and UHB-LEDs are hot stuff in a second sense. All of the important LED properties are very sensitive to the temperature at the diode junction. These properties include color, efficiency, total light output and lifetime. Virtually all speakers discussed how these thermal properties affected their product designs and applications.
For example, Michael Fusco of LED Specialists discussed the use of LEDs in boats, primarily luxury yachts, to replace halogen incandescent lamps, which is the current standard. He said how his company had to design the fixtures to bring the heat out the front of the fixture into the air-conditioned cabin. Heat sinks and cooling fins could not be on the back of the fixture because the space between the ceiling and the deck was normally very thin, about 1.5", and the deck was often in the blazing Caribbean sun. Maybe he can take me along for the next round of product field testing.
Perhaps the extreme example of thermal problems was the LED light source designed by PerkinElmer for Volkswagen to use in an unspecified testing application. Michael Kramer of PerkinElmer said if this source had been populated with white LEDs instead of the red LEDs requested by Volkswagen, it would have produced 140,000 lumens from its 1,984 LEDs. This light output is the equivalent of a 6kW xenon lamp - a lamp that is used to light up digital cinema projectors. To maintain the LED temperature, the system used a massive, water-cooled copper heat sink. One of these 8.5" square units was on display in the PerkinElmer booth in the exhibition area and I could hardly lift it, it was so heavy.
A wide variety of companies presented information on how their materials and package designs would help alleviate thermal problems. There were 26 speakers and about 60 exhibitors at the conference and each one seemed to have a solution or a partial solution to the thermal problem.
The thermal problems with HB-LEDs were not the only problems discussed at the conference. I would say the number two technical problem mentioned by many of the speakers was colorimetry and the number three problem was drive circuits. And of course, the cost problem trumps all the technical problems.
For a complete, 11 page review of this conference, see the November issue of Large Display Report, the new name for the Insight Media newsletter formerly known as Projection Monthly with Flat Panel Coverage.
