Foot print area & height reduction of LEDs and its impact on Junction temperature

Implications: Cree is becoming a 'total LED company'. It has chip capability to produce SiC based LED chips. It has packaging capability by acquiring Cotco. It has fixture capability by acquiring its own creation LLF. It has now created tutoring center in China to train engineers/technicians in China to be ready for promoting its products. It has LCD backlight application capability by joint work with Lite-on. By reducing 'foot-print' dimension of its XP-E and XP-C to 3.45 mm2, it is promoting its product for application to LCD TV backlight and bill board display where the 'foot-print' and height are more important comapred to lighting application.  

Analysis: The impact of reduction in 'foot-print' area and height will create impact in LCD TV backlighting and in some models of Desk-top LCD backlighting. For notebook, it will not create any impact because the light guide for notebook is thinner close to 1.5 mm and less whereas the height of the lamp is 2.1 mm. For high brightness application, the junction temperature of LEDs are generally close to 100 C. Redcution in 'foot-print' can cause increase in junction temperature. The increase in junction temperature leads to deterioration in performance of LEDs. This phenomena is well known to LED manufacturers like, Lumiled/Philips, Nichia, Osram, Cree, Toyoda Gosei. While considering 'foot-print' area, the optimization should have been done. To what extent it is done, is based on the manufacturer. For the same 'foot-print' area the LEDs from manufacturer to manufacturer will vary in terms of junction temperature and subsequently the performance during life. This needs to be evaluated before feeling the impact of reduced 'foot-print' and height.