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CiTY said:
I wonder if this "upgrade" will make it to the Luxeons? 1W,5W...
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I spoke with a Nichia rep, and he said ~50 lumens per watt 5mm devices will be the first ones shipped. (Hopefully this is a packaged 50 lumens per watt since the article mentioned 60l/w). Some time later they will make the same die available in small SMT packages for backlights, etc.
I asked if the technology is being migrated to the high power LEDs, and he said "not for a while". The two major techniques they use to get the efficiency increase are physical changes to the die to increase light extraction efficiency and the use of an electrode pattern that absorbs less of the light produced. Apparently they are still using the same recipe to make the chips - it's just that they are able to extract more of the light that used to stay trapped in the LED die.
Assuming Nichia is quoting 50l/w for a packaged device, a new 5mm 50L/W Nichia would generate 3.5lumens at 20mA and 0.07watts of power. So you'd need ~15 LEDs to make your 50 Lumens. You could probably overdrive them to ~35mA and get ~65 lumens. If they can be had for ~$1, then fifteen 5mm LEDs will be cheaper than buying Luxeon LEDs for that amount of light, right??
I did obtain a sample 1.2W, 17-20 lumen warm white. Nichia added some red phosphor to the mix and the result is supposed to be a nice warm white with great color rendering. They have some work to do. My sample has a lens to produce a 40 degree beam. Looking at the lens, one sees a very large blob of dark gold phosphor with two bond wires coming out of it. The phosphor is thick enough to mask the die shape. Lighting the device up produces a beam with a reasonable circular shape, but a few rings at the edges. The light is a blue sort of white in the very center that quickly turns to a deep butter color and an almost orangy color at the edges. It's not very pleasing /ubbthreads/images/graemlins/sick.gif, but I'll try again at higher current when I can heat sink the thing. The higher current may improve the color, but the beam will certainly remain uneven like the luxeon low domes. Looks to me like Nichia might benefit from the phosphor deposition technology in Lumiled's high domes. They will be offering non-warm ~30 lumen 1.2w LEDs.
The rep said volume production for their 1.2W LEDs won't be until around February 2004. This is the second time they have slipped out the schedule and they will be about three quarters late. Arrghh. Looks like Luxeons will remain the only 1 watt plus option for the time being. Perhaps Nichia is not ready to ship these yet because they know the Luxeon HD's produce more evenly colored light. Maybe Nichia wants to get their devices "right" before shipping them? Lets hope so - we need some healthy competition out there!!!
