Color bins - what is the cause?

David_Campen

Enlightened
Joined
Jun 29, 2004
Messages
674
Location
California
Why is there such a variation in the color of Luxeon LEDs? When I go to the hardware store to buy a fluorescent lamp I can know that the color will be uniform across a make of tubes. What is different about LEDs?
 

FirstDsent

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Joined
Jan 4, 2006
Messages
560
Location
Columbia, South Carolina
My guess:
They're a ***** to make compared to Fluorescent tubes. If Lumileds could make all their Luxeon III emitters VWOH they would. As it is, they probably come up with one as a fluke in 1:1,000,00 units. They promised to call me when they get another one. I will fly to their lab on my pig to pick it up.
Micro or even Nano variation in critical tolerances makes a big difference. I believe all white Luxeon emitters of a particular model (Lux I, Lux III, Lux V, etc.) are intended to be the same. The different flux, color, and Vf bins are the result of tiny unintended variances and sorted electronically into the various bins. It's all accidental, but they can't control it better. I believe this to be true at least in part, but it is mostly inferred from the multitude of discussions that I have skimmed on CPF. Honestly, if most of it weren't over my head, I would read more carefully.

Bernie
 

stjohnh

Newly Enlightened
Joined
Jan 13, 2006
Messages
93
As I understand it, the problem has to do with minute variations in depositing the phosphor coating on the blue LED. The blue light from the led excites the phosphor coating to produce a close-to-white light. The chemistry of compounding the phosphor coating is well worked out (many years experience putting phosphors in CRT tubes and fluorescent bulbs), but depositing the coating onto the diode consistently is troublesome.

This set of articles has lots of technical info on this:
http://www.ledsmagazine.com/articles/features/1/4/2

Holland
 
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