> The question is, how could one characterize these LEDs to determine 
> what
> they should be driven with? Simply done though.... I would like long
> life, since the housing that will be made around them will be 
> difficult
> to change in order to retrofit or replace the LEDs, and any 
> replacement
> will probably be from a totally different device. I also don't want 
> to
> arbitrarily dim them down either. Being wrong enough to reduce life 
> from
> 100k hours to 90k hours is probably OK, but being so far off as to
> reduce it to hundreds of hours won't do.

Not directly applicable but here's a relevant, useful and salutary 
page for Luxeons showing projected lifetimes with junction 
temperature.

        http://www.lumileds.com/technology/reliabilitytool.cfm

Apart from bonding wire issues, you MAY be able to get some idea about 
lifetimes using an Infrared Pyrometer to measure die temperatures with 
LEDs. (In the absence of W/C heat transfer data an easier or better 
way of doing this is not immediately obvious to me. If anyone can 
suggest an easier better way please do.

For example, brain having engaged, one may be able to do delta-I / 
delta-V tests which *should* give junction temperature independent of 
LED construction. More on this if interested.



            Russell


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