Dead LS?

ResQTech

Flashlight Enthusiast
Joined
Jan 15, 2003
Messages
1,151
Location
NJ, USA
Can you physically see if a Luxeon is dead? Is the phosphor a different color? Do the wires become unattached?
 

evan9162

Flashlight Enthusiast
Joined
Apr 18, 2002
Messages
2,639
Location
Boise, ID
If you ramp way too much current through one (like 3A+), you're likely to have fused one of the bond wires open. If you examine the emitter very carefully (easiest on a high-dome) you may be able to make out a break in the bond wire and/or discoloration/burning colors on the bond wires.

I supercooled a 1W white HD, then ramped up the current to see what the limiting factor for current was. After the luxeon gave up the ghost, I examined the die and bond wires to find that the bond wire had fused open (with quite interesting remains).

Here's a picture:
bondwire.jpg


the bubbled and dark blotches around the bond wire were not present before the experiment. When the wire fused open, it likely caused some arcing, and possibly boiling of the gold wire (hence the dark blotches and bubbles).
 
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