LS heat causing de-solder?...

[papasan]

yesterday i attempted my second de-engineering on a luxeon star (the first, a white, ended in tradgedy as i ripped the cover off of the base seperating the die from the power leads)...this second LS had been used a bit, it was the load for the first few ZLT+ iterations...

anyhow, i had been way overdriving this LS before i took it apart...before i had gotten the .1 ohm resistor to measure the current flow accuratly i had been driving this LS at .5A or more unknowingly...

so when i ripped the culminator holder off of the board the LS just popped off...i thought this was sort of odd because of the amount of effort i put into trying to remove the first LS from it's board...enough effort to destroy it utterly...

the thing is, it wasn't just the glue that had been seemingly compromised by the hightened heat, the leads had become de-soldered all by themselves...the LS seriously just fell off the board...

at first i put it down to lously QA over at luxeon, but now, thinking about this particular LS' history, i'm not so sure...

curious if anyone else has had any experience with something like this...makes me think twice about over-driving future LSes very much...

 

[dat2zip]

papasan,

Just curious if you used solder wick to when you removed the wires to the LS? If so, is it possible you de-soldered the leads and left no solder behind?

Then when removing the collimator support you cracked to remaining solder joint of the leads during the removal process.

Just a guess. I've almost let the smoke out of my first three and pushed them repeatly to 600mA (and beyond).

I think I am extremely lucky in that all my first three are still around and working.

As long as you didn't break the emitters you can glue them back onto another aluminum plate or heat sink. (Using thermal epoxy)

 

[lambda]

Papasan,

Heat probably played no part; I've had the same experience with a new unused Luxeon. Too bad it don't work like that all the time, as I too have a nice "Luxeon paper weight" that displays the internal chip with the lens/leads ripped off it.

Now days I press firmly on the LED lens when removing the collomator holder for fear the glue could cause another fatality......

 

[signals]

I did the same thing... While trying to cut the collimator support the Luxeon emitter just popped off the board, and both leads broke. I just Arctic Silvered it to a heatsink, and it's functioning perfectly in my MagLite now. I don't think it had anything to do with heat. I had not seriously overdriven it.

-Kevin

 

[papasan]

i pulled the culminator out of the assembly, i cut the black plastic culminator holder down to the PCB on two sides and then wiggled/used a box knife to seperate the culminator holder from the PCB...when i pulled the second half of the holder off the LS just fell off the PCB...no soldering gun and no desoldering braid was used at all...the box knife was never in contact with the LS adhesive nor did i wiggle the LS at all, just the culminator holder...there was solder on the leads and solder on the PCB, the leads were not broken at all, the LS seems to be in perfect shape (although i haven't tested it yet), just looks like it had a hot iron placed on both leads and then removed from the board with no braid...

sounds like it just may be a QC issue, just odd that the solder *and* the adhesive failed in the same LS...

considering how hot the heatsink was getting while the LS was lit i can imagine the solder getting hot enough to flow...of course, it depends on the type of solder luxeon uses also...

 

[Daniel Ramsey]

its always the neg (-) that has the highest current flow, try a higher percentage of silver based solder for less current bonding resistance.