Whow... Did I Just Damage My Lamina BL3000???

Yesterday I was trying some new heat sinks with my red BL3000. The sink I had was adequate enough to cool the LED for a short time but I guess I didn't put enough thermal grease between the junctions of the heat sink and the LED. Anyways, I turned on the power supply and slowly juiced it up to 6.7 volts (normal running voltage) when after a little bit I noticed some activity on the array. A few of LEDs where blinking and some shut down!!! So I killed the voltage to it right after I noticed it. I put the array back on the old sink using the same grease (very thin film of it by now) and turned it back on with low voltage. The whole array was running stable but I had it down low, as I turned it up it seems that now only one led was "shutting down" and by pressing my finger on it I could absorb some of it's heat and it would turn back on. I'm not goanna run it anymore until I get some more grease (hopefully tomorrow) and ill post the results. But what would cause this??? I don't know how badly I damaged the (Ga, In) crystals if that is even the case; they are all still the same color and intensity. Maybe it was the traces on the PCB expanding from the heat??? Anyhow... do ya think I ruined my BL's life expectancy??? Because whatever I did it can't be good.






I loved that thing.... (stupid me!)






Great thanks to all of those who can answer with Intelligence or experience!

umm... what is the current you are putting through it?

is the thermal grease of good quality?

are you using a thin film of the grease? as the thinner the better.

are you using a fan or something to cool the heatsink too?

Perhap the heat is creating an open circuit. Crank it on high and check it with a multimeter.

Jeff

You should be using a current source, not a voltage source, to drive LEDs. Driving LEDs with an adjustable voltage source is a bad idea, since you never really know how much current is flowing.

See this thread for details:
http://candlepowerforums.com/vb/showthread.php?t=77221

You likely destroyed one or more of the LEDs in the array (delamination and/or fused internal electrical connection such as a bond wire). Pressing down on it may cause the electrical connection to be re-connected, or sandwich the delamination back together.

I recently destroyed a BL-4000 in the same manner - several of the internal dies don't light, flicker, or are very dim. This was caused by a switching circuit I was experimenting with. It was supposed to have current regulation, but it was very unstable and would jump up to extremely high current levels given the right circumstances.

evan9162 said:

You likely destroyed one or more of the LEDs in the array (delamination and/or fused internal electrical connection such as a bond wire). Pressing down on it may cause the electrical connection to be re-connected, or sandwich the delamination back together.

Click to expand...

I kind of thought that too. but even when i lightly touch one of the affected dies with a peice of ice it comes back to life.

the grease im using is "Type 120, Thermal Joint Compound, from EG&G". but when i was testing the BL3000 and did all of this, the grease layer was almost only a little thicker then a finger print!!

Thermal grease is supposed to be as thin as possible. It's not supposed to serve as a separation layer between the device and heat sink, it is only supposed to fill in microscopic imperfections in the metal-metal surface mating. You want as much metal-metal contact as possible, with thermal compound only filling in the gaps between the surfaces where there would normally be air.

Again, like i said, it's probably the pressure "repairing" any damage that was caused, and not the ice or heat sinking of your finger.

Do you know how much current you were pushing through the device? I don't see a current meter or even a resistor on your setup. Like I said, driving from a voltage source (like an adjustable voltage power supply) is bad. You need a proper current source to drive LEDs properly.