High power LEDs and ESD susceptibility - question

[Probedude]

I bought some SSC P4 U-bin emitters from both KD and DX. The parts came in 'tape and reel'. I took one out, took a half dead 9V battery (since this is what was within arms reach) and proceeded to light up the emitter momentarily. Nice and bright and I didn't feel much heat from the package.

I then went off and showed the wife at the emitter size and how well it worked to flood the room with light. This time it was turned on a bit longer. Still the package was not above ambient.

Went back to my desk, tried to turn it on again and now it's dead.:sigh:

Took it to work, looked at it under a microscope
- bond wires look fine
- as much as I can make out, the die looks fine.
- I measure a diode drop in continuity from one terminal to the mounting base of the package but I get NO continuity from one terminal to the other, OR the other terminal to the base of the package.

ESD? I don't think it was heat. The 9V battery was pretty flat so it couldn't deliver the amps.
- from one terminal there are 3 bond wires. 2 go to the emitter die, one to a diode that is mounted on the substrate. What is that used for?

Any ideas what caused this LED to fail?

TIA,
Dave

Edit: Just looked at the datasheet and ESD spec is 20KV human body model.

So maybe it didn't die from ESD. I wasn't walking across the carpet, rubbing a balloon through my hair, etc. .. .

 

[Ray_of_Light]

I blew two P4 while I was conducting a V/I plot of it.

The ESD diode is a 4.5 V Zener that, when reverse biased, can resist only to few mA. Even a drained 9 V battery can destroy it.
Use ALWAYS a drop resistor when powering an SSC P4. In this manner, the LED will be protecting the ESD diode, since it is enough a 10 mS transient at 5 volt to kill the ESD diode.
When the ESD diode is forward biased (in the sense you are powering the P4 backwards, and it doesn't lit) it seems can take much more abuse in terms of current: at 50 mA there were no damage. I haven't gone further on the measurement.

Anthony

 

[Probedude]

The ESD diode is a 4.5 V Zener that, when reverse biased, can resist only to few mA. Even a drained 9 V battery can destroy it.
Use ALWAYS a drop resistor when powering an SSC P4. In this manner, the LED will be protecting the ESD diode, since it is enough a 10 mS transient at 5 volt to kill the ESD diode.
When the ESD diode is forward biased (in the sense you are powering the P4 backwards, and it doesn't lit) it seems can take much more abuse in terms of current: at 50 mA there were no damage. I haven't gone further on the measurement.
Anthony

Just so I'm understanding you:
- the small diode in the SSC P4 case is a zener to protect the emitter die

The odd thing is that my ESD diode still appears to work fine but the main emitter die isn't.

I've been playing with Ultrafire's 5 mode emitter which is direct drive at the high setting and there are a few other lights that use direct drive off an RCR123A so I mistakenly thought a dead 9V would be low enough, especially under load.

Thanks for the info.

Dave

 

[Ray_of_Light]

[/QUOTE]=The odd thing is that my ESD diode still appears to work fine but the main emitter die isn't.


I tried to destroy the ESD diode with a reversed high current pulse. Definetively it died, and the LED appeared to work fine soon afterwards. Only that, after few minutes, the LED was not lighting up if the direct current was less than 20 mA.

The P4 deserves a more detailed investigation with a curve tracer, to find out what is inside it. For the time being, just avoid hooking it up to direct voltage source, since something weird happens when it is presented a voltage above the Vf.
A resistor in series with the LED eliminates the problem.

We shall see. I am using a lot of P4 for their flexibility.

Anthony

 

[VidPro]

Any ideas what caused this LED to fail?

. .. .

i would have to belive it was the heat and the overpower.
because - -

a 9v alkaline rested , even dead can punch out some juice for a while at least, one last gasp of power for a second, even if it cant output current over time. a better choice of playing or even reversing (accidentally) is a lithium coin cell, i never fried a "white" led with one of them, just a 2.2v red.

and you said it was a loose emitter , tape and reel, not on a "star" item, so temperature can go balistic quick.

http://www.candlepowerforums.com/vb/showthread.php?t=185732
(esd discussion)

course i am just guessing, but YOU would know if you were shuffling around on carpet with insulated soled shoes, and jumping sparks off of things while walking about.

 

[FlashCrazy]

Try the LED again, this time applying the positive battery lead to the slug of the emitter, instead of the leg. If it works, then the diode is open.