how to test LEDs (production)

Thread Starter

Kardo22

Joined Mar 12, 2014
41
Hi,
I'm trying to think how to test LED assemblies (heat sink PCB and wires to connector). LED is LXZ1-5070 that says :LUXEON LEDs are not designed to be driven in reverse bias .
I thought 5V and series resistance of 2,7+2,7ohm is OK but what is the LED is assembled in reverse.

I tried on one and it didn't destroy it.

So my question: was I lucky or will those LEDs usually survive reverse 5V?
 

MisterBill2

Joined Jan 23, 2018
4,580
For a production check to verify both correct polarity and operation within specifications, I suggest a system to monitor both terminal voltage and current. The first check would be to apply a voltage just high enough to assure that the LED would be conducting, and read the current to verify that it is conducting at least the minimum expected current. That check verifies both polarity and that the device is connected. The second test would be to operate the device in a current regulated mode at the intended current, and verify that the forward drop voltage is correct. It could also be done by application of the intended source voltage and verifying that the current is within the required limits. To verify that the heat-sink attachment is within specification you need to run the test a bit longer and verify that the change in forward voltage drop and current do not go out of limits. That portion of the test may take several seconds, so you will probably want a lot of test stations to keep an adequate production rate.
You will also want to have a 4-terminal (Kelvin) connection scheme to avoid errors due to connection resistance variations.
 
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