We been seeing some "random" LED failures and some someone suggested static electricity could be the cause. I've never heard static electricity is a problem with LEDs. Anyone have any comments?
Electronic – LEDs and static
led
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Best Answer
LED's are easily damaged by a differential reverse voltage much less than the Human Body Model of 1kV @ 100pF. Almost all discrete LEDs are rated for Vr = 5V max (meaning reverse biased) where leakage currents in uA rise rapidly and deform or burn out a much smaller semiconductor gap than the forward biased diode. This reverse polarity is the one that kills LED's. It can start with ones being dimmer and have higher junction capacitance then greater failure levels are too dim and short out.
You must observe all ESD/EOS precautions unless protected by design.
Anecdotal
It was about 10 yrs ago my client then, was saying "these LEDs are no good".
They had ramped up to ~100k / year annually of custom 5mm LEDs and they were seeing about 1~2% field failures. However, with 20 parts per unit that translated into 10% field rejects overseas in Swiss tunnels and furthermore, their customer had a 3 mos withholding clause to prove reliability and pay for their wireless powered LED sidewalk installation order.
It was a crisis. Yet I was confident the parts were perfect. So I flew "down under" to see what could be done immediately.
The parts I ordered were prepaid, custom-built-to-order with my detailed datasheet e.g. 20 Cd, "single bin" for voltage, intensity and dominant wavelength. They were better than anything else in the market and were "qualified" by the client. They were all 100% tested and sorted to my specs with yields that affect the cost.
My inspection of their evolving process changes found at least a 15 opportunities for improvement from incoming to outgoing. "shelf grounding, hand-solder thermal stress, plastic injection molding etc. The only thing I could not protect against was the injected hot plastic into the final assembly from hopper to conveyer, so I did the best thing possible. Order immediate replacements with Zener protection, and included in spec for all future buys. I was able to get them in 2 weeks with a rush order.
Problems solved. I suggest you do the same.