Oxidized diodes

08.08.2016 20:41

Out of curiosity, I salvaged these three LEDs from an old bicycle light that stopped working. Rain must have gotten inside it at one point, because the copper on the PCB was pretty much eaten away by the electrolysis. The chip that blinked the light was dead, but LEDs themselves still work.

Three LEDs damaged by water compared to a new one.

It's interesting how far inside the bulb the steel leads managed to oxidize. You can see that the right hand lead (anode) on all LEDs is brown all the way to the top, where a bond wire connects it to the die. I would have thought that the epoxy makes a better seal. For comparison, there's a similar new LED on the right. It's also interesting that the positive terminal was more damaged than the negative. On the right-most LED the terminal was actually eaten completely through just outside the bulb (although poking the remains with a needle still lights up the LED, so obviously the die itself was not damaged).

Posted by Tomaž | Categories: Life

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