LED – SMD LED Went Out Quickly After Soldering

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I soldered an SMD LED (that cost $55) to the board by setting the aluminum board on a kitchen skillet that was heating up. I did my best to control the heat. It usually takes only a minute of heat and the LED sinks down, and I pick it up out of the skillet immediately thereafter.

This time, unfortunately it took a few tries before I got it right. Upon testing my LED, at first it worked, but after only 5 minutes of testing, it was flickering and then finally stopped shining.

The datasheet says it can be reflow soldered up to 5 times, the max time for max soldering temp is around 50 seconds. I don't have a reflow soldering system. I don't think I went too over the soldering time, if I did go over at all.

Was it my solder job that caused this LED's demise? What can I do differently now that I've ordered another damn $55 LED?

Best Answer

What can I do differently now that I've ordered another damn $55 LED?

If you're certain current was ok, then the flickering makes me think you disconnected one of the bond wires on the actual AlGaN chip. That would suggest you got too hot.

Things you can do to improve your improvised reflow:

  1. You can buy a thermocouple online for a fraction of what that LED costs. Get one and check what the temperatures are without the diode in so that you get a sense of how fast the board is going to heat up. Then tape the thermocouple close to the diode so you can monitor temperature while reflowing.
  2. If you aren't already, get 60/40 lead solder paste so that you minimize the temperature required.
  3. If you find that the skillet heats up too much, one option is to not reflow with the skillet at all, but rather just use it to preheat to a safe temperature (e.g. 150C) and then use an iron to melt the paste. This is more annoying but it gives you more control over the device temperature.

If all else fails, you can also buy UVC LEDs presoldered onto starboards.

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