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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?

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  • \$\begingroup\$ Are you sure the circuit is good? \$\endgroup\$
    – Ron Beyer
    Commented Mar 18, 2020 at 1:03
  • \$\begingroup\$ Datasheet for the LED? How are you controlling the temperature to the datasheet max soldering temperature ? \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Mar 18, 2020 at 1:04
  • \$\begingroup\$ Was this circuit working with another LED, or is this the first test? High power LEDs need a big heatsink or they will overheat and fail. \$\endgroup\$
    – Mattman944
    Commented Mar 18, 2020 at 1:07
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    \$\begingroup\$ @JaredCravens I can't even read your question. I got stuck right where it says "$55." And I can't seem to read past that point for some reason. I need to get into the SMD LED business or something. I'm sorry to ask a distracting question, but what is it about the LED that makes it cost that much? Did you do a custom batch with Diodes, Inc? (And no, although I wouldn't have tried what you tried I also can't think of a good reason given your description why it would no longer work. Picture? And yes, I'm sorry for your loss here.) \$\endgroup\$
    – jonk
    Commented Mar 18, 2020 at 1:37
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    \$\begingroup\$ I feel your pain, UV-C LEDs are freaking expensive. Any reason you couldn't just use a soldering iron instead? \$\endgroup\$
    – swineone
    Commented Mar 18, 2020 at 2:42

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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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