I need to replace an LED but cant reflow it

Here are the facts:

I somehow killed an LED I now have to exchange but I cant disassemble it far enough to reflow it. So basically I have to replace the LED from above. Does anyone have a tip for that? I know there was a video about SMD with a soldering iron somewhere here.. but I cant find it.

That’s going to be tough when it’s still on the heatsink. The iron will not be able to heat it enough, heat will be pulled away. You need to get the star out somehow, or at least off the heat sink. still would be tough.

Good luck, maybe someone else knows how.
What kind of light? Maybe we can help with dis-assembly. Pics?

Selfbuilt. I can get it hot enough to solder to.. I mean I could disassemble it, but I dont want to, its a lot of work. :D

I see. Well if you can get the dead LED off and clean it up, solder paste may get hot enough to allow the new guy to stick. Or if no solder paste, just tin the LED pads, tweezer-hold it on the star pads, and get as much heat into the star as possible (I use a 150W iron that might be enough). As soon as the solder melts and the LED sinks into place remove heat, hold a few seconds until solder turns solid and hope it didn’t overheat something :wink:

I suspect this is the thread you’re talking about:

Soldering it by hand with all that heatsinking is NOT going to be easy…

PPtk

Thanks PPtk, thats what I was talking about. :)

Coincidentally I just found it a few minutes ago. I was almost sure it was one of your videos but as its not listed on your youtube channel I didnt find it at first..

Well I thought about heating the whole assembly up to 80°C first, shouldnt do any harm and should make the soldering easier. I'll see how it goes tomorrow, enough for today. I still cant figure out how I could possibly have killed that emitter, I didnt even touch it with the soldering iron..

Either too much heat, too much current or both… That’s how emitters die…

Yup, but the weird part is that it died after the massive heat part was over.. and it still worked by then. :D

Those Nichias are soo sensitive..

would a heat gun work? I’ve seen that used for reflowing LEDs but wouldn’t have a clue how to do it myself.

I did it per PilotPTKs video. It was really hard because my copper heatsink wicked the heat away like hell.. but I did it now. Its not as pretty as reflowed, but its OK. Its behind an optic so nobody will ever see it. :D

Thanks again to all of you and especially PilotPTK. :)