need a de/re-soldering tip

[lacek]

Hi,
I would like to fix a LED light bulb that got broken. I would like to replace a faulty LED diode (actually now i think I need to replace three and solder a new in the emply plot.

The diodes also have three pads below.

I have the following question?:
- what is the proper technique of desoldering these diode
- what is the equipment I need.

Is it a hot air rework station such as in the following EEVBlog video:

?

Right now I have discovered that soldering station even with the most fine tip is not the solution (does not heat up - the plastic enclosure of the diodes melts easily).



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[P90]

LED bulbs are a mostly disposable item...

a hot air gun will do the business...

[sleemanj]

The trouble is that is an aluminium PCB, it's effectively a pretty big heatsink, and there is a center pad under each led also soldered.

Hot air might do it, but you would probably be wise to pre-heat the PCB, atthe very least you are going to have to take it out of the enclosure, which is also aluminium by the look of it.

You could try just using pliers to crush the bad LEDs and then come in with a hot iron and a fat tip pre-loaded with a solder blob to quickly melt the existing solder and clean up the pads.

[lacek]

Super, thanks for both replies. The enclosure is fortunately (for soldering) actually plastic. Just looks more cool in that light.

[P90]

It's most likely lead-free soldered, if you flow some leaded i.e. 63/37 solder on the joints, you'll find it easier to desolder.

[RoGeorge]

Any hot air station works just fine if you have a a preheater.

If you don't have a preheater, then slowly heat the whole aluminium PCB for a couple of minutes with hot air circling above the PCB, but without reaching the melting point. 100-150 *C will be enough. Then turn up the air temperature and heat only the LEDs you want to be removed. Pick them up with some metal tweezers after the solder has melted. Do not apply any force.

For soldering, use the same technique. Before preheating, put some solder paste on all 3 soldering point on the PCB, and some extra flux. If you have a steady hand, then you can press down the LED after the solder paste has activated, for a better thermal contact. Otherwise, it will do just fine without pressing down the LED.

I just did that a couple of days ago, mostly to see if the hot air station has enough heating power. During desoldering/soldering, the aluminium PCB was standing all the time on a thick wooden block to conserve the heat. The wooden block gain some burnt marks, but the LEDs were way cleaner than the ones from the picture above, even after desoldering then soldering them back twice. The ones from the pic looks like they were very, very overheated. Good luck!

[BMack]

Ever since we bought a electronic hot plate(preheater) changing LEDs have become super easy. Previously I had used a hot air station and heated the bottom of the board first...or used cheap flush cutters to cut the LED then use the hot air station.

Some LEDs have pads under the LED, if this is the case there is no way you can do this with a soldering iron.