How to reflow solder an LED emitter on a PCB or MCPCB.

My very first reflow using a sinkpad an XHP70 with a skillet and hot plate. I will purchase a Infrared thermometer from Harbor Freight to do some testing and also see how hot the sinkpad gets as soon as the solder paste turns into liquid solder. :slight_smile:
BTW, Harbor Freight is having a good sale right now in my area, so I can purchase an Infrared thermometer with a coupon for $17.99! I guess that’s a good deal…lol… :question:

Nice job Willie. That looks pretty darn good for a first attempt. Looks like the emitter is sitting down all the way. I see the extra solder beads were pushed out the sides, and the dome is still in tact. What more could a guy ask for :slight_smile:

Thanks! Appreciate the compliment! I just followed what you had said in your video and it came out almost as good as yours…hehehe I did test it afterwards using a 3.7V lion, but that wasn’t enough voltage. So I put another cell in series and that did the trick…lol Only ran it for a few seconds. Wow, I touched the bottom of the sinkpad to see how warm it was and my it gets hot…lol :smiling_imp: BTW, Thanks for your tips and videos! :+1:

This is really very helpful to me.
Thank you for the video!

Thanks for the tutorial. Saved it to my favorites for future reference.

I was curious how the emitter was centered then I found your vid, duh, it's the BOING BOING BOING of course! LOL Thanks for great vid and details man!

Cheers!

Huge thank you for this video! Looking forward to to doing my first emitter swap and now I feel (relatively) confident. :slight_smile:

Hi there :)…

I had “Curious cases of Benjamin Button” recently with newest batch of noctigons. Symptoms were that after re flowing everything was tested and works flawlessly(mode selection and everything) and when you assemble it to flashlight I got High mode only :smiling_imp:
So atiny is trying to change modes(i can hear high pitch noise) but high mode still remains…

That happened around 5 times out of 50 emitters so I guess it could be that what Mitko mentioned.

I did not try yet but I think electrical insulating thermal glue like AA or Fujik(if it really must be used) can resolve this issues if they ever happen to you.

Indeed, sometimes you wont be having a short connection but just a modes lost( it stucks on high), or like on some of my drivers offtime memory function disabled

That is so irritating… A lot of effort to assemble everything and than wtf happens! :frowning:

Mitko what is your method of correcting this issue?

I’ve had a similar result when there is power bleeding off to ground to led negative on the driver board. High mode always.

If there is a short of some kind in the MCPCB the best solution would be to just dump the mcpcb and use another one. Trying to prevent a short with thermal epoxy would likely result in having to use a layer so thick it would negatively effect the thermal path.

No first version is not for sure. Triple checked that.

It is pita to reflow dedomed emitter on new mcbcp since I can’t use tap from above cause I’ll damage perfect emitter.

Great video. I guess on a chemically dedomed LED you don’t tap the emitter. How do you remove the excess solder then?

You reflow them before dedome :wink:

OK….
Thanks. :slight_smile:

So you would solder mcpcb with domed emitter to flashlight and then you would de solder it, de dome it and then solder again?

Nah… This is not right technique.

I usually reflow around 10-20 emitters and check them on my test rig and then de dome all of them at the same time so there are ready to go.

We are talking about curious cases when everything works on testing rigs and yet it does not work when assembled in flashlight.

Edit:

I just saw you were not replying to me. But it is ok lol :smiley:

Um, no… Solder the LED to the mcpcb you want and then dedome it.

Where did you get the other part from?..

Edit: Saw your edit :slight_smile:

Mitko and myself just want to point on this:

Wow that is great, thank you!
I particularly appreciate the intentionally casual technique, and lack of precision shown, to highlight the effect of surface tension with the wetted solder.

Very illuminating video, I had no idea that the leds could tolerate that duration of time at the solder’s melting point, or that thermal shock was the greater issue. I would have hurried it and had poor joints and raised, heat shocked emitters if I’d tried it on my own experimentally.

This is something that I’ve been putting off learning to do, I’m now quite inspired.
Thanks again.

If you reflow an LED try to stay within the heat up and cool down speed in the reflow diagram, too fast is bad for the LEDs lifetime