My first LED reflow (it didn't exactly go smoothly)

Flashlight Modding and DIY Parts
1

After seeing so much creative work from the modding community here, I was inspired to take my own crack at it!

Host: Massdrop sent me a Copper Tool AAA with a cool Cree emitter instead of a warmer Nichia emitter, so that seemed like a great candidate to mod.
Emitter: I ordered some LH351D 5000K emitters from Sofirn in the hopes of one day using them - today seemed like the day!

First step, removing the pill. Turns out the head of the light was pretty securely glued, and I spent a long time trying to force it out.

After attacking it with an array of pointy tools, I unscrewed it with the use of a strap wrench, a hair dryer, and needle-nose pliers filed to be pointy.
The decimated contacts bear testament to the abuse the head endured until it finally relented.

With the hardest part out of the way, I reflowed the LED without issue.

…Kidding, I overheated the PCB to the point of delamination, added too much solder, and dropped the whole thing several times. It took me many, many tries to center the emitter.
With the puckering of the board and excess solder around the LED, I was shocked I hadn’t somehow shorted it out.

(Also, the back of the PCB is smeared with solder from the soldering iron I heated the PCB with. I gave up trying to clean it off.)

But with everything put back together, you can’t tell how unsightly the innards are.
And with a stroke of luck (finally), the reflector fit perfectly around the LH351D, no centering ring needed.

Now for some beamshots (mostly just for peace of mind that I didn’t cook the LED to death during the reflow)!
Order from left to right: Sofirn SP10S (LH351D), Copper Tool AAA (LH351D), Sofirn SF14 V2.0 (Cree XP-G2)

The LH351D emitters are the same colour, and they look nicer than the XP-G2. Looks good to me!

Thanks for joining me on my first reflow adventure! And thanks to all the modders that gave me the confidence to try it.
I look forward to working more with electronics…but I think I need to improve my precision before I torture another emitter like this.

2

My first reflow wasn’t that long ago, and I remember using too much solder and overheating the MCPCB while trying to remove the excess solder. My second reflow went even worse. I didn’t realize that I had the LED in the wrong orientation on the MCPCB, and when it didn’t light after I put it back in, I assumed that I had damaged the LED. I tried reflowing it two more times, before I realized my mistake. Fun times.

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It works, that’s the most important part. If you have a heat source that’s adjustable, you can add a little solder to a old mcpcb that’s not being used and turn your heat up slowly and give it time to stabilize at that setting. Keep turning up the heat and giving it time to stabilize until the solder flows, mark or note your setting. Now you have the perfect temp, settable each time that your particular solder flows at.
The frying pan on the stove method might work a little better for you to control temp.

Soldering paste will also make reflowing easier.
With the right setup the led should jump right into place and no centering is needed. It will tend to be attracted to the soldering pads like a magnet. I do give the led a little tap on the dome with a sharpie (plastic cap) to release some of the extra solder and seat properly like matt does in the video.

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Congrats on ending up with a working light after that struggle.
Solder paste and a small pan make for easier reflows for me after screwing up a lot. Just put solder paste on mcpcb, place led and double check the led +/- is correct, turn on the stove and when the solder flows give the led a tap with toothpick so the excess solder pops to the side, remove pan from stove and allow to cool normally, and most of the time the little solder balls of excess on the side can be removed with a small pick or just pop right off. Rarely, a solder iron to remove them.

Sometimes freezing the head of a light glued with loctite, then hitting it with the heat gun/hair dryer and a strap wrench will make the glue break free more easily. Just put it in the freezer for an hour or so before you plan to try and break it open. Obviously give the electronics time to dry before you fire anything up with a battery after this in case there was any condensation.

5

I used to do reflows by heating the bottom of the star with a soldering iron. However, this did leave some solder on the underside.

To fix this, after reflow I’d give the bottom of the star a few swipes with a handfile. Solder would still be visible, but the star appeared flat at least.

I still do reflows the same way, except I now have a soldering station with hot air gun. I use the hot air gun instead of the iron to heat up the bottom of the star. Works better and leaves no residue.

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hey thanks for sharing your story.
I remember that my first ever reflow was on a skillet on a hot plate. It actually was really successful and I was amazed how easy it was. THEN, I bought a hot air/reflow machine and it got really, really difficult. all subsequent reflows were more difficult than the very first one.
Also, I don’t do them very often, so I get out of practice quickly.

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Congratulations!

I agree the most recent batch of drop Tools are a bitch to open.

Ive torn the wires on two of them, when the driver pulled out of the pill.

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Congratulations!

I know how proud you are. I was, and it was not too long ago. You can use your oven and a smoothly coated pan along with an IR meter. Thermal grease helps.

But: Now you’re not only collecting flashlights but also LEDs :smiley: .

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Wow, thank you all for the supportive comments and helpful advice!

You’ve given me tons of great ideas on how to approach this the next time around.
I think I’ll go looking for solder paste and an electric hot plate - the videos make it look so simple!

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I use to do the same exact thing. My first few reflows back in the led caveman days were done with a cigarette lighter. It worked but sometimes my finger didn’t like it too much and it turned the bottom of the mcpcb black with suit. It cleaned off ease enough but messy. How times have changed. :sunglasses:

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Nice job Serlite. :+1:

I use a pancake skillet that is no longer used by the family. It maxes out at 430 degrees Fahrenheit which is perfect for reflowing LEDs. Soldering paste is also very helpful.

I’ve read that it’s best to slowly heat up the LED and then slowly cool it down for reflowing.

Once the soldering paste has liquified, I move the LED back and forth to make sure it’s centered. I then hold it down with a cotton swab to expose the excess solder and swipe it away with a toothpick in order to have the LED as close as possible to the board.

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Good soldering paste makes a big difference.
If I was only going to buy one and I had to choose between a hotplate and a hot air station.
I would pick the hot air station, it just has so many other great uses besides reflowing leds.
If money isn’t a problem then buy both. The hotplate makes reflowing super easy.
Hot air station will require a little practice but its easy enough once you get the hang of it.