advice on soldering led into a light with integrated shelf

I use a cheap 25-year-old 40w Radio Shack soldering iron. No on-off switch. Didn’t even come with a stand (I added one separately).

Here’s what I do:

  • Place the star into position with thermal grease underneath (I use AS5).
  • Check the length of the wires. Pull the wires through the holes and place them over the pads. Make sure they aren’t too long or too short.
  • Pre-tin both the wires and bondpads with solder. I used to use conventional solder for this, but now I almost exclusively use solder paste.
  • Make a toothpick tool. Use a scissors and chop off the tip of the wide end of a flat wooden toothpick so that the tip is completely flat. Then use a triangular file to make a notch in the tip of the toothpick. If done right the tip of your toothpick should look like a miniature 2-pronged fork.
  • Place the light in table vise with the head face-up. With one hand, use the forked end of the toothpick to press the wire firmly into the bondpad. In my experience using a toothpick in this manner is much easier and creates a better, flatter bond than the conventional method of holding it in place with tweezers. A notched toothpick is just the right shape to keep the wire in position and unlike metal tweezers it won’t suck heat from your solder joint.
  • Use your other hand to hold the soldering iron to the wire and the bondpad. Ideally the tip of the iron should touch BOTH the wire and the bondpad. Do not just touch the top of the wire without touching the bondpad.
  • Leave the tip of the iron in place until the solder melts. The solder should not be bulged up at the edges of the bondpad. If done properly it should flatten out and meld into the edges of the bondpad.
  • Continue to leave the tip of the iron in place several more seconds just to be sure everything is melted. To create a strong bond, both the wire and bondpad need to be hot enough to melt the solder. The solder should not be melting just from direct contact with the iron.
  • Remove the iron, but keep the toothpick holding the wire in place.
  • After a few seconds remove the toothpick.
  • Inspect the bond to insure it looks clean. If not, redo it.

Jake, I’ve had better luck using a chisel tip vs the hoof tip you’re referring to.

I always (always) solder the wires at the emitter first, then trim my wires to length, then solder to the driver. I have yet to see flashlight where it was easier to do driver first.

I like the hoof tip myself for the higher mass at the tip but each to his own. Tin the wires and the pads before assembly leaving just a bit of extra length and screw in the driver retainer which will help hold the mcpcb off the shelf and slip a piece of pop stick underneath. Flux on the pad, hold the wire down with a notched bamboo skewer(longer than a toothpick and stronger than a used long match), iron on high and press flat. Slide the iron aside so the solder doesn’t form a peak and repeat. A short piece of paper straw keeps flux spatter off the die. Pull the shim, unscrew the retainer, press into place, and rescues the retainer. Rinse with alcohol and soft bristle toothbrush.

Thanks for the toothpick tip, I’m going to try that next time :student:

Assuming a good solder, your approach sounds good. Like keltex78, I try to keep the base off the pill/shelf, but sometimes the base is alredy reflowed to a massive head.

Since most/all the flux is quickly boiled off the base blob, wire lead, and solder iron tip, I like to put some flux on the the wire lead and/or base solder blob. Really helps the solder to liquefy.

I kinda do the opposite with good results. I solder the wires onto the driver with a little extra length. Then I mock up the assembly with driver and star in place then trim the wires to get the shortest length possible.
Tin the wire ends and pads on the star. Put it all back together - don’t forget thermal paste- and I hold the wire ends down with a small flathead screwdriver.
I put a good size blob onto the iron tip. Crank up the soldering iron to max and attach the wires holding the wire in place with the screwdriver.
That’s my method - works for me.
Then have a beer admiring your awesome solder joint.

+1 absolutely.

When you put the blob on the star contacts, do you see the blob flow out to the edges & become more of a “fillet” than a “blob”? It will look more like something flowing out of the circuit board, rather than something being squashed onto it. If you can see the bonding of the solder you put on, to the pad, that part should be fine.

When you “mend the two”, does that mean the blob on the tip flows over the wire and bonds to it smoothly and at time same time it merges with the blob on the star’s pad? As with the pcb, that smooth flow of the solder to the wire shows it’s getting a good grip. If so, that part is likely to work perfectly too. You can save some time by “tinning” the wire by melting solder onto it; and I have a really hard time soldering if I do not tin the parts first. Then your iron only has to melt solder at the joint, not heat up leads, wires or pads.

This is really one of those cases where if it looks good it probably is good; and we can’t see it. Just keep thinking “Hot, Quick, and Minimal”. Hot enough to get the joint hot enough to melt the solder, as Quickly as possible to keep the heat isolated to the joint, and use Just Enough solder to hold.

As always, the best way to be sure is to finish the project and turn it on!

And be sure to let us know how it comes out!

You guys are good! Thank you. I was building an m1 for my brother, and I wanted to be sure I was doing alright. You ALL helped me out to get a bit better with the iron. I tried the chisel point with great success, it was much easier than the horse hoof for me. I did the drag so I don’t get the peak of solder, I used some tweezers to hold lead down but I want to try the wooden stick method next. I have to be up for a 13 hour shift in about 5 hours. But I will try to post s pic of the work tomorrow The light did turn on measures to a peak of 3 amps on my craftsman DMM. Long thin original leads. So it must be a bit higher. Mtn fet driver with driver bypass wire. Xml2 high cri
Thanks again for all of the great tips. I hope others find this thread, it will definitely make things easier on us newer members that have only modded a handful of lights.

Well done JD. A light which switches on after being modded is a good mod. :slight_smile:

I just put together 2 Convoy M1’s and a BLF X6 and I used a chisel head soldering tip too. I pushed the wires back into the shelf until only the portion that was to be soldered onto the board showed and bent them as much as possible so that they laid more of less over the pads. I then pushed the wires down with a popsicle stick and hit them with the soldering iron. Came out pretty well with only a tiny solder blob on the pads and wires.

I also tinned the wires first and put flux on it before soldering them. They all sit low enough so that they don’t touch the reflectors but I put kapton tape over them just because I’m paranoid.

For me slow and careful was the way to go.

I think it’s amazing (and even inspiring) to note how many perfect solutions there are to this one problem.

I use 23 or 24 AWG solid wire salvaged from Cat6 or Cat5 LAN wire, which is just fat enough to get an entry-level mod flowing full current, but way too fat and stiff to do the twisting thing mentioned above. Not that there’s anything wrong with the other method, I just can’t do it with these wires. 23AWG soft copper + solder will rip that wee LED+ pad right off the driver! Using Stranded wire, derating (30% for the wire in Patch Cables) pushes the gauge into the 20 - 22 AWG neighborhood, which is both hard to find and hard to work, and probably puts as much strain on the joint as the solid wire does.

I learned on HF radios etc. to keep every length of every trace, wire or lead As Short As Possible, as Solar suggests. This is the only way I can find to do that.

This. A #0 Flat (especially hollow ground) does an excellent job of sinking the heat away from the insulation, which on Cat6 is frail and easily destroyed. I do like the suggestion of a “fork” notch in the tip, so I may carve one in one of mine.

I see my friend & neighbor ImA4Wheeler has already dropped a link to this thread in my “Buried Treasure” thread, so apparently we’re all doing more Good than we thought here!

Once again we make ‘BLF’ into the BEST Light Forum! Thanks!!

I prefer 22 AWG Silicone wire for LED leadwires. Silicone won’t melt like PVC and is much more flexible than Teflon. I find it the optimum size for driver wires. I tried 18 AWG Silicone wire but found it awkward to work with. More heat is needed with iron to melt it, it gets stiff, and it won’t fit through the center hole in a triple Noctigon driver. 22 AWG gets the job done and is much easier to work with.

Since with Silicone there is no risk of melting the insulation, a screwdriver to sink heat away from the insulation isn’t needed. I use a notched toothpick instead.

The notched toothpick has the following advantages:

  • Very narrow and won’t get in the way of your iron.
  • Does not sink heat away from the solder making it easier and quicker to get a good bond.
  • Can be reused, but is completely disposable.

Thanks for the toothpick idea. I’ll have to try that next time.

OH yes. It is. It didn’t even smoke or glow red :wink:
Thanks

≈4.107 years later…

Hello! :-)

Just to comment that I've had trouble soldering wires to emitter MCPCBs “down the hole”, using a 2.4mm chisel tip (Hakko T18-D24). Every time in these assemblies (a C8S, an M1 and an M2) I've resorted to solder wires to the MCPCB first, install the MCPCB in the cavity tucking in the wires, and then solder the wires to the driver. But it's a bit awkward, imho (or maybe it is just me leaving the wires rather short).

I find surprising some of you prefer chisel tips to solder the wires to the emitter in the cavity. Once the MCPCB is laying on the cavity shelf it sinks the heat quite fast so maybe I should find a way to avoid :???: this, or buy some really big arse “hoof” tip like a T18-C4.

In any case, I only have two tips (D24 and B) so I think it is time to at least get another. Thank God I've found compatible tips from other brands because I cannot find Hakko tips for affordable money where I live:

  1. https://www.aliexpress.com/item/4000990046883.html ATTEN brand.
  2. https://www.aliexpress.com/item/33010782109.html Mechanic, like the solder paste.

Mechanic has some non-usual tips, like

this massive one. If the size figures are correct that is even thicker than a (Hakko) 4C.

Wellp, just wondering what should I get, and what should I change concerning my procedures.

Barkuti
I have had the same issues. I’m no expert by any means but here is my experience.

I have done the same as you and done wires to mcpcb pads, fed through the host and then soldered to driver. I had a time when I built about 20 convoy m21a’s all at the same time. Doing it the aforementioned way was easiest as I figured out the wire length needed on the first light, then I cut all the wires the proper length and then soldered all the wires to the mcpcbs. Getting the wire length just right and having something to hold the head and the driver for you (something like helping hands for the driver and anything that will hold the head at the right height for the driver and not let it roll away is good) are important steps. It’s even easier if your drivers have through holes where the + wire goes directly to the spring for the battery contact. That lets you tilt the driver super close for the negative wire and then do the positive wire after the driver is secured with the retaining ring.

I also have a hakko CF4 tip. If I do wires to driver and then mcpcb, I use it. It’s a big tip like the one you listed (mine is only tinned on the angle section though). It works really well too. I do like other people and hold the wire down with a small precision flathead screwdriver (the toothpick idea sounds good too though). Hold the wire in place, smash down with the big tip and everything is pretty much instantly melted together. You can get the wires shorter this way too. Short enough you can pretty quickly pop the wires off the driver by accident. Checking for shorts is important here but I have only ever had this happen with drivers that came from overseas and had the wires pre-attached. One down side to the tip is of course the size can make getting into certain places more tricky especially if you its deep and narrow.

I use both techniques and feel I have good results with both. Some drivers come with wires pre-attached and when this happens I use the big tip just so I have to fool with wires less. of course pre-tinned wires, pads, clean tip, flux, etc. all go a very long way too. That big tip is also awesome for solder blobs on flat top batteries.

I hope that helps.

P.S. My wife grew up in Riogordo, not terribly far from you I guess :slight_smile:

hello, after spending a lot of money in diferent tips i get an old and cheap ceramic tip with a old and cheap 60w soldering iron. i cut the tip at 90° and about 2mm diameter. pre solder led´s contacts and wires. keep the wire in place with a flat screwdriver and just a touch with the soldering iron from the screwdriver in line with the wire, side to side. perfect and flat solder, and cheap.

the C tips are 45° and at least in convoy L21A´s and C8´s doesn´t fit the angle that you can get.

hope you can understand my argentian english :smiley:

Thanks for the contribution Superstocker. So you came here for a vacation and found you had to take extra baggage? Not in the bad sense, of course. ;-)

I hear you Coyote2710, I would also prefer the tip to be less slanted but that is how they are made. A mallet head would be ideal.