Oh yeah…first few attempts at this failed miserably…found that a perfectly clean tip (I run mine in a brass wool cleaner bucket) with a tiny blob of solder and a quick wipe on the leads with ample flux bridges quickly, if the tip is dirty solder has a mind of it’s own…wrecked several drivers learning how to do it right
My method
A. bend legs 1 and 3 down gently
B. tiny dab of super glue gel (10-15 second bond time) on top of host chip, place 2nd chip and hold till bonded
C. apply a good amount of solder flux to pins being soldered
D. clean the bejesus out of the tip till it’s shiny shiny, apply a small blob of fresh solder to tip
E. quickly touch leg needing soldering at the base/pad then drag tip up and away from the driver, bond is usually instant and works well
Doesn’t hurt to have some of those magnifying glass headband either even though the focal point is only like 3-4”
Head-Wearing Elastic Band Magnifier with LED Illumination
The light(s) are a joke (dim as heck), but it has a bunch of lenses you can click in, and, with different powers, the focal distance is different, i.e. at 1.5x, it’s like 8” or something.
I had eye surgery earlier this year, and my close vision sucks now, and I don’t think I could solder anymore without these babies!
I’ve only done a few, but I bent the legs down, which helps keep the chip in place a little, but makes the gap small enough for the surface tension to keep the solder bridged without having to glob on the solder. My first one was so bad, I don’t know how much solder I went through. It became my practice piece because I was certain I’d probably burned the chips up on the inside from how much I reworked it! But yeah, bending the legs helps, and superglue sounds like a great idea, because that’s the hardest part is keeping the tiny part perfectly positioned so that you can tack down that first leg.
All good, but I simply put the driver in a desktop vise (HarborFreight), and hold the chip down with a pair of bent tweezers, while soldering. As long as you bend the 7135 legs down, the tweezers will hold the 7135 in position well. I'd rather not use a super glue because with heat, it can produce some nasty gas.
I got a NiteCore HC50 headlamp I use now for soldering, etc., plus magnified glass's, drug store types - couple of strengths. Think I got them from DX, Manafont -- one of those at the time... The HC50 is fine on the middle setting (3 of 5) and doesn't get hot for the full time of a 18650 discharge. On settings 4 or 5, it will get hot...
Hmm, yeah, cyanoacrylate vapor is probably not as soothing as rosin flux. Nothing more relaxing than rosin flux wafting past your nose as you harmoniously join a tinned wire with its mating thru-hole. Once you get one leg tacked down, you’re in the home stretch, since if you do one leg at a time, the soldered leg should keep everything in place (unless you linger too long on one joint. You don’t have to let it linger. Or you’ll fry chips like me)
On the topic of glues and SMD soldering, I’ve seen some boards with SMDs where the components have not only been soldered, but also glued down with either red or clearish-yellow glue, very hard stuff. This stuff just some kind of non-outgassing, high temp epoxy?
One last thing I tried but gave up on was using thick solid core wire as a spacer for the tab. Once I get the two chips’ tabs soldered together, I figured it’d be a cakewalk soldering the two legs, but this ended up not working as well as I had hoped. The wire ended up being more like a very smooth wheel, and whenever the solder liquified, the chip instantly moved somehwere where I didn’t want it. However, I did have good luck using a thinner wire as a temporary post to tack the other chip’s leg to, solder the opposite leg, remove support post and solder that leg, and finally, do the third connection.
Would have been easier had I had some aligator clips or something like that to help me out…. Then, I wouldn’t have bothered with all the other methods of retaining the chip’s positioning long enough for me to solder. Alligator clip would have been easiest, and added benefit of extra thermal mass might buy a few more seconds of rework time
Joining the tabs is easy. Turn the PCB vertical, with the tabs at the top, and drop a blob of solder into the gap. Hold the iron there until the solder sucks onto the tabs, remove the iron, and you're done. If you use both gravity and the solder's surface tension so that they're working together instead of trying to pull the solder where you don't want it, it goes a lot easier.
Nice on those interesting glasses…they look MUCH lighter than the ones I got from Amazon, and yes the cheap o’ light on mine are woefully weak…this is why I bought a cheapo elastic headband, and either use a Sipik SK68 or one of my Convoy C2’s in it for light (the T6-4C makes everything much more distinct and the colors more brillian)
Yes I had to learn this too, the hard way.
CA gas in the eyes and fingerprints are visible forever where the fog goes…
And if someone thinks Fujik would be suitable…no that doesn’t work too.
Alligator clip is easy, everyone has them and with two free hands it is much easier to solder.