I got some questions regarding soldering that came up with my recent soldering training projects.
1. What am I doing wrong when I solder the LED wires to the MCPBP inside the flashlight head and the solder sticks a bit to the iron when I pull it away? So the solder is not a blob but has some sort of spike. This only happens sometimes, but I don’t know when and why.
I pre-tin the -/+ pads, put the MCPCB inside the head. Then pre-tin wires. Apply a bit of flux to the MCPCB, hold the wires in place with tweezers and heat the solder up again.
2. Why does drag soldering ICs not create bridges between the pins and what am I doing wrong when it happens?
3. Can I reuse solder if I apply flux everytime I heat it up again? Or should old solder always be removed?
My opinion below, just my own view on things and they might be wrong (I am not a pro myself)
1) I had this when the temperature wasn’t high enough, solder stuck to everything. Added a few degrees and it was more fluid for longer.
2) Solder shouldn’t and won’t stick to anything but the pads and the SMD part (and the iron or copper/desolder braid). Solder mask won’t allow it.
3) I randomly reuse solder but it rarely happens. I have a “old solder box where I collect it and might use it to projects where I need ”weight” (when filling a pill or something like that).
1 The tip is to cold, with the heatsinking from being installed in the light (the bodies job after all) the tip is cooling off to fast, that’s why the solder sticks to it and is pulled up into a sharp hook.
2 The surface tension of the liquid solder should maintain separation but you’re using to much solder. Use less and it should stay separate. Hint you don’t have to start all over, just wick some of the blob up off the pins, enough solder should remain to still have solid connections (best to verify this with a DMM & visual inspection w/ magnification)
3 Nothing says you can’t and you’ll need less Flux the second time around. Another hint; use as little Flux as possible. I mean at first it’s ok to apply liberally but as you get better remember the less you apply the less you have to clean up.
1. As the other commenters said, wrong temperature.
2. From what I know: fluid tension. Sticks to the legs but not the soldermask. If you get bridges, you did use too much solder. I get good results with a piece of 0.5mm rosin core solder across the legs of the ic
3. In practice: Yes you can. But if you want to do it proper, remove the old (unkown) solder and then apply new solder. As for the amount of flux: I prefer a lot and pay in cleaning. But good fluxing makes a huge diffierence in how easy it is to solder.
Also, do yourself a favor and use leaded solder. It’s a debated topic but it’s simply better to work with as long as you don’t have to adhere to workpace safety protocols.
Any experience on Kester 44 vs 285. Also the datasheet states that 44 residue is not cleanable with IPA. Any alternative to the expensive flux cleaners?
I just Google “285 vs 44” and see the flux used in 285 is 186 in solid form. If you’re dead set on rosin core solder I’d choose the 285. The 44 is much more aggressive and will be MUCH harder to clean
1. When this happens to me it is usually because of a dirty (oxidized) solder surface. Not enough flux. The surface oxide prevents the solder from returning to the preferred round shape as the iron is pulled away.
When solder starts acting like snot, it means it’s either too cold or too oxidised.
Too cold makes it “sticky” as the surface air-cools and almost solidifies around the molten center. If you move it slightly, you can see it start to… “look crunchy” (ugh, hard to describe).
Oxidised, it forms a “skin” on the outside and doesn’t wet to anything.
Oh yeah, look up “organic flux”. Clear blue liquid, like washer-fluid for your car, sizzles nicely, boils off, leaves zero residue as far as I can tell. I can re-melt little leftover solder-balls with that stuff and it works like it’s right off the spool.
One place where I worked, they were nice enough to fill a pint-bottle with it (out of their gallon-jugs ) which I’m still using today. A teeny bit goes a long way.
70 or 90% IPA. It cleans with a toothbrush and very light scrubbing. If you went a bit heavy on flux drop a few drops of alcohol on it and let it sit 5sec before brushing with said toothbrush.
1. To cold or using a iron with not enough power.
2. The surface tension of the liquid solder should maintain separation. If not you are using to much solder or not enough heat or not enough flux.
3. If you reflux you can reuse the solder without problems. But if the original solder is lead free solder i would remove the old solder and use leaded solder.
I have 3 rolls of this stuff (my secret stash). When we cleaned out an old workplace i found this solder and i could´t throw it away :innocent: . Have to get more information about the exact composition and the flux they use. It is my first choice when soldering springs and big stuff. It is wetting like crazy. If my usual solder is not working i get this out of the box. To bad it is very thick. Not for soldering fine stuff.
As said, it’s mainly a matter of adding some extra flux grease before soldering the wire to the LED board.
A hot iron helps too, because it will provide a nice burst of heat to the wire and solder pad.
The hotter the iron (within reasonable temps) the faster you can make a weld, without heating up the whole lot because it takes too long (when using lower temps)
In the Kester chart, mid-range temp 60/40 has a melting range of 361 deg to 460 deg so it will need to remain stationary after soldering until it cools below 361 deg or a weak joint will occur.
Also in the Kester chart, mid-range temp 63/37 does not have a melting range but a melting point, so it cools/hardens instantly. So it is the most desirable type in my opinion.
Most Flashaholics use the no-clean solder and flux.
https://www.kester.com/knowledge-base/faq#45519-saponification-saponifiers-in-an-aqueous-cleaner-can-be-used-to-remove-rosin-flux-residues
CLEANERS
Saponification: Saponifiers in an aqueous cleaner can be used to remove rosin flux residues.
Saponification: Saponifiers in an aqueous cleaner can be used to remove rosin flux residues. What the Bio-Kleen #5768 saponifier does is react with the outside layer of flux and soften it up. Literally turning it into a soap. You need a spray cleaner so that this soap layer will be washed away which then allows the Bio-Kleen to react with the next layer. Rinse that layer off, etc. The problem with ultrasonic removal is that the outer layer is slightly dissolved and that is the end of the reaction. In the meantime the solder is being exposed to an alkaline condition. The exposed solder turns a dull gray as the surface shine is etched off by the caustic solution.
) which I’m still using today. A teeny bit goes a long way.
