A similar question was asked about a year ago, but I believe my case is slightly differnet.
I have 8 small thermistors (Mouser 527-SC30F103AN) which I need to interface with a Mega to make 8 separate heating loops. The thermistors are in a humid chamber about 1m away from the arduino. So I was going to pass the leads through 1 mm diam holes in the chamber lead, silicone-seal the holes, and solder the leads to thicker cables (say gauge 24-28) which then go to the Mega.
The leads are ~4mil in diam [100 um, I know it's not the finest :)]. Are there any special tools and tricks to do this (other than a fine tip for the iron)? The protruding leads are ~10mm long; the rest of leads is in a polymide shell for water immersion (the thermistor is rated for that). Should I assume the exposed leads are coated with some kind of insulating laquer to prevent them from shorting inside the polymide shell? Will this laquer burn off when I try to tin the leads?
The spec sheet recommends wrapping the leads around the thicker cable before soldering, but with 10 mm lead length I am not sure if there is much to be wrapped. The parts are about $8 each, I am prepared to ruin a few before I get it right.
Try to scrape-off the lacquer (enamel?). Use flux and see if you can solder it.
Use heatshrink tubing over the solder joint when done.
There is a kind of "tinsel" wire" that's VERY difficult to solder.
Another option might be butt-splice crimp connector. But they are bulky, not really made for tiny wires, and you need a crimp tool. I'd probably also use heatshrink over the crimp connector to help support they small wire.
Thank you for taking the time to respond. I use crimping connections all the time, but, as you say, I did not think there would exist a connector that small.
Are you saying the thermistor I've got uses this tinsel type of wire?
Use an iron with a wedge tip so the heat is applied over a large area. Liquid flux will generally outperform anything else. Put on heatshrink before and wrap the thin wire around the thick wire. Plenty of heat, and it should work.
OK. Out of couriosity, I checked if there exists shrink tubing that would tightly wrap a 0.1mm wire when shrunk, and the finest one DK has goes from 0.36mm to 0.2mm. But then I am sure my joint will be much thicker than the thicker cable anyway.
Maybe there is a misunderstanding. If I have a piece of shrink tubing to fit over a 1mm wire, when I heat it, the shrink tubing shrinks so that the wire joint is gas safe. Gas safe means that not even a gas can get in there, the glue embedded in the shrink tube melts and completely seals the joint. I always get this stuff
Dual Wall Adhesive Lined Marine Grade Heat Shrink Tubing Seals Against Moisture Corrosion and Air Leakage
I was able to solder the part with no major issues: turns out the polymide-insulated leads were 2x longer than I expected. I get kOhms as stated in the ratings.
I built a portable fume hood with acrylic sheets and aluminum profiles and a horiculture blower at 250 m^3/s. Got 1 m/s face velocity which happened to be within ashare standards. The flux worked quite well and as you said each cable had its own bit of polymide insulation. Did not even have to get a special tip for my iron. Resistance between sensors is within 0.1% from each other so I think it mostly went well.
