Hi y’all,
This is a bit of an unusual question, but I thought I’d ask here since so many of you have mad soldering skills:
I’m about to send up a second Pico Balloon with my students, and one of the challenging parts is connecting the antenna. It’s a resonant dipole on the 30m band, so is very long, and weight must be optimized. My local club says they’ve found 36awg is the best ratio of strength to weight. Only problem is, the wire is so thin the iron can actually melt it during the process of stripping / tinning it. I’m using a Hakko 888 with default settings (750) and lead free solder.
The first balloon, I fed the antenna wire straight to the PCB, then just heated the hole and filled it with solder. Then of course followed up with strain relief as the wire exited the board. It worked OK, but I never got great signal reports, possibly because some of the enamel remained down in the hole.
This second balloon, I’m using the club recommended procedure of taking 30ga wire (I’m going with the Kynar stuff) a few inches off the PCB, then soldering that to the 36ga wire. Any tips on making this solder joint as good as possible? Should I try and scrape the magnet wire? Turn down heat? Use leaded solder? Any thoughts appreciated. Thanks!
I tried a couple of lower temp settings, including 700 and 666. They both seem to strip enamel better, perhaps because they are melting it rather than scorching it? Anyways, I think I’m going to go with the lower heat, and use a hook joint to go from 30awg to 36awg. And Kapton tape for strain relief.
If anyone has further thoughts on this, I’d love to hear them, as we’ll be doing more launches in the fall. Thanks!
You do get low melt solder which is about 180 degC. I’ve never used it so can’t comment on its performance. I would use some wet and dry to remove the enamel. You could also consider paste and hot air as an alternative.
When I had a project with some really durable enamel coated magnet wire, someone suggested I rub the wire with the soldering iron on top of an aspirin pill. It actually helped. Make sure you’re in a ventilated area because I have no clue what the fumes contain. Gently scraping with an xacto knife may help too, but I’m not sure at that gauge if it’s practical.
FWIW this sounds a lot like something you should be crimping and not soldering.
You can get “magnetic wire connectors”, it’s an entire category on digikey! I’m guessing at 30m the “not super rf aspect” won’t matter? For some reason my link isn’t working but it looks like this:
Lead free solder can dissolve copper. I’ve had to do thermal stripping of small wires in the past, and too much time at too high a temperature with lead free will completely dissolve through a small wire.
I’ve since been doing the thermal stripping with leaded solder, and had no such problems. I make the connection with lead free.
The ‘enamel’ on this particular wire was much more difficult to remove than normal enamled wire and could take a few minutes per end, rather than the few seconds I was used to.
