Problem Tinnning Very Small Stranded Wire

[muttleytm]

I broke a micro USB receptacle off of a circuit board and am trying to get it operable again. It only uses the ground and one of the connections to supply voltage.

I tried lining up where the power connection line was and then re-soldering the socket to the board and then with a very small soldering iron trying to get the power line connected. That didn't work.

It was suggested to me that I should try to solder a short length of a small diameter flexible wire to the contact on the circuit board and the other end to the correct terminal on the USB socket and then solder this back on to the board.

I was trying to use a length of stranded wire from an old set of earphones. The wire is copper and the diameter is very small. It had some strands of nylon or something along with the copper conductors for strength. I separated these strands from the copper wire and removed them.

I thought tinning the wire would make things easier. First I tried using a very small tipped soldering iron on the very small wire. The iron was hot enough to melt the solder, but, even after I had the iron on the wire for a long time, the solder wouldn't stick to the wire. I was using a good grade of rosin core electrical solder. I then tried using a mini butane torch to heat the wire. I could get it red hot and start melting the insulation, but, the solder still didn't flow and stick to the wire.

Do they sometimes put some sort of coating on the wires that might be causing this?

I will also try putting flux on the wire first and see if that helps.

I'd appreciate any feedback.

 

[alfa88]

Wire wrap wire (coated 30 AWG solid core tinned copper) works for me most of the time for this kind of thing

 

[KJ6EAD]

The wire you're trying to use is called litz wire. As you suspected, each strand is coated with a layer of insulation. There are methods of stripping that include high temperature solder pots, abrasives and strong chemicals such as hot lye solution. You'd probably be better off using some type of hook-up wire or wire-wrap wire such as alfa88 suggests.

 

[shrtrnd]

Like KJ6EAD said. The wire you're trying to use has an insulating coating on it, that's
why you have a hard time soldering it. It can be simple laquer, or something else.
Whenever I do what you're trying to do, I use an exacto knife or very fine grit burnishing
paper to get the insulating coating off the wire, so I can solder to it.