Soldering MicroUSB Plug: Repairing Broken Phone Charger and Tackling Non-Stick Solder Issues

Hello

I will add that I have not soldered much in my life, but I have recently encountered a problem.

I wanted to repair a broken phone charger, to do this I had to solder one cable to the microUSB plug. I was terribly surprised because I could not solder it, tin stuck to the wire as much as possible, but nothing and nothing wanted to stick to the plug. In the red circle in the picture I marked an area where I can't solder anything (anticipating the question, I didn't want to solder the wire there).



Finally, I decided that I would do like my colleague some time ago and just use the Droplet. It was more of an experiment, but a colleague claimed that the droplet of current does not conduct and that it can be safely glued on 5V. This way I was surprised again because the droplet did not hold anything and after the place marked in red it just flowed down and in this way I sealed it so that it could not even be inserted into the phone, it can be thrown away.

My question is: why couldn't I solder in this place ?? I need some special tin or something ??

The soldering iron and tin that I use are:
https://sklep.avt.pl/pistoletowa-lutownica-elektryczna-vtsg130n.html
https://sklep.avt.pl/cyna-f-1-00-lc60-fiolka.html

And where is rosin, or better - solder paste or flux? Yes, I know that this LC60 binder already contains (trace amounts) flux, but this is often not enough.

Scratch with sandpaper or nail file, it will grip for sure.

I used rosin in such a way that I first put the soldering tip in the rosin and then lightly spread it over this marked area, after a while I tried to apply tin and nothing remained unchanged.

Maybe with solder paste or flux to finally catch it.

I will also try it later with sandpaper and it really should do the trick

Tin doesn't get it for you, because the element is probably slightly warmed up. A bit problematic here because you have plastic everywhere and it is possible that reheating it will not be so easy not to burn the whole thing. This piece of metal can also be protected and you will find it difficult to solder to it. It's best to drive over with sandpaper, cover it with rosin or better flux. Maybe try for an aspirin or a more corrosive flux. Warm up the elements to be joined together, add some flux and solder. Before that, you can whiten some of this place in the picture with tin. If you get the tin for it, you're practically successful. When coating with tin, wipe the tip and the element always improves the case.

The droplet has not caught on too dirty surface.