Seen a few posts lately asking about using thin copper wire for jumpers on controller boards, so here's what I've learned fixing boards for years. That hair-thin stuff on little spools, the kind sold for coil winding, is usally around 0.1mm and coated in clear enamel. It looks copper but the coating is an insulator, so it won't take solder until you burn or scrape it off the ends. It also snaps if you look at it wrong, and it carries basically no current. Fine for tracing signals on a microscope, wrong tool for jumpers.
For controller work you want solid wire around 30 AWG, the stuff sold as wire-wrap or kynar wire. It's thin enough to solder between pads without bridging neighbors, but stiff enough to lay flat and hold its shape. Strip a few mm, tin both ends first, then tack one end and pull slightly taut before soldering the other. If you're bridging two points on the same layer, flux is your best friend, more than the wire itself.
One thing I wish someone had told me early: pop the battery out or disconnect it before you solder anything inside a controller. Heat near a battery is how you turn a cheap repair into a new controller. Then practice on dead hardware first, not the pad you actually play on.