The ESP Guitar Company

Awesome thank you

I'd like to add that in general you should not buy any solder labeled as "lead free." choose a 60/40 or 63/37 (this is the sn/pb ratio) rosin (flux) core solder labeled for electronic use as pus said. again, make sure the solder you buy has lead in it. the diameter of the solder is not terribly important. I prefer a larger diameter (.032" or .8 mm) as it's faster to make a joint, and speed is important when soldering electronics.

if you do indeed go about replacing any of the wiring, removing the solder at any of the junctions you're replacing will make your life easier... depending on how old your guitar is, the solder used at the factory might be lead-free, in which case you will need to jack up the temp of your iron (I would suggest 850 degrees F for desoldering lead-free joints) and use a desoldering pump or wick. you can then replace the wiring you need and redo the joints with your leaded solder (lower the temperature or your iron when you do this, 650-700 F is good... maybe a bit higher if the substrate is big like on the back of a pot). unless you're comfortable working with your iron inside the control cavity, you should remove the electronics as much as possible from the control cavity and protect the surface of your guitar (protect both from the iron directly and from any hot gobs of solder or flux that may fall or fly off) before bringing the iron in.