When soldering, make sure U remove previous solder (or cut off) and your connection is shining (= not "cold" soldering). As Jeffloistarca, created the connection without the solder and secure it by soldering. Bare wire WILL oxydize but, as Onhwy61 notes, you'd eliminate an extra material from that conductor chain (not to mention the soldering, i.e. TWO materials?) so, better.
Good luck!
Good luck!