The copperwire we used was 0.13 mm thick. Soldering iron tip 0.4 mm.
We also used surgical tape for securing isolation and fixation.

holes masked for drilling.

middle hole was drilled

bend copperwire middle was soldered to processor

view from other angle

taped soldering and connection to RP6

back side and ugly soldering to connection pad

back side from other angle

top side again from directly above

back side with cooling attached and everything secured with tape.