Solder metal fills this gap by capillary action ... A slight twisting motion ensures even coverage by the flux. Remove excess ...

The rosin acts as flux for the solder ... the soldering iron can be used to remove small amou nts of excess solder from the joint. Wipe the solder and burn rosin off by pulling the tip across ...

The video below shows attempts to tin a few pins on a similar card-edge connector and remove the excess with toilet paper. The tests are done using 63:37 lead-tin solder, plus and minus flux ...

To avoid this, use a rosin flux on the wire strands you solder together ... Finish up by cleaning off excess dielectric paste.

The solder flows into, onto and around the materials via wetting and capillary action helped along by the flux. No excess solder should be flowed onto the joint. Just enough solder to create the bond ...