Originally Posted by c0rr0sive
Something to remember, just because a solder joint is on top of a PCB, doesn't mean that is the actual connection, motherboards have several dozen layers of PCB, some in the range of 64+ layers, that jack could easily connect to a CENTER layer and be harder to solder into place where it gets a connection.
That's why its usually a good idea to try and get the flux to go though
the PCB socket, rather than just around it. I'm not able to do it myself (not quite that good at soldering), but I know of people that are good at it, and they get it to vacuum through the PCB hole.