DaveC wrote:

Jon Elson wrote:

Usually I take 1-2 full seconds of vacuum while
swirling the tip, this gets ALL the solder out of the plated through
hole.

Any air flow (vacuum) after the initial sucking is a waste. The molten
solder is sucked away and the continuing air cools the area and... no more
molten solder.

The idea is to heat, heat, heat (as much as you determine is safe) and hit
the vacuum once. Repeat the whole process if required. If it is required,
usually longer heating period or higher heat is necessary.
The vacuum has to last long enough to remove ALL the solder in one go. If
it doesn't, the tiny remaining bits of solder don't conduct heat to the far
end of the pin. With the hollow copper desoldering tip on the joint, it
does NOT cool off, in the second or two it takes to pull all the solder out.

I wish you could see this Pace unit work, it is totally amazing! I fairly
routinely desolder some 68-pin connectors, and they just fall off the board
when you are done.

Jon