There might be no pad left on some of those pins, looking at the pics. That said, a combination of these will work:
A solder sucker - terrible name but yeah, thats what it does. Make sure to get the silicone tip so that you get good vacuum between the tool and PCB. If you haven't successfully removed the solder, you might want to add more solder to "close" the pad so that the vacuum will work better on the next attempt.
Desoldering wick. It will draw the solder via capillary effect. Use plenty of flux and DON'T rub the pads.
For larger connectors, preheat or hot air might also help.
What usually works is to add some fresh solder. Use the soldering iron tip to remove most of the solder by holding the board vertically, then touching the iron tip (also vertical) below the pad and allow the solder to flow down onto the iron tip.
You should have pads and holes that are filled with solder but not much solder above the pads.
Make sure that the iron tip is well tinned for this next step.
Make sure the circuit board is freely movable. In other words, unplug as many connectors as possible.
Use the iron to heat one pad / hole. Keep the iron tip on the pad as long as necessary for the solder to melt completely. Then quickly rap the end of the board closest to the holes onto your table surface.
The soldier will fly out of the hole onto the table surface.
If the hole is not completely clean, re-solder the hole with a bit of solder. While the solder is still molten, rap the end of the board against the table again.
This works well but you may have to practice a bit to get good at it.
Since it seems like the question is really just how to remove the remaining solder (presumably so that you can e.g. put a new pin header in there), this works in a pinch:
Support the board above a non-critical surface like a paper towel.
Have a soda straw handy, then apply the hot soldering iron and just enough solder (hopefully flux core) to fully melt the solder that is there.
Then quickly move the soda straw firmly over the hole and forcefully blow.
Solder is usually blown through the hole onto the surface below. Cut the end of the straw square and repeat as needed.
You can clean up the holes on each side as needed with a very clean hot soldering iron tip.
My experience is that I can rarely get a combination of solder wick and a solder sucker to get the job done if there are more than two or three pins to de-solder. Here I am referring to removing the original component, not just removing the rest of the solder, but I think this information applies to both situations.
I have a hierarchy of measures of increasing efficacy and effort (or expense). First I try number 1, and if that doesn't work, number 2, and if that still doesn't do it, I pull out the 'big guns' of number 3. I don't claim to be a soldering expert, but this is what works for me.
- Solder wick / solder sucker
- Solder wick / solder sucker + hot air gun to heat the pcb near the component, and of course a regular solder iron.
- If neither of those work, then this has ALWAYS gotten the job done for me: Chip Quick SMD Removal Alloy, along with the solder wick and/or solder sucker. Even though it is made for SMD, it has worked well for through-hole components too. It is a very low-temperature solder, which you apply after you have removed as much of the original solder as you can. Because of its low melting point, it gives you much more time before it solidifies, enabling you to work on many pins at once. It will also mix with the old solder and make it easier to remove..it seems to be thicker too and come off more easily (the solder sucker seems particularly effective here). You have to be sure to remove it well afterwards before putting the new component in. It is expensive, but you don't need to use very much of it. Buy it once and keep it around, and it can save you a lot of time and frustration when nothing else works.
I have been somewhat successful using a solder sucker. You have to blob solder in the hole so that the hole is blocked with solder. Put the board in a vice or clamp of some sort. Hold the soldering iron on one side of the hole, and hold the solder sucker directly on top of the hole on the other side of the board. Give the iron time to thoroughly heat up the solder. It must be liquid all the way through. Use flux, too.
Then timing is key. Lift or tilt the iron just a tiny bit a split second before pushing the button on the solder sucker. The sucker can't get the solder out if the iron is blocking the hole. So you have to tilt it or lift it just a bit right before sucking. But if you wait more than a split second, the solder will turn back into a solid and it won't work at all. It is tricky but it can be done.
Just to be clear, if you are holding the solder sucker against the TOP side of the PCB, then the iron should be on the BOTTOM side of the PCB. The nozzle of the sucker should be sealed against the pad around the hole.
After that, I typically put flux on the hole and re-melt the tiny amount of remaining solder to make it tidy. Sometimes this closes up the hole a bit, but usually not, or not completely.
If possible, shove a pin through the hole to mechanically open it up if it is a tight fit.
I bought a blade soldering tip specifically for this purpose. Makes it safer to remove and install without cleaning up the holes. You need solderwick to clean up those holes and you may need to add more solder before removing it to fully clean the holes.
I find you often need to press a round iron tip into the wick so it depresses into the hole just a bit, but the tip cannot be too small or else the wick will act as a heatsink and not get hot enough. Use the largest tip you can get away with. You may need flux too if you've gone at it multiple times and failed since it is no longer clean and fresh.
This less formal method can make a useful addition to the methods suggested by others.
Summary: Sharp impact of board with a melted solder blob on it will dislodge the blob. Experience can turn this into a useful method.
- Hold PCBA in one hand.
- Add blob of extra solder to pad - this adds to what is there already, but makes it easier to dislodge the whole amount.
- Heat until nicely liquid while trying to not do so long as to damage pad.
- Strike PCBA sharply against a solid surface.
The impact will dislodge solder blob largely whole.
This will splatter on impact so do it in an appropriate location.
Experience will show what combination of blob size and impact impulse will best work. Can be remarkably effective.
Practice on something unimportant first.
For years I patiently wrestled with desoldering braid and solder suckers, rarely with clean results. Nowadays, once the component is removed and I'm trying to clean up the hole of excess solder, I simply use a small hand drill (essentially a screwdriver handle with a drill bit chuck) to ream out the hole. It is shocking how quick and effective this is. It honestly feels like cheating.