Do the pins have to be soldered to the boards, or are they press fits that will remain in place? Some of them are in rows of three, and look impossible to get to the middle row to solder. Plus I'm leery of causing heat-related damage to the boards while soldering.
The soldering of ALL pins to any PCB is ALWAYS done from the bottom. That way not only are they ALL easy to get to, but the connection is also much much stronger.
The pin will stick out beyond the PCB's pad just a little and the soldering iron's tip should contact BOTH the pad and the pin until solder melts when touched to any area
where the pin and pad meet (NOT the soldering iron's tip!!). Pins are only really needed when one plans to use a connector, otherwise you can simply insert the wire into
the hole where the pin would go and solder it directly.
So when you get that block of pins with the board just snip the bent ends off what your not using & pull or wiggle the rest of it out.
This is, or course, to be done to the block of pins BEFORE they are on the PCB.
NEVER EVER NEVER try pulling a pin out of any PCB unless you're actually desoldering it when doing so.
Reheating the connection of the pin to the pad until the solder is molten
while carefully removing it by pulling and wiggling is risky enough, but attempting to remove it cold
is just begging for ruining the PCB by ripping out the pad, and likely a good portion of it's associated trace(s) with it too.
One of the problems when trying to remove a pin from molten solder is that the action of grabbing the pin (especially with something like pliers-> use tweezers) adds
"heat sinking" to the pin which will cool it below the melting point of the solder while you're attempting to extract it unless the process is done really quickly
(BUT WITHOUT EXCESSIVE FORCE).
The preferred method is to employ the use of a "solder sucker" to remove the bulk of the solder, then following up with some "desoldering braid" to completely remove
any remaining solder to the point that the pin is completely physically free to be removed stone cold.
The safest (and easiest) thing to do is just leave those pins alone or cut them off close to their base if you're sure you won't be needing them.
