Un-soldering

[Timko]

I realized I made the wires on my toggle switch for my compressor too small, so I attempted to unsolder them and replace them with longer wires.  Well, I am pretty sure no switch is being added now, because it seems like I burnt off the pads that accept solder .  It's not a catastrophic thing since the switch added a little additional compression (now it's just a shorter compression).

But after this minor issue, I think I'd be interested in the correct way to unsolder components from a board.  I'm sure this won't be the first time I have to do this.

[copachino]

first with something sharp you can remove the soldermask and solder direct to the pcb, or find the near pad in the same route to solder there.


what i do for cables its using a stand to hold the pcb then with one hand and some pliers softly pull the wire while im heating the solder, the a solder sucker will clean the pad for you

[micromegas]

I don't use a solder sucker, but what I do is the following:
1. secure your pcb with a helping hand or something like that
2. use a clean solder braid
3. heat the solder to melt it first, that way desoldering is easier after
4. apply some solder to your iron tip, if it is possible use the same solder you used to solder the switch
5. locate the braid over the solder pad and then put your the tip of your solder on it with gentle pressure
6. when the braid starts to saturate with solder, move it gently (if it offers some resistance stop! you can lift a pad. Leave it there, apply some new solder to the iron tip and start heating again) so a new piece of impollute braid makes contact with the soldering.
7. do this several times but don't stay too long with the iron over the pad/braid, as you can burn the pcb or melt the mask. While you are waiting, cut the saturated part of the braid.
8. once you've removed a large amount of solder (if not all of it) from the connections do as copachino said and pull softly with pliers while heating with the iron.

[Timko]

Thanks guys.  I'm sure this will come in handy the next time I need to rewire something.

[lincolnic]

Don't be discouraged if solder braid doesn't work for you -- I've been building for five or six years and I still can't use the braid. I use a solder sucker instead. It's pretty easy. Just heat the pad until the solder melts (should only take a couple of seconds), then quickly suck out the solder. Only takes about as long as heating up the connection.

If you have a vise or some other kind of helping hands, it may make it easier to orient the board vertically, heat from the top of the PCB, and use the sucker from the bottom. Or if your iron tip isn't too big, you can probably fit the sucker and your iron on the same side of the board.

As an alternative, next time you cut wires too short (we all do it) you can try splicing another piece of wire onto what you have rather than desoldering them.

[rullywowr]

Braid works really well especially if you add flux to it first.  A solder flux pen works well for this. 

[Coda-effects]

Unsoldering can be a pain in the a**, take your time.
The solder braid works quite well, just pay attention in order not to burn the PCB.

Beware: do not forget that the braid become very hot when you use it! (happened to me, I burnt myself badly...)

[pickdropper]

Braid works really well especially if you add flux to it first.  A solder flux pen works well for this.

+1.  Another trick with the braid is to add a bit of solder to the tip of your iron.  It may seem counter-intuitive to add solder when you are desoldering, but it helps in quicker heat transfer and generally makes desoldering braid work better.

[Timko]

I think I'm going to try to cut away some of the board and re-solder the switch straight to the trace.  So a question on that.

The first post in this thread has a schematic of the board.
http://www.diystompboxes.com/smfforum/index.php?topic=99892.0

It looks like the switch goes to the right pad of R10, but I'm unsure of where to connect the 2nd wire.  Based on the perfboard layout and the circuit schematic, it looks like it goes to ground.  If that's the case, can I just connect it straight to ground?