Looking for advice from those experienced in soldering switches

[jcoffin1981]

I've soldered and desoldered a few boards and have gotten somewhat good at it.  This one Poker is giving me some issues.  After replacing all the switches and cleaning/lubricating the stabilizers there were two switches that were not working.  I took them out and replaced them.  Still not working.  At this point I'm having a heck of a time desoldering the switches and took like 5 or 6 attempts.  The solder was balling up in a funny way and I just could not completely remove it all (see pics below). 

I finally got them out with a bit more prying than should be necessary.  I can see there is a bit of damage to the pads, but by soldering a wire to to switch prongs and trying various contact points on the board I can see it is still possible for the switch to work.  My question is this-

1. What can cause the solder to ball up like this and then be impossible to suck it all up?  It looked more like mercury than solder.
2.  Would it be okay to coat the switch prongs with a little solder before inserting it in an effort to make better contact, especially with the pads on the opposite side, or anywhere contact is possible?

Forgive the crude drawings

[suicidal_orange]

Solder itself doesn't flow that's why you use flux.  If you don't have any separate flux (you don't need it doing through hole with good solder) you can add some new solder to the problem pins and it should stop the balling and suck up nicely.

If you've pulled the plating out of the hole adding solder to the switches probably won't help connect them on the other side
but as long as they go through easily it can't hurt.  As you say, it shouldn't be a problem to make them all work though.

[tp4tissue]

that seems normal balling to me..

are you using the solderpult?

lube it for more suction.

[jcoffin1981]

I have a flux pen which works well and I have used at every solder joint.  Despite that it is still doing this.  I have just never seen it ball like that.  Maybe it's the surface of the PCB which is repelling the solder.  Usually it makes a nice mound.  What can I do; I'll change the tip and try more flux. 

It's strange, you can desolder 40 joints perfectly in a row, then there is one which takes 8 tries to remove.  This is what damages the pcb.  Is the pad truly the only point which the switch contact connect with the board?  Is it okay if it contacts only with the keycap side where there is a pad as well?  The damaged pad interrupts the connection with the switch contact and the negative side of the diode.  This is problem with at least one of the switches.  I can run a small piece of wire between the switch contact and the negative diode as long as the other side of the switch is making contact where it should.

[jcoffin1981]

Well, I can slide a piece of copper wire down the thru hole and the contact will touch the pad on the other side.  With the other thru hole I can take a piece of copper wire and run it to the negative diode.  This is the only way I can get the switch to work.  Does anybody else have any good ideas for when the switch pads are destroyed on the pcb?  I just cannot make it work with solder alone.  I'm sure I'm not the first person this has happened to.

Yes by generously applying the flux pen I stopped most of the balling.  The board has some residual flux from the original soldering.  However, desoldering the joint a few times probably vaporized the residual flux.

[SpAmRaY]

What solder are you using and what temperature is your iron?

[jcoffin1981]

I'm using "DKE DE" 63/37  1.2% flux at a diameter of 0.5mm.  I'm desoldering at 360-370C.  I'm soldering at 350 - 360C.  Not super premium solder, but should be good enough to get the job done.

[jcoffin1981]

It's not pretty, but it worked.  I soldered the base of the other contact on the keycap side of the pcb.  What a pain in the rump.

[suicidal_orange]

If you're using flux the other option for balling is a missing contact (pulled out hole/pad) as the PCB is non-metallic so the solder wosn't stick to it.  I still struggle with the mysteries of why a couple of pins per board are so much harder than the rest so can offer no help there!

That's a very tidy repair though, good work

[tp4tissue]

I'm still not understanding the problem,

Is that solder there NOT melting?

also what solder sucker are you using?

[jcoffin1981]

The pads on the pcb side are gone and the switches were not making a connection.  Because the pads are gone is the reason the solder is balling; I should have realized this. It also makes it difficult to desolder when it does that because when you try to desolder it only half the solder comes out and the rest forms a tube or cylinder as it pulls on itself back towards the board.  It doesn't want to travel up the sucker it keeps pulling itself together.  I have a Engineer SS-02 and a LyonsBlue sucker.  The cheaper 5 dollar one actually works better.  The SS02 has a nice soft tip which conforms to the surface, but the other one is a lot more powerful.

The pad on the opposite side is intact, so with the switch on the right I put a wee bit of solder at the base on the switch side to make contact.  It's almost impossible to get it to flow down the thru hole, even with flux.  I just put a tiny bit of solder there to anchor the switch and no I didn't melt it all the way.  If the solder melts on the opposite side I'm worried it will pull the tracers up if I ever try to remove the switch, so I barely heated it.  The pad on the bottom of the pcb doesn't actually connect to anything, it connects on the switch side. 

On the left side, with the broken pad the contact to negative side of the diode is interrupted, so I ran a wire.  I had to do this with two switches.  Now everything works except for backspace.  Maybe the switch is bad, but I guess I gotta take it off and see what the heck is going on.

[tp4tissue]

got it..

just use a wire and jump it to the nearest copper..