Novice solderer here, need advice on desoldering a keyswitch

#1

Hey there.

I have a couple of model 01 keyboards, one of which has a faulty switch. This time around, I elected for Keyboardio to send me a replacement switch and to try the repair myself; I can solder enough to complete a partial keyboard kit by soldering my own switches, so I hoped that’d be enough to see me through the repair.
Unfortunately, I’ve run into trouble desoldering the current switch, and I understand that it’s important to do this cleanly so I don’t damage the contacts on the board when trying to remove the switch.
After multiple attempts applying the iron to the join to melt the solder, I still can’t remove it with the desoldering pump; even if the solder looks like it’s melted again. I’ve tried a range of temperature settings (up to 480ºc, from memory?) without luck. I’m assuming the issue is that I haven’t sufficiently melted the solder in the hole, but I’m wary of damaging the board with high temperatures.
Any advice from anyone who’s replaced a switch without breaking their keyboard? Has anyone written up a guide to this anywhere?

#2

It helps to flood the solder joint with fresh solder, which will mix with the existing solder and make it all flow more easily.

Definitely keep it as cool as you can manage; otherwise you might lift the pad from the PCB and then you’re looking at adding bodge wires. (Speaking from experience on that one…)

#3

Since I never happen to have any solder wick around I use inertial de-soldering. Heat up one hole until it’s flowing and then quickly slap it against something. Not hard enough to crack the board but enough so the solder flies out of the hole. I have a rubber mat on my desk that’s good for this but you can also use your leg (wear pants). Do this for both holes until they seem pretty clear. The switch will still probably be stuck from the small amount of solder that’s left. Take the switch apart, grab the copper switch mechanism with needle nose and pull on it (lightly!) while heating the through hole and it will come out.

The main things you want to avoid are heating the hole up for so long the things start to burn and pulling too hard on anything while the solder is not flowing as you can easily pull off PCB the plating.

#4

When I worked on replacing a switch, I started by using the spring-loaded desoldering sucker. Once I gently heated the solder I put the pump right down over the top of it and released it.

While that cleared a good deal of it, there was still some left holding it to the holes. What worked for me on the last bit was to gently pull up on the switch while applying a little heat first to one leg of the switch and then the other. That allowed me to start slowly backing the switch out and after a few tries of that the last of the solder let loose.

Once I got the switch out I used the desoldering sucker to clean up the last little bit of solder on the pads.

Like others have mentioned one of the big hazards is applying too much heat or for too long. You won’t need a lot of heat, just enough to start making the solder melt and don’t let the iron dwell on it too long.

It’s also key that the tip of your iron touches both the leg of the switch and the pad so that both are properly warmed to release the solder. I usually try to angle the tip so that it’s touching the leg more than the pad since I’m afraid of burning the pad.

Good luck! Hopefully some of that is helpful :slight_smile: