I'm trying to replace a microswitch, but I had trouble desoldering it and now I'm worried I damaged the PCB pads. There's brown material covering the contacts that doesn't wipe away easily with isopropyl alcohol. I'm not sure whether it's leftover flux, conformal coating, or exposed PCB material. This is my first soldering project, and I'm also having trouble getting fresh solder to spread properly. Did I ruin the pads, and is there a way to confirm or repair them?
2 Answers
For removing a switch, preheat the board and use a broad chisel-style tip with plenty of flux. The goal is to heat all three contacts at once so the solder melts together and the switch can be pulled out without prolonged heating. Repeatedly heating one pin at a time can delaminate or lift the pads. If the pads are already gone, the repair will require tracing where each connection leads and soldering small wires to those points.
The brown areas look more like exposed PCB material, which usually means the copper pads may have lifted or been removed. A quick test is to add a little solder: it should wet and stick to an intact copper pad, but it will bead up or refuse to adhere to bare board material. The surface also looks unusually goopy, so check whether you accidentally applied conformal coating rather than flux, since that can prevent solder from bonding.
This is my first soldering attempt, and I probably made things worse by not using flux at the start. I’ve done some research, but I still can’t get the solder to spread properly. I’m not sure whether the problem is my technique, the tip shape, or the condition of the pad.