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First of all, I'm sorry you all had to see this, but this is the first soldering I ever did, and now the left and right click of my mouse aren't working. All the other buttons, the sensor & lights still work though.

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Okay, so I wanted to change the clicky-switches on my mouse. So I got myself a cheap soldering set, opened the mouse up, set the soldering iron to 200 as per manual and noticed the solder isn't really liquifying. So I bumped it up to 400 or something, then it started doing what I wanted it to do.

I noticed a little bit of blackening on some spots, but well, I thought no wonder, it's hot after all, and I also had a bit of a hard time getting the solder off which is why I had the iron on the pcb for quite some time! I was a bit concerned for the "metal-pads" (?) that have gotten really loose and even fell off, but I just put them back on as good as possible and hoped for the best. Got as much solder off with my soldering pump and got the switches off after some wiggling. Those were 3-pin and I put on 2-pin switches that's why 1 hole is left open by the way.

Putting solder on was kinda the easiest part for me, though I imagine it's way too much? Not sure if that might be a problem. I was almost proud of myself, until I connected it to my PC and noticed the left an right click buttons not working.

So I guess I might need some pointers to how I can get this to work, or if it's even fixable, and how I can "test" if it's technically still working. Also I read something about using flux... well that didn't really come with the soldering set, so I didn't use any because I didn't know any better. Might that be the problem here?

Thankful for any help!

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  • \$\begingroup\$ Are you sure you soldered the tactile switches in the correct orientation? That or a "cold joint" seem most lilely to me. A cold joint is where the pads or pins don't get hot enough for the solder to flow onto them and bind properly. Unless you went really overboard, you're not likely to have damaged both switches electrically. \$\endgroup\$
    – TypeIA
    Feb 19, 2023 at 15:24
  • \$\begingroup\$ Hey thanks for the answer! Is there always a right and a wrong orientation? Honestly I didn't really think about it, but they are both in the same orientation so that might be plausible. After a quick google search, a cold joint could be fixed by just re-heating then? \$\endgroup\$
    – Slackton
    Feb 19, 2023 at 15:29
  • \$\begingroup\$ Try using a Solder sucker and Solderwick to suck up solder and try to clean the spot without burning them, if can be helpfull to add more solder to aid removing, do not leave you soldering iron more than 4/5 seconds on the same spot to avoid burning stuff. It's a fiddly job, sometimes it helps to move one side a bit, wait to cool, than try to attack the other side and repeat the proces, ease the switch a bit up, wait to cool and try the other side again and bit by bit move the part. you could strip some wire to get access to the intern conductors to repair damages on the PCB, a fiddly job. \$\endgroup\$ Feb 19, 2023 at 15:47
  • \$\begingroup\$ I will try redoing it with a wick I guess, thank you! But do I have to do anything about the metal pads? Or are they not important? \$\endgroup\$
    – Slackton
    Feb 19, 2023 at 16:38
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    \$\begingroup\$ Are you sure the switches will work put in just those two holes? Also, 400 °C is much too hot for a soldering iron (and if the manual says to use 200, that's definitely °C, not °F); you may have damaged the tip by oxidizing it. Something like 300 to 320 °C would be better, or maybe 350 °C if it's stubborn. I don't know why the manual would suggest 200 °C; that's barely enough to melt 60/40, and definitely not enough to melt any common lead-free solder. \$\endgroup\$
    – Hearth
    Feb 19, 2023 at 16:48

2 Answers 2

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You appear to be working on carpet. Don't do that. ESD can damage components. If you don't have a proper anti-static mat, a piece of corrugated cardboard will do.

First thing is to use some 99% isopropanol to clean up the board so we can see what's going on under that flux and carnage.

I can see where one pair of traces goes (or went). It would be easy enough to jumper the traces (perhaps with a couple strands removed from stranded wire, small is fine) but clean the area first and inspect carefully so you can ensure there are no shorts.

I can't see where the top trace on the other switch goes (or, more likely, went) but cleaning the board should solve that. I suggest again inspecting for shorts and jumpering both traces to pins regardless of whether they look or test okay.

Once it is working I suggest a dab of 5-minute epoxy under the switch bodies since the structural integrity of the connections is pretty compromised at this point. You can test with it open, but do not do that on a piece of carpet (ESD effects are more easily fatal when a circuit is under power).

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  • \$\begingroup\$ A wooden desk works fine too, for hobbyist purposes. \$\endgroup\$
    – Lundin
    Feb 20, 2023 at 8:52
  • \$\begingroup\$ @Lundin Probably, though a thick polyurethane finish might not be great, which is why I omitted mentioning it. A wood cutting board or unfinished plank would be fine. \$\endgroup\$ Feb 20, 2023 at 15:08
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To offer some feedback on what went wrong here:

  • Normal commercial solder (lead free) melts at around 220°C. This means that the minimum temperature you should be using on the solder iron is around 250°C. This is a common "beginner setting" for soldering, as it makes the whole soldering process slower, but with less risk of frying everything.

    Professionals typically set the temperature to 350°C. Going even beyond that is for special work only, like when you try to solder something to a badly designed PCB without thermal relief. Most of the time you would rather change to a large chisel tip instead of raising the temperature though.

  • You should only heat up a joint for a few seconds. This looks completely fried so I suspect that you've heated it significantly longer and with too high temperature. You will end up damaging the PCB and/or components like that.

  • When you de-solder something as a hobbyist, you would use a solder wick copper braid. Practice using one on some dummy PCB first, because it is very easy to get the braid stuck on the pads and thereby ripping them off. In this case the most viable route is to first heat up both pads simultaneously, remove the component and then clean up with the wick braid.

    Otherwise for removing through-hole components like these, a de-soldering station is much easier to work with but I guess you don't have access to one.

  • Apart from too much heat, damaged pads and too much solder, the joints actually look somewhat ok. It is hard to tell if they have wetted against the pads or not. You could cover both joints in flux (for example by using a flux pen - get one called "no clean flux"), heat them up briefly and try to gather excess solder on the tip. If that doesn't help, the pads are probably toasted.

As for how to salvage the PCB, Spehro has given some good advise. Find some traces or vias where the signals go and mount wires between the button legs and those locations. (Or cut off the tin legs of any through-hole component and use those.)

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