Help with PCB malfunction during soldering

I was soldering an XD68 PCB today and I thought it went well. But when I went to test it, most of the bottom row (everything from the spacebar to the right edge of the board) did not work. I don’t know a lot about PCBs but the fact that a whole row doesn’t work implies to me that I’ve messed up the circuit somehow. I have another untouched XD68 that I have compared it to, and there doesn’t seem to be anything obvious wrong (any surface mount components that appear to be missing are also missing on the untouched board). The only thing I can see is that I managed to scrape the PCB with a metal tool at one point, and it is between the spacebar and the rest of the keys to the right of it (see photo). I doesn’t look like the traces are actually broken, but I’m not really sure. Any advice about how I might proceed?

If it was my PCB, I would apply flux to that area, add solder to my iron tip and drag solder across all of those exposed traces, being sure not to bridge them. Should fix it. Then apply kapton or other insulating tape.


Thanks I did try that without any luck. The second time, I tried scraping back the solder mask a bit to make sure that I was getting everything, and I think it looks pretty good visually, but no luck.

If you look at the photo above, you’ll see that the scrape is in between the space bar switch and the rest of the switches to the left in the photo (or to the right if the board were right-side up). I would have thought that if even the traces in this location were cut, the spacebar would still work, but I really don’t know.

Is there anything else that might be the issue? I did test the board before starting, just for the record.

can you upload a high resolution image of the PCB?

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Blind shot, but maybe it’s not that one faulty trace? Maybe it looks good because it is, and some other mark is actually causing the problem. Maybe a through look over might help?

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I tried taking a photo with my DSLR but it wasn’t detailed enough, so I put it on my flatbed scanner. The board is slightly too long to fit, so a small amount of either end is cut off. The parts in the red square are the keys that aren’t working. Click the link below for the full res file.

I did dig out the multimeter and tested the scrape for continuity, and it appears to be ok. No bridges either.

High-res scan

Unscrew all the stabilizers just in case the is a short?

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I literally just did that before coming here. :smiley: No luck though. I really don’t know what the issue is.

And you found continuity from those traces to the controller? Not sure what pins they go to. Looks like the all go through a via to the other side before they come back out by the MCU.

I don’t really know what I’m doing, but I did find at least one pin in the non-working section that connects to a pin on the MCU (on both the untouched the messed up boards). I may have to give up on this one. Annoying since I don’t really have a good way to desolder these switches, stabilizer, or plate.

Oh, do you not have a desoldering pump? I have one spare if you need it.

Thanks for the offer. I do have a manual one but I have not had good luck with it. I can do a handful of switches but not 68

If it’s getting from the switch to the MCU it should be working. You sure you didnt flash a different firmware?

I haven’t flashed anything. It worked before soldering.

But did you try to reprogram it just in case? Fire up VIA and make sure those keys have codes assigned?

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I just tried flashing it using QMK Toolbox with the default XD68 firmware and there’s no change (with the exception that the bottom LEDs changed from white to red).

Keep the suggestions coming though - they are appreciated!

There are desoldering pumps and there are desoldering pumps. You want a good one like the SS-02 or soldaput with a silicone tip.
Without the tip you are pretty much setup for failure.

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I wish desoldering irons were cheaper. It makes the chore such a breeze. I could easily desolder that PCB in about 5 minutes. Also a great tool to have so that you don’t worry about messing up while soldering. It’s a confidence booster tool.

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Funnily enough, I do have an SS-02 Solder Sucker, but I got it a couple of years ago and almost never used it. The one that I had trouble with was the ECG J-045-DS, which is a soldering iron with an integrated rubber squeeze ball. I had trouble getting consistent results with that.

But I tried out the SS-02 just now, and while desoldering is still a huge pain the butt, it’s definitely doable. I’ve managed to remove about half of the switches so far. A few needed me to add more solder before removing them. The plan is to remove everything and try again on the spare PCB. So fingers crossed.


Well, I desoldered the original board completely and transferred the switches, plate, and stabilizers to the spare PCB. After soldering, it appears to work fine. I still don’t know what I did wrong the first time, but it had been a long time since I had soldered anything, and I could tell that things went much more smoothly during my second attempt. Thanks again for the help everyone.

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