biessea wrote on 2022-09-30, 10:42:
It is possibile to solder the place where I have did the mess? Can I add tin, and rebuild traces where they were before?
I don't think you can repair the board by just adding tin (solder). PCBs are build in a way that makes solder to flow away from any areas that are not copper - even if you remove the solder resist lacquer at certain spots. If a gap is more than around half a millimeter, solder tends to connect to both sides of the gap, but does not bridge across. The newly broken traces, the ones connecting to pins 11 to 17 (maybe including 18) of U11 are below the chip if you re-solder it, so you can't add a small piece of wire to bridge the gap after you reinstalled U11.
The damage can be fixed, though. You need to add copper where you Dremeled it away. One way would be to cut replacement traces and pads from adhesive copper foil, as seen here: https://www.youtube.com/watch?v=X3UC_TFikPk . You can just put tape over the hole you drilled, and puch it with a needle after you glued it down. You need to run the foil up to the trace, and connect it using solder. The key point is that you bridge the gap using the copper foil, so the issue that solder won't flow across the gap is mitigated. You need to cut the copper foil pieces carefully to not create shorts. Be patient doing it. Use good tools, like an exacto knife (or a good clone). Use a small soldering iron tip. Use a magnifying glass. Add extra flux (electronic grade no-clean flux) if the solder doesn't like to connect the way you want. Especially with extra flux, solder easily connects where no gap is, and flows away from gaps (removing short). Have solder braid at hand to remove excess solder. Don't start without having the stuff I mentioned. You likely will need flux and solder braid. You can try to get lucky with just the flux that's inside your rosin-core solder wire. Experience is that you need more flux than you get when melting the solde wire, so you will get too much solder when your have enough flux. The extra solder will start creating random solder bridges (short circuits) and is difficult to remove unless you wick it away using solder braid. My experience is: I will likely run into a situation with too much solder. Getting the solder away without braid is difficult even with some practice, so I need to stop working, go buy some braid and continue working the next day. The same is true about flux. Without extra flux, you will waste lots of time trying to get the solder where it should go, you will needlessly burn traces and make things worse. Don't try to fudge around, have flux and add flux.
The PCB holes you drilled through originally were metal-plated connecting the top and the bottom layer. Possibly you damaged the plating in a way that they no longer connect the top and the bottom layer. In that case, use a solder iron with a fine tip and solder the IC pins separately both at the front side (top layer) and the back side (bottom layer). You can perfectly use the IC pins as replacement for the metal plating, but it only works if connected on both sides.
Be prepared that doing this work properly takes a lot of time. If it is your first time doing this kind of PCB work, expect three to four hours. You don't have to complete it in one go. Take a break if you feel the need to. You will be faster if you keep fit during work than if you skip breaks and get tired. When you are tired, you will mess up things that require you to start over. If it takes you a week woring half an hour a day, it's OK. The result will likely be way better than working 4 hours continously without any breaks. You might want to try cheap glasses sold as reading aid (around the +3 diopters grade) to get closer with your eyes to the board, as a replacement for magnifying glasses. The reading aid has the advantage that you still have a stereo image and can see the depth, and that you don't need to mount a magnifying glass using some tool.
