Sometimes it’s necessary to do a PCB repair. If the actual board is cracked you are going to have to do something about that, just repairing the tracks won’t work. Use epoxy resin to glue the crack. If there is space on the component side or top side of the board glue small pieces of scrap PCB along the crack to give it extra strength.
Epoxy resin is perfect for repairing broken PCB's. The above picture shows the type that I favour because you just press the dispenser and two equal amounts are emitted ready for you to mix. I'm now using Gorilla 25ml Epoxy as I've found it to be incredibly strong.
The epoxy resin glued board.
In the picture above, the board has been glued and the excess resin has been cleaned off.
In the above picture, after the board had been glued the track breaks were very fine and it was possible to run solder over the tracks to repair the connection.
Repairing a PCB track.
If you have a small break in a track you may think you can just put a blob of solder over it. You can have a track break as thin as a hair but trying to bridge it usually won’t work, it seems unbelievable as it’s so easy to bridge the gaps between tracks on Vero board and they seem miles apart.
As the copper track on the PCB is broken it will usually be lifting off the board as well. Scratch some of the solder resist off the track a short way from the break. How short will depend on the space available and the broken track. If you scrape the resist off too close to the break where the track is lifting you will just make it lift even more so go a few millimetres away to where the track is still firmly fixed.
Do the same on the other side of the break and then tin the two bare copper newly created “pads”. Next using a offcut of component lead bend it along the repair if it’s not a straight track and then bend it upwards to give your long nose pliers something to hold on to. Tin the end of the component lead and hold it with the pliers and heat the tinned component lead and the tinned “pad”. It should now be holding in place. You can now properly solder the second pad and component lead. Then properly solder the first joint that you just made. You should now have a decent track repair.
Sometimes you may have to repair a track that has been burnt out because it’s had too much current because of a fault. In this case there’s usually not enough track left to use the above method.
In this case you can trace the track back to a component hole. Trace back both side of the burn to component holes and prepare a short wire to solder it to the back of the component pad. I make the lead longer than it has to be so the wire can lay flat without going near to any component leads. Sometimes the sharp component lead can push through the insulation on wire and create a short where there shouldn’t be one. You may have a few tracks to do this to so it makes it easier to use different colour wires so you don’t solder to the wrong one.
Another reason for repairing a PCB is one that has been etched over zealously and a couple of tracks on an otherwise good board have been eaten away. There is a product that is an electrically conductive paint. You simple paint it on the PCB where you want the track to be. It is available from Amazon and comes in the form of a tube Bare Conductive Electric Paint Glue Electrical Solder Conducting PCB Repair 10ml and a pot Bare Conductive Electric Paint Glue Electrical Solder Conducting PCB Repair 50ml. You can use a small brush to accurately paint. The product from Amazon is quite cheap compared to the older conductive silver paint which was expensive.
Hopefully this article has given you a few clues as to the best way PCB repair for your circumstances. You may also find that you need to mix the above methods to come up with the best PCB repair.