Well, having a bad day and burned part of the PCB on 2 motherboards. I was installing into an old Compaq case for my neighbor. I left a mounting screw where it shouldn't have been. Two motherboards later I realized the mistake. What I get for doing this at 11 PM after a long day at work. Thankfully these were cheap PCChips boards so I was only out 85 dollars.
Long story short, there is an isolated part of the motherboard that is damaged. If I tape a small piece of aluminum foil to bridge the gap in the PCB track the motherboard will boot up however the display flickers and one can tell that the motherboard is not working so well. Any advice on how to fix damage on the surface of a PCB caused by a short like this? I don't want to simply try and return these motherboards since I think this would be rather dishonest given my mistake. Not much experience in small electronics repair so any obvious advice is appreciated.
How many traces are damaged? Trace repair can be done. But its not for the feint of heart. The copper traces usually have a paint or protector over it. You have to carefully scrape or sand this off on both sides of the break to be able to solder to the copper traces. You then need a pencil soldering iron with a very fine point tip. There are two ways i do this. One is a direct bridge repair. The other is a wire bypass repair. On the direct bridge repair, i find some find multi strand wire and take it apart to get a single strand. If its coated, then i scrape the coating off with a razor blade. Then i try to carefully tack it on the the board on both ends with solder. Then i form fit it to the damaged traces and try to flow solder on the whole length of the repair wire. Note if there are many small traces close together this is dicey because you can easily cause a solder bridge when you do the next one.
The other way is to use a small insulated wire to bypass the traces. In the past, i have used wirewrap wire to do this. You can heat the ends and tin them without stripping the insulation off. You then find a point somewhere on either side of the break to solder on each end of the wire bridge. The cleaning the paint off the copper applies here too.
If its a large ground plane type of trace, i save old clippings off resistors or such to use as bridges.
If your NOT proficient soldering and have the right tools, i would not recommend doing this.
Good luck.
Bob Urz
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If you're pretty sure that the only problem is the burnt trace(s), then fixing the trace more permanently may well fix it. Besides soldering a wire across the trace, there are also pens that have an ink with metal dispersed in it... you can "draw" a new trace on the circuit board. I am not sure how fine of a line these will write; I just know they exist.
To use one of these, you have to make sure the good ends of the damaged trace are bare (by scraping or heating the coating away), just like for soldering a wire. Then, start drawing on the bare part of the trace, and continue across the gap to the other bare part of the trace. It will probably help if the gap area is relatively smooth, and not rough. Once you're happy that the motherboard is working, you might seal the repaired trace with something like clear nail polish to keep it from oxidizing.
If you live in a big enough city, there is probably a local electronics distributor (not Radio Shack) where you can go and buy one over the counter. If not, you can get them from several mail-order stores. Digi-Key sells Circuit Works conductive pens in both "standard" and "micro" tips for $17 each (but they will charge you another $5 if your total order is less than $25). Mouser sells a Tech Spray pen for $13, and the same Circuit Works pens for $16 each, no minimum order.
If you want to try and solder a wire across the gap, you might have more success if you can solder to where the ends of the trace are. Follow the broken trace (with a magnifying glass) to see if it ends at a component lead. Usually, the place where the component lead is soldered to the board will offer a bigger "target" to solder to than the skinny trace. It might end at a via, which will look like a little circle. The via may go all the way through the board and the trace might continue from the via on the other side of the board, or the via might only go through a couple of layers (most PC motherboards have multiple layers, most of which you can't see). If you can't tell where the via comes out, then you'll have to just bridge the gap instead of going to the end of the trace.
If you do solder a wire and the wire ends up being less than an inch or so, you might seal the whole thing with clear nail polish as above. If the wire is longer, use a couple of drops of epoxy or hot glue along the middle of the wire to hold the wire to the motherboard, and just seal the ends with the solder joints.
If you decide you want help, a local TV shop might be able to do it for you - watch out for the minimum labor charge, though. Another place to try is a local vo-tech school that has a class in soldering and circuit board assembly; the instructor might turn your boards into a class project, or be able to point you at an "A" student who will solder for food (or a few bucks, or whatever.) If there are any companies in your town that do electronic assembly, somebody there will know how to fix it, but it might be hard to get to them through the front desk... see if you can make friends with one of the assemblers and offer to buy her (usually, but not always, it's a her) a nice lunch or an hour's worth of time to fix the boards.
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