What is considered a "professional" PCB trace repair?

[Randall]

a little epoxy won't help some..

Oh boy, does THAT look familiar!


And I never did figure out what exactly happened here.

[R.G.]

There's a difference between repairing broken/lifted traces and repairing burned PCB base stock. In tedmich's very telling photo, you see a bit of PCB underlying stock that has been burned and carbonized. If there is sufficient voltage/current available, those burned areas are what we used to call "PCB Cancer". The carbonized areas conduct, and if there is enough power available, they will heat up and continue burning through the base stock. It is particularly dangerous if the board/traces carry AC mains power, as there is a near-infinite source of power for continuing to eat the PCB stock.

I designed and worked on power supplies with logic voltages in the multi-hundred ampere range and also on AC mains PCBs, and this was something we all had to be aware of.

To repair a board that's this damaged, you have to either cut the damaged section away and replace it somehow, or as tedmich said, replace the whole board somehow.

[bsco]

I was lucky enough to take a board repair course....we had to grind out the burnt areas, fill them back in,drill the holes,lay the pads and traces,install the parts and install a conformal coating.....single and double sided....of course the boards are out of the chassis and on the bench....very enlightening experience.......

[bsco]

Oh boy, does THAT look familiar!
[ATTACH=CONFIG]30332[/ATTACH]

And I never did figure out what exactly happened here.

Is it possible that flux residue when left over a period of time will cause some of this type of damage?? Esipecially in high voltage/current areas?? Whenever I break out the soldering iron, I always clean up the area after.....

[tedmich]

Oh boy, does THAT look familiar!
[ATTACH=CONFIG]30332[/ATTACH]

And I never did figure out what exactly happened here.

in my case Bad Ruby tube caused protection diode to 'spload ...yours looks like conductive liquid (Mountain Dew?) was spilled into amp and after drying arc'd everywhere maybe... Thats a lot of corrosion!

3M copper foil is good stuff, although adhesive is conductive so FR4 has to be pristine (no carbon traces!)

[Shadrock2]

I want to thank everyone for discussing this issue. I've obtained several good idea's for how to proceed.

I like the idea jumping cracked traces with clipped component leads.

Those are some messed up circuit boards in those pictures.

I guess I always shied away from using epoxy. My dear late friend (who used to post here as Rob Mercure many years ago) never liked epoxy and I know the metal bonding automotive epoxy is conductive. But... JMF is right that epoxy is what the better PCB's are made of so the general purpose stuff should be fine. Or is their a specific type or brand of epoxy that is used for electronics?

[tedmich]

just nothing with fillers typically, so any decent clear epoxy works well.

[nevetslab]

3M copper foil is good stuff, although adhesive is conductive so FR4 has to be pristine (no carbon traces!)

In that application of the 3M copper foil, there wasn't any deep burns from burning open the P/S trace. But, even though I had thoroughly cleaned the board before laying down the replacement foil, I never even thought about the conductivity of the adhesive they use on that foil. No longer have my Electrometer (for measuring up into the tera-ohm range), so I'll have to see what I can use for checking that. Good point!