Repairing PCB Substrate Damage?

[Rofflesaur]

What's recommended for repairing holes and burns in PCBs? I've attached a photo below of the kind of stuff I'm dealing with. While it's not actually necessary, and the damaged traces will be replaced with jumper wire, I think leaving it looking like this can be slightly unprofessional. Is there any type of filler compound for this purpose? Perhaps green epoxy, or some kind of epoxy with color added maybe?

[TiN]

Cut out black charcoal area and make patch PCB to restore connections. Black charcoal is conductive/leaky, so whatever you do, you must remove it all. 

[T3sl4co1l]

Yes, but I don't know what compounds are intended for the purpose, aside from UV cure soldermask, which you can get.  (And, I guess, will need to fix the sanded-down soldermask here! )  If nothing else, a bunch of that goo, maybe with some chopped fiber blended in, would probably do well.

I know even multilayer PCBs can be repaired in this way, just a matter of how much time you're willing to spend fixing something to mil standards.

Tim

[Armadillo]

Looking at the LDO LM2940, I would say its the DC power supply region as in contrast to RF or oscillator circuits where you ought to be more concerned.

The "carbon" should be lightly sand away but this also breaks the hard layer and may expose the lower fiber layers to moisture absorption and hence more current leakage.

Since FR4 is essentially compressed fibrous reinforced epoxy, I would;
0. Lightly sand the carbon away then clean with IPA
1. repair the vias [if damaged] with thru-hole sleeves. then repair tracks with copper foil tape
2. brush thin layer of epoxy on top [only for deep crater sanded areas]. Then after it dried,
3. brush the UV green oil solder mask to the areas and where the tracks are exposed.

 

[Teledog]

I agree with Armadillo.

Personally I'd use a dremel/rotary tool with a burr to grind out the burned area, assuming it's NOT a multilayer board
Wear a mask/goggles (imagine crazed dentist?) 
Fill with epoxy - they do have plastic/glass filler powder at some plastics distributors.

I've never bothered with coloring it..the customer generally knows there was a major problem..why try to conceal it?
If they want it perfect, buy another board.

And yes, replace the traces with jumper wires, yada, yada..
(looks like there was a well vapourized component there...not to mention the corroded traces leading up to it) 

[AllTheGearNoIdea]

Very Old but there is still a lot of really good information in these old pace video.

https://youtu.be/7o4ZWlG6mmo

[eliocor]

If not too charred, you can "clean" the PCB with the following fiberglass bristle pen:
https://uk.rs-online.com/web/p/pcb-cleaning-brushes/0514868
https://uk.rs-online.com/web/p/pcb-cleaning-brushes/0514874

very useful tool for PCB reworking: it can also be used to remove soldermask.

[wraper]

Remove all charred PCB material and restore all connections with bodge wires. It's a relatively small area and seems there are no components on it, therefore should be quiet straightforward to do. I don't think that filling the hole gives any advantage it this case, only makes the job more difficult.