Corner of PCB burning/shorting

Hey all,

I have a PCB thats burning on one corner.

Its being fed 24v which is what it should be...
But each time i turn in on the board sparks about once every second on that corner and the led's on the board go out each time it sparks.

Its a very slow burn on the corner... not a once off bang..

As you can see its far away from any components...

Has anyone seen this before?

I feel like if i was to chop off that corner it would sold the issue...

I believe its a dual layer PCB.
A backlit photo shows the copper stops before the edge but the burnt bit is dark to the edge..
Is it possible once it shorted once it will continual to jump between the layers?
If I chop it off will it be enough to stop it from shorting?

Hi Russell, 10/10 for photos... what seems to be happening is the carbon from the arcing is producing further low ohm shorts , cutting the corner off should not do any damage as it looks like no components or tracks in that area. I would take a risk and take quite a lump off perhaps to within 2 mm of the hole plating ?

A tad worrying..... If you are getting sparks every second, then there is a capacitance build up... Is the power plane positive? If the capacitance isn't dealt with and you do cut the board down... Where will it go then!!

Never seen a fault like that before. Possibly caused by a copper whisker left when the board was cut in manufacture. You're lucky the bad bit is not close to other components. As granddad says, I'd hack a lump off, clean up any burrs and inspect under high magnification.

Russell Lewis said:

Its being fed 24v which is what it should be...

Click to expand...

and during the "sparking "

Tried cutting it.

Bingo,
Works great!

I guess once it arched it bridged and kept shorting from there on.

Fingers crossed it doesn't bridge again but it should be ok. Initially i cut a small bit off. The PCB started working again. then i forced a few sparks between the layers with a screw driver and it didn't bridge the two layers. Must have been a big surge that caused the fault in the first place..
So I cut some more off, filed it back (see photo)
If a few forced archs doesn't make it bridge again then it seems pretty solid..

Thanks all for the help

Nice. Still looks burnt right on the corner. I'd remove that bit.

This can often happen if you bring the copper planes/pours all the way to the edge of the PCB. You should always pull it back at least 15 mil (0.381mm) from the edge of the board to prevent the planes from shorting together.