How to avoid a carbon formation on PCB?

[gravi]

Hi,
We have designed an PCB and tested it's performance in lab and tested in field for about 2 years and found Every functionality OK but we have observed some kind of dust black in colour looks like carbon is formed on PCB will this affect the performance of the PCB in long run. Can Anyone suggest me to avoid this carbon formation on PCB.


With Regard's,
Ravi Kumar

 

[sabeti_1990]

Re: Carbon on PCB

hi
if be possible give a picture from it
have your pcb a silk screen on the top of board ?
it may be because of your soldering wire

 

[ASIC]

Carbon on PCB

where would this "carbon" come from?

 

[pranam77]

Re: Carbon on PCB

Carbon formation on PCB is not possible. It may be a copper layer oxidized appearing like black spots. If a photo is given will try to guess more about that.

 

[tanuki]

Re: Carbon on PCB

Copper is oxidized to a black finish to improve laminate adhesion.

If it's copper oxide, dilute sulfuric acid will dissolve the particles, making the resulting solution blue ( or blue tinted, if there are enough particles.).

If it's carbon, even concentrated sulfuric acid will not dissolve it. However it can be burned rather easily, where as any metal oxides will be unaffected but high temperatures.

More info: **broken link removed**