Homebrew PCBs

morriso2002 wrote:
> Hi all,
> 
> I obtained some surplus PCB material recently which was pre-coated 
> with some sort of photo resist. The coating is red/orange coloured 
> and in poor condition. My question is, How can I get this stuff off? 
> I have tried acetone, alcohol, soap & water, citrus cleaner and 
> Shellite (a hydrocarbon based solvent) all to no or little avail.
> 
> Anybody recognise this stuff and know how to remove it?
> 
> Thanks,
> 
> Morris

Its most likely negative dry film resist. If so then room temp 3~5% NaOH 
will strip it off in a 5~10 minutes (no scrubbing as it will swell and 
just lift off the copper). You'll damage the copper removing it any 
other way. Most common solvents and household cleaners won't touch these 
photoresists once polymerised.