Homebrew PCBs

On Fri, 2003-05-16 at 12:55, grantfair2001 wrote:
<snip>
> 
> By the way, ammonia does react with copper, according to my AMEX, "Do
> not use with copper or aluminum". I imagine brief contact with dilute
> solutions *might* be ok but I would check with a chemist first to see
> what risks if any, exist for human health.
> 
  Using off-the-shelf generic ammonia works wonderfully for stripping
boards coated with dry-film resist.  However, as you mentioned it does
react with copper, although rather slowly.  I've never noticed any
problems with corrosion/discoloration until yesterday when I left a
couple boards in it for over an hour.  At that point it had turned the
copper blueish gray in places and it was not fun having to scrub it
off.  Dry-film resist that has been "baked" too long (to fixate the
developed film) or been overexposed a lot takes a while to strip using
concentrated developer solution; ammonia will strip it in inside a
minute's time.

Larry