Homebrew Circuit Boards: Methods? Supplies?
ard at p850ug1.demon.co.uk
Wed Sep 14 17:48:17 CDT 2005
> Developer and stripper are not etchant. After applying and exposing
> photoresist, one uses developer to remove the unexposed (or exposed
> for positive) photoresist without affecting the exposed (or
> unexposed) photoresist. After etching the excess copper away with an
> etchant, the polymerized photoresist is still present on the
> protected copper traces and must be removed using a stripper.
Most photoresists can be 'soldered through' so it's not necessary to
strip them. On the other hand, boards look a lot better if you do strip...
The method I've always used is to etch the board as usual, wash it, then
give it another (longer-than-normal) UV exposure with no artwork -- thus
'fogging' the remaining resist. Then pop it back in the developer and it
will all strip off nicely. Remember on most photoresist boards, the bits
that are exposed to UV are the bits you want to etch away (the artwork is
black for the traces, etc), so the resist that's been exposed is the
stuff that comes off.
> So, when using a photoresist system, one needs developer, etchant and
> stripper. However, I suspect that the stripper, at least, may be
> some commonly available chemical such as acetone. And I believe that
> Tony mentioned that developer is usually just a strong alkalai.
It's actally not _that_ strong. Strong enough to feel 'soapy' (it
hydrolyses the fats in your fingers), but not strong enough to cause an
alkali burn in my experience.
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