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Re: Etching copper type

I have not done any etching for this particular usage, but I can answer
more generally.  You can get a fairly deep etch with FeCl, though as you
take the copper away, it degrades the effectiveness of the etchant.
Also, in my experience, FeCl, on longer etches, gives a much more rough
cut, in the deep troughs, than do acids.  This is not so much of a
problem when you're printing with the surface (and it's no problem at
all when you're just removing a thin surface layer on a plastic or resin
pc board).  Some people say FeCl undercuts the resist more than other
acids.  My experience is the opposite, mostly because FeCl cuts slower
(unless you thin the acid way down).  And anyway, FeCl, though not the
nicest stuff in the world, is far less nasty to have around and to work
with than nitric acid.

As far as precision of line is concerned, that is mostly a product of
the means of applying or removing the resist.  Photoetch processes
should be more than adequate (I have almost no experience with them
personally, but know the results).  Position the piece to be etched
carefully, not far beneath the surface, and the same depth all over.  As
long as you don't have too much copper already suspended in your
etchant, it should etch evenly enough.  You you can speed it up by
heating the stuff up before you put the piece in (DON'T boil it).


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