Homebrew PCBs

Malcolm Parker-Lisberg <mparkerlisberg@...> writes:
> Thanks for the link, so the speed is determined by presenting fresh
> etchant continuously. Any thoughts on what affects the undercutting?

Well, the metal is 2 mil thick, so you get 2 mil of undercutting.
Once you've started etching through, the sides of the hole are exposed
to etchant also.

I suspect undercutting can be reduced by preferentially etching
through rather than aside, such as a spray etcher or a float etch,
which simply removes the spent etchant in "that" direction more than
in the "other" directions.

Etching from both sides can, of course, cut undercutting in half.  If
you can align the two masks properly.