Re: gEDA-user: home-made dremel "drill press"

[Tomaz Solc <tomaz.solc@xxxxxxxxxx>]

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Hi

> I'm thinking of switching from toner transfer to photomask.  Then, I 
> can drill the board first and use the holes to line up the print.

I've been using masks almost exclusively to make my boards.

I don't think that drilling holes for components before exposure is a
good idea. If you drill before applying the photoresist, you will get
uneven thickness around the holes due to surface tension.

On the other hand if you drill the board when the photoresist is already
there you risk damaging it. At least the "positiv 20" I'm using is very
soft even when dried with hot air and you can easily scratch it (when
etching double sided boards I stick little bumps on the board to protect
its surface from the bottom of the container with acid)

What I do is drill two pilot holes before applying the photoresist in
the unusable border around the circuit and use them to align the masks
before exposure. It's not perfect though and I have experimented a bit
with some other techniques (for example aligning the top and bottom
masks before slipping the coated board between them).

Best regards
Tomaz
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