> >
> > Also, I would need developer, and I think that is.
> Sodium hydroxide, about 12g/L. Two teaspoons is about right.
Proprietry developers (supposedly safer to handle than NaOH) are also
available and some boards specify different strengths for this. For a lot
of boards the rate is 50g/l but some boards I have been using recently
require only 25g/l. As I'm not sure how these strengths relate to NaOH I
now use the proprietry developer.
I think I used to use 7g/l NaOH. If you get it too strong it will strip
/all/ the resist off the board, exposed or not.
> > After printing in trasparent paper, I need to fix it to the board in a
> > dark room (using tape maybe?) and then put it into the light box for 5
> > or 10 minutes.
> You don't need a darkroom.
Best avoiding strong sunlight though, I think.
> I just put the transparency in contact with the board (print side
> down), make sure it is positioned correctly, and put the board and
> transparency on the glass. I then put a heavy book on top of the board
> to ensure it is pressed down. You have to experiment to get the correct
> exposure, it mainly depends on the distance from the lamps. I use 13
> minutes.
These days I find as little as three minutes with my present light box.
> >
> > Then go out, put it in developer a few minutes more, and then ferric
> > clorhidre.
> That's right. The unexposed resist goes purple in the developer so you
> can take it out and rinse it when all the purple has gone.
??
The purple, or dark green, or whatever other colour dye they use,
represents the image, the final PCB layout, so should be clearly visible
at the end of development.
I use an ordinary photographic dish and find that brushing gently over the
board with an ordinary paintbrush during development seems to help the
process along
> >
> > More or less, is that it?
> Yes
> > Developer liquid can be stored and reused many times?
NaOH seems to last fairly well but the propietry developer does not - a
couple of days, perhaps, in a sealed bottle.
Stuart