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Subject: Re: [Homebrew_PCBs] Re: Sodium Carbonate!

From: Adam Seychell <a_seychell@...>
Date: 2008-02-19

Andrew wrote:
>
>
> > Lots of people wrote:
> >
> > ...ABOUT SODIUM CARBONATE
>
> Does this dry film resist people are
> playing with not develop under sodium
> silicate?
Correct.
>
> The pre-sensitised boards I use prefer
> sodium silicate over other developing
> chemicals.

Is that a 'positive' (exposed areas wash away in developer) resit ?

The negative dry film resist must be developed in Na2CO3 and should be
%0.9 to %1.1 concentration, at 25 to 35 deg C. Interesting, high
concentrations (>%10) actually slow down the development process.
The very high pH of sodium silicate will strip negative film right off
the board. You use NaOH at %1~%10 to strip it off board.