Homebrew PCBs

On Mon, 27 Sep 2004 20:21:36 -0000, Phil <phil1960us@...> wrote:

> I mixed up a batch of HCl and H2O2 and got good etching (which was
> mostly from the HCl).  There were some bubbles but no chlorine gas.  I
> etched 6 double sided boards that were on average 20x20 CM in the
> first session.  The etchant turned the well described emerald green.
> 3 days later, I went to etch another board and got no (or r-e-a-l-l-y
> slow) progress.  I bubbled it for about 18 hrs total (with 2 airstones
> - lots of bubbles).  Still no etching.
>
> I got a hydrometer and the density is 1.075.  This is well below the
> 1.17 recommended by
> <http://users.rcn.com/rexa/Projects/CuCl_ech.html>.  From the HCl and
> H2O2 I put in, the s.g. should have been 1.029 so I assume that the
> difference, 0.046, is from the etched copper in the form of CuCl.  It
> appears I have too weak a cucl solution by about 1/4 but I'm not 100%
> sure about the chemistry here.  Everything I've read says that it
> doesn't take much copper at all so I'm a bit at a loss here.  I need
> to get pH measuring capability but the density is clearly wrong.
>
> Any suggestions for fixing?  The page mentioned above recommends CuCl
> salts which I have no idea where to get and probably shouldn't have to.
>
> I'm going to put a couple pieces of copper in over night to see if I
> can get more copper into solution but its not clear to me that will
> actually work.

Adding copper will not help much.
If you add H2O2, does it go? if not HCl is missing (it usually is bluish  
then).
Get the two-eyedroppers titration gear.
If there is copper, HCl, and H2O2 it must go.
My hydrometer shows about 1.16, and it does go without H2O2, though slow.
It takes a while before there is enough copper to go on it's own. H2O2 is  
so
cheap it isn't required to add any scrap copper.

ST

P.S.: i wonder if really none of you has a ultrasonic cleaner.
I'd like to know if toner is cleaned by it or not.