Homebrew PCBs

I learned something new today.  This is the second time I used CuCl2 to etch
circuit boards.  The first time it was a fresh batch of 15% HCl + 3% H202 in
a 1:1 ratio.  This worked very well.  I brought out the same batch again
several weeks later.  Since, it was stored in a clear container, all of the
H2O2 was gone due to light exposure.  I didn't think it was a problem since
there was no brown CuCl present.  However, what I did not know is that the
board builds up a layer of CuCl over the board.  This layer is insoluble and
prevents the board from etching further.  It sat in the tank for almost the
whole day because I could not find my H2O2, and it was just a scratch test
anyhow.  It still had not etched.  I finally found my peroxide.  I tossed a
little in and it finished in 5 minutes.  So I guess one needs a shot of
peroxide if an aerator is not used.  One would guess that it would need to
be evaporated to keep the solution strong if one was adding peroxide every
time.  Too bad that I couldn't add Cu (II) Perchlorate or something to keep
the Cu+ oxidized to Cu++.  This would keep the solution from getting dilute.

Chris KQ6UP


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