I have experienced uneven etching using CuCl too. I etch my boards horizontally facing up, and the etching happens from the edge to the center of the board, and takes about 30minutes to have an 8x6" board done. The end result is perfect and the traces look fine, although I'm a bit concerned about the time too. I think my mix needs more oxigen too.
Fp
www.tonepad.com
----- Original Message -----
From: grantfair2001
To: Homebrew_PCBs@yahoogroups.com
Sent: Sunday, May 04, 2003 9:59 PM
Subject: [Homebrew_PCBs] First pcb etched with CuCl
Even though my tank of etchant is far from the deep green color which
shows it is at an optimum, I decided to etch a small board tonight. I
hung it in the etchant above the aerator. (I drilled a hole in one
end and hung it from an insulated wire).
In about 25 minutes one half (the part closest to the etchant surface)
was etched clear. It took another 25 minutes to get the other half
clear. I finally had to hang it upside down to get it cleared. A
horizontal pcb holder is in the planning stages.
In the first 20 minutes or so, I noticed part of the copper on the PCB
was light grey in color. I suspect this was CuCl(I) because when I put
a small amount of green etchant from the tank lid on this area, it
disappeared. This also suggests that there is lots of CuCl(I) still in
solution.
I measured the pH again with indicator paper. The paper showed red (2)
after I emptied the second 4 litre jug of HCl into it a few days ago.
However, today it was 3 (or higher, if the the pH is higher yet and
the etchant is discoloring the indicator paper).
Although there is green etchant on the inner surface of the tank top,
a drop of tank etchant dropped on the same lid is dark brown. So a lot
of CuCl(I) needs to be converted. I am waiting for some fine bubble
diffuser hose. Unfortunately most fish farming is done on the east and
west coasts of Canada, and I am more or less in the middle between the
two.
So things are progressing, if slowly, I am learning about the CuCl
approach, and I have etched my first board. In spite of the long dunk
it looks just fine with all traces intact. Because I haven't had a
totally clear recipe to operate from, things have gone slowly. But I
hope my experience will make it easier for anyone who wants to use
this appraoch in the future.
Grant
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