Jack Evans wrote:-
>We are in the process building a new inner layer facility and are
>considering using Cupric Chloride etchant. Does anyone out their have
>any suggestion on the safest, cleanest way to control the process ?

There is a lot of information on this at
http://www.pcbfab.com/ineretch.htm
which, thanks to Rudy Sedlak, is extremely helpful.

I have recent experience of putting in this process and opted for
Hydrogen Peroxide as the oxidiser. If I used sodium chlorate, the
company which recovers the spent etchant could not plate out the copper
so easily. Disposal costs are covered by the value of copper reclaimed.

It is very economical to run at around 150 gms/litre of copper take up.
HCl is kept at 60-65 gms/litre, the Redox potential is set to keep the
cuprous between 1 and 2 gms/litre (as long as there is some cuprous
present, you won't evolve chlorine gas).

It is very clean and safe as long as you avoid mixing peroxide and
hydrochloric acid so procedures to prevent this must be watertight.

We use redox potential to dose peroxide, conductivity to dose HCL, and
SG to dose water. Etch rates are very consistent and undercut minimal.

Good luck.
--
Paul Gould
[log in to unmask]
Isle of Wight,UK

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