We have successfully added aqueous ammonia to our
etcher for many years. However, as others have pointed
out, adding aqueous ammonia will introduce water.
Some water is actually desireable for a small start &
stop operation in order to dilute the etchant and
therfore reduce the chloride level.  Too much will
introduce problems leadingn to sludging.  I would say
be cautious about adding more than  a liter or 2 per
day.
Peter Blokuis




--- "May William D (Dean) CNIN"
<[log in to unmask]> wrote:
> Due to the start/stop nature of our pcb shop I am
> looking to control the pH
> of an ammoniacal copper etcher using aqueous
> ammonia.  After the etcher has
> not been used for a couple of days to a week the pH
> has dropped somewhat.
>
> I would use a metering pump to add the ammonia to
> the sump of the etcher.
> Are there any concerns I should be aware of before
> setting the aqua ammonia
> up?  What grade of ammonia must I use so that I
> don't contaminate the
> etchant?  Can you add ammonia too fast to cause a
> problem?  Can you add too
> much over time?
>
> Are there other ways to accomplish the goal?  Is
> there a proper way to
> introduce anhydrous ammonia so that the solution can
> properly metabolize the
> anhydrous into the solution?  It seems to me that
> contact time with the
> anhydrous would need to be considered for it to do
> any good?
>
> Thanks for your consideration!
>
> Edward A. McAtee
> Crane Division, Naval Surface Warfare Center (NSWC
> Crane)
> Harnessing the Power of Technology for the
> Warfighter
> Code 6086, Bldg. 38
> 300 Highway 361
> Crane, IN 47522-5001
> Ph:  812.854.3892
> Fax:  812.854.1174
> Email:  [log in to unmask]
>
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