Sarah,
You can controll the pH in the etcher by opening of the vent ( when it is
going up) or by additions of ammonia ( when pH is dropping).Have in mind two
possible problems:
1) ventilation is a essential part of etching ( oxidetion from Cu+1 to Cu+2)
since this is the only source of oxygen.Some replacement of air is vital
regardless of pH
2)the weakest point of automatic control based on pH is the pH itself.You
have to look for very stable pH electrodes and very good cleaning and
calibration procedures.Most of industrial pH meter can shift by 0.2-0.3 pH
within hours.Such deviation will probably ruin your process.
Good luck
Edward Szpruch
Eltek , process engineering
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel  ++972 3 9305050 , Fax  ++972 3 9309581
e-mail   [log in to unmask]

> -----Original Message-----
> From: Sarah Boutwell [SMTP:[log in to unmask]]
> Sent: ה אוגוסט 26 1999 18:44
> To:   [log in to unmask]
> Subject:      [TN] etching pH controllers
> 
> Hello everybody
> I would like to add a pH control system to my ammoniacal copper etcher
> that would open and close a vent based on the pH of the bath.  Does anyone
> know of a company that supply me with something like that?
> Thanks
> 
> 
> Sarah Boutwell
> Manufacturing Engineer
> Johnson Matthey Advanced Circuits
> [log in to unmask]
> 612-684-5079
> 
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