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June 2006

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Subject:
From:
John Burke <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Burke <[log in to unmask]>
Date:
Mon, 12 Jun 2006 16:23:02 -0700
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That’s funny, most people were wondering why Monday afternoon was so far
from Friday looking forwards and such a short time ago looking
back........and the balance of the group was wondering whether they could
get away from their desks to catch the end of happy hour................8-)

I am sure the group will give you a serious answer, I am just working up for
Friday...........8- )

John

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Adam Seychell
Sent: Monday, June 12, 2006 4:03 PM
To: [log in to unmask]
Subject: [TN] cuprous ions in ammoniacal chloride etching

I am wondering if there is a simple test for cuprous ions in ammoniacal 
chloride alkaline etching, and thus determine when to increases or 
decrease the air ventilation intake of the etching machine. I am brewing 
my own chemistry based on typical operating parameters of ammoniacal 
chloride etchants.

Copper   2 ~ 2.5 Molar
Chloride  4.5 ~ 5 Molar
pH      8.0 ~ 8.6
Temp.   40 ~ 45 °C

I discovered just like with acid cupric chloride etching, that when the 
cuprous content reaches to even small concentrations then the etch rate 
is severely affected. In the lab, I tested as little as 5g/L of 
dissolved copper in the cuprous state will slow etch rate, and at 10 g/L 
it becomes virtually a stand still. For acid copper chloride etchants, 
the loss of its bright green color is a quick indicator of cuprous ions 
being present, and even 0.5 g/L will show beginnings of color change. 
However in alkaline etching the cuprous ions do not appear visible or 
change the solution color. I have heard about ORP (oxidation-reduction 
potential) probes used in acid cupric chloride machines. Can these same 
probes be used in ammoniacal chloride etchants ?

My chemistry is a bit poor, although I'm wondering if is possible to 
make such a probe, using a standard reference electrode (e.g Ag/AgCl ) 
and a piece of copper wire as the indicator electrode.


Adam Seychell

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