First off, regarding any reaction that generates or used chlorine gas it
requires a thorough understanding of the operation and chemistry of the
system. Only personnel with proper equipment and that definitely includes
very good ventilation with a fume scrubber on the ventilation system, and
more importantly a good understanding should attempt to do this as the
reaction basically involves the addition to the solution of chlorine gas or
creation of chlorine gas in the solution and you do not want this nasty
chemical in your breathing area Chlorine gas really can kill you, and if it
does not get you when you breath it can cause chemical pneumonia. A good
chlorine detection and alarm system should also be installed.
I would suggest you talk to your etcher machine supplier, or if you are just
contemplating this talk to Marshal Gurian at ASI 602-276-7361 (who makes
etching systems)as they have a lot of experience.
Over the years there have been a number of units to add the HCl and sodium
chlorate starting with Vis-U-Etch or the Chemcut colormetric solution color
monitoring system. ORP overcomes a problem that all the colormetric systems
had at one time or another of salts plugging the line to the colormetric
cell but even with it some maintenance is required as the chemistry is
corrosive, it does not know which copper you want to keep (the system
wiring) and that which you want to remove ( the excess copper on the board).
I have used both chlorine gas and chlorate/HCL and for ease of operation
the chlorate is IMO easier to operate. Opening the chlorine gas cylinders
requires a vacuum which means you need an injector large enough to generate
a good vacuum.
Here are some literature references you might want to look at.
Steady State Etching of Copper-Cupric Chloride, Sodium Chloride Baths,
L.Missel and F.D.Murphy, Metal Finishing, December 1969 p47-52,58.
Steady State Regenerative Etching: A Technology Review, Marshal Gurian,
ASI, Electronic Packaging and Production July 1978, p32-36.
Etchant Fountain of Youth? Circuits Manufacturing, November 1976, p
72-73.
I also think I heard that chlorine gas cylinders must now be in a enclosure
that completely contains and neutralizes all gas if their is any accidental
releases and you may want to ask about whether this is a requirement.
[log in to unmask]
The opinions expressed here are those of Ted Edwards and may or may not
reflect the opinion of my employer.
----------
From: Ted Stern
To: [log in to unmask]
Subject: FAB: Cupric chloride regeneration with sodium chlorate
Date: Wednesday, January 22, 1997 1:07PM
I was wondering if any of you fabricators out there would provide me
with information on the following:
a. method of regerating CuCl2 final etch with sodium chlorate,
including sodium chlorate concentration, HCl additions, rate of
additions, equipment used;
b. method of automated control (ie. ORP control versus colormetric
control); and
c. opinions on the ease of use (or lack thereof) of sodium chlorate
versus chlorine gas;
Thanks for you help!
Ted Stern
612-479-6525
[log in to unmask]
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