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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.

Ted.A.Edwards@CAS.honeywell.com
The opinions expressed here are those of Ted Edwards and may or may not reflect the opinion of my employer.

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--BeyondBoundary_2_Thu_Oct_23_08:57:34_1997__4823
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Hi Jack,

I’m sure by now you have received many opinions on the Cupric etch & regeneration schemes, but I must put in my two cents worth. I have utilized both the HCl/Peroxide and the Sodium Chlorate/HCl systems. I worked extensively with the Peroxide system at TI, in both the etching and the regeneration system. We utilized the Venturi Injection system, mentioned by others for injecting the peroxide, but found, for our system, that the timing sequence would not allow enough HCl to be injected. We, therefore injected the HCl directly into the sump. We controlled the Normality of the HCl with a Rosemount Conductivity controller and the Oxidation Potential with an ORP sensor/controller. The ORP must be controlled within a certain range to prevent Cl gas from evolving as well as obtaining a stable etch rate. To me this was the better system. While working at Sandia Natl Labs, we utilized the Sodium chlorate system. I was informed by Steve Wall at Chemcut ( now Ato-tech) that the Sodium Chlorate/NaCl system might wear on the nozzles more than the other system. The only explanition I can come up with for the increased wear would be that there might be some undisolved solids present. At Sandia, the shop was smalland could not afford the extensive piping for the plumbed HCl and Peroxide, therefore the choice to utilize Sodium Chlorate was taken. We utilized HCl in lieu of the NaCl to avoid undisolved solids and wear on the nozzles. The control was much the same as that at TI and the system worked very well. A word of caution about Sodium Chlorate, is that as the Dry salt it is percussion sensitive, being a strong oxidizer, it can detonate on jarring or pressure ( if it is in conjunction with flammables watch out). This is not a problem when it is in solution. In the small shop at Sandia, both the Chlorate and the HCl were Injected into the sump, from small drums via positive displacement pumps. An excellent resource for the Cupric System is Don Ball of Chemcut (now Ato-Tech). I'm not sure he is still with them. He has written numerous articles on the system. In no way would I try the CL regeneration system, the risk is just too great in my opinion. If I can be of further assistance you might want to contact me off line.

Good luck, Les Connally
HYPERLINK mailto:X1Les@TI.com X1Les@TI.com