Hi Dave:

The short answer to your questions about using Sodium Chloride and/or Sodium
Chlorate in Cupric Chloride is "it depends".   I have some understanding of
the subject based on a study of the chemistry of the reaction, argueably one
of the smartest guys around on the subject is Don Ball, of Atotech, State
College, PA.  Don has actually done significant amount of experimental work
on the subject, and perhaps part of why I think he is so smart is that the
conclusions he arrived at by experimental work agree with my conclusions
based on theoretical considerations only.

The long and short of it is summed up in some papers that Don has written,
and copies are available from him, if you have enough clout, i.e., are a
customer potential.

Part of the answer though depends on the method of control that you are
using.  If you use the ideal combination of ORP, Baume', and acidity by
conductivity, then Hydrogen Peroxide and HCl are as good as it gets.  ANYTIME
you use Sodium salts to replenish, you will be forming Sodium Chloride as
by-product, and this will to some extent lower the maximum Baume' that you
can run the etcher, and potentially slow your etch rate.

Many years ago, one of the colorimetric controllers REQUIRED the use of
Sodium Chloride, and this, along with the use of Sodium Chlorate was promoted
as being safer, as it was less prone to Chlorine gas release.  It became
quite popular for that reason, as well as the fact that it was consistent in
its etch speed.  Unfortunately, it was also SLOW, and actually resulted in
Cupric Chloride actually getting a worse rap than deserved in terms of etch
rate.

All around, from what I am seeing in the industry, I would recommend staying
away from Sodium Chloride completely, and if you are successful in using
Hydrogen Peroxide, stay with it, changing to Sodium Chlorate will not help,
and may hurt.

The key issue to optimizing Cupric Chloride etchant is to get good control of
all the variables, and stick to Don Ball's recommended parameters.

Rudy Sedlak
RD Chemical Company

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To subscribe/unsubscribe send a message <to: [log in to unmask]>   *
* with <subject: subscribe/unsubscribe> and no text in the body.          *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************