Dear Ms. Xiao:

To achieve the level of etching performance you specified will require tight control of
both chemical and mechanical variables.  In addition to ORP, S.G., conductivity (acid
N) as a method of chemical control, I believe it is worth your while to examine
turbidimetric control.  (Visit http://www.oxfordvue.com.)  In terms of cupric chloride
bath chemistry, a comparison of the operating parameters between ORP and turbidimetric
methods of control is as follows:

           Method of Control                ORP                Turbidimetric

                 Cu (total), g/L             150-180                  210-235
                   HCl, N                        1 - 3                   0.02-0.04
                   Baume'                      29 - 31                    38-40

As there are varying theories and opinions regarding a comparison of the performance of
these two processes (in terms of edge factor, etching speed, periodic maintenance
required, breadth of operating window (margin for error), safety, etc.; it is
recommended you ask for, and contact references from several users.

Regarding mechanical variables, it is recommend you process sample panels in equipment
as closely resembling your equipment as possible; and preferably equipment operating
both methods of chemical control.  When evaluating process equipment, be sure to
document nozzle type, spray pattern, distance of nozzle to the surface of the panel,
spray pressure, estimated solution throughput through the manifold (hp of manifold
pump), number of sumps and means of sump recirculation, etc.  Variables such as number
of guide rollers and number of guide wheels per roller can have a larger impact than
one would anticipate on etching performance, hence be as detailed as possible.

Good luck and feel free to contact me if you have additional questions.

Regards,
Ted Stern
877-272-1272

Shirley Xiao wrote:

> Dear Technetters:
>   Does anyone has experience to get 7 mil/7mil line
> width/gap out of 3 OZ copper foil by inner layer
> etching (CuCl2, HCL, H2O2)? Is there any concerns
> about undercut or peel strength?
>  How about the etch factor for CuCl2 etching? Can we
> get 3?
>
> Thanks and best regards
> Shirley
>
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