Greetings Wayne,
I realized that I did not really respond fully to your message of yesterday.
You are right in your thinking and observations based on current best
practices and it is a detail that should be corrected/clarified/brought current. I
was recounting experiences that likely don't hold well today with current
chemistry and equipment.
My experience was primarily been with copper ammonia alkaline etchants
beginning in the early 1970s and etching equipment not up to today's quality.
We observed occasions where the sharp corners when fluid exchange was not
good and copper etching irregular where this occurred.
One of the curious things about alkaline etch chemistry is that the etch
rate of the chemistry increases with metal concentration which is the genesis of
the suggestion based on the observations at the time.
As you suggest, design tools are not likely to make acute angles without
permission. Again, the more important reason today remains the one mentioned
earlier and related to simple mechanical issues and electrical performance.
A very good article on alkaline etch by Karl Deitz can be found at the
following link if you have interest.
_http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/techtalk/TT02
05.pdf#search=%22%22etch%20rate%22%20%22ammonium%20chloride%22%22_
(http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/techtalk/TT0205.pdf#sear
ch=""etch%20rate"%20"ammonium%20chloride"")
Thanks for your observations and comments.
Kind regards,
Joe
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