We are having a significant problem with quickturn cards coming in 
overetched, and we're trying to understand some things about the process of 
etching.
     One question that has come up is:  Is it possible for etching to be 
greater in one area of the card over another? If so, how is this possible, 
and what are the design considerations for this?
     Some here contend that every feature should etch down by the same 
nominal amount, say .002 inch, whether the feature is an .008 trace or a 
large ground plane, since the whole PCB is exposed to etchant at the same 
time.  Is there fault in this thinking?
     Thanks in advance.

Jim Ennis
Adtran Inc
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