you are absolutely correct Mark. let your PCB suppliers adjust the gerber 
 to meet your finished line specs. everyone has a little different etch 
 factor.


______________________________ Reply Separator _________________________________
Subject: PWB artwork
Author:  [log in to unmask] at corp
Date:    11/16/95 4:36 PM


I have a question for the Printed circuit Manufacturers. First a little 
history. The PWB design group in my company adjusts the artwork (track width & 
Spacing) to conpensate for the loss of copper during the etching process. I 
have a concern that the etching depends on each PWB manufacturers process and 
that each manufacturer would like to make his (or her) own adjustments to the 
artwork / gerber data to achieve the final engineering requirements Which we 
also specify on the drawing (Example shown below)
 
     Minimum conductor spacing:
     External layers to be .008 inch after plating and fusing or solder 
     coating. Internal layers to be .008 after etching.
 
     Minimum conductor width:
     External layers to be .010 inch after plating and fusing or solder 
     coating. internal layers to be .010 inch after etching.)
 
I feel that we are over controlling the PWB manufacturers. Is this true? Please 
provide feedback. Thanh you in advance.
 
 
                            Mark Foster
                            Address: [log in to unmask]