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Date: Mon, 12 Aug 1996 11:47:09 -0400
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Subject: Min. line width and spacing
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     TechNet's,
     
     
     What is currently the tightest line width and spacing which 
     can be done in high volume?
     
     What is the cost impact, if any, of going from 5/5 to 4/4 or 
     4/3 on a 4 layer, .020-.025 board in selected areas?
     
     What board processing steps are most affected?
     
     Are there ways of minimizing the impact?
     
     

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======== Fwd by: Tony King / N ========
Image and etching are the two processes most effected by the tight line and
space technology, though spacing is much more critical than line width to
the manufacturer. The best improvement to minimize the processing problems
is to minimize the locations where spacing is reduced.  In reviewing many
customer designs, I believe minimum space is programmed into the design
software and then used everywhere by that software. Tight spacing may not be
needed in 50%-75% of the design, but the program faithfully maintains this
spacing anyway.  The design therefore becomes much more difficult than
necessary. Manufacturers may have 4 mil capability for example, but success
will be much greater if the locations for problems are reduced. Cost will
obviously be based on the difficulty level of the design.  The key to
manufacturing is DFM, design for manufacture ability. Use the extremely
tight features only when/where necessary, not everywhere.

Tony King
Elexsys International Inc.
Nashua N.H.
603-886-0066
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