Rick,
The best method to eliminate shorts is to perform "root causes analysis".  In 
other words identify where the short occurred.  There are three primary tools 
used today: CAM Design Analysis, Automatic Optical Inspection, and Electrical 
Test.  These may be obvious but are the best tools today to ensure high yields.

A Design Analysis program can verify netlists and summarize design spacing 
values.  An optical inspection systems can optically compare the bare board 
against the orignal design and highlight in-process defects.  This tool can be
used throughout the process to inspect: the master phototool, the working photo-
tool, the developed resist image, and the post etch panel.  As the final 
gateway, electrical test is used to prevent any board with a short being sent  
to a customer.  Using these tools can help eliminate defects only if corrective 
action is taken to eliminate the cause of the defect.

George Murray
Gerber Systems


Rick wrote:
> I have been tasked to eliminate the defect of shorts on PWB's.  Other than the 
> obvious etch defects, what are some causes of shorts that other companies have 
> seen ?  Could the raw material be part of the problem ?  Could the defect be 
> "buried via" related ?  I would appreciate any inputs or thoughts on the 
> subject.
> 
> Thanks in advance,
> 
> Rick Haynes
> Process Engineer
> Texas Instruments
> e-mail   [log in to unmask]
> phone    512/250-7823 
> 
>