Testing to Gerber Extracted netlists proves the manufacturing process.

Testing To CAD netlists (IPC-D-356 standard) proves that layout and rout
from the CAD systems and manufacturing is correct.  

One of the problems testing with CAD data is that it doesn't always match,
2 of the most problem areas that I see are;

1.  Isolated 'GND's' where on a 'GND' plane there is a isolated 'GNDA' that
is either not totally split or is tied through a signal layer.  Since 'GND'
and 'GNDA' are considered separate nets when sorting the netlist this will
generate a short at test.

2.  Test points especially on BGA devices that have single point nets
(SPN's).   Typically there are matching vias to BGA pads and the CAD system
will call the via 'N/C' and the associated BGA pad 'N/C'.  This will
generate a short because they are connected.

Another disadvantage to CAD netlist testing is no Mid point optimization
and no Trace information for Computer Aided Repair for manufactures.  This
is due to where the netlist is generated from.  

If you need to verify the design off the CAD to the Gerber I would
recommend to do a CAD to Gerber Netlist Compare.  This can be accomplished
prior to releasing the PWB for manufacturing.  This is preferred.
Jeff Garland
Sales Engineer
Lavenir Technlogy, Inc.
603-431-6279
[log in to unmask]

----------
> From: Andy Wolf <[log in to unmask]>
> To: [log in to unmask]
> Subject: FAB: PWB electrical testing
> Date: Friday, April 18, 1997 10:11 AM
> 
> 
> Can anyone elaborate on the differences between testing
> PWBs to gerber data versus testing to customer-supplied
> netlists?
> 
> What are the advantages for the customer if he/she provides
> a netlist?
> 
> Is there a standard (or even commonly used) netlist format?
> 
> Thanks in advance,
> 
> Andy Wolf
> RMS Information Systems
> [log in to unmask]
> 
>
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