[PCB_FORUM] Re: mysterious via shifting

Ed,
I've seen this problem occasionally when using "Fanout by Pick".  Seems 
like it happens to some bga's but not all. Cadence was unable to reproduce 
this problem. 
Don ...........................




Ed Caldwell <Ed.Caldwell@xxxxxxxxxx> 
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05/19/2006 08:10 AM
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Subject
[PCB_FORUM] mysterious via shifting







Anyone experience a mysterious shifting of vias in Allegro 15.2 s126 
(v15-2-51EU) (12/14/2005) i86... ? 

The design is in mils to 2 decimal places. The vias are in a 0.8 mm BGA 
(spaced at 31.50 mils apart). Somehow the group of vias within the 
rectangle pictured below shifted by 0.10 mils sometime during my edits - 
cause unknown... 



It is important to note that I did not change the database resolution - it 
has remained (mils to two decimal places). The only thing I changed was 
the routing grid which I switched between 25 mils, 5 mils and 0.1 mils as 
I was working in different areas of the layout and I was not working in 
the area where the vias shifted. 

Puzzl_Ed 

Ed Caldwell 
Electronic Design Services, LLC 
Canton, GA - USA

JPEG image

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