[PCB_FORUM] Re: mysterious via shifting
- From: Ed Caldwell <Ed.Caldwell@xxxxxxxxxx>
- To: icu-pcb-forum@xxxxxxxxxxxxx
- Date: Mon, 22 May 2006 09:39:25 -0400
Hi Patrick,
You are probably on the trail... I placed the vias in the BGA footprint in
mm (0.8mm). The shift is likely derived from the rounding to mils in the
tool which may have occurred when I experimented with the "Fanout By Pick"
command. I never ran fanout on the BGA, my experiment was on a bypass cap
for another IC. I also tried to add another decimal point to the database
but Allegro would only allow 2 for mils.
Oh the woes of unit conversion!
I was curious if anyone else had similar experience... I opted NOT to use
the "Fanout By Pick" command in the master copy and the 0.8mm BGA is
holding up so far.
Thanks for the input.
"westfeldt" <westfeldt_nbcd@xxxxxxxxx>
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[PCB_FORUM] Re: mysterious via shifting
I'm not sure when Allegro decides it has an unconnect, but if you fanned
out, copying at 31.5 mils, 5 copies gets you a .02mil error. I don't
really see how this is the mechanism for your problem, but you do have a
tiny error in your 31.5mils spacing, should be 31.496.
Patrick Westfeldt, Jr.
720-406-0887
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Ed Caldwell
Sent: Friday, May 19, 2006 6:11 AM
To: icu-pcb-forum@xxxxxxxxxxxxx
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
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