[PCB_FORUM] Re: Dynamic Planes on Large Boards

Guess I'll chime in on this one too.
We use dynamic positive planes also.
 
I only work locally, never on the network.
I also have all scripts etc locally. I do however
use our symbol library located on the network.
But once all the parts are placed and updates are done I edit away
free from network servers going up and down.
 
I only use the round acute angles. I'm very afraid of forgetting something
when artwork creation time comes around. And I never rely on the software
to prompt me for these things. Burned too many times.
 
We also usually increase clearances on external planed areas. Although this
is not always doable if the external planes are used for impedance calculations.
I always try and add most voids to the plane manually (Yes I'm totally anal 
about
this stuff) but it does make the shapes very clean. I really don't know if it 
saves you any time,
in fact It probably increases the computing time don't you think? I'll trade 
here for a clean
area of copper. I have got burned really bad because of slivers and very thin 
solder resist 
because of relying on the software to do everything so I tend to try and help 
it out.
 
Regarding .4 it is a can of worms. Cadence has done a tremendous amount of
work making shapes better but in my opinion this still needs some work because 
of exactly what
you express. So much of a designer's time is spent editing designs after the 
planes are completed.
Moving them off board leaves vias used for stitching purposes totally 
disconnected from anything.
This can off course be a horrible mistake to make if the vias connect to some 
other plane as they are
all brought back onto the board. Like I said earlier, I still do not trust the 
software to keep the nets
associated to each and every via.
For these reason's I am more and more choosing to leave the shapes on the 
design. I just go to the Setup
>Drawing Options window, and DISABLE the Shapes, Dynamic Pour. Then when I go 
>for a quick walk
I'll update to smooth and do a db fix.
 
I have never understood why Cadence always says to process the planes at the 
end of the design.
(I'll keep my expletives to myself here) 
I have tried the Rough option and it does increase system response but it is 
still TOO SLOW for me.
Incidentally, our typical board size is 14 inches by 10 inches and either 14 
layers or 16 layers with wither
6 internal planes or 8 internal planes. And they are getting split two or three 
ways on several layers now
because of all the different voltages we use. You are probably doing at least 
this and probably worse.
So good luck to you.
 
Hopefully Cadence will see this and come up with some more super duper 
improvements. I really worry
about stitching type of vias not keeping their net association when moving all 
the planes off board. I know 
there is a ""keep net to via" type of selection but still do not trust it. We 
also have lots of older designs created
with 13.6 and 14.2 software and upgrading to 15.5 takes a fair amount of time.
 
You didn't mention which version of Allegro you are using? I think I read that 
15.5 offer some increased response
time for shape editing but can't be sure about this. Maybe some else knows for 
sure?
 
Let me know if you come up with any gems.
dave mattice
-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx]On Behalf Of Unruh Barry
Sent: Tuesday, August 15, 2006 12:56 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Dynamic Planes on Large Boards
 
All
      My apologies if this has already been covered on this forum.
 
     Does anyone have any tips for dealing with dynamic planes on large boards?
I like the features it offers but chews up too much memory.
 
These are some of the things I do to reduce processing time....
 
1. Work on a local disk rather than swapping across a network.
2. Use straight rather than round acute angles.
3. In the case of external planes... push out the clearances in order to 
minimize the complexity of the plane.
4. In the case of edits to a layer with an existing dynamic plane...
       Disable the dynamic shapes and move off to the side until the edits are 
done, then move back and change to smooth.
 
Maybe the rough mode has some benefits?
Any other methods?
 
Barry Unruh
Thomson Grass Valley

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