[PCB_FORUM] Re: Planes: Negative vs. Positive?

Group:
I've never used negative planes, even if when the files were too big we used two floppies to store files.
 
I haven't been able to set-up the auto router using positive plane. The gnd pins always routed as a net.

This may be easier now. Haven't tried lately.
Sam

-----Original Message-----
From: gnieski_mike@xxxxxxx
To: icu-pcb-forum@xxxxxxxxxxxxx
Sent: Thu, 19 Jul 2007 11:18 am
Subject: [PCB_FORUM] Re: Planes: Negative vs. Positive?

        Isnt the beauty of the positive planes the fact that you have multiple choices of control not only at the parameter (local and
        global shape parameters) level, but at the pin/via level with properties. For pins/vias you can control spoke width and direction,
        oversize on the gap clearances and whether you want a void per drc, anti-pad or no void. 8 diiferent parameters for a pin.
 
        thanks,
        Mike Gnieski
 

From: icu-pcb-forum-bounce@xxxxxxxxxxxxx [mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Austin Franklin
Sent: Thursday, July 19, 2007 2:06 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Planes: Negative vs. Positive?

Hi Gary,
 
No, I'm not kidding.  I wasn't aware that the two were determined by entirely different criteria.  To me, that is not intuitive, and certainly isn't the same with other tools I've used.  IMO, they both should give the same results ultimately, or at least should be able to be configured so that they do.  But, thanks for the explanation.  I use positive planes now, I used negatives in the past, but in other tools I used them in, they didn't DRC correctly.
 
Regards,
 
Austin
 
-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx [mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx]On Behalf Of Macindoe, Gary
Sent: Thursday, July 19, 2007 1:52 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Planes: Negative vs. Positive?

You’re kidding, right Austin?
 
With negative planes, the clearance is determined by the padstack and with positive planes, the clearance is determined by the shape parameters (changeable on a shape by shape basis).
 
 
Gary E. MacIndoe
PCB Design Engineer
Fort Collins, Colorado
amd.com
gary.macindoe@xxxxxxx
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx [mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Austin Franklin
Sent: Thursday, July 19, 2007 11:20 AM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Planes: Negative vs. Positive?
 
Hi George,
 
Why would the openings around pins be any different between positive and negative planes?
 
Regards,
 
Austin
-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx [mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx]On Behalf Of george.h.patrick@xxxxxxxxxxxxxx
Sent: Thursday, July 19, 2007 12:58 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Planes: Negative vs. Positive?
 
Positive plane layers have a much larger opening around pins.  This is fine if you are doing low to medium speed boards (roughly < 200 MHz clock speed), but on high-speed designs the impedance discontinuities created by the huge opening around the pins are significantly greater on a positive plane than on a negative plane.
 
We use negative planes for this reason, and we always use Valor to check our artworks to make sure we haven't shot ourselves in the foot :)
 
YMMV
 
--
George Patrick
Tektronix, Inc.
Central Engineering, EDS Applications Support
P.O. Box 500, M/S 39-512
Beaverton, OR 97077-0001
Å 503-627-5272 (voice)     Æ 503-627-5587 (fax)
http://www.tektronix.com    http://www.pcb-designer.com
 
"Off-Grid and Proud of it!"
-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx [mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Bob McCreight
Sent: Thursday, July 19, 2007 06:51
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Planes: Negative vs. Positive?
The design team I work with is split one which to use, negative or  positive planes.
What are the pros and cons of each? What do most people prefer to  work with?
We are currently using 15.5.1 but evaluating 16.x for possible future  migration.
  
  Thanks for your feedback.
  
  Bob McCreight, C.I.D.

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