Bob,

      Here are a couple of things you may want to consider:

 

1) If you need capture pads (regular positive pads) on a plane layer for
blind or buried vias that do not connect to that plane, you must use a
positive plane layer in order to have regular pads.

 

2) When you use positive planes, you must use a clearance void (or
anti-pad) diameter large enough to clear the regular pad of a plated
hole (unless you set up complicated and exotic padstack definitions). On
extremely dense boards or areas such as a .5mm BGA, these clearances may
starve power connections or degrade signal integrity. Negative planes
allow you to effectively shrink the anti-pad size because you only have
to provide clearance around the plated drill hole itself, not the drill
and the regular pad. In these instances, neg planes could improve signal
return current paths on your planes and provide more current carrying
capacity of the copper webs between vias in dense areas.

 

Regards, 

Patrick Courtade CID

Dallas CAD Manager

7Core

Voice:  214-347-4274

Cell:  214-437-5851

<http://www.7core.biz/> www.7core.biz <http://www.7core.biz/> 

 

      

 

-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Silicon Valley Chapter - IPC
Sent: Thursday, July 19, 2007 8:35 AM
To: [log in to unmask]
Subject: [DC] Planes: Negative vs. Paositive?

 

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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