For low layers count PCBs - leave all the non-functional pads: the
Z-axis distance between the layers is big, and the NFPs are important to
strengthen the via barrels.

For high layers count PCB (say - above 8 layers) - the NFPs can be
selectively removed. We allow manufacturers to remove the NFPs in every
other layer - but only in power layers: removal of the NFPs here shrink
the clearance around the drilling, and by this enhances the width of the
metal residues between the holes. In case of small pitch BGA these
residues are very small...

Ofer Cohen
Seabridge - a Siemens company

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jeffrey Bush
Sent: Wednesday, February 09, 2005 17:13
To: [log in to unmask]
Subject: Re: [TN] Removal of Non-functional pads

The more pads the more hole quality suffers from drilling.  Also the
thermal/mechanics of a PTH with pads on more layer than needed is
affected adversely.

Non-functional pads should be removed.

Jeffrey Bush
Director, Quality Assurance and Technical Support

VERMONT CIRCUITS INCORPORATED
  76 Technology Drive - POB 1890
    Brattleboro, Vermont 05302
      Voice: 802.257.4571.21 Fax: 802.257.0011
           http://www.vtcircuits.com
 

-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]] 
Sent: Wednesday, February 09, 2005 9:54 AM
To: [log in to unmask]
Subject: Re: [TN] Removal of Non-functional pads

I have always considered non-funct. pads as being desirable, because
they help compress the prepreg layes into a compact mass which would
reduce nasties like CAFs etc. At the same time, the extra copper keeps
the drill bit cooler by conducting more heat away.

Brian

Pete menuez wrote:
> Can someone explain the advantage of removing non-functional pads on
> innerlayers? We are contemplating adding non-functional pads to our
designs
> but want to understand the impact if we do.
>
> Thanks
>
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