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1995

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Subject:
From:
Fred Paul <[log in to unmask]>
Reply To:
Date:
Wed, 31 May 1995 09:00:27 DST
Content-Type:
TEXT/PLAIN
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TEXT/PLAIN (44 lines)
My perception of the prevailing theory is that the inclusion of the 
nonfunctional pads strengthens and anchors the barrel of the hole to the MLB. 
I have never heard anyone discuss experiences that would support or 
contradict this theory.  Including them may be an advantage on designs where 
field repair is expected (Mil Spec requirements?).  We recommend that our 
internal customers (designers) exclude non-functional pads from internal 
planes and include them on signal planes.

The presence of the non-functional pads allows the flexibility of bare board 
testing those sites in the event of an AOI bottleneck or maintenance shut 
down. On the other hand, excluding them on internal planes increases the 
etching process window on those designs where the clearance between the 
nonfunctional pad and the plane is small (<.005").

I will also be interested in other responses from those that have had real 
experiences that may support or refute the inclusion of these pads.

On Tue, 30 May 1995 13:47:24 TOM HYBISKE wrote:

> From: TOM HYBISKE <[log in to unmask]>
> Date: Tue, 30 May 1995 13:47:24
> Subject: Nonfunctional Lands
> To: [log in to unmask]
> 
> I would appreciate hearing from any board manufacturers concerning 
> the inclusion or exclusion of nonfunctional lands from internal planes 
> or signal layers.  IPC-D-275 is vague on this (para 5.3.2.5) by 
> stating "should be included" rather than "shall".  I've always 
> included unused pads on internal layers because I was told it aided 
> in the plating and support of the hole.  I was recently asked by a 
> vendor to replace our traditional donuts on the plane layers to a 
> complete void (my guess was it would give them an additional .010 
> radius to work with). This precipitated a conversation about wether 
> we need unused pads on internal signal layers as well.  How do you 
> feel about this?
> 
>                                     Tom Hybiske
>                                     [log in to unmask]
> 





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