Denny

Adding on to Phil's comments below.  The 40% was in MIL-P-55110C in and 
before 1980.  Part of the results of IPC Multilayer Round Robin V 
indicated that a lot of quality product was being rejected do things like 
the teardrop voids, and resin recession.  The "thermal-zone" concept was 
proposed by George Smith, shortly after the round robin's release, and 
the specifications changed to eliminate the resin recession evaluation 
after stress.  It was kept for quite some time in the prior to stress 
microsection and as Phil said, due to a lack of industry problems with 
the condition, was further removed as a rejectable requirement.  

I'm sure more history is out there.  I missed the meeting where they 
plucked the magic 40% out of the air and plugged it into the spex in the 
first place, so others will have to supplement if you need more.

Regards
Dave

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David W. Bergman, V.P of Technical Programs
IPC
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On Wed, 18 Sep 1996 [log in to unmask] wrote:

> Dennis 
> 
> The statement about "Hole wall dielectric/plated hole separation" is a direct
> carry over from IPC-RB-276 Table 10 which as been in existence since 1992. It
> is the intent to allow hole-hole-wall-pullaway to any extent as long as the
> hole is not collapsed and the function is not degraded.  This was a change
> from IPC-ML-950 which only allowed 40% hole-wall-pullaway.  This is the first
> time any question has come up since RB-276 was issued and the suppliers and
> users seem satisfied.
> 
> Phil Hinton 
> [log in to unmask]  
> 
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