Dewey,Jeff, Chris - Thanks for the feedback. Let me make sure to attend the next 6012 phone conference. Carelessly, I missed the last one on 26 Oct.

If I were a customer, I would not discriminate in favor blinds and burieds, but have them treated the same as through-holes.  Louis Hart

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey (EHCOE)
Sent: Wednesday, November 02, 2011 9:48 AM
To: [log in to unmask]
Subject: Re: [TN] Microsection of blind and buried vias

Yes, and since I am working on the mark-up of IPC-6012 and Table 4-3 I
would like some agreement on this. Randy Reed and I are operating in a
small window of time. The panes are bearable; transparency is not.
Dewey

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
Sent: Tuesday, November 01, 2011 4:59 PM
To: [log in to unmask]
Subject: Re: [TN] Microsection of blind and buried vias

Depends upon the need for registration assessment on the other via
structures.
Robisan does not believe that 6012/2221 or 31032 requires such testing
for (legal) conformance assessment.
The argument is that the thru holes provide some measure, even though it
may well be from a different drill cycle.
I was there when the magic "minimum of 3 holes" verbiage went in,
without the opposing corner mention.  I believe that was the intent, at
the time.

Several discriminating OEMs require the assessment for acceptance.
However, to my knowledge, all are open minded to other assessment
techniques including electrical, drill-and-look, maybe x-ray, and I
would think Compunetic's novel x-sect approach.  Why don't you just try
to sell them that?

This is a current topic on the 6012D calls due to the amending of the
tables for the A/B-R.

Chris Mahanna
Robisan Lab



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Louis Hart
Sent: 2011/11/01 7:18 PM
To: [log in to unmask]
Subject: [TN] Microsection of blind and buried vias

Technetters, my question deals with the number of microsections of blind
or buried vias, per panel, required by IPC-6012.

For plated holes, one thermally stressed A/B coupon is required per
panel. A second A/B coupon, from the corner opposite to that from which
the thermally stressed one was taken, is required to be microsectioned
in a direction perpendicular to that of the first per panel to check
internal annular ring. (I have not been calling for thermal stress of
the second A/B.)

Does 6012 require a second microsection coupon for blind and buried
vias? (I have collected a number of opinions, and have one of my own.)

I have noticed that MIL-PRF-55110 does not require a second blind or
buried vias. As I read it, the requirement is for a single coupon per
panel, thermally stressed, for each blind of buried via. MIL-PRF-31032
does not, it appears to me, explicitly address the number of blind and
buried microsections required.

Thanks for any comments or insight.

Louis Hart
Compunetics
Monroeville, PA
USA
[log in to unmask]<mailto:[log in to unmask]>
412-858-1272


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