Hey John,
Yes and Yes.  Although I don't think it is the only conflict.
While hole wall plating voids are covered by 3.6.2.1, 3.6.2.2, and 3.6.2.11,  one could pretty easily make an arguement that for the treatment for isolated thin areas, 3.6.2.11 supplants the others.  Do I think we should have to make such interpretations?  NO.
 
My larger concern is that, in order to observe other attributes, we have already oversampled 7X.  So this idea of 1 vs. 2, or random versus endemic (to the panel or lot) is confounded by the fact that sampling is way to big.
 
In my opinion, to follow the intent of the authors we should take three holes only from an additional 27 panels (maybe no thermal stress).  If no isolated thin areas are observed, then we would invoke 4.2.2 to sample the same panel (3 holes only) that showed 2 isolated areas the first time.  If, by chance (by my calculations ~90%), all referees show no isolated thin areas, then the lot would be found to be conforming.
 
Ridiculous?  Yes.
 
My larger point is to soapbox about the use of coupons.  I believe that a primary outcome of the (Traditional) Test Coupon committee work will be to highly suggest that coupons SHALL be used for conformance testing.  This case is an example why.  I'll be submitting more.  Oh -boy!
 
Secondarily, I would highly suggest that 6012 look into the use of non-zero defect (for some attributes), and double sampling tables for Class 2 product.
 
Chris
 

 
________________________________

From: IPC-600-6012 on behalf of John Perry
Sent: Mon 11/20/2006 11:46 AM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] 6012 plating void referee



Hi Chris,

Can you confirm for me that you are referring to 3.6.2.11 of IPC-6012B,
where it states that such isolated areas should be considered a void:

If copper thickness less than the minimum specified in
Table 3-2 is detected in isolated areas, it should be considered
a void and resample in accordance with Table 4-2
using samples from the same lot to determine if the defect
is random. If the additional test coupons or production
boards have no isolated areas of reduced copper thickness,
the product which the test coupons or production boards
represent are considered acceptable; however, if reduced
copper thickness is present in the microsections, the product
shall be considered nonconforming.

The wording in this paragraph seems to define what constitutes the
number of "additional test coupons or production boards" that should be
sampled in this case by saying "resample in accordance with Table 4-2",
although to me there seems to be a conflict because 4.2.2, Referee
Tests, calls out only two additional microsection sets for defects
considered to be isolated or random.  Do you also see a conflict here?

Thanks,

John Perry
Technical Project Manager
IPC
3000 Lakeside Drive # 309S
Bannockburn, IL 60015
[log in to unmask]
1-847-597-2818 (P)
1-847-615-7105 (F)
1-847-615-7100 (Main)

-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Chris
Mahanna
Sent: Monday, November 20, 2006 9:20 AM
To: [log in to unmask]
Subject: [IPC-600-6012] 6012 plating void referee

Hello group,

We have a customer who is applying a fresh set of eyes to some 6012
details.
He bought ~1000 panels of class 2 product and ask us to perform
structural integrity conformance testing.  There are no A-B coupons, so
he sent 27 arrays.  We took one board from each array and pulled 4 rows
of holes. We do this over sampling in an attempt to level the playing
field with coupon work.  For instance there should be (at least) 12-
layer 2 or N-1 plating connections to observe...
So anyway, although I don't remember exactly, there was about 20 holes
per panel sectioned.
Great lookin boards, but... of the 27, 15 of them exhibited one isolated
thin area of plating (a void) and 1 of the 27 had two isolated areas.

Although I have a opinion, I believe that there is not a unique answer
to the proper "6012 disposition" of this lot.

Any ideas?  Don't forget section 4.2.2.

Thanks in advance,
Chris

Chris Mahanna
Quality Manager
Robisan Laboratory Inc.
6502 E 21st Street
Indianapolis, Indiana 46219
phone 317.353.6249
fax 317.917.2379