Hello Pete,

As you know, the IPC standards establish minimum acceptability
requirement for the inspections performed.  If the product does not meet
these requirements it becomes non-conforming.  This does not necessarily
mean scrap.  It means that with our generic standard, the samples did
not meet the stated requirements and must be dispositioned outside the
standard.

It is the fiduciary duty of any testing organization (internal or
external) to note all anomalies to the standard found anywhere in the
sample taken.  As you correctly stated they may be, but are not required
to be manufacturing experts, but they are required to be experts in the
requirements of the standard.

This particular inspection requirement is meant to detect laminate voids
"not" induced by Thermal Stress (ie. The "thermal zone" exclusion) or
voids affected by thermal stress in an area where they should not be
affected (between the holes, .003" away from the copper).  The
appearance of voids anywhere outside the thermal zone is specifically
what this criteria is meant to detect.  The ".003" reference in the
standard is meant only to define the area where "not" to inspect (due to
thermal stress damage).

The void issue you describe may certainly be attributable to a valid and
typical cause that may have no relevance to the board or the end product
needs.  It may also be indicative of a quality issue that could affect
the end product in cases where it is not assignable to the cause you
mention.  Changing the inspection criteria to ignore this won't change
that fact. In these "out of the ordinary" cases (thick board, high layer
count, low pressure area, etc...), it is up to the board supplier and
purchaser to work acceptability of this non-conformance out between
them.  It is an unfortunate fact that our standards will only cover
PCB's that fit into the big part of the bell curve (close to normal).

 
Best Regards,
 
Bob Neves
Chairman
Microtek Labs
+1 (714) 999-1616
+86 (519) 5487808
[log in to unmask]
www.TheTestlab.com
 
 
 

-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Menuez,
Pete (IE) @ CIN
Sent: Friday, July 21, 2006 5:06 AM
To: [log in to unmask]
Subject: [IPC-600-6012] Inspection area of coupons

All:

We have a third part lab perform full Group A inspection on all boards
we buy for Space Flight.  This lab takes unused A and B coupons, pots,
reads and reports. We have recently come up with a situation that is not
clearly identified in either of the board specs 6012 or 6013.  

The question simply stated is 'does the entire mounted coupon get
inspected or is there a defined measurement that says inspect everything
within these boundaries'.  

What happened is this. The lab cross sectioned some rigid flex boards
and rejected them because of laminate voids.  The laminate voids are
located more than .100" from the nearest hole.  6012/6013 do not clearly
state how far away from the hole you inspect the cross section.  In this
case the non conformance is located in a low pressure area - in an area
where there is no copper at all in a .250" thick 27 layer board.  This
lack of foil does not happen on the board itself.  This is a somewhat
irrelevant fact because the lab isn't being asked to be a lamination
expert. I just thought I'd throw it in because someone might ask why
there are lam voids.

The spec defines Zone A as the entire hole/pads plus .003" past the
farthest reaching pad, internal or external.  Zone B is defined as the
space between the holes minus the .003" that was given to Zone A.
Reference figure 3-8 in IPC-6012.

My interpretation is that the evaluation zone therefore extends from
.003" to the left of the farthest left hole to .003" to the right of the
farthest right hole and that any area outside this is not to be
evaluated. Is this the correct interpretation or is there something that
says you have to look at more of the coupon? 

For some reason the picture in IPC-6013 that depicts the inspection area
only shows two holes.  I would assign the same logic as I did for 6012.
No matter how many holes there are in the coupon the inspection zone
stops 3 mils to the left of the left hole and 3 mils to the right of the
right hole.

Finally regardless of which interpretation is correct I believe there
should be a clear statement in each of the specifications stating the
boundaries.

Thanks for your time,



Pete Menuez
Supplier Quality Engineer
L-3 Communications Cincinnati Electronics
7500 Innovation Way
Mason, Ohio 45040
[log in to unmask]

513-573-6401 Voice
513-573-6767 Fax







 



Pete Menuez
Supplier Quality Engineer
L-3 Communications Cincinnati Electronics
7500 Innovation Way
Mason, Ohio 45040
[log in to unmask]

513-573-6401 Voice
513-573-6767 Fax

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