Exactly.
What you need is a path, a potential, moisture, ionic contamination or a
source for ionic contamination and time.
I found CAF once when a Teflon board had hole wall pull away that was
filled with plating solution.
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
235 Stafford Rd., West, Unit 103
Nepean, Ontario Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
[log in to unmask]
-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: November 16, 2012 2:03 PM
To: TechNet E-Mail Forum; Paul Reid
Subject: RE: [TN] Root cause for measling-crazing
Paul,
That is correct. Most CAF incidents I have seen were associated with
some type of abscess within the PWB that allowed water and flux or other
impurities to become entrapped. When that is combined with a significant
difference of electrical potential, the CAF begins and grows over time
until its resistance reduction reaches the point where catastrophic
failure takes place.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid
Sent: Friday, November 16, 2012 12:55 PM
To: [log in to unmask]
Subject: Re: [TN] Root cause for measling-crazing
The problem is that crazing is a path for conductive anodic filament
(CAF) growth. The gap is so small you can get water to wick up the gap
due to capillary action. If the water wicks up between two conductors
with a potential between them then you can have conductive anodic
filament formed between the two adjacent conductors. The resulting short
occurs over time.
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
235 Stafford Rd., West, Unit 103
Nepean, Ontario Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: November 16, 2012 1:29 PM
To: [log in to unmask]
Subject: Re: [TN] Root cause for measling-crazing
Folks,
If the resin system fails to adhered/bond to the surface of the woven
glass weave bundle I can see where one could see an anomaly on the
exterior of some thicknesses of raw boards, measling/crazing. This may
not hold true for very thick HDI boards. In a cross section one can
see a torn artifact involving the glass rod. My concern is when the
glass rod is not damage and a gap/space is visible. What then?
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Glidden, Kevin
Sent: Friday, November 16, 2012 11:53 AM
To: [log in to unmask]
Subject: Re: [TN] Root cause for measling-crazing
Interesting. 610 seems to offer different criteria, but criteria which
I have always struggled to understand and agree with. 610 reads that
both measling and crazing are externally observable, with the primary
differentiator being that measling is thermally induced and crazing is
mechanically induced. But the photos don't seem to match what I have
seen in reality. I have seen instances where it is absolutely known the
condition was caused by mechanical means, but the condition looks more
like the photos 610 offers for measling, and I have seen solder related
conditions that look more like the 610 photos for crazing.
-----Original Message-----
From: Paul Reid [mailto:[log in to unmask]]
Sent: Friday, November 16, 2012 11:54 AM
To: [log in to unmask]
Subject: Re: [TN] Root cause for measling-crazing
Hi Victor,
In my mind they are different failure mechanisms.
Measling is small blisters that are a separation of the epoxy and the
glass fibers as a group. In a cross section you can see a blister type
of separation. Measling is usually found by a visual examination of the
board so it is on the outer layers of the dielectric.
Crazing is a separation of the epoxy from individual glass fibers. In a
cross section you can see long silver air gaps running the length of
fibers viewed form the side or half moon cracks around fibers when you
look at the fibers on end. Crazing is most often found in cross sections
and is not visible by visual inspection.
Both can be enhanced by mechanical stress (thermal stress).
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
235 Stafford Rd., West, Unit 103
Nepean, Ontario Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: November 16, 2012 11:07 AM
To: [log in to unmask]
Subject: [TN] Root cause for measling-crazing
Fellow TechNetters:
Are the above artifact cause by the wettability of the resin to yarn,
woven glass cloth rods, interface? Then this artifact is enhance by
mechanical stress. I am trying to understand the terminology so that
it is not misused.
"X"
From: Hernandez, Victor G
Sent: Friday, November 16, 2012 7:14 AM
To: TechNet E-Mail Forum ([log in to unmask])
Cc: Hernandez, Victor G
Subject: Laminate, Resin recession-dry glass bundle
Fellow TechNetters:
Can any of the gurus out there comment on the above terminology and
perhaps share a photo. What is the worse than can occur within the
laminate with such artifacts.
"X"
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