Bev
CuSO4 or CuSO3CH3 are only possibilities if these salts are insoluble in acid. The reason CAF grows from the anode is because the salt formed at the anode is insoluble in that acidic environment.
Laura
Sent wirelessly from my BlackBerry device on the Bell network.
Envoyé sans fil par mon terminal mobile BlackBerry sur le réseau de Bell.
-----Original Message-----
From: Bev Christian <[log in to unmask]>
Date: Tue, 27 Nov 2012 01:48:41
To: <[log in to unmask]>
Subject: Re: [TN] Root cause for measling-crazing
I agree with Laura. However, I will add that CALCE talks of CFF (conductive
filament formation). From listening to the CALCE researchers, I think that
CFF covers CAF AND copper filaments. The problem with using CFF is in the
wrong context, it is too broad.
SO FAR Laura and researchers working with her have only identified copper
hydroxy chloride and the bromide equivalent, but that does not mean that
there could not be other salts that form CAF, like CuSO4 or CuSO3CH3. I'm
not saying likely, I'm just saying possible.
Bev
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Laura J Turbini
Sent: Monday, November 26, 2012 4:19 PM
To: [log in to unmask]
Subject: Re: [TN] Root cause for measling-crazing
Hi Paul,
CAF grows from the anode. Copper filaments grow from the cathode. If it is
just copper it is not CAF.
Laura
-----Original Message-----
From: Paul Reid [mailto:[log in to unmask]]
Sent: November-26-12 3:57 PM
To: Laura J Turbini; TechNet E-Mail Forum
Cc: Bill Birch; Jason Furlong
Subject: RE: [TN] Root cause for measling-crazing
Hi Laura,
Sorry it took so long to get back to you about this.
I thought that CAF was copper or copper salts that bridge the two different
conductors. What I saw was a dark grey scale like growth between the two
conductors. What we found was that a coupon that we had been testing was
showing variable resistances between the power and sense circuits when we
put the coupon over a coffee cup. Don't ask me why we put the coupon over of
coffee cup but that is what we did. We determined that the resistance change
was due to the humidity as this resistance change did not vary due to
heating. We then split the coupon in half and added a drop of distilled
water between the power and sense PTHs. What I saw was some blue coloring
coming into the solution. I applied 6 volts between the two holes and the
conductive fiber grew before my eyes (using a scope). I assumed that this
was a conductive anodic filament. I assumed the blue was from plating
solution that was trapped behind the gross hole wall pull away.
So what your saying is that it is only Cu(OH)3Cl or CU(OH)3Br that can be
classified at CAF? What color are these filaments when we find them in cross
section. We think the CAF can be a copper filament. What we have found is
copper filaments that propagate down spaces between the epoxy and glass. Is
this not CAF?
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: Laura J Turbini [mailto:[log in to unmask]]
Sent: November 16, 2012 3:18 PM
To: 'TechNet E-Mail Forum'; Paul Reid
Subject: RE: [TN] Root cause for measling-crazing
CAF, conductive anodic filament, is a copper salt which grows from the anode
to the cathode. The salt is either Cu(OH)3Cl or Cu(OH)3Br in cases where a
high bromide-containing HASL fluid has been used. In the case where
excessive plating salts were found, did you verify that the filament was not
just copper metal growing from the cathode? Do plating salts contain
halides, or only sulfate? Has anyone run SEM/EDX on the filament?
The presence of a bias voltage, moisture, and an easy path can be conducive
to copper dendrite formation along the glass fibers as well as CAF. The
close spacing between mechanically drilled holes on the some board designs
causes cracks between the anode and cathode holes. When the holes are
plated, plating salts can get into the holes and become conductive in a
humid environment - but that is not CAF.
Regards,
Laura
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid
Sent: November-16-12 2:10 PM
To: [log in to unmask]
Subject: Re: [TN] Root cause for measling-crazing
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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