Sorry for the late response but I was off on vacation, so wasn't following this thread, off line, but interesting reading none the less.
Most of the measling issues I have privy to are the result of soldering on OLD LEGACY boards. I believe it is due largely to the entrainment of moisture within the board structure. We have found that IF the board is heated, either baked or with a heat gun to a temperature in the 140 deg range, the measling during soldering is greatly reduced. I think that the OLD, OLD, OLD resin formulations were not as robust as current formulations.
Pat
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dennis Fritz
Sent: Friday, November 16, 2012 1:44 PM
To: [log in to unmask]
Subject: Re: [TN] Root cause for measling-crazing
Laura, copper plating solution contains a fixed amount of chloride - that is the anode corroder. That is say 50 ppm, depending on plating chemistry supplier. BUT, the copper plating solution must have 100-1000 times as much sulfate, since that is the anion for the whole bath. Doubt the chloride came from the copper plating, since there is some free choride from the epoxy reaction - less than 900 ppm in the epoxy?
-----Original Message-----
From: Laura J Turbini <[log in to unmask]>
To: TechNet <[log in to unmask]>
Sent: Fri, Nov 16, 2012 3:27 pm
Subject: Re: [TN] Root cause for measling-crazing
CAF, conductive anodic filament, is a copper salt which grows from the anode o the cathode. The salt is either Cu(OH)3Cl or Cu(OH)3Br in cases where a igh bromide-containing HASL fluid has been used. In the case where xcessive plating salts were found, did you verify that the filament was not ust copper metal growing from the cathode? Do plating salts contain alides, or only sulfate? Has anyone run SEM/EDX on the filament?
he presence of a bias voltage, moisture, and an easy path can be conducive o copper dendrite formation along the glass fibers as well as CAF. The lose spacing between mechanically drilled holes on the some board designs auses cracks between the anode and cathode holes. When the holes are lated, plating salts can get into the holes and become conductive in a umid environment - but that is not CAF.
Regards,
aura
-----Original Message-----
rom: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid
ent: November-16-12 2:10 PM
o: [log in to unmask]
ubject: Re: [TN] Root cause for measling-crazing Exactly.
What you need is a path, a potential, moisture, ionic contamination or a ource for ionic contamination and time.
I found CAF once when a Teflon board had hole wall pull away that was filled ith plating solution.
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
35 Stafford Rd., West, Unit 103
epean, Ontario Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
[log in to unmask]
----Original Message-----
rom: Stadem, Richard D. [mailto:[log in to unmask]]
ent: November 16, 2012 2:03 PM
o: TechNet E-Mail Forum; Paul Reid
ubject: RE: [TN] Root cause for measling-crazing Paul, hat is correct. Most CAF incidents I have seen were associated with some ype of abscess within the PWB that allowed water and flux or other mpurities to become entrapped. When that is combined with a significant ifference of electrical potential, the CAF begins and grows over time until ts resistance reduction reaches the point where catastrophic failure takes lace.
-----Original Message-----
rom: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid
ent: Friday, November 16, 2012 12:55 PM
o: [log in to unmask]
ubject: 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 o capillary action. If the water wicks up between two conductors with a otential between them then you can have conductive anodic filament formed etween the two adjacent conductors. The resulting short occurs over time.
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
35 Stafford Rd., West, Unit 103
epean, Ontario Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
[log in to unmask]
----Original Message-----
rom: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
ent: November 16, 2012 1:29 PM
o: [log in to unmask]
ubject: Re: [TN] Root cause for measling-crazing Folks,
If the resin system fails to adhered/bond to the surface of the woven lass weave bundle I can see where one could see an anomaly on the
xterior of some thicknesses of raw boards, measling/crazing. This may
ot hold true for very thick HDI boards. In a cross section one can
ee a torn artifact involving the glass rod. My concern is when the
lass rod is not damage and a gap/space is visible. What then?
Victor,
-----Original Message-----
rom: TechNet [mailto:[log in to unmask]] On Behalf Of Glidden, Kevin
ent: Friday, November 16, 2012 11:53 AM
o: [log in to unmask]
ubject: Re: [TN] Root cause for measling-crazing Interesting. 610 seems to offer different criteria, but criteria which I ave always struggled to understand and agree with. 610 reads that both easling and crazing are externally observable, with the primary ifferentiator being that measling is thermally induced and crazing is echanically induced. But the photos don't seem to match what I have seen n reality. I have seen instances where it is absolutely known the ondition was caused by mechanical means, but the condition looks more like he photos 610 offers for measling, and I have seen solder related onditions that look more like the 610 photos for crazing.
----Original Message-----
rom: Paul Reid [mailto:[log in to unmask]]
ent: Friday, November 16, 2012 11:54 AM
o: [log in to unmask]
ubject: 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 ibers as a group. In a cross section you can see a blister type of eparation. Measling is usually found by a visual examination of the board o it is on the outer layers of the dielectric.
Crazing is a separation of the epoxy from individual glass fibers. In a ross section you can see long silver air gaps running the length of fibers iewed form the side or half moon cracks around fibers when you look at the ibers on end. Crazing is most often found in cross sections and is not isible by visual inspection.
Both can be enhanced by mechanical stress (thermal stress).
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
35 Stafford Rd., West, Unit 103
epean, Ontario Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
[log in to unmask]
----Original Message-----
rom: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
ent: November 16, 2012 11:07 AM
o: [log in to unmask]
ubject: [TN] Root cause for measling-crazing Fellow TechNetters:
Are the above artifact cause by the wettability of the resin to yarn,
oven glass cloth rods, interface? Then this artifact is enhance by
echanical stress. I am trying to understand the terminology so that
t is not misused.
"X"
From: Hernandez, Victor G
ent: Friday, November 16, 2012 7:14 AM
o: TechNet E-Mail Forum ([log in to unmask])
c: Hernandez, Victor G
ubject: Laminate, Resin recession-dry glass bundle Fellow TechNetters:
Can any of the gurus out there comment on the above terminology and
erhaps share a photo. What is the worse than can occur within the
aminate with such artifacts.
"X"
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