I do too.
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: Dwight Mattix [mailto:[log in to unmask]]
Sent: December 17, 2013 1:05 PM
To: TechNet E-Mail Forum; Paul Reid; [log in to unmask]
Subject: Re: [TN] Crazing
+1 Paul
In any case (and regardless of the spec), when out playing sourcing
games... I look at crazing and wicking from fab to fab as a
relative indicator of a) how skilled/disciplined they are at drill
and b) how far along the accountants are into their destruction of
the fabs technical capability. >:-}
At 07:03 AM 12/17/2013, Paul Reid wrote:
>Hi Gerry,
>
>Based on the responses from "everyone" I am sure that crazing is a
>defect that is a concern. It is just that one company is playing
>"specmanship" with IPC's rules and I don't like it.
>
>The rules state that a microsection is not needed to inspect for
>crazing. Therefore, according to the fabricator, one cannot inspect for
>crazing using a microsection. The specification does not state that a
>microsection is prohibited in the inspection for crazing however. IPC A
>600 states that crazing ".. does not require a microsection
evaluation".
>
>Regardless of how I found the defect it is the intent of IPC to reject
>this condition if it violates 50% spacing rules.
>
>I found this condition "along the way" and I raised the flag. That is
>all I can do.
>
>
>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 Gerry Gagnon
>Sent: December 13, 2013 8:49 PM
>To: [log in to unmask]
>Subject: Re: [TN] Crazing
>
>Hi Richard,
>
>Have enjoyed your posts over the years and agree with you frequently.
>
>The answer is that it "depends".
>
>Yes, the magnifications and switching rules are the "front matter" that
>a lot of folks gloss over from time to time.
>
>I am sure that if you were looking to verify a certan non-conformance
>and found something along the way that was lethal for your product or
>application, you would have no problem raising that flag.
>
>By the way "along the way" is just a figure of speach I was using.
>Definitely not proper specification language.
>
>Gerry
>
> > Date: Mon, 9 Dec 2013 12:52:28 +0000
> > From: [log in to unmask]
> > Subject: Re: [TN] Crazing
> > To: [log in to unmask]
> >
> > I am not sure I accept that "along the way" theory completely.
> > Prevalent in all of the IPC standards, all defect categories are
>provided a magnification level for inspection. For example, if a
>non-metallic particle is seen on the PWB while inspecting solder joints
>at 20X magnification on a conformal coated CCA, the inspector is
>supposed to switch to the required magnification for the particulate
>matter (4X-7X). If the particulate matter cannot be seen at that range,
>it is not considered to be a defect.
> > If you want to entertain your "along the way" theory, then have fun
>counting up the rework hours to strip away the coating, remove the
>particles, clean, dry, and re-coat. No matter what you do short of
>building all product in a Class 10 clean room, this unnecessary rework
>will never end.
> >
> > Of course, one must understand that there are certain exceptions to
>this; I am just saying that you cannot allow an "along the way"
>philosophy in the factory. It will put you out of business.
> > In regards to your example, two questions come to mind:
> >
> > 1. What is the magnification required when inspecting for
particulate
>matter between conductors at the PWB level, and what is the minimum
>electrical clearance between the two traces you describe? If the
>material was visible at the required magnification, it was an escape,
>and should have been caught at the higher magnification you describe
>anyway, and is a real defect.
> > 2. Did you measure the resistance again after the tiny piece of
>material was removed, and did it make any difference?
> >
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerry Gagnon
> > Sent: Friday, December 06, 2013 7:21 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] Crazing
> >
> > Hi Paul,
> >
> > Hope you and Bill B. are doing fine.
> >
> > I am assuming that you you were looking for something else and
>detected a "non-conforming" level of crazing.
> >
> > In my mind, this is an easy one because you found the
non-conformance
>"along the way" while examining your microsection.
> >
> > Let me give you an easier analogy.
> >
> > While examining a region of an IST test coupon in transverse mount,
I
>find a tiny piece of material bridging two conductors at high mag.
> > Clearing away the conductor surfaces enough to measure if there is
a
>resistance, I get a value in the MegOhm range.
> >
> > Is it a short?
> >
> > Unless things gave changed, Bare board continuity thresholds will
not
>detect this phenomenon.
> > Let's also say that innerlayer AOI (if performed) has a very high
>escape rate for this type of phenomenon or may not even detect it at
>all.
> >
> > Is the phenomonon a short per IPC A-610?
> > My answer is yes, it is an unwanted connection, albeit a high
>resistance connection, and is difficult to detect.
> >
> > Does the fact that I found this short in a cross section under high
>magnification, while I was looking for something else, change anything?
> >
> > I don't think so, and I do not think IPC A-610 allows
non-conformances
>that are found "along the way".
> >
> > Have a good one.
> > Gerry
> >
> >
> >
> >
> > > Date: Thu, 5 Dec 2013 16:05:41 -0500
> > > From: [log in to unmask]
> > > Subject: [TN] Crazing
> > > To: [log in to unmask]
> > >
> > > I was just on a conference call where we found crazing (a
separation
>
> > > between glass fibers and the epoxy system), in a microsection. The
> > > fabricator stated that this had to be evaluated looking at a board
> > > macroscopically and could not be evaluated microscopically.
> > >
> > >
> > >
> > > Crazing is called out in IPC-A- 600 in section 2, paragraph 2.3.2
>page
> > > 18, which is "Externally Observable Characteristics". In A-600
there
>
> > > is picture of a microsection showing the defect but it states that
a
>
> > > microsection is not required.
> > >
> > >
> > >
> > > In IPC 6012-2010 crazing is call out in 3.3.2.2, page 12, which
>states
> > > (I am paraphrasing), "Crazing shall not violate greater than 50%
of
> > > the distance between adjacent conductors..." The document then
>refers
> > > to IPC A 600.
> > >
> > >
> > >
> > > What is your take on their argument that crazing should not be
> > > evaluated microscopically as per IPC?
> > >
> > >
> > >
> > > 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]
> > >
> > >
> > >
> > >
> > >
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