Hey Paul,
I agree with everything you've said.
Also, I'm with an OEM now. If I were the customer in this case and you show me what you have now, I'd tell the supplier to contain the material and work out a solution......quickly.
Gerry
> Date: Tue, 17 Dec 2013 10:03:25 -0500
> From: [log in to unmask]
> Subject: Re: [TN] Crazing
> To: [log in to unmask]
>
> 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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