Well, ain't that a crappy situation! Been there.
Nothing like suppliers who try to hide behind nuances in written statements. Obviously they aren't into a long term relationship. I'll bet the IPC left out some critical supportive phrase to the spec, such as "Generally, crazing is visible without resorting to a microsection." Maybe someone on the forum can put that in the hopper for the next rev.
Anyway, you will need to do more work to straighten this out. You need to show that the incidental crazing found in the microsection is not an anomaly, and that it will affect the useful operational lifetime in your environment.
Usually, defects like this are not isolated, so finding others at the same lamination plane in the circuit board shouldn't be difficult. And finding one that you can show is visible without a microscope shouldn't be ridiculously difficult either. This is the easy way out of the conundrum.
You can also look behind the spec at the reason it exists. Probably it has to do with maintaining isolation between conductors. Perhaps you can set up an environmental qualification test which shows the observed defect definitely creates a problem with passing an industry standard biased humidity/temperature test. This is obviously somewhat expensive and time consuming, and then you need to work with your customer and the fabricator to figure out a way to move forward.
Wayne Thayer
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid
Sent: Friday, December 06, 2013 11:08 AM
To: [log in to unmask]
Subject: Re: [TN] Crazing
Hi Gerry,
What we were doing was the MRB part of the investigation.
I contend that this is a "non-conformance", it is crazing and it violates the 50% spacing rule. The fabricator states that it is an artifact of microsectioning and if it is crazing it cannot be evaluated by microsection due to the IPC documents.
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 6, 2013 10:44 AM
To: [log in to unmask]
Subject: Re: [TN] Crazing
Hi again Paul,
One last note.
In my wording notice that I used the word "non-conformance", not defect, reject, scrap, junk, etc....
The next step is MRB, where the real decisions/action get made in light of the facts, and in conjunction with customer involvement.
Gerry
> Date: Fri, 6 Dec 2013 08:32:37 -0500
> From: [log in to unmask]
> Subject: Re: [TN] Crazing
> To: [log in to unmask]
>
> Hi Gerry,
>
> Bill and I are doing well.
>
> I concur with your thoughts. If you find something using a method that
> is not required for the defect, it's still a defect.
>
> I am not happy with the idea that because I found the crazing during a
> microscopic examination it does not count.
>
>
> 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 6, 2013 8:21 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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