I sure do, I will send citations.
Bhanu Sood
Center for Advanced Life Cycle Engineering (CALCE)
Test Services and Failure Analysis Laboratory
Room 0128, Glenn L. Martin Hall
(Building 088)
University of Maryland,
College Park, MD 20742
Tel: +1 (301) 405 3498
Fax: +1 (301) 314 9269
e-mail: [log in to unmask]
Skype: calce_umd
website: www.calce.umd.edu/TSFA
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On Dec 9, 2013, at 4:11 PM, "[log in to unmask] " <[log in to unmask]> wrote:
> Bhanu,
> Do you have any experimental proof of your first sentence?
> CAF/drops in insulation resistance is one of numerous effects of crazing.
> 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: Bhanu Sood <[log in to unmask]>
> Date: Mon, 9 Dec 2013 18:54:45
> To: <[log in to unmask]>
> Subject: Re: [TN] Crazing
>
>
> CAF/drops in insulation resistance is one of numerous effects of crazing.
> Changes in Df and lower mechanical strength are possible. The epoxy/glass
> separation can act as temporary storage site of liquid phase process chemicals,
> this can lead to more widespread delam during soldering. Speaking about specs
> and IPC conditions (if ever there were one), will a thorough incoming inspection
> detect crazing? In certain silane treated glasses, crazing may not appear until
> final build or in field.
>
>
> On 12/9/2013 10:58 AM, Paul Reid wrote:
>> Hi ted,
>>
>> Thanks for the input.
>>
>> I think that crazing is a defect that needs to be addressed because of
>> the tendency for conductive anodic filament growth. Back in the '80s
>> this was not such a big deal. In 2013 with three mil lines and spacing
>> and grid sizes of 20 mils, crazing is a big deal.
>>
>> It's not the magnification. It's the cross section that is the issue.
>> What the fabricator is saying is that there is no cross section
>> evaluation for crazing called out in 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 Theodore J Tontis
>> Sent: December 9, 2013 9:42 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Crazing
>>
>> Why wouldn't it just be considered a process indicator?
>>
>> After all, a process indicator is not a defect and it indicates a
>> non-desired output that would warrant further investigation or counter
>> measures to correct? The material is still deemed acceptable just not
>> ideal.
>>
>> I do believe it is not a defect and agree if we were to identify every
>> concern found under magnification above the specified/agreed upon
>> requirement, there would be a long list of issues to address and costs
>> would skyrocket. Isn't that why we have standards for this sort of
>> thing?
>>
>> Ted T
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
>> Sent: Monday, December 09, 2013 6:52 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Crazing
>>
>> 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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>
> --
>
> Bhanu Sood
>
> Center for Advanced Life Cycle Engineering (CALCE)
> Test Services and Failure Analysis Laboratory
> Room 0128, Glenn L. Martin Hall (Building 088)
> University of Maryland
> College Park, MD 20742
>
> Tel: +1 (301) 405 3498
> Fax: +1 (301) 314 9269
> e-mail: [log in to unmask]
> Skype: calce_umd
> website: www.calce.umd.edu/TSFA <http://www.calce.umd.edu/TSFA>
>
> Confidentiality Notice: The information contained in this e-mail
> and any attachments may be legally privileged and confidential.
> If you are not an intended recipient, you are hereby notified that
> any dissemination, distribution or copying of this e-mail is strictly
> prohibited. If you have received this e-mail in error, please notify
> the sender and permanently delete the e-mail and any attachments
> immediately. You should not retain, copy or use this e-mail or
> any attachment for any purpose, nor disclose all or any part of the
> contents to any other person.
>
>
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