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October 2009

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Subject:
From:
Dwight Mattix <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Dwight Mattix <[log in to unmask]>
Date:
Wed, 21 Oct 2009 10:32:51 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (211 lines)
At 10:08 AM 10/21/2009, Paul Reid wrote:
>Hi Ian,
>
>Yes.
>
>We have seen adhesive failure between glass bundles (not individual
>fibers) and C-stage epoxy. It is rare but it happens.

not so rare with some reason systems esp if related CE (that will 
remain nameless to keep it collegial here). :-)

>If the
>delamination is between the B-stage and the C-stage we usually blame the
>B-stage. On occasion we get adhesive delamination between the C-stage
>and the copper foil particularly with reverse bearing foils.
>
>
>
>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] <mailto:[log in to unmask]>
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Ian Hanna
>Sent: October 21, 2009 11:44 AM
>To: [log in to unmask]
>Subject: Re: [TN] delamination signatures
>
>Hi Paul -- there could be adhesive failure, or delamination, in c-stage
>no? Ian
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid
>Sent: Wednesday, October 21, 2009 9:53 AM
>To: [log in to unmask]
>Subject: Re: [TN] delamination signatures
>
>Hi Chris,
>
>I think that the signatures of material damage should be taken as an
>indicator not an absolute for determining root cause.
>
>I cannot bring myself to call cracks in areas that were never laminated,
>adhesive delamination. I can thank my colleague Jason Furlong who, years
>ago, said to me "If that area was never laminated how can you call the
>crack delamination?" As it stands now I can't call cracks in the middle
>of the B or C stage adhesive delamination. For me if the crack does not
>follow an internal interface it is "cohesive failure" not adhesive
>delamination.
>
>If we can agree that adhesive failures tend to be a breakdown of an
>internal interface, cohesive failure a breakdown of the epoxy system and
>crazing a separation between the individual glass fibers and the epoxy
>system then these symptoms may give indication of where to look for root
>cause. At least this interpretation of failure signature could direct
>you to look into areas that would contribute to those types of failures.
>
>Consider the alternative. If each delamination signature does not narrow
>the area of investigation for root cause then one could naively start
>with material shelf life and storage, move to lamination (cycle, times,
>pressures, platen planarity, heat distribution, etc), go on to drilling
>(feeds, speeds, and hit count etc) and proceed through the other 97
>steps of PCB fabrication, (not forgetting oxide coating, cleaning,
>rinsing etc.). If that investigation is not fruitful then move on to
>design and methods engineering variables like grid size, % resin etc.
>You might find out in the end you were using a DICY cured laminate in a
>lead/free HDI application and the material damage was cohesive failure.
>
>There may be hundreds of root causes of material degradation I can think
>of at least a hundred. I say - Let the cross section talk to you and
>narrow your investigation based on observation and experience.
>
>Don't forget... when in doubt bake! It doesn't much help but it does
>give one reason to hope.
>
>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] <mailto:[log in to unmask]>
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
>Sent: October 19, 2009 9:24 PM
>To: [log in to unmask]
>Subject: [TN] delamination signatures
>
>Hello TN,
>
>I'm wondering how certain one can be about the root cause of delam.
>simply by reading its signature.  Our experience is similar to Paul
>Reid's (post attached below).  One obvious question: what about when it
>is both co and adhesive failure?
>Are there other features to the signature that are important in
>determining primary root cause?
>
>Chris
>
>------------------------------------------------------------------------
>------------------
>
>My sense is that moisture induced delamination presents as adhesive
>delamination that is horizontal cracks that resemble blisters and are
>located at a laminated interface (b-stage to c-stage or copper, or along
>bundles of glass). It may be that the vapor pressure exerted by trapped
>moisture induces a mechanical failure at laminated interfaces.
>
>Material degradation induced delamination more often presents as
>cohesive failure that may exhibit cracks with vertical sections, often
>bifurcating and spanning across b-stage and c-stage material, even
>through glass bundles, and tend to propagate with sharper angles. This
>failure mode appears to be more a chemical degradation of the epoxy
>system.
>
>Sincerely,
>
>Paul Reid
>
>
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