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November 2005

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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:
Tue, 29 Nov 2005 10:15:33 -0800
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Haven't seen the photos posted yet.  But a few questions come to mind...

How many metal layers in the flex?
Is it circumferential cracking?
Where in the via is the cracking occuring?
         At the knee, in the center, at an innerlayer post interconnec, or...?
Is the cracking associated w/ a visible mfg defect in drill quality or plating?

dw


At 07:03 AM 11/29/2005, Werner Engelmaier wrote:
>Hi Mumtaz,
>Not having seen pictures, I am reduced to guessing. particularly since you
>did not say how thick the flex circuit is.
>But when you get copper cracking, it always means that the ductility and
>strength of the Cu was insufficient for the loading conditions. Thus,
>there are 3
>possibilities alone or in combination:
>(1) the properties of the copper deposit are bad;
>(2) the loads [thermal expansion, bending, etc] are too high;
>(3) geometric stress concentrations create loading conditions too severe for
>the available material properties.
>A good root-cause-analysis can give you the answer of the causes, which then
>allows you to improve the situation as needed.
>
>Regards,
>Werner Engelmaier
>Engelmaier Associates, L.C.
>Electronic Packaging, Interconnection and Reliability Consulting
>7 Jasmine Run
>Ormond Beach, FL 32174 USA
>Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
>E-mail: [log in to unmask], Website: www.engelmaier.com
>
>
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