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July 2000

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Subject:
From:
Ken Patel <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 11 Jul 2000 09:52:39 -0700
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Dear Engelmaier,
I am attaching a picture which will tell you a whole lot. This crack is not
in a foil. This is a radial crack and originated in the hole and then
expanded radially due to most likely z-axis expansion. I do not know if it's
a circumferential crack or not.

We kind of know that it's due to thermal expansion and we think that the
board should withstand a normal assembly process. As we are finding cracks
at PTH via, we do not see why someone has to do any rework there which may
cause similar defects. So, what kind of the laminate condition make it easy
to break apart and for that matter what kind of assembly condition can make
that kind of havoc.

re,
ken patel


At 08:36 AM 7/11/2000 EDT, Werner Engelmaier wrote:
>Hi Ken,
>You have to be more descriptive about where you find those cracks. Are the
>cracks in the foil of layer #5, are they innerlayer separations at the
>interface between the foil and the electroless flash, or are they innerlayer
>separations at the interface between the  electroless flash  and the
>electroplated copper. The loading conditions are the same in each case
>(severe thermal expansion mismatch most likely in an area the has seen manual
>soldering operations/rework), but the root cause/solution options are
>different. From your incomplete description, the cracks may even be in the
>PTH via barrel.
>
>Werner Engelmaier
>Engelmaier Associates, L.C.
>Electronic Packaging, Interconnection and Reliability Consulting
>7 Jasmine Run
>Ormond Beach, FL  32174  USA
>Phone: 904-437-8747, Fax: 904-437-8737
>E-mail: [log in to unmask], Website: www.engelmaier.com
>
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______________________________________________________ Ken Patel Phone: (408) 490-6804 1708 McCarthy Blvd. Fax: (408) 490-6859 Milpitas, CA 95035

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