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June 1999

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From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 9 Jun 1999 23:33:36 EDT
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In a message dated 5/17/99 20:37:49, [log in to unmask] writes:

>hi everybody,
>We've been doing some studies on assembly of CSPs , namely ones like the
>tessera 46 I/O, FCT ultra CSP to name a few. We assembled these packages
>on
>micrivia-in-pad patterns. These are 15/13.5/11 mil pads with 6 mil design
>microvia, using photo/laser/plasma tech. We are seeing voids, as big as
>the
>microvia, and they sit exactly at the via opening. The process we use is
>pretty robust, using nitrogen for reflow and the problem is seen for both
>solder and flux. The reliability data is still not out,but we expect the
>voids to make a diffrence.
>Would appreciate some inputs on why/how? and what to do/what not to do?
>Parvez M.S. Patel

Hi Parvez,
Sorry, for not replying earlier to you query.
You did not say what kind of reliability data (what test) you will be
developing. However, the most critical one is creep fatigue reliability. In
this test, based on T-cycling not T-shock (which is not creep fatigue based),
voids have not proven to make any real difference in the solder joint
reliability.
I would be interested to know about your results.

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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