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September 2002

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 26 Sep 2002 13:25:38 EDT
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>Moonman stated that Werner Engelmaier wrote the book on CGAs.
A: Only regarding their reliability.
>Can you explain any problems in the use of CGAs?
A: Manufacture and assembly are more difficult; CGAs do not self-center
during reflow; they are more susceptible to damage from vibration and
mechanical shock.
>In manufacturing, how reproducible is the assembly using CGAs?
A: With proper care, no real problem.
>What solder is best to use in soldering the CGA to a ceramic device?
A: Eutectic or near-eutectic Sn/Pb.
>Papers I have read state that the thermal cycling longevity of solder joints
to
>ceramic devices with 100 mil CGA is 45 times longer than that of the
equivalent BGA. >Is this correct?
A: One cannot make a blanket statement like that. Depending on the details
increases in fatigue life are possible, but you certainly would have to have
a proper 'Design for Reliability' to achieve this.
>Is there a leaded solution to the problem of assembling
>ceramics to Glass/Epoxy for LCCs that would be better?
A: Yes, there are clip-leads that work exceedingly well;  see my paper:
Engelmaier, W., and A. I. Attarwala, "Surface-Mount Attachment Reliability of
Clip-Leaded Ceramic Chip Carriers on FR-4 Circuit Boards," IEEE Trans.
Components, Hybrids, and Manufacturing Technology, Vol. CHMT-12, No. 2, June
1989, pp. 284-296.

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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