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| Reply To: | TechNet Mail Forum. |
| Date: | Wed, 17 Dec 1997 22:51:36 EST |
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In a message dated 12/17/97 14:01:17, you wrote:
>Engelmaier:
>Then how about plugging of the vias using epoxy, will it be less reliable or
>more reliable. Also fab house can't completely fill the via barrel using
>epoxy (may be 30% of the barrel will be filled) and they won't recommend
>filling of vias from both side as entrapped moisture can remove the plug
>from one side during thermal excursion. Also they can not fill all the vias
>- may be 90% vias will be covered.
>What you recommend from reliability point of view?
>re,
>ken patel
Hi Ken,
I am not aware of any study on this issue, and I have not done any either— so
all I can give you is a semi-educted guess. The epoxy is softer than solder
and because it does not wet solder will have a different geometry at the
filled/unfilled interface. Both of these facts make the epoxy plug less of a
reliability threat to the PTV barrel. On the other hand, the epoxy will have a
larger CTE than the epoxy, which could make things worse, except that the
partial fill near the MLB surface should make this not a real problem enhancer
either. So, my 5˘ says, that I do not think partial epoxy fills represent a
real reliability threat.
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]
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