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

At 10:16 AM 12/17/97 EST, Engelmaier wrote:
>Hi,
>There is a lot of mis-information floating around on filled vs unfilled
>plated- through vias (PTVs).
>Completely filled PTVs are the most reliable, partially filled PTVs the least
>reliable, and unfilled PTVs less reliable than completely filled PTVs, but not
>by much. However, since nobody can guarantee that all PTVs in a MLB will be
>completely filled with solder, it is much better to prevent solder filling to
>avoid the occurence of partially filled PTVs.
>Having said all that, it must be pointed out that all of this is only an issue
>of practical importance if the product application has an operating
>environment with some severity.
>
>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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______________________________________________________
Ken Patel                       Phone:  (408) 490-6804
575 Cottonwood Dr.              Fax:    (408) 490-6859
Milpitas, CA 95035              Beeper: (888) 769-1808

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