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Subject:
From:
"Michaud, James (STP)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 16 Sep 1998 08:30:40 -0500
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Marcelo -

        Hello. I am a Reliability Engineer working for a Medical Electronics
company. We're currently reviewing BGA reliability. We'll be producing
equipment for hospital Emergency Rooms.

        I've noticed the discussion on BGAs you've been involved in.
        I'm concerned about BGA reliability issues. You mentioned "there is
a lot that the industry still do not know about reliability." In your
opinion,
        what are the most critical BGA reliability issues? Our guys think
plastics are better than ceramics. What do you think?

        James Michaud
        Guidant-CRM/CPI
        Dept. 5512, MS F240
        4100 Hamline Ave. N.
        St. Paul, MN 55112-5798
        (612) 582-7842



> -----Original Message-----
> From: Chan, Marcelo [SMTP:[log in to unmask]]
> Sent: Wednesday, September 16, 1998 6:55 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] X-ray for open joints on BGA's ?
>
> Hi Werner,
>
> How is life in Florida? In response to your e-mail, I do agree that all
> things
> being the same, a higher stand-off will decrease the magnitude of the
> localized
> stress and thus increase the reliability of the joints according to
> published
> data... but I do disagree with your statement about 'having nothing to do'
> with
> the other input that people have given...increasing stand-off height may
> be the
> most important, but it is not the only reason.... there is a lot that the
> industry still do not know about reliability... reliability is application
> dependent...and I wish that the only issue with using ceramic BGAs with
> high
> temp solder (balls or columns) was stand-off height...but we know better
> now,
> but we still need to keep conducting reliability tests to know even
> more...
>
> marcelo
>
>         -----Original Message-----
>         From:   Werner Engelmaier [SMTP:[log in to unmask]]
>         Sent:   Tuesday, September 15, 1998 12:42 PM
>         To:     [log in to unmask]
>         Subject:        Re: [TN] X-ray for open joints on BGA's ?
>
>         Hi 'eholton', Marcelo, & Steve,
>         Lets remember why there are high-melt solder balls and columns on
> CBGAs;
> it is
>         to reduce the strains on the solder joints due to the large
> thermal
> expansion
>         mismatch between the ceramic and the FR-4 by assuring large solder
> joint
>         heights (stand-offs). It has nothing to do with cleaning, package
> weight, or
>         devices generating heat. For BGAs, particularly CBGAs, a reflow
> profile
> with a
>         peak temperature of 219C is too low even for eutectic Sn/Pb
> solder.
>         Even with high-melt solder balls you should get nice fillets
> because of
> the
>         eutectic solder paste.
>         The reliability of the solder joints goes up roughly with the
> square of
> the
>         stand-off height.
>
>         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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