Just add one:

To high pressure during auto load (no soft landing)

Siggi

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-
Kind regards / Mit freundlichen Grüßen

Dr. Siegmund Zweigart
New Technology Manager

Solectron GmbH
Solectronstrasse 2              Fon. ++49 7032 998 194
D - 71083 Herrenberg         Fax  ++49 7032 998 222

e-mail: [log in to unmask] <mailto:[log in to unmask]> 
internet: www.solectron.com <http://www.solectron.com> 
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        ----------
        From:  Francis Sun [SMTP:[log in to unmask]]
        Sent:  Mittwoch, 11. Dezember 2002 17:00
        To:  [log in to unmask]
        Subject:  [TN] Solder ball causes

        Hello,

        I would like to compile a list of what may cause solder balls to
form after
        reflow for our internal consumption.
        Can anyone add to my limited knowledge on some of the causes that
can
        create solder balls?
        My knowledge is limited and some may not be correct. If any are not
correct
        please point them out.
        If there is a comprehensive list available in the public domain, it
would
        be great if someone can point me in the general direction of where
it is
        located.


        Some of the causes that I sort of know of:   !! BE WARNED !! some or
all
        may not be correct. :

        Moisture from substrate and components
        Dry solder paste
        Wet solder paste?
        Stencil aperture(s) too big
        Wrong pad geometries
        Poor mixing of solder paste
        Solder did not reach room temperatures?
        Solder paste passed shelf life?
        Environment to humidity?
        insufficient heat
        Dwell time under liqudius is too long?
        Dwell time under liqudious is too short?
        Time interval too long between solder application and reflow?

        Any help is appreciated.


         Happy Holidays to all

        Francis Sun
        MARK IV Industries
        (905) 624-3025 ext. 1235
        Fax: (905) 624-4572

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