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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