H Simon,
Some BGAs come with voids already in the solder balls--you mmay want to check
for this. The problem with this scenario is reduced solder volume.
If your processes create the voids, it is only a problem if a shear test
shows a failure mode through the solder balls with voids rather than near the
interfaces or pads.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 386-437-8747, Fax: 386-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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