Morning Jim,
I would approach the problem by asking the question, how did the balls get
there?  2 obvious answers are:  the paste was misprinted & the reflow
profile was incorrect.
The misprint is easy to fix but the profile may take some tweaking:  solder
balls are a result of paste being dried too quickly (creating the skin
effect) and also from paste not being dried enough, prior to the reflow
zone.
Are the balls under each chip or under certain chips in a particular area of
the board?  Does your profile match with the solder paste manufacturer's
suggested profile?

Steve Sauer
Mfg Engineer
Xetron Corporation

-----Original Message-----
The solder balls seem to be
stuck under the chip components.  They are very difficult to see,  you have
to actually tilt the board sideways and look under the components.

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