Dear TechNet,
My company has been  asked to bid on assembling a board that would have
two BGAs on the topside and two more BGAs mirrored on the bottomside.
That is, they will be directly across from each other on both sides. I
never done them on both sides. So far, everything that I have done has
been on one side only. Has anyone done them on both sides before?
 
  I am figuring xray will be a problem as after the second side is
placed, because the pads/balls will mirror each other on both sides.
Would I be able to tell the difference between the two BGA connections?
Suggestions?
 
Will I need to epoxy the first side BGAs so they would not drop off
during my second reflow? Wouldn't I need to epoxy them after first
reflow so that the balls could collapse?
 
Thanks,
Larry Koens 
SMT Manufacturing Engineer
E.I. Microcircuits 
Mankato, MN

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