I would have to say you are correct, the testing for opens on
BGAs is difficult, even with the HP 5DX machine we have here. I can't
recall having seen a single open joint on a properly reflowed
collapsible BGA, but we have seen them on non-collapsible.
     How would you attempt to verify that the package is parallel to
the board surface? I know some of the OMPAC plastic packages that we
use will occasionally be lower in the center than the edges, although
not by very much.
     I look forward to other comments from Xray users about this
subject.
     Paul Quintin
     Data General

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