I'm with Dave on this one. In my opinion, it'd be much more cost effective to add an alignment legend. Speaking from experience, as I've hand placed many BGA's, all you really need to do is hit the pads. Even with Pb Free Chemistries, the part should self align. And I'm not even sure where you'd put alignment pins on the bottom of a BGA. And considering the artwork on the PCB required for a BGA, QFN, LGA or CSP component, where would you put the alignment holes on the board?
My 32 cents...
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