The questions I have are related to back-to-back BGA assembly on
     double sided surface mount designs.  A common application is reverse-
     pinned memory devices, i.e. which lets both parts share similar
     signals (data line, address line, etc.).  Specifically,

     1.   Are the BGA's commonly mounted with their pads exactly mirror
     imaged?

     2.   Can they share common vias?

     3.   Are there any known reliability issues with implementing directly
     mirrored pad configurations?

     Bruce Tostevin
     Benchmark Electronics
     Hudson, New Hampshire

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