Use the same process as any other SMT process with a few Precautions.
1) BGA are very susceptible to moisture, bake them if they have been exposed.
2) Inspect Solder paste before placement, 100% (this is normally the biggest
gotcha)
3) If placement is off, do not attempt to "tweak" the part, remove clean board
and part and reapply solder paste.
4) Profile with a thermocouple attached to the solder ball, (drill a small
hole through the board and feed the wire from the bottom (a ball closet to the
middle is best)

Hope this helps

Mike

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