BGA soldering can be performed in air.  It usually depends on the fluxing
system used.  If your flux requires nitrogen, then you should use nitrogen.  We
solder BGAs in air.

As far as the thermal profile, the heat required to reflow the solder balls in
the center of the device is typically more than what would be required for QFP
leads.  Basically, you should re-profile your assemblies when switching from
QFPs to BGAs.

Jim Marsico
(516) 595-5879
[log in to unmask]

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