Bill,
The Thermal Shock of freeze mist can stimulate or cause a crack of a marginal BGA ball but
the main concern i would have is that the Freeze Mist will cause water to condense out
of the atmosphere. The condensed water will create an electrolyte and, assuming you
are doing this with the power on the board, you will grow dendrites under the BGA and this will cause shorts on high Z lines. This will cause masking of the original defect.
Any 'power on' cold temperature testing that causes the board to go through the dew point should be avoided.
See IPC-TR-476, Sandia Labs Report SAND 75-0616, Aerospace Report TOR-0075, NASA CR-61194, MSFC Alert MSFC-68-8, GSFC Failure analysis FAR10-012 and 1160,
for additional info on the hazards of electrochemical migration and dendritic growth on PCBA's.
Paul Signorelli

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