Posted on January 14, 2015 at 08:31According to datasheet, table Thermal characteristics, Storage temperature range, it may go up to 150 deg.C. However, this does not include impact on FLASH. Elevated temperature undoubtedly reduces retention - charge leakage from the floating gate increases exponentially with temperature, unfortunately the exponent and its variations are process dependent, so it's almost impossible to say anything binding without the assistance of the manufacturer.
A rough estimate can be made from the datasheet data, though: retention at 85 deg.C is 30 years, and at 105 deg.C is 10 years, i.e. a 3x decrease in retention for cca 20% increase of temperature; thus further 20+20% increase in temperature should result in 3x 3x = 9x decrease in retention, resulting in roughly 1 year. OTOH, you are not going to keep it in autoclave all the time; if it's there say 10% of time and the rest of the time it is at say up to 50 deg.C (which is roughly the operation temperature of the chip at room temperature, dependent of course on the clock frequency, power supply etc.) where temperature impact on retention is negligible, IMO it should be quite safe to say the data in FLASH are OK for a couple of years, maybe up to 10.
Still bear in mind, that there might be more complex failure mechanisms ahead, so again, nothing definitive can be said without the manufacturer's comment.
JW
