Jeff -
The Max temp you shouldn't exceed for an application depends upon the
application.  There can't be a set "max temperature" because everyone's
assembly compoistion is different.
Usually it is a component that has the "lowest thermal threshold of pain" but
it could be (if, for example, there are components on the board that can
withstand fairly high temperatures) the substrate, maybe even the solder
paste.  It is up to you to determine whatever it is that is the Most
Vulnerable Component (MVC) on the assembly.  Whatever that it is, I suggest
taking the temperature its manufacture says it shouldn't exceed and subtract 5
deg. C from that value as a buffer.  The resulting temperature should not be
exceeded anywhere on the assembly.  This defines the upper limit of the reflow
temperature envelope at peak.  The lower temperature, Full Liquidus Temp or
Reflow Temp is defined by the solder paste manufacturer and is usually about
25-30 deg C above the alloy's melting point.

Phil Zarrow
ITM, Inc.
Durham, NH  USA
www.ITM-SMT.com

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