It's not normally called the melting temperature, it's normally called somthing like the highest rated temperature.
Some components are stable right up to their melting temperatures leaving little room for error.
For example, my Athlon XP is stable at 83 degrees and beyond, and AMD says the Palomino core melts at a little over 90. I found that stat in a whitepaper on the AMD site. I can't seem to find a compilation of those stats anywhere.