........
>
>Now that we can get heat rise on a trace, which I had some data on before, what
>is a safe operating temperature?  If board browning or mask discoloration
is the
>primary limitation for your design, at what absolute temperature does the mask
>begin to be damaged?  If we know the absolute temperature, then we know the
>ambient+rise.
>

The general bent of this thread seems a little strange to me.

As a general rule of thumb in electronics, it seems reasonable to
allow 2-3x safety margin on most critical design decisions - especially
those concerning power dissipation levels. It would seem that even so
much as thinking about driving traces to the point where they are
heating up or glowing or discoloring the pcb might be like flying
too close to the sun on waxed wings.