Maybe my brain is starting to fade already, but I can't figure out how to
select the appropriate temperature curve when calculating PCB trace widths
versus current requirements.

If you use the chart in IPC-D-275 or IPC-2221, you have to select a curve to
get your minimum trace width.
If you use a calculator, it will solve for the temperature rise, but you
still must know if it is acceptable.
So what is acceptable? Anything that won't make the material hit Tg?
I even re-read the proceedings of Doug Brooks class at the Design Conference
(excellent, but no help regarding temperature)

The easy answer is "Well, the engineer will know what is acceptable"
but what if the input from "over the wall" is to "Just use the worst case"?

Am I missing something?

Jack

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