Hi Kai,

Yes. Changing the slew rate, or transition time, of a component can dramatically impact the performance of a circuit board. It isn't a matter of current. It has to do with the E-field setting up in the conductor.

This is counter-intuitive to most people, but the speed of an individual electron moving through a conductor isn't that fast. If you could flag an individual electron and watch it move along a wire, you'd find that in most cases you could walk faster than it migrates. (In some very high voltage/high current applications you might have to jog or run to keep up.) Remember, higher current implies more electrons, not necessarilly faster ones. It might also help if you remember that the first electrons to flow out of the conductor into the load do not start out in the source. They start from rest at the end of the conductor closest to the load. It will take a surprisingly long time for an electron that actually emerges from the source to enter into the load.

It is the E-field that propogates along the conductor at approximately the speed of light. And it's the speed at which the electric field propogates that matters. If the trace is long enough that the current is flowing at the source end before it starts flowing at the load end, then you will get signal reflections in the trace, and they can be bad.

If you want literature on this subject I would refer you to a text book. In particular I recommend "High Speed Signal Propogation" by Howard Johnson (ISBN 013084408X). Look it up on www.bn.com or www.amazon.com and you will also find similar recommendations.

Good Luck.