Trace self-inductance relationship with width

because magnetic field cancelation will be better

when a trace's width become wider.

best regards

Self inductance occurs because of the expanding magnetic field created by a changing current within a conductor.

Picture in your mind a thin current "strand" in the center of a conductor. As the current through that thin "strand" changes, the magnetic field around the current "strand" changes. If the "strand" is thin enough, the field lines are cutting through the adjacent copper of the conductor and inducing opposing current in the same conductor in which the "strand" is located. The opposing current delays the buildup of the total current - exactly what an inductor does.

Now, look at what is really happening. The current in the conductor isn't confined to a "strand" - it is distributed throughout the conductor volume. The same current flowing in a wide conductor has a lower current density (fewer electrons per unit volume) than when it flows through a thiner conductor. Or, another way to look at it using "strands" again to visualize the current, the total current is made up of an infinite number of "strands" distributed across the cross section of the conductor. Each "strand" has a lower current in the wide conductor that a similar "strand" in a narrow conductor for the same total current. The resulting field per strand is then smaller in the wide conductor than it is in the narrow conductor. Less magnetic field strength means less induced opposing current, which translates into lower apparent inductance.

To sum up - the wide conductor has less self inductance than the narrow conductor because it has a lower current density. There are fewer electrons per unit volume flowing in the wide conductor than are flowing in the narrow conductor for the same total current. Fewer electrons per unit volume means less generated magnetic field per unit volume.