Elementary, Mr. Watson: PCB Education in the Midst of the Storms
Beyond Design: How Signals Survive the Hostile PCB Environment
Connect the Dots: What Designers Should Know About Non-conductive Via Fill
Lightning Speed Laminates: Skin Depth and Its Interaction with Final Plated Finishes
Skin depth is the depth within a conductor where the majority of the radio-frequency (RF) current resides. Imagine looking at a cross-sectional view of a circular wire and being able to see how much current is within that cross-section. If the current is supplied by a battery and is direct current (DC), the amount of current is distributed evenly across the cross-sectional area of the wire. The current density is the same everywhere in the area of that wire.
If you change the current source to a sinusoidal alternating current, then you will find that there is more current on the outer edges of the wire than in the middle of the wire. If you increase the frequency a lot, you will notice at some point there is no current in the middle of the cross-sectional area of the wire, and the majority of the current is on the very outside edge (skin) of the conductor. That is the basic concept for skin depth.
To read this entire column, which appeared in the December 2018 issue of Design007 Magazine, click here.
