RF Skin Depth Calculator
Calculate the current penetration depth in conductors at high frequencies.
At 1 GHz, 63% of the current flows within the outer 2.09 µm of the Copper conductor.
Skin Depth Quick Facts
Engineering Principles: Skin Effect & Depth
The skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface. 'Skin Depth' is the depth at which the current density reaches 1/e (about 37%) of its surface value.
ω=Angular Freq, μ=Permeability, σ=Conductivity.
Rule of thumb for Copper traces.
Effective resistance increases as skin depth decreases.
Technical Notes
- •At microwave frequencies (GHz), current flows in a extremely thin layer (microns).
- •Surface roughness of the PCB copper becomes critical when it exceeds the skin depth.
- •Skin effect increases the effective resistance and inductance of transmission lines.
Frequently Asked Questions
Why does Skin Depth matter for PCB design?
As frequency increases, current is crowded into a thinner layer of copper (the skin). This effectively reduces the cross-sectional area of the trace, increasing its resistance (AC resistance). This leads to higher signal loss (insertion loss) and heating in high-power applications.
How does Surface Roughness affect Skin Effect?
If the surface roughness of the copper foil is comparable to or larger than the skin depth (common at frequencies >10 GHz), the current must follow the 'hills and valleys' of the rough surface. This increases the effective path length, significantly increasing resisistive losses beyond the standard skin effect predictions.
What is the skin depth of Copper at 1 GHz?
At 1 GHz, the skin depth of standard annealed copper is approximately 2.09 micrometers (µm). Since standard 1oz copper is 35µm thick, the vast majority of the copper cross-section is unused by the current.