EMC Question of the Week: September 10, 2017

The skin depth in copper at 100 MHz is,

1. about 7 microns
2. about 7 millimeters
3. about 70 centimeters
4. about 7 kilometers

Answer

The correct answer is "a". Skin depth can be calculated using the equation $\delta =\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$\sqrt{\pi f\mu \sigma }$}\right.$ where μ is the permeability of copper (μ₀ or 4π x 10^-7 H/m) and σ is the conductivity of copper (~ 5 x 10⁷ S/m).

For reference, the thickness of the half-ounce copper commonly used in printed circuit boards is 0.7 mils or about 18 microns.

Have a comment or question regarding this solution? We'd like to hear from you. Email us at This email address is being protected from spambots. You need JavaScript enabled to view it..