The skin depth (δ) of RF in copper at 1420 MHz can be calculated using the formula:
δ = √(2/(ωμσ))
Where:
- ω = 2πf (angular frequency)
- μ = μ₀μᵣ (permeability of copper ≈ μ₀ = 4π × 10⁻⁷ H/m)
- σ = conductivity of copper ≈ 5.96 × 10⁷ S/m
At f = 1420 MHz (the hydrogen line frequency):
δ = √(2/(2π × 1420 × 10⁶ × 4π × 10⁻⁷ × 5.96 × 10⁷))
δ ≈ 1.73 micrometers (μm) or about 0.0017 mm
This extremely shallow skin depth means that at 1420 MHz, the RF current flows in a very thin layer near the surface of the copper conductor. This has important practical implications.
And for aluminum:
δ ≈ 2.12 micrometers (μm) or about 0.0021 mm
So aluminum’s skin depth at 1420 MHz is about 23% larger than copper’s (2.12 μm vs 1.73 μm), which makes sense since aluminum has lower conductivity.
Practical implications:
- Aluminum requires slightly thicker plating or surface layers for the same effectiveness
- Still very shallow, so surface condition remains critical
So copper tape and aluminum tape should be quite sufficient for forming “stuff” at the H2 line. Note the caution re surface condition.
The formula and calculations are correct