Etched anode foil capacitance - QuickField simulation example
Capacitance of the capacitors depends on the size of the electrode surfaces. To increase the surface area, anodes of the aluminum electrolytic capacitors are are electrochemically etched.
How to find electric field concentration near holes in capacitor foils?
Answer Typical applications Geometry
Given
Task
Solution
Results
In this example we calculate the capacitance of the film with a cylindrical pit which represents a small part of the electrolytic capacitor.
Engineering question
Set up a 3D QuickField Electrostatics problem for an etched capacitor foil structure and evaluate electric field concentration near holes from computed field results.
electrolytic capacitor electrodes, etched aluminum foils, capacitor dielectric structures
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Simulation problem
Problem Type
3D problem of electrostatics.
Relative permittivity of aluminum oxide ε = 10.
Calculate the capacitance of a film with a cylindrical pit.
We apply electric potential +1V to anode and -1V to cathode. QuickField then calculates the electric potential distribution and the stored electric field energy.
The capacitance is 2*Energy / (Potential difference)².
The geometry model features symmetry, so we simulate only a quarter of the full model.
Stored energy 5e-14 W. Potential difference is 2V. Capacitance is 2*5 e-14 / 2² = 0.025 pF per 5μm*5μm of the foil area.
Anode foil specific capacitance is 0.025 / (5e-6*5e-6) = 100 nF/mm².
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