QuickField

A new approach to field modelling

Main >> Applications >> Sample problems

Interdigital capacitor

interdigitated capacitor capacitance, PCB capacitor, thin film capacitor, interdigital capacitor model

This is an example of the interdigital capacitor simulation, performed with QuickField software in both 2D and 3D formulations.

Problem type:
Plane-parallel problem of Electrostatics,
3D extrusion model of Electrostatics.

Geometry:
Interdigital capacitor Determine the self-capacitance of the interdigital capacitor. 0.5 mm 0.25 mm FR4 board Trace - Trace +

Trace thickness 40 μm. Board thickness 0.4 mm.

Given:
Relative permittivity of the FR4 dielectric ε = 4.7;
The voltages applied to capacitor plates are -0.5 and +0.5 V.

Task:
Determine the self-capacitance of the interdigital capacitor.

Solution:
Interdigital capacitor is designed to be made by the microstrip lines on the PCB. Its capacitance is defined by the air gap between the electrodes. To correctly simulate the interdigital capacitor we need a full 3D analysis.
However, for brief evaluation of the capacitance we may use 2D approach. We can virtually straighten the capacitor and calculate the capacitance between two planar electrodes in 2D. As the length of the model, we take the length of the mid-line along the capacitor gap, which equals to L = 7250 micrometers.
Capacitor capacitance in both 2D and 3D formulations can be obtained from the energy of the electric field W and the potential difference U:
C = 2W / U²

Results:
Interdigital capacitor capacitance in 2D: C = 2 * 1.54e-13 / 1²= 0.31 pF.
Interdigital capacitor electric stress

Interdigital capacitor capacitance in 3D: C = 2 * 1.27e-13 / 1² = 0.25 pF.
Interdigitated capacitor capacitance

  • Download simulation files (files may be viewed using any QuickField Edition).
  • Transformers simulation with QuickField. Part 2

    Product
    Order
    Evaluation request
    Editions
    Version history
    Packages
    Components
    Programming
    Consulting

    Applications
    Industrial
    Educational
    Scientific
    Sample problems
    Success stories
    Customers

    Support
    Webinars
    Virtual Classroom
    Online courses
    Customer login
    Glossary
    QuickField help
    FAQ

    Downloads
    QuickField Student Edition
    User manual
    Data Libraries
    Video
    Free tools

    News
    Product News
    Events
    Publications
    Subscription

    Contacts
    Tera Analysis info
    Resellers
    Contact us
    Online chat
    About us