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How to extract the capacitance between deflected parallel plates ?

Posted Apr 17, 2012, 12:09 a.m. EDT Low-Frequency Electromagnetics, Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization, Studies & Solvers Version 4.2a 3 Replies

Chang-Shun Liu
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Dear all,

I have a problem extracting the capacitance between two parallel plates when one of them is deflected due to electrostatic force.
(1) The two parallel plates are made of Silicon and are biased at 0V & 1V.
(2) There is an Air layer in between the two plates.
(3) I used three physics to analyze the case : Solid Mechanics, Electrostatics and Moving Mesh.

So far, it seems I can only extract the capacitance when there is no electrostatic force induced deflection. The capacitance doesn't change with different electrostatic force (deflection). I think the main problem in my simulation is lack of a "Link" between Solid Mechanics and Electrostatic Physics which can bring the mechanical effect into the electrostatic analysis.

Can anyone help me with this problem ?
Please find my .mph file in the attached document.

Thank you so much !!!!

Pantani
3 Replies Last Post Aug 7, 2012, 3:51 p.m. EDT
COMSOL Moderator

Hello Chang-Shun Liu

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Paolo Minotti
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Posted: 1 decade ago Jul 16, 2012, 7:54 a.m. EDT
I'm interested, too!
I'm interested, too!
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jul 17, 2012, 2:46 a.m. EDT
Hi

first of all you have the EMI physics that couple ES/EC and solid with ALE embedded

then I have a few rearks on your model:

if you lower electrode is fixed, you can supress it fully (less to mesh and to calculate), ES does not allow "transport" of charges hence defining the lower air interface as a GND is enough.
The structural part is then only the top block, the ES the middle "air" block (or both).
And push up your ALE node as first physics node (if I remember right check the doc), here order of the physics nodes are important, structural has its own "ale" by the spatial deformations and should therefore be after the ALE to overwrite whatever needed

then in your ALE do not constrain fully the lateral sides of the air this will not allow the mesh to deform correctly

meshing: I would suggest to mesh as a surface with "extra fine" the top boundary, then sweep it through the thickness with at least 3 elements in the thickness per layer

--
Good luck
Ivar
Hi first of all you have the EMI physics that couple ES/EC and solid with ALE embedded then I have a few rearks on your model: if you lower electrode is fixed, you can supress it fully (less to mesh and to calculate), ES does not allow "transport" of charges hence defining the lower air interface as a GND is enough. The structural part is then only the top block, the ES the middle "air" block (or both). And push up your ALE node as first physics node (if I remember right check the doc), here order of the physics nodes are important, structural has its own "ale" by the spatial deformations and should therefore be after the ALE to overwrite whatever needed then in your ALE do not constrain fully the lateral sides of the air this will not allow the mesh to deform correctly meshing: I would suggest to mesh as a surface with "extra fine" the top boundary, then sweep it through the thickness with at least 3 elements in the thickness per layer -- Good luck Ivar
Vishnu Nair
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Posted: 1 decade ago Aug 7, 2012, 3:51 p.m. EDT
hi i am modeling a capacitor where i am giving 2 positve voltage to both the terminal so that the field is send outside and when i bring a object near it (floating potential) there should be change in capacitance which is not happening can anyone help. see the attachment

i am getting the wave but the capacitance dont change .
hi i am modeling a capacitor where i am giving 2 positve voltage to both the terminal so that the field is send outside and when i bring a object near it (floating potential) there should be change in capacitance which is not happening can anyone help. see the attachment i am getting the wave but the capacitance dont change .

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