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Capacitively Coupled devices (Pixel detector)
Posted 22 apr 2016, 05:15 GMT-4 Low-Frequency Electromagnetics, Results & Visualization Version 5.2 7 Replies
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Hi all,
I am new at COMSOL and I have been struggling to find how I can perform the simulation and extract the results that I need.
Problem:
I work at ATLAS/CERN and I need to simulate a appreciatively coupled pixel detector that we are studding.
Basically we have a pixel sensor glued to a readout chip.
You can imagine the pixel sensor as some copper pads isolated of each other by an insulator. Under these pads, on the other side of the glue, there is the pads of the readout chip.
If you think about an 3x3 matrix on both sensor and chip, I need to simulate how the charge, or voltage, changing in the middle sensor pixel will affect the other 9 pads in the readout chip.
Basically, a matrix of parallel plates capacitors and I need to check the cross capacitance.
Where I am:
I already have a complete 3D model of the detector (form SOLIDWORKS) and I already positioned everything in COMSOL (materials; terminals and ground, and etc...).
For that I am using the electric currents physics with a small-signal analysis, frequency domain study.
I am able to see the electric fields and potential.
Does anyone know how to extract the cross capacitance or a good reference material for that?
Attached there is a picture of the cross section of the device. It shows 1/4 of the chip if the octagonal pads of the sensor, on top, and the pads of the readout chip exposed on bottom.
Many thanks in advance.
I am new at COMSOL and I have been struggling to find how I can perform the simulation and extract the results that I need.
Problem:
I work at ATLAS/CERN and I need to simulate a appreciatively coupled pixel detector that we are studding.
Basically we have a pixel sensor glued to a readout chip.
You can imagine the pixel sensor as some copper pads isolated of each other by an insulator. Under these pads, on the other side of the glue, there is the pads of the readout chip.
If you think about an 3x3 matrix on both sensor and chip, I need to simulate how the charge, or voltage, changing in the middle sensor pixel will affect the other 9 pads in the readout chip.
Basically, a matrix of parallel plates capacitors and I need to check the cross capacitance.
Where I am:
I already have a complete 3D model of the detector (form SOLIDWORKS) and I already positioned everything in COMSOL (materials; terminals and ground, and etc...).
For that I am using the electric currents physics with a small-signal analysis, frequency domain study.
I am able to see the electric fields and potential.
Does anyone know how to extract the cross capacitance or a good reference material for that?
Attached there is a picture of the cross section of the device. It shows 1/4 of the chip if the octagonal pads of the sensor, on top, and the pads of the readout chip exposed on bottom.
Many thanks in advance.
Attachments:
7 Replies Last Post 27 apr 2016, 03:47 GMT-4
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Posted:
8 years ago
Dear Mateus,
there is a perfect example for you: the touchscreen sensor. It comes as an app but you can of course also study the underlying model. It uses a 10x10 electrode matrix and the feature terminal sweep to derive the capacitance matrix.
www.comsol.ch/model/touchscreen-simulator-30841
Best regards,
Sven
there is a perfect example for you: the touchscreen sensor. It comes as an app but you can of course also study the underlying model. It uses a 10x10 electrode matrix and the feature terminal sweep to derive the capacitance matrix.
www.comsol.ch/model/touchscreen-simulator-30841
Best regards,
Sven
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Posted:
8 years ago
Dear Sven,
beautiful. Many thanks for your help. That's exactly what I need.
I already took a look in the application and managed to implement it on my geometry.
Now I have, what I believe to be, the Maxwell capacitance matrix.
But, I got some (new) questions now.
I believe that the capacitance should change with the frequency of the signal. This is not being taken into account in this model, right?
Also, what is the parametric sweep doing? Does it change the terminals voltages from 0 to the voltage set, for each terminal?
Thank you for your help, once more.
Cheers,
Mateus
beautiful. Many thanks for your help. That's exactly what I need.
I already took a look in the application and managed to implement it on my geometry.
Now I have, what I believe to be, the Maxwell capacitance matrix.
But, I got some (new) questions now.
I believe that the capacitance should change with the frequency of the signal. This is not being taken into account in this model, right?
Also, what is the parametric sweep doing? Does it change the terminals voltages from 0 to the voltage set, for each terminal?
Thank you for your help, once more.
Cheers,
Mateus
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Posted:
8 years ago
Hi Mateus,
1) The capacitance should only change with frequency, if you have a frequency dependent material and you use, of course, a frequency dependent study. Otherwise it's a property that depends on geometry only.
2) A parametric sweep is a general functionality, that changes the value of a parameter and performs a sequence of simulations. IN particular, a termail sweep, will change the number of the active terminal (where a signal is applied) and hence allows to calculate the capacitance matrix.
Sven
1) The capacitance should only change with frequency, if you have a frequency dependent material and you use, of course, a frequency dependent study. Otherwise it's a property that depends on geometry only.
2) A parametric sweep is a general functionality, that changes the value of a parameter and performs a sequence of simulations. IN particular, a termail sweep, will change the number of the active terminal (where a signal is applied) and hence allows to calculate the capacitance matrix.
Sven
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Posted:
8 years ago
1) The capacitance should only change with frequency, if you have a frequency dependent material and you use, of course, a frequency dependent study. Otherwise it's a property that depends on geometry only.
2) A parametric sweep is a general functionality, that changes the value of a parameter and performs a sequence of simulations. IN particular, a termail sweep, will change the number of the active terminal (where a signal is applied) and hence allows to calculate the capacitance matrix.
Hi Sven,
you said that the capacitance should only change with frequency. But then you said that the capacitance is a property that depends only on the geometry. Can you clarify it for me, please?
Also, I understand that the parametric sweep perform sequence of simulations, sweeping between any thing that I set as a parameter (parameter name in this case).
So you said that in our case it changes the active terminal, where a signal is applied.
But the capacitance wouldn't change as a function of this signal, such as frequency that the signal is applied? And, is it possible to change the amplitude of the signal applied?
Many thanks once more.
M.
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Posted:
8 years ago
HI Mateus,
my sentence 1) was a conditional clause containing an if statement.
Capacitance is a function of geometry.
IF (material properties are frequency dependent)
THEN (capacitance is additionally a function of frequency)
I hope I am not missing your point, but the above should be understood from revising a simple plate capacitor. en.wikipedia.org/wiki/Capacitor_types C=epsilon*A/d
Sinca A and d are geometrical quantities the only way a frequency dependency can enter is by dependence of epsilon on it. Additionally, the capacitance is typically not a function of the signal amplitude either (unless you have a nonlinear material).
In principle everything of the above effects can be included but you would need to bring it in by suitable material data, but it should be clarified thoroughly beforehand where you actually want to go.
Best regards,
Sven
my sentence 1) was a conditional clause containing an if statement.
Capacitance is a function of geometry.
IF (material properties are frequency dependent)
THEN (capacitance is additionally a function of frequency)
I hope I am not missing your point, but the above should be understood from revising a simple plate capacitor. en.wikipedia.org/wiki/Capacitor_types C=epsilon*A/d
Sinca A and d are geometrical quantities the only way a frequency dependency can enter is by dependence of epsilon on it. Additionally, the capacitance is typically not a function of the signal amplitude either (unless you have a nonlinear material).
In principle everything of the above effects can be included but you would need to bring it in by suitable material data, but it should be clarified thoroughly beforehand where you actually want to go.
Best regards,
Sven
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Posted:
8 years ago
Hi again Sven,
and many thanks for all the help.
I see. You are right.
I am interested in perform a frequency study because my glue layer indeed change its dielectric constant, epsilon, as function of the signal frequency applied on the terminals.
But, as you said, I believe that I can reproduce the result of the Frequency Dependent Study by performing a Parametric Sweep in the capacitance variable for the material that makes my glue layer, right?
So I created a new variable (named dielectric_constant) in the Parameters <- Global Definitions that will be my dielectric constant, and inserted a second parameter in the Settings of the Parametric Sweep with the Parameter Value List containing the range of values that I want to scan.
On the Material Contents of my Materials list (from comp1), I wrote the name of my variable (dielectric_constant) in the Value field of the Relative Permittivity.
Doing so, with the Parametric Sweep, the Relative permittivity should be scanned, right?
But this created a new question for me.
Under Global Definitions -> Parameters (following the touch screen example) I created a variable called terminalName and on the Parametric Sweep I scan it over the number of the terminals that I have in my model.
But how the Parametric Sweep of this Global Definition changes the active terminal if in the Terminal Settings (under Electrostatics) this terminalName is not being used?
And also, I was interested to know how the signal is applied on the terminal, and if I can change its value, to understand and implement it in future simulations, to understand how an AC signal is transferred from the sensor to the readout chip. But I believe that I can do that by selecting the Terminal Type to charge and changing the Initial value for the voltage, right?
Many thanks once more,
Mateus
and many thanks for all the help.
I see. You are right.
I am interested in perform a frequency study because my glue layer indeed change its dielectric constant, epsilon, as function of the signal frequency applied on the terminals.
But, as you said, I believe that I can reproduce the result of the Frequency Dependent Study by performing a Parametric Sweep in the capacitance variable for the material that makes my glue layer, right?
So I created a new variable (named dielectric_constant) in the Parameters <- Global Definitions that will be my dielectric constant, and inserted a second parameter in the Settings of the Parametric Sweep with the Parameter Value List containing the range of values that I want to scan.
On the Material Contents of my Materials list (from comp1), I wrote the name of my variable (dielectric_constant) in the Value field of the Relative Permittivity.
Doing so, with the Parametric Sweep, the Relative permittivity should be scanned, right?
But this created a new question for me.
Under Global Definitions -> Parameters (following the touch screen example) I created a variable called terminalName and on the Parametric Sweep I scan it over the number of the terminals that I have in my model.
But how the Parametric Sweep of this Global Definition changes the active terminal if in the Terminal Settings (under Electrostatics) this terminalName is not being used?
And also, I was interested to know how the signal is applied on the terminal, and if I can change its value, to understand and implement it in future simulations, to understand how an AC signal is transferred from the sensor to the readout chip. But I believe that I can do that by selecting the Terminal Type to charge and changing the Initial value for the voltage, right?
Many thanks once more,
Mateus
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Posted:
8 years ago
Hi,
I think I understood how the terminals are changed.
In the Electrostatics Settings, under Terminal Sweep Settings, I can activate the terminal sweep clicking on the check box and insert the sweep parameter name.
Somethings are so easy to use that sometimes do a complicated action is simple and I think that I need to do something more.
First time using COMSOL… lots of things to learn.
Cheers,
Mateus
I think I understood how the terminals are changed.
In the Electrostatics Settings, under Terminal Sweep Settings, I can activate the terminal sweep clicking on the check box and insert the sweep parameter name.
Somethings are so easy to use that sometimes do a complicated action is simple and I think that I need to do something more.
First time using COMSOL… lots of things to learn.
Cheers,
Mateus