FastFieldSolvers Forum
FastFieldSolvers Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
 All Forums
 FastFieldSolvers
 FasterCap and FastCap2
 Best way to describe this mix of dielectric.
 New Topic  Reply to Topic
 Printer Friendly
Author  Topic Next Topic  

tnt

Belgium
2 Posts

Posted - Sep 24 2024 :  19:03:22  Show Profile  Reply with Quote

So I have this 2D structure :

ht*ps://i.imgur.com/9TJcowL.png

It's 2 wires on a chip, 0.36u thick, 0.15u wide, separated by 0.2u
The dielectric below them is k=4.5. The dielectric in the same layer as them is k=4.2 but there is also a sidewall coating for each of those wire that is 0.03u thick and k=3.5

What's the best way to describe that ?
Below is what I came up with but it seems extremely verbose and if I go to more complex wires / layers, this is becoming unwieldy.

Cheers,

Sylvain



```
* 2D

C m2_top 4.2 -0.35 0.0 +
C m2_bot 4.5 -0.35 0.0 +
C m2_side 3.5 -0.35 0.0

D dc_left 4.2 3.5 -0.35 0.0 -0.35 0.0 -
D dc_right 4.2 3.5 -0.35 0.0 -0.35 0.0 -
D dc_left_bot 4.5 3.5 -0.35 0.0 -0.35 0.0 -
D dc_right_bot 4.5 3.5 -0.35 0.0 -0.35 0.0 -


C m2_top 4.2 0.0 0.0 +
C m2_bot 4.5 0.0 0.0 +
C m2_side 3.5 0.0 0.0

D dc_left 4.2 3.5 0.0 0.0 0.0 0.0 -
D dc_right 4.2 3.5 0.0 0.0 0.0 0.0 -
D dc_left_bot 4.5 3.5 0.0 0.0 0.0 0.0 -
D dc_right_bot 4.5 3.5 0.0 0.0 0.0 0.0 -

End

File m2_top
S trace -0.075 0.18 0.075 0.18
End

File m2_bot
S trace -0.075 -0.18 0.075 -0.18
End

File m2_side
S trace 0.075 -0.18 0.075 0.18
S trace -0.075 -0.18 -0.075 0.18
End

File dc_left
S nild4_c -0.21 0.075 -0.18 0.075
S nild4_c -0.21 0.075 -0.21 -0.075
End

File dc_right
S nild4_c 0.21 0.075 0.18 0.075
S nild4_c 0.21 0.075 0.21 -0.075
End

File dc_left_bot
S nild4_c -0.21 -0.075 -0.18 -0.075
End

File dc_right_bot
S nild4_c 0.21 -0.075 0.18 -0.075
End
```

Enrico

543 Posts

Posted - Sep 27 2024 :  19:34:57  Show Profile  Reply with Quote
Hi Sylvain,

I'm afraid this is it. I've not checked the file for correctness, but your point is about the complexity of the geometrical description. I understand it, but actually you need to be able to specify in a generic enough format your geometry. Trying to simplify the input would possibly lead to limitations.

In general, for simple geometries you can prepare the input file by hand. For more complex arrangements I would suggest using either a script (if your geometry is amenable to scripting) or a CAD from which you can then export the geometry and convert it to the FasterCap format.

In general, I recommend FreeCAD as this is a parametric 3D CAD, fully open source and free, that works well also for 2D design. It is in the list of ToDo to extend the currently available ElectroMagnetic Workbench for FreeCAD to support not only FastHenry and VoxHenry but also FastCap and FasterCap. However so far I found no sponsorship, so the project is still in plan but not advancing very fast (there are some Python scripts to export 3D meshes from FreeCAD to be used in FasterCap, but not for 2D geometries, I'm afraid).

Should you be interested in either contributing or sponsoring, you can contact me via email

Best,
Enrico
Go to Top of Page

tnt

Belgium
2 Posts

Posted - Sep 28 2024 :  22:04:08  Show Profile  Reply with Quote
One thing I'm not sure how to write in the input file is semi-infinite planes.

If you look at the diagram, there is a separation plane between K=4.5 and K=4.2 diagram which I'm not actually representing in my input file ATM. I just described the little "square" of K=3.5 on each side of the conductor, but the boundary that exends to infinity isn't specified anywhere.
Go to Top of Page

Enrico

543 Posts

Posted - Sep 30 2024 :  11:22:37  Show Profile  Reply with Quote
Hi Sylvain,

there are no semi-infinite planes possible in FasterCap. Everything is considered finite (even if, of course, in 2D the depth is infinite..).
If you need to model a large plane, just make it large enough. If it is large, possibly you don't need to close it on the far side - even if physically it should be.

Best,
Enrico
Go to Top of Page
   Topic Next Topic  
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
FastFieldSolvers Forum © 2020 FastFieldSolvers S.R.L. Go To Top Of Page
Powered By: Snitz Forums 2000 Version 3.4.06