Author 
Topic 

tnt
Belgium
2 Posts 
Posted  Sep 24 2024 : 19:03:22

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
542 Posts 
Posted  Sep 27 2024 : 19:34:57

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



tnt
Belgium
2 Posts 
Posted  Sep 28 2024 : 22:04:08

One thing I'm not sure how to write in the input file is semiinfinite 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.



Enrico
542 Posts 
Posted  Sep 30 2024 : 11:22:37

Hi Sylvain,
there are no semiinfinite 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




Topic 


