How do I subtract metal around a via passing through a ground-flood for EM Extraction in Microwave Office?

Hi Eric,

VIA and MLIN are appropriate for what you are trying to do.    +/- layers will perform the boolean op during the extraction as well as being visible in the 3D view.

Please take a look at the lpf in the demo PDK "AWR_RFBoard_2layer" where you'll see $STRUCT_TYPE statements used to define the vias, in this case with/without the cutouts for each layer.  You can find it by going File>New_with_Library>AWR_Example_Libraries>AWR_RFBoard_2layer then open the lpf in the text editor.

You need to set the SNAME secondary parameter on the VIA model to select the appropriate STRUCT_TYPE for the pcell to draw.   You'll also need to add a STRUCT_TYPE to your lpf for each specific via type you want it to draw.

Best Regards,

Graeme

Hi Graeme, 

This sounds exactly what we need. I gave it a try with the RFBoard_2layer example just as you described, but when I created a VIA and put an MLIN over it there wasn't a hole around the via like you show in your 3d picture.  Did you make any other changes besides the step-by-step that you made above?  I tried to follow it but I must be missing something.  

In your 3d picture, what is the square around the VIA?  Is it an MLIN? Did you change the shape properties of any of the layout elements?

Thank you for your help!

-Eric

The square was to represent my ground flood and it's drawn on the Cu_01+ layer.   Per the via setup in the lpf, a cutout is automatically subtracted from it by using a larger circle of Cu_01- in the via stack.   With the MLIN, it's drawn using the linetype which is made up of the Cu_01 and Cu_01- layers.   That way the -ve layer draws a cutout in the ground flood and the solid layer can connect to the via straight through the cutout the via's -ve layer is generating.

I think I got it:  I added an LPF layer called Layer01_Cu_01+ with only Cu_01+ so I can use it as the line type for the MLIN.  In the picture below the purple is just a piece of metal on Cu02+ drawn with ctrl-b and the copper color is an MLIN with the Cu_01+ line type.

Questions:

• What did you mean by "-ve" layer?
• I looked but did not find the documentation for $STRUCT_TYPE_BEGIN/END.  Where are the flags defined for LINE_TYPE and STRUCT_TYPE?
  • Is there complete LPF documentation somewhere?

I think I got it:  I added an LPF layer called Layer01_Cu_01+ with only Cu_01+ so I can use it as the line type for the MLIN.  In the picture below the purple is just a piece of metal on Cu02+ drawn with ctrl-b and the copper color is an MLIN with the Cu_01+ line type.

Questions:

• What did you mean by "-ve" layer?
• I looked but did not find the documentation for $STRUCT_TYPE_BEGIN/END.  Where are the flags defined for LINE_TYPE and STRUCT_TYPE?
  • Is there complete LPF documentation somewhere?

Well I haven't found the LPF and STRUCT_TYPE documentation, but I have learned about flags through experimentation in case others find this useful:

• Flags are binary flags appear to be added (or'ed) together: 1, 2, 4, 8, ...
  • 1: structure is square (0) or round (1)
  • 2: faces snap to center (0) or side (1)
  • 4: unknown, but used by the Cu_01 and Cu_02 layers in the VIA0-3 structures in AWR_RFBoard_2layer.lpf
  • 8: unknown, but used by the Cu_01- and Cu_02- layers in the VIA0-3 structures in AWR_RFBoard_2layer.lpf
  • The SMTpad struct also uses flags 10,11,12,13,14 which might indicate deviation from the binary flags being or'ed together