The original bridge.geo has two ribbon vias. The re-built structure is exactly the same as the original ones. In case we want to build some square solid vias instead of ribbon vias (see Figure 4.26), how can we do it?
We start from the structure in Figure 4.20b with the gap filled. If you have changed the structure discussed in last section, you can try to rebuild it following the instructions in Section 8.
Step 1 Select Edit->Undo to recover the structure in Figure 4.20b from the bridge structure created by elevating the polygon in the gap for the bridge. You should get exactly what is shown in Figure 4.20b.
Step 2 Press down Shift key and click at the polygon at the filled gap to select it. Select Edit->Change Z-Coordinate command. The Change Z-Coordinate dialog shown in Figure 4.21 comes up again.
Step 3 Please change the New Z-Coordinate from 10 to 12. Remember un-check the Keep Polygon Connection check box before you select OK button.
The polygon filling the gap is elevated. However, the connections to other polygons are not kept or there are no 3D polygons between this polygon at Z = 12 to other polygons at Z = 10 (see Figure 4.22). We are going to build two via pads on the polygon at Z = 12 from the edge (1, 2) and edge (3, 4). Edge (1, 2) means the edge formed by vertices 1 and 2.
Figure 4.22 The elevated polygon without connections to Z = 10.
1 2 3
4
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Step 4 Select Edit->Select Vertices command. Check the No.3 Layer at Z = 12 and uncheck the No.2 Layer at Z = 10. We are going to select the vertices 1 and 2 at Z = 12 while we do not want to select the corresponding vertices at Z = 10.
Step 5 Window the vertices 1 and 2 to select the edge (1, 2) at Z = 12. Select Adv Edit->Continue Straight Path command. MGRID will detect the width of the path = 5 and set some default values for the Path Start Width, Path End Width and the Path Length. In the Continue Straight Path dialog (see Figure 4.23).
We are allowed to create a path with tapered width of any length you want. Since we are building a square via pad, we just select OK to continue. A square pad is continued from the edge (1, 2) as shown in Figure 4.24. The connection between the rectangle and the square pad is guaranteed. The square pad should be exactly over portion of the polygon at Z = 10. This is important for us to use the following command to create the via. We are going to select all the vertices (or all the edges of the square pad) to build the via.
Figure 4.23 The Continue Straight Path dialog.
Figure 4.24 The structure with the 1st square pad created.
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Step 6 Select Edit->Select Vertices again. Check the No.3 Layer at Z = 12 with other layers unchecked in the Layer Window again. Window all the vertices of the square pad to select them. In fact, the vertices 1 and 2 of the rectangle in Figure 4.21 are also selected. However, the edge (1, 2) is coincident with the corresponding edge of the square pad. We will consider only 4 edges of the square pad are selected.
Step 7 Select Edit->Add Via on Edges command. The Add Via on Edges dialog comes up (see Figure 4.25). It lists all the selected edges. Again, it indicates 4 edges are selected even though an additional edge (the edge (1, 2) from the rectangle in Figure 4.22) is selected. MGRID automatically detects the edge is coincident with another selected edge and it will not count it.
In IE3D 10.x and earlier version, MGRID will not do any connection at the end for the added via if no matching vertices or matching edges are available. On MGRID 11, you can see there is an option “Build Electrical Connection at End Z”.
Figure 4.25 The Add Via on Edges dialog.
Step 8 Enter the “End Z-Coordinate of the Via” as 10. We want to build the via from Z = 12 to Z = 10.
Please make sure the “Build Electrical Connection at End Z” is checked. Select OK to continue.
MGRID built the via. The 3D view looking from the bottom is shown in Figure 4.25. You can see the rectangle at Z = 10 underneath the via is broken down into 2 polygons. One of the polygon is a square matching the shape of the via pad. Basically, MGRID automatically build the connection for you starting from version 11. If you want to make sure the electrical connection is there, you can select the rectangle at Z = 12 and use the Adv
Edit->Connection->Check Connection command to check it. MGRID will indicate to you the connection from the rectangle at Z = 12 to the via and to the polygons at Z = 10.
Step 9 Please repeat the Step 4 to Step 8 for the other via on the edge (3, 4) in Figure 4.21. You should get the structure saved in .\ie3d\samples\bridge1.geo with rectangular solid vias. The final structure is shown in Figure 4.26.
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The solid vias are in fact hollow vias with metal on the sides. This is not an approximation.
Mathematically, they are the same as solid vias and they are very accurate in the modeling.
Figure 4.26 The via built with the Edit->Add Via on Edges command with guaranteed connection.
Figure 4.27 The bridge structure with rectangular solid via.