Snap Vias

1Introduction

Snap Vias is a productivity add-on for Siemens EDA Xpedition that places vias precisely at the centers of circles you have drawn on user layers. Each via lands exactly on its circle, takes on the net you choose, and is locked in place.

The tool is most useful when a component manufacturer recommends a specific pattern of vias underneath a part — a common requirement for RF components. You can capture those recommended locations by drawing a circle on a user layer at each spot (often built right into the component footprint). With those circles in place, Snap Vias drops a via on every one of them in a single step, so the finished board matches the manufacturer’s recommendation exactly instead of relying on hand placement.

The Snap Vias window. From top to bottom: choose the via, choose the net, then place the vias.

2Requirements and Setup

• Xpedition must be running with your board design open before you start the tool. Snap Vias connects to that active session automatically when it opens.
• Circles marking your intended via locations must already exist on one or more user layers. These are frequently part of the component footprint, but any circles drawn on a user layer will work.
• The tool reads the vias (padstacks) and nets that already exist in your design, so the board should be set up with the via type and the net you intend to use.

3The Snap Vias Window

The window has just three things to set, working from top to bottom: pick the via you want to place, pick the net the vias should belong to, then place them. Each is described below.

3.1 Choosing the Via

The first drop-down list, near the top of the window, is where you pick the via to place. It lists the via padstacks that are available in the current design. One entry is already selected when the window opens, so you only need to change it if you want a different via. Whatever you select here determines the size and type of every via the tool places.

Pick the via to place from the list of vias available in your design.

3.2 Choosing the Net

The second drop-down list is where you pick the net the new vias will belong to. It lists every net in your design. Unlike the via list, nothing is selected here when the window opens — you must choose a net yourself before placing vias. All of the vias placed in one run are assigned to the net you choose here.

Pick the net the placed vias will connect to.

3.3 Placing the Vias

The button at the bottom of the window places the vias. When you press it, the tool puts one via at the exact center of each circle you have selected, assigns it to the net you chose, and locks it in place. Only selected circles are used — any other shapes you happen to have selected are ignored.

Press this to drop a via on each selected circle.

4Typical Workflow

A complete pass from start to finish looks like this:

1. In your layout, confirm that circles mark every via location you want — usually these are drawn on a user layer as part of the part’s footprint.
2. Select the circles you want to fill with vias.
3. Start Snap Vias. It opens in front of the layout and reads the available vias and nets from your design.
4. Choose the via you want to place from the first list (or keep the one already selected).
5. Choose the net the vias should belong to from the second list.
6. Press the button to place the vias. A via appears centered on each selected circle, assigned to your chosen net and locked in place.
7. Check the result. To fill circles that belong to a different net, repeat the process for that net.

5Tips & Troubleshooting

• Nothing happens when I place vias: Make sure you selected the circles in the layout before pressing the button. If no circles are selected, there is nothing for the tool to act on.
• It asks me to pick a net: A net must be chosen before vias can be placed. Choose one from the second list and try again.
• Only some shapes got vias: The tool only acts on circles. Arcs, lines, and other shapes on the user layer are ignored, even if they are selected.
• The vias won’t move after placement: Placed vias are locked on purpose, so they stay exactly on the manufacturer’s recommended spots. If you need to move or remove one, unlock it first in the layout, then edit it as usual.
• All my vias ended up on the wrong net: Every via in a run takes the net chosen in the second list. Delete them, choose the correct net, and place again — working one net per pass.
• The tool can’t connect when it starts: Confirm that Xpedition is running with your design open before launching Snap Vias, and that automation access to Xpedition is set up on your machine.