Replace Vias

1Introduction

Replace Vias is an ExactCAD productivity tool for Siemens EDA Xpedition. It lets you swap the vias in your layout for different vias quickly and in bulk, working directly on the design that is open in your Xpedition PCB session.

The tool began life as a simple “replace this via with that one” helper. Over time it grew to do far more. Today it can also reassign the net on vias and mounting holes, and—most powerfully—perform an automatic, board‑wide replacement in which each via is swapped for the most appropriate member of a set of vias you define. This last capability was created to turn ordinary vias into test points for flying‑probe testing, choosing a different via for each location depending on whether the surrounding area allows a solder‑mask opening on the top, the bottom, both, or neither.

As multilayer boards adopted more complex via structures, the tool also learned to work with via spans, so that through‑vias, blind and buried vias, and microvias can each be selected and replaced on the correct layer range.

2Requirements & Setup

• Siemens EDA Xpedition must be running with the design you want to modify already open.
• A valid ExactCAD license that includes Replace Vias must be installed. If you have not yet applied your license code, use the ExactCAD Licensing tool first.
• The tool reads the via padstacks and nets directly from the open design, so no separate import step is needed.

3The Window at a Glance

Everything happens on one screen, organized top to bottom into three working areas:

• Direct replacement (top): select vias and swap them for a single replacement via, and choose the layer spans involved.
• Net reassignment (middle): change the net assigned to selected vias or to mounting holes.
• Global Via Replacement (the bordered box): define sets of replacement vias and let the tool automatically choose the right one for every via on the board.

A status line and progress bar run along the bottom, and a red exit button closes the tool.

4Selecting the Vias You Want to Change

Before you can replace vias or change their net, you need to tell the tool which vias to act on. You can select them by hand in Xpedition, or you can let the tool select them for you in one of two ways.

4.1 Selecting Every Via of One Padstack Type

The first drop‑down list near the top, labelled for auto‑selecting by padstack, lists every via padstack available in your design. Choose a padstack name and the tool immediately highlights every via on the board that uses that padstack. The status line confirms how many it is selecting and tells you when it has finished. This is the fastest way to grab all vias of a single kind—for example, every standard signal via—in one click.

4.2 Selecting Every Via in a Span

On the right side of the top area, the upper of the two span lists (Span to Select) shows every via span that exists in your design, written as a layer range such as 1 - 8. Pick the span you want, then press the small button beside Select all Vias in a Span. The tool selects every via whose start and end layers match that span—a reliable way to isolate, say, all the buried vias between two specific layers without disturbing through‑vias or microvias.

5Replacing the Selected Vias

Once the right vias are selected, the second drop‑down list at the top (Select a Replacement Via) lets you choose the via padstack you want to put in their place. It lists every via padstack available in the design.

The lower span list on the right (Span for Replacement Vias) controls which layer range the new vias are built on. This matters when the replacement is a blind, buried, or microvia: set this list to the span the new vias should occupy. The replacement keeps each via at its exact location and on its original net, and it preserves the fix/lock state of the via it replaces.

With the replacement via and the replacement span chosen, press the small button beside Replace selected board Vias with the Replacement Via. The progress bar fills as the tool works, and the status line reports the result when it is done.

6Changing the Net Assigned to Vias and Mounting Holes

The middle area of the window reassigns nets. It does not change any padstacks—it only changes which net an object belongs to.

Start by choosing the target net from the Select New Net drop‑down list, which contains every net in the design. Then use one of the two buttons beneath it.

6.1 Changing the Net on Selected Vias

The button beside Change Via Net assigns the net you picked to every via that is currently selected. If you have not chosen a net, the tool reminds you to do so first. The status line reports how many vias were changed.

6.2 Changing the Net on Mounting Holes

The button beside Change Mounting Hole Net assigns the net you picked to the mounting holes that are currently selected. If the name in the list is not a valid net, the tool asks you to try again. This is handy for tying mounting holes to a ground or chassis net.

7Global Via Replacement — Vias as Test Points

The bordered box at the bottom is the tool’s most powerful feature. Instead of replacing vias one kind at a time, you define replacement sets and let the tool decide, via by via, which replacement is correct for each location. This was built to convert vias into flying‑probe test points.

7.1 The Idea Behind a Replacement Set

A via can only serve as a probe test point if the solder mask is opened over it so a probe can touch the copper. Whether that opening is possible depends on what sits directly above and below the via. A component body or existing solder‑mask feature on one side may block an opening there.

So for each kind of via in your design, you supply four alternative vias—one for each situation the tool might find at a given location:

When you later run the global replacement, the tool inspects each via on the board, looks for components and solder‑mask features just above and below it, decides which of the four situations applies, and swaps in the matching via automatically.

7.2 Building a Replacement Set

Inside the bordered box:

1. From the top list (Vias Used in Design), choose the via you want to define a set for. This list shows the via padstacks currently present in your layout. If a set already exists for that via, its four choices fill in automatically so you can review them.
2. In the four lists under Replacement Options, choose the via to use for each situation: no clearance, top clearance, bottom clearance, and top‑and‑bottom clearance. Each list offers every available via padstack.
3. Press the small button beside Create Via Replacement Set to store the set. All four choices must be filled in first. If a set already exists for that via, the tool asks before overwriting it.

Repeat for every via type you want handled. The tool can hold a separate set for each.

7.3 Running the Global Replacement

When your sets are defined, press the button beside Replace All Board Vias with via replacement sets. The tool walks through every via on the board; for any via that has a replacement set defined, it examines what is above and below that exact location, picks the matching one of the four choices, and replaces the via. The status line names each via as it is checked, and the progress bar tracks the run. Vias whose padstack has no set defined are left untouched.

7.4 Saving and Loading Your Setup

Defining sets for a complex board takes effort, so the tool can save and reload them. The two small buttons at the lower right of the box handle this:

• Save Setup writes all of your currently defined replacement sets to a file stored with the design, inside its Config folder.
• Load Setup reads that file back and restores the sets. If a set being loaded conflicts with one already defined, the tool asks before replacing it. If no setup file has been saved yet, it lets you know.

8Typical Workflows

Swapping one kind of via for another

1. Auto‑select all vias of the type you want to change, or select them by span.
2. Choose the replacement via, and set the span the new vias should occupy.
3. Press the replace button and confirm the result in the status line.

Re‑tying vias or mounting holes to a net

1. Select the vias (or mounting holes) you want to move.
2. Pick the target net from the net list.
3. Press Change Via Net or Change Mounting Hole Net as appropriate.

Converting vias to flying‑probe test points

1. For each via type, build a replacement set with the four solder‑mask variants.
2. Save the setup so you can reuse it.
3. Run Replace All Board Vias and let the tool choose the right via at every location.

9Tips & Troubleshooting

• Nothing happens when I replace: Make sure vias are actually selected first (or that the auto‑select list is set to a span option). The replace button acts on the current selection.
• The tool can’t connect to Xpedition: Confirm Xpedition is running with a design open before launching Replace Vias.
• “No license code has been applied”: Run the ExactCAD Licensing tool and apply your code, then restart Replace Vias.
• A replacement via lands on the wrong layers: Check the Span for Replacement Vias list—it determines the layer range of the new vias.
• “Create Via Replacement Set” seems to do nothing: All five lists in the box (the source via plus the four options) must be filled in before a set can be stored.
• I want my sets back after reopening the design: Use Load Setup; the file is kept with the design in its Config folder.