Place Designators

1Overview

Place Designators is an automation tool that runs alongside Mentor Xpedition PCB Designer. Its purpose is to automatically or interactively position the component reference designators (RefDes) — the text labels such as “U1”, “R3”, “C12” — on your PCB layout, on either the Assembly (Assy) layer or the Silkscreen (Silk) layer.

Without this tool, engineers must manually drag and position each RefDes label one at a time. Place Designators can process an entire board in much less time, intelligently scanning candidate positions around each component and selecting the best fit based on your configured rules.

1.1 What the Tool Does

• Connects to an active Xpedition PCB design session automatically when launched.
• Places Assembly RefDes labels on the Assy fabrication layer.
• Places Silkscreen RefDes labels on the Silk fabrication layer.
• Supports both fully automatic placement and step-by-step interactive placement.
• Reports components that could not be placed successfully so you can address them manually.

1.2 Prerequisites

• Mentor Xpedition PCB Designer must be open with a PCB design loaded before launching Place Designators.
• The setup_parameters.txt file must be present in the same folder as the Place Designators executable. It contains default values for text sizes, fonts, and placement factors.
• The tool runs as a separate floating window alongside Xpedition. You can switch between the two windows while using it.

2Main Window — Top Bar

These controls appear at the very top of the main window, outside any group box. They apply globally to both the Assy and Silk sections.

Control	Purpose & Behavior
Keep On Top(checkbox)	When checked, the Place Designators window stays in front of all other windows on your screen — including Xpedition. Useful when working interactively so you can see both the tool and the PCB at the same time. Uncheck it if you need to view something behind the tool window.
Max Cross Distance(text box)	Sets the maximum distance (in mils) that a RefDes label may be placed away from its component when the tool places the text near the center of a component’s edge. Default: 20 mils.
Distance Past Part(text box)	Sets the maximum distance (in mils) that a RefDes label may extend past the end of a component when the tool places the text along the edges of a component. Default: 10 mils.
Save PCB(button)	When clicked, saves the current PCB design file in Xpedition. Use this periodically or after a successful auto-placement run to preserve your work.

3Assy RefDes Section

The “Assy RefDes” group box contains all settings and controls for placing reference designator text on the Assembly layer of the PCB. The Assembly layer is typically used for documentation and manufacturing assembly drawings.

3.1 Text Size Settings

3.2 Placement Scaling Factors

These three numeric fields adjust how the placement algorithm sizes and positions the RefDes text. They are unit-less multipliers. Experiment with small changes if default results are not optimal for your board density.

3.3 Component Scope

These radio buttons determine which components on the board are processed during an Assy placement run.

3.4 Assy Action Buttons

4Silk RefDes Section

The “Silk RefDes” group box contains all settings and controls for placing reference designator text on the Silkscreen layer. The Silkscreen layer is printed on the physical PCB for identification during assembly and rework.

The Silk section contains more options than the Assy section because silkscreen placement is more complex: it must avoid copper traces, via pads, and other silkscreen graphics to remain legible on the finished board.

4.1 Text Size Settings

4.2 Placement Scaling Factors

These five numeric fields tune the Silk placement algorithm. They work the same way as the Assy factors but apply to silkscreen text.

4.3 Component Scope

4.4 Move / Don’t Move Lists

These two checked list boxes give you fine-grained control over which component types are included in or excluded from a Silk placement run.

4.5 Silk Placement Behavior Options

4.6 Lock / Unlock Controls

Locking a RefDes label prevents the tool from moving it in future runs. This is useful after you have manually fine-tuned a label’s position.

4.7 Net Classes to Avoid

This checked list box is populated with all net classes defined in your PCB design. Checked net classes are treated as obstacles by the placement algorithm, preventing RefDes labels from being placed on top of those traces.

4.8 Scan Steps

4.9 Silk Action Buttons

5Error List Panel

The Error List panel occupies the right side of the main window. It tracks components whose RefDes labels could not be placed successfully during an Auto Place run.

6Interactive Placement Window

The Interactive Placement window opens when you click “Assy Interactive Place” or “Silk Interactive Place” from the main window. It allows you to manually control where RefDes labels are positioned for selected components.

To use: select one or more components in Xpedition, configure the desired options in this window, then click GO! to move the text.

6.1 Text Type

6.2 Board Side

6.3 Text Location

These radio buttons specify where relative to the component the RefDes label should be placed.

6.4 Text Orientation

6.5 Size Controls

6.6 Alignment

The Alignment group snaps the RefDes labels of multiple selected components to a common edge position. Select two or more components in Xpedition first, then click the desired button. All labels move to match the most extreme label in that direction, without changing their position on the opposite axis.

6.7 Nudge

Shifts the RefDes labels of all currently selected components by exactly 5 mils per click. Use nudge for fine-tuning a label’s position after a GO! placement when it is close but needs a small adjustment.

6.8 Actions

7Status Bar

8Exiting the Application

9Setup Parameters File

The file setup_parameters.txt lives in the same folder as the Place Designators executable. It defines the default values loaded into the tool each time it starts. Edit it with any text editor to change defaults for your team or project.

Key parameters in the file:

10Typical Workflow

10.1 Full Board Automatic Placement

• Open your PCB design in Xpedition and launch Place Designators. The tool connects automatically.
• In the Assy RefDes section, click Setup Layers for Assy.
• Verify the Max/Min text sizes and factor values. Leave defaults if you are unsure.
• Select All Components, then click Assy Auto Place. Watch the progress bar.
• When complete, review the Error List. Click each entry to zoom to that component and decide whether to fix manually or use Try Select Comp Again.
• Repeat for the Silk RefDes section, clicking Setup Layers for Silk first.
• Click Save PCB when satisfied, then EXIT.

10.2 Fixing Individual Problem Components

• Click the problem component’s RefDes in the Error List. Xpedition zooms to it.
• Select the component in Xpedition.
• Click Try Select Comp Again to let the tool attempt auto-placement for just that one component.
• If auto-placement still fails, open the Interactive Placement window and manually set the position.
• Once placed acceptably, click Mark as Fixed, Remove from List.

11Tips & Troubleshooting

• If the tool reports “Unable to connect to the Xpedition session,” make sure Xpedition is fully loaded with a PCB open before starting Place Designators.
• If many components end up in the Error List, try increasing Max Cross Distance or Distance Past Part slightly to give the algorithm more room.
• On very dense boards, reducing the Min text size allows more components to be placed automatically rather than failing.
• Use Unlock All before a fresh full-board re-run so the tool can revise all previously placed labels.
• The Correct Stroke Width, Font, Orientation button is a useful cleanup tool after importing designs from other systems.
• Save the Error List using Save Error List before exiting so you can reload it in the next session.
• Modify setup_parameters.txt to encode your preferred default values so you do not have to retype them each session.