Polygon Pour

Parent page: PCB Objects

A Polygon Pour (brighter red) being used to create a large GND area on a board.

Summary

Polygon pours are used to create a solid or hatched (lattice) area on a PCB layer. Also referred to as copper pours, polygon pours are used to fill irregularly shaped areas of a board, automatically pouring around existing objects and connecting only to objects on the same net as the polygon pour. A polygon pour is a group design object - that is, it is made up of simpler primitive objects, either regions, or tracks and arcs.

On a signal layer, you can place a solid polygon pour to define an area for carrying large power supply currents, or as a ground-connected area for providing electro-magnetic shielding. Hatched polygon pours are commonly used for ground purposes in analog designs.

Availability

Polygon Pours can only be placed in the PCB Editor. You can place them directly or create them from selected primitives. To place a polygon, switch to the required layer then click Home | Pour | 

Placement

After launching the command, the Polygon Pour dialog will open:

Define the properties of the Polygon before placing it.

1. Select the polygon Fill Mode; these are discussed in more detail below.
2. Select the required net in the Connect to Net drop down.
3. Note that each polygon has a Name, which is a system-defined name that is based on the layer and the net. Enter your preferred Name.
4. Typically that is all that needs to be set before placement; click OK to begin defining the polygon shape.
5. Position the cursor then click to anchor the starting vertex for the polygon.
6. Move the cursor ready to place the second vertex. The default behavior is to place two edges with each click, with a user-defined corner shape between them. Refer to the Placement Modes section below for more details on changing corner modes.
7. Continue to move the mouse then click to place further vertices.
8. After placing the final vertex, right-click or press Esc to close and complete placement of the polygon. There is no need to manually close the polygon since the software will automatically complete the shape by connecting the start point to the final point placed.

Placement Modes

• While placing a polygon there are five available corner modes, four of which also have corner direction sub-modes. During placement:
  • Press Shift+Spacebar to cycle through the five available corner modes: 45 degree, 45 degree with arc, 90 degree, 90 degree with arc, and Any Angle.
  • Press Spacebar to toggle between the two corner direction sub-modes.
• When in either of the arc corner modes, hold the  or  keys to shrink or grow the arc. Hold the Shift key as you press to accelerate arc resizing.
• Press the 1 shortcut key to toggle between placing two edges per click or one edge per click. In the second mode, the dashed edge is referred to as the look-ahead segment (as shown in the last image in the set below).
• Press the Backspace key to remove the last vertex.

Press Shift+Spacebar to cycle through the five available corner modes, press the 1 shortcut to toggle placement between two edges or one edge.

Polygon Fill Modes

The polygon pour placement engine can construct polygons from either solid regions or from a combination of tracks and arcs. To help you decide which of these to use, consider the following:

• Region based polygons result in far fewer objects being placed, making for: smaller files; faster redraws, file opening, DRC and net connectivity analysis; and smaller output files since the region object is fully supported in Gerber and ODB++.
• Track/Arc based polygons allow a hatched polygon to be created by setting the Track Width to be smaller than the Grid Size. Note that they can also be solid by setting the Track Width to be larger than the Grid Size.
• Outline Only polygons are Track/Arc polygons without the internal tracks and arcs.

The same Polygon poured using regions, then poured using tracks/arcs.

Defining a Polygon from Selected Objects

As well as interactively placing a polygon, it can also be created from a set of existing track and arc objects that define a closed shape. To define a polygon from an existing closed shape, select all primitives that form the closed shape then click Home | Pour | 

The polygon will be created with its Fill Mode set to Outline and the Is Poured option disabled, and therefore, it will be an empty polygon. Note also that the original selected primitives are not removed, and therefore, the new polygon will not be visible since its outline lies along the centerline of the selected objects. The selected objects can now be deleted or moved to another layer (via the Inspector panel) to reveal the new polygon. If this is confusing, another approach is to select the objects to be used, switch to a different layer, then run the Define From Selected Objects command to create the polygon on that layer. Enable Single Layer mode (Shift+S) and you will see the outline of the new polygon. Double-click to repour the new polygon as solid or hatched then enable the Is Poured option.

Since the Define from Selected Objects algorithm uses the centerline of the selected objects, it requires that the start and end locations of touching objects are exactly co-incident (at the same location). If this is not the case, a Confirm dialog will open and give the location where the algorithm failed, and also providing the opportunity to instruct the algorithm to attempt to define the polygon from the edges of the objects instead. As long as the selected objects overlap slightly, this option should create a polygon, with the edge of the polygon tracing the outer edge of the selected objects.

Graphical Editing

This method of editing allows you to select a placed polygon pour object directly in the workspace and change its size, shape, or location graphically.

Changing Polygon Pour Shape and Location

Click once on a polygon pour object to select it, which puts it into edit mode. The outer shape of the polygon object is defined by a series of edges: where each edge is represented by an end vertex at each end, shown as a solid white square; and a center vertex in the middle, shown as a hollow white square. Each end vertex represents the location where two edges meet.

A selected Polygon Pour

• Click and drag A to move the applicable end vertex.
• Click and drag B to move the applicable center vertex, effectively creating a new end vertex and splitting the original edge into two.
• Click anywhere along an edge, away from editing handles, and drag to slide that edge.
• Ctrl+click anywhere along an edge, away from editing handles, to insert a new end vertex.
• To remove an end vertex, click and hold on the vertex, then press the Delete key.
• Click anywhere on the polygon – away from editing handles – and drag to reposition it. While dragging, the polygon can be rotated or mirrored:
  • Press the Spacebar to rotate the polygon counterclockwise or Shift+Spacebar for clockwise rotation. The Rotation Step size is defined on the PCB Editor – General page of the Preferences dialog.
  • Press the X or Y keys to mirror the polygon along the X-axis or Y-axis respectively.

Non-Graphical Editing

The following methods of non-graphical editing are available:

Via an Associated Properties Dialog

Dialog page: Polygon Pour

This method of editing uses the following dialog to modify the properties of a polygon pour object.

The Polygon Pour dialog

The Polygon Pour dialog can be accessed during placement by pressing the Tab key.

After placement, the dialog can be accessed in one of the following ways:

• Double-click on the placed polygon pour object.
• Place the cursor over the polygon pour object, right-click then choose Properties from the context menu.

Quickly change the units of measurement currently used in the dialog between metric (mm) and imperial (mil) using the Ctrl+Q shortcut. This affects the dialog only and does not change the actual measurement unit employed for the board as determined by the 

and  buttons in the Home | Grids and Units area of the main menus.

Via the PCB Inspector Panel

Panel page: PCB Inspector

The PCB Inspector panel enables the designer to interrogate and edit the properties of one or more design objects in the active document. Used in conjunction with appropriate filtering, the panel can be used to make changes to multiple objects of the same kind, from one convenient location.

Other Polygon Editing Features

Poured vs Unpoured

Polygons have an unpoured state. When a polygon is in the unpoured state, it is represented by a thin line that defines its boundary, as shown in the image below.

The same polygon shown poured on the left and unpoured on the right.

An unpoured polygon can be:

• Reshaped.
• Moved to a new location.
• Repoured via the right-click menu or the Home | Pour | Polygon Pour submenu.
• Unpoured again via the right-click menu.
• Detected by the Unpoured Polygon design rule (Electrical category). When detected, a message will open and give the option to repour any unpoured polygons. If they are left unpoured, they will then be highlighted as a rule violation.

Changing Between Poured and Unpoured

Since the poured state is simply an attribute of each polygon, it is very easy to switch between poured and unpoured. You can:

• Toggle the Is Poured option in the Polygon Pour dialog or the PCB Inspector panel.
• Right-click on a polygon then select the appropriate Set To Poured or Set To Unpoured command from the Polygon Actions sub-menu.

Rebuilding Polygons

If you have changed the design within a polygon, it will need to be repoured to clear any violations created by the design changes. Since a polygon pour can exist in poured and unpoured states, the term 'Repour' becomes slightly inadequate. To better describe the process of reanalyzing and recalculating a polygon, the more appropriate term 'Rebuild' is employed. To rebuild polygons, right-click over a polygon in the workspace then use the appropriate Rebuild command from the Polygon Actions sub-menu.

Cutting a Hole in a Polygon (Polygon Pour Cutout)

To create a cutout, or hole, inside a polygon, place a polygon pour cutout on top of the existing polygon. To do this:

1. Click Home | Pour |  then select Polygon Pour Cutout.
2. The cursor will change to a crosshair, starting inside the boundary of the polygon. Click to define the starting location.
3. Move the cursor across the polygon. The cutout is actually a Region object with the Polygon Cutout option enabled. Press Shift+Spacebar to cycle through the region corner modes.
4. Continue to click and move the mouse to define the cutout outline.
5. Right-click to exit polygon cutout placement mode.
6. The original polygon must now be rebuilt to pour around the new cutout.

An example polygon pour cutout within a polygon pour that is poured (left) and unpoured (right).

Exploding a Polygon Pour

A polygon pour can be converted to its set of primitive objects by using the Explode Polygon To Free Primitives command (for the polygon under the cursor) or the Explode Selected Polygons To Free Primitives command (for one or more currently selected polygons). Solid polygons will revert to region primitives, while hatched polygons will revert to tracks and arcs. Once exploded, a polygon pour object can no longer be manipulated as a group object.