Altium Designer Documentation


Created: 09.06.2022 | Updated: 09.06.2022

Parent page: PCB Commands

The following pre-packaged resource, derived from this base command, is available:

Applied Parameters: ShowInBoardPlanner=1


A common feature on rigid-flex boards is the selective use of coverlay material. This insulation layer is cut and laminated onto specific areas of the board (Board Regions), and because of this selective use, custom coverlay is often referred to as bikini coverlay. As well as its use in specific areas of the board, custom coverlay can also be positioned anywhere in the layer stack. Custom coverlay is added in the Layer Stack Manager and the shape manipulated in the workspace in Board Planning Mode, once the Custom Coverlays option is enabled in the Board Region dialog for the required region of the board.

This command is used to place a Coverlay Polygon within an existing board region within the current design whose Custom Coverlays option has been enabled. It facilitates the crafting of a specific shape for the coverlay and allows you to get the coverage just the way you need it without having to accept the default coverlay, which simply blanket-covers the entire board region.

A coverlay polygon is derived from the Polygon Pour object and is limited in functionality to just being used as a means of creating a custom coverlay shape. For detailed information about this object type, see Coverlay Polygon.


This command can be accessed from the PCB Editor when configured in Board Planning Mode. Ensure that the required coverlay layer is the active layer in the main workspace then choose the Design » Place Coverlay Polygon command from the main menus.

The current viewing mode for the PCB document can be changed using the corresponding commands from the main View menu. To switch to Board Planning Mode, use the command of the same name or use the 1 keyboard shortcut.


After launching the command, the cursor will change to a cross-hair and you will enter polygon placement mode:

  1. Position the cursor and click to anchor the starting vertex for the polygon.
  2. 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.
  3. Continue to move the mouse and click to place further vertices.
  4. 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 as the software will automatically complete the shape by connecting the start point to the final point placed.

Placement Modes

When defining the shape of the polygon, there are five available corner modes, four of which also have corner direction sub-modes. During definition:

  • 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 this 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.


  1. Coverlay is automatically added to cover the entire area of the board region is was added to. Behaving like an additional solder mask layer, openings are automatically created for component pads in accordance with the applicable Solder Mask Expansion design rule, or the settings in the Properties panel if the Solder Mask Expansion setting has been manually configured to override the design rule. The automatic coverlay is also formed as a polygonal object and can be selected and reshaped (or deleted) as required.
  2. A hole within a coverlay can be made by placing a Coverlay Cutout (a Region object set to behave as a Polygon Cutout). To do so, use the Design » Place Coverlay Cutout command from the main menus.
  3. User-defined coverlay changes, such as modifying the shape of the automatic coverlay or placing additional coverlay objects, are removed if the Custom Coverlays option is turned off in the Board Region dialog for the applicable board region.
  4. Custom Coverlay is a mask layer and behaves as an additional Solder Mask layer. Solder Mask layers normally display and output as a negative, that is, the objects you see on the screen become holes in the fabricated mask layer. The on-screen presentation of Solder Mask can be configured to display as a positive if preferred (and therefore also the coverlays).
  5. In standard 2D display mode, the custom coverlay is shown as if it is on the top/bottom solder mask. This is simply a display feature. When output is generated, the top solder mask and the top custom coverlay are written out as separate data as are the bottom solder mask and bottom custom coverlay.


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