Planning Rigid & Flex Regions for Your PCB in Standard Rigid-Flex Mode in Altium Designer

There are two rigid-flex design modes available in Altium's PCB design software. The original, or standard mode, referred to as Rigid-Flex, supports simple rigid-flex designs. If your design has more complex rigid-flex requirements, such as overlapping flex regions, then you need the Advanced Rigid-Flex mode (also known as rigid-flex 2.0). The mode is chosen in Tools menu in the Layer Stack Manager.

The fundamental difference between the modes is that in the original mode, the board shape is split into separate board regions by placing a Split Line, and that Split Line remains as an object defining where one board region ends and another begins. In the Advanced mode each board region is placed separately, or if a larger region is Sliced it becomes two separate region objects. In the Advanced mode, the edges of adjacent board regions define where those two regions meet, not the presence of a Split Line. Because of this difference, there is no Split Line object when the board is in the Advanced Rigid-Flex mode.

Learn more about Designing a Rigid-Flex PCB

The View menu has three PCB editor working modes with easy-to-remember shortcuts, allowing you to quickly switch between:

  • Board Planning Mode (1)
  • 2D Layout Mode (2)
  • 3D Layout Mode (3)

The default behavior when switching between 2D and 3D view modes is to retain separate zoom and orientation settings for each view mode. If you want to see the same location and orientation of the board as you switch, press Ctrl+Alt+2 or Ctrl+Alt+3, instead of 2 or 3.

You've just opened a PCB and are wondering if it is using the standard rigid-flex mode or the advanced rigid-flex mode?

You could open the Layer Stack Manager to check. Alternatively, switch to Board Planning Mode (1 shortcut) and have a look at the Active Bar:

Standard Rigid-Flex mode
Advanced Rigid-Flex mode

You divide the Board Shape into two regions by placing a split line. This is done with the PCB editor in Board Planning Mode. Board Regions are the areas between the Split Lines, and are assigned a default region name.

Placing a Split Line

To place a Split Line:

  1. Select View » Board Planning Mode (or press the 1 shortcut) to enter Board Planning Mode.
  2. Select Design » Define Split Line to enter Split Line placement mode (access this command quickly by using the D, S keyboard sequence).
  3. Click within the board shape to begin the Split Line definition process. One end of the line will attach to the closest point on the board shape outline to where you clicked, the other end of the line will attach to the cursor.
  4. Position the cursor in the required location then click once to place the second end. The split line will remain blue if the location is valid. An invalid location (e.g., outside of the board shape) will cause the split line to turn red. If you click to place while it is red, the split line will be removed.
  5. You remain in Split Line placement mode, ready to place another Split Line if required. If not, right-click or press Esc to exit Split Line placement mode.

Board Regions are the areas between the Split Lines, and are assigned a default region name.

A board is split into distinct regions by placing a Split Line, which runs from one edge of the board shape to another edge.
A board is split into distinct regions by placing a Split Line, which runs from one edge of the board shape to another edge.

The board has been split into a number of distinct regions by placing Split Lines. Note that bending lines have also been placed.
The board has been split into a number of distinct regions by placing Split Lines. Note that bending lines have also been placed.

Moving a Split Line

To move a Split Line:

  1. Select View » Board Planning Mode or press the 1 shortcut to enter Board Planning Mode.
  2. To relocate the end of a line, click, hold and drag it to the required location around the perimeter of the board shape. The cursor will be constrained to the current snap grid.

The Board Region will be redefined by the new position of the edited Split Line.

The Split Line will remain blue while dragging to a permitted location that will still result in a valid split. If the new location for the end being moved is invalid, for example on the same edge of the board shape as the anchored end, the Split Line will turn red. Attempting to place while the line is red will result in the removal of the Split Line.

Select and drag a Split Line end node to redefine a Board Region area.
Select and drag a Split Line end node to redefine a Board Region area.

Removing a Split Line

To delete a Split Line:

  1. Select View » Board Planning Mode or press the 1 shortcut to enter Board Planning Mode.
  2. Click and hold by one of its end points, then press the Delete key. Alternatively, click, hold then move an endpoint to a point around the board shape that results in the split turning red (signifying an invalid split), then release.

To delete one or more existing split lines from the active board, you can also use the Design » Delete Split Line command from the main menus when in Board Planning Mode. After launching the command, the cursor will change to a cross-hair and you will enter split line deletion mode. To delete a split line, position the cursor over one of its ends (its editing handles) then click or press Enter. Continue removing further split lines in this way or right-click or press Esc to exit split line deletion mode.

Assigning a Layer Stack and Editing the Board Region Name

Related page: Defining the Layer Stack

When a new board is created, it will have a single region, named Default Layer Stack Region. This region will be assigned the default layer stack named Board Layer Stack.

When you split a board shape into multiple regions, each new region is also assigned the default layer stack, with the original region named Default Layer Stack Region, and subsequent regions named using the format Layer Stack Region. If the required layer stacks have been defined in the Layer Stack Manager, then each region can have its stack assigned and also can be given a meaningful name.

Each region displays a label that shows its name and the name of the layer stack assigned to it in the form Region Name - Layer Stack Name. If the layer stack is flex-enabled, this will also be indicated by (flex). Enabling the flex setting for a stack is done in the Layer Stack Manager.

To assign a layer stack and name a region:

  1. Select View » Board Planning Mode or press the 1 shortcut to enter Board Planning Mode.
  2. Click the Multi-Layer tab at the bottom of the workspace to make it the active layer (if the layer tab is not visible, press L to open the View Configuration panel to enable it).
  3. Double-click on the board region to open the Board Region dialog. If the region does not select and the dialog open, make sure that the Selection Filter is not excluding Regions.
  4. Assign the Layer Stack by selecting the required stack from the Layer stack drop-down.
  5. Edit the Name as required.
  6. One board region must have the 3D Locked option enabled to define the physical ground reference for the 3D display mode.
  7. Click OK to accept the settings and close the dialog.

Double-click on a board region to define the region's name and assign a layer stack.
Double-click on a board region to define the region's name and assign a layer stack.

The Board Region dialog can also be opened by double-clicking the required Stackup Region in the Layer Stack Regions mode of the PCB panel. The PCB panel will automatically display this mode when you switch to Board Planning Mode.

Summary of Creating Regions by Splitting the Board Outline

The board shape is divided into separate board regions by placing Split Lines. There are a number of ways the board shape can be defined. The video below demonstrates using an outline created from lines and arcs on a mechanical layer. Once the overall outline has been defined, it is split into the different rigid and flex regions.

Defining the Board Shape and Regions:

  • The board shape can be defined interactively in Board Planning Mode (View » Board Planning Mode), or it can be defined based on an existing outline in 2D layout mode (View » 2D Layout Mode), as demonstrated in the video above.
  • To define the board shape from an existing outline, select the outline in 2D layout mode and run the Design » Board Shape » Define Board Shape from Selected Objects command. The software will trace along the centerline of the selected track/arc objects to define the outer edge of the board shape. Note that the ends of the outline tracks/arcs must be coincident for the tracing algorithm to be able to follow the centerline. If it fails, the tracing algorithm will offer to attempt to trace along the outer edge of the selected objects.
  • To define the board shape interactively, switch to Board Planning Mode (1 shortcut) and select the Design » Redefine Board Shape command. The standard region object placement behaviors apply during board shape definition, use the Snap Grid and workspace Guides to help with this process. Enable the Board Shape option in the Snap Options palette to give the best level of control during board shape editing. Learn more about Understanding the Snap Behavior.
  • To define the Name and assign a Layer stack for each region, double-click on the region. Alternatively, set the PCB panel to Layer Stack Regions mode, where you can examine and edit the regions and bending lines.
  • To split a Board Region into two smaller regions, use the Design » Define Split Line command. The command places a straight line between two click locations, when you click within the board shape the first location will be on the board edge closest to where you clicked. Move the cursor to locate the second location, then click a second time. Click and hold on the vertex of a Split Line to move it to a new location.
  • The location and shape of an existing Board Region can be edited. Run the Design Design » Edit Board Shape command, then use the standard polygonal object editing techniques to adjust the shape.
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