Defining Bending Lines for Your PCB in Standard Rigid-Flex Mode in Altium Designer

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

To define how a flex board should bend, you place one or more Bending Lines. The Bending Line defines where on the surface of the flex region that the bend is to take place. The Bending Line also defines the angle and radius of the bend as well as the width of the strip of board surface that is being bent. Bending Lines are placed and edited with the PCB editor in Board Planning Mode (View » Board Planning Mode, or press the 1 shortcut).

A Bending Line is placed over the flexible region and configured so the board can fold 180 degrees. This video demonstrates placing a Bending Line in Standard Rigid-Flex mode.

Placing a Bending Line

To place a Bending Line:

1. Select View » Board Planning Mode or press the 1 shortcut to enter Board Planning Mode.
2. On the Mutli-layer tab, select the Design » Define Bending Line command.
3. Click inside the board region where the Bending Line is to be placed, one end of the line will attach to the edge of the region closest to the click location, the other end will attach to the cursor.
4. Position the second end in the required location then click once to place it.
5. You remain in Bending Line placement mode, ready to place another Bending Line if required. If not, right-click or press Esc to exit Bending Line placement mode.

The PCB panel in Layer Stack Regions mode displays Bending Lines data. Double-click on an entry to open the Bending Line dialog. 

Three Bending Lines have been placed on this flex board region. The width of the orange strip is the Affected area width.

Moving a Bending Line

To modify the location of an existing Bending Line:

1. Select View » Board Planning Mode (or press the 1 shortcut) to enter Board Planning Mode.
2. Click once to select the Board Region the contains the Bending Line. The handles for all bending lines within that region will be displayed.
3. To relocate the end of a line, click, hold and drag the node to the required location on the perimeter of the board region outline. The cursor will be constrained to the current snap grid and/or existing design objects.
4. The bend location will be redefined by the Bending Line's new position.

Select and drag a Bending Line end node to change bend's positioning on the board.

Precisely Locating a Bending Line

When a Bending Line is moved, the handle will snap to locations on the current Snap Grid. As it is moved, it can also be snapped to existing design objects, such as lines on a mechanical layer. The image below shows a Bending Line handle being positioned on the end of a line on layer Mechanical 2 (highlighted by the number 1). Note that the mechanical layer must be the active design layer for the snap behavior to work.

The number 1 refers to a Bending Line handle being snapped to a line on Mechanical 2; note that this layer is the active layer.

To show the above process in more detail, the images below show the construction lines that have been placed on Mechanical 2 in 2D Layout Mode that accurately define upper and lower reference points that can be used to place a 45 degree Bending Line.

The board in 2D Layout Mode showing the construction lines to help accurately place the diagonal Bending Lines.

The board in Board Planing Mode showing the diagonal Bending Lines that were snapped to the construction lines on Mechanical 2.

Removing a Bending Line

To remove a Bending Line:

1. Select View » Board Planning Mode (or press the 1 shortcut) to enter Board Planning Mode.
2. Click and hold one of its end points then press the Delete key. Alternatively, select and delete a bending line entry in the PCB panel Bending Lines region.

Configuring the Bending Line Properties

Board regions, Split Lines and Bending Lines are examined and edited in Board Planning Mode (press 1). Bending Lines can be edited interactively in the design space or they can be edited via the PCB panel when it is set to Layer Stack Regions mode. To display the panel, click the Panels button at the bottom-right of Altium Designer, then select PCB from the menu. In the panel, select Layer Stack Regions in the drop-down at the top of the panel. In this mode, the panel shows:

• The available board layer stacks in the Layer Stacks region.
• The Regions assigned to those stacks in the Stackup Regions region.
• The Bending Lines defined in the selected Region in the Bending Lines region.

To edit the properties of a Bending Line in the PCB panel:

1. Bending Lines can be edited in either 2D Layout Mode (press 2) or Board Planning Mode (press 1).
2. Enable the Select box at the top of the panel.
3. Select the Board Region that contains the Bending Line in the Stackup Regions area in the PCB panel.
4. Select the Bending Line from the list in the panel's Bending Lines region. The bending line will be highlighted (selected) on the board if the PCB panel's Select option is enabled. A Bending Line entry can also be deleted from the Bending Lines region.

5. Double-click on the Bending Line entry in the Bending Lines region to open the Bending Line dialog as shown in the image below.

   

6. In the Bending Line dialog, edit two of the first three properties, for example the Radius (the distance away from the bend surface that the bending center-point is located) and the Bending Angle (the angle that the surface of the flex region is to bend). The third property - Affected area width (the width of surface area that will be bent for the given Radius and Bending Angle) - will be calculated automatically (more on this below). Note that each Bending Line's Affected area width is displayed as an orange shaded region.
7. In the Bending Line dialog, set the Fold Index as required to define the sequence that the bends are folded when the Fold State slider in the PCB panel or View » Fold/Unfold command is used, which are used to fold the board in 3D mode. The bend with the lowest value is applied first, through to the highest value.

Summary of Defining Bends

A bending Line is a linear object that is placed across a region to define the location, radius and angle of the bend that is to be applied to that flex region of the board.

Defining a Bending Line:

• Bending Lines are placed in Board Planning Mode (1 shortcut).
• To place a Bending Line, run the Design » Define Bending Line command.
• Place the Bending Line across the flexible board Region. It is not necessary to precisely touch each edge of the region with the start and end of the Bending Line, the software will automatically extend it (if too short) or reduce it (if too long). At least one end of the Bending Line must touch or pass over the edge of the Region.
• To edit the properties of a Bending Line, click anywhere within the region to display the verticies for all Bending Lines within that region, then:
  • Double-click on the vertex of a Bending Line to open the Bending Line dialog, or
  • Display the PCB panel and set it to Layer Stack Regions mode, where you can examine and edit the Regions and Bending Lines.
  • Set the Bending Angle and the bend Radius and as required.
  • Bends are folded in the order of their Fold Index, use this feature when the folding order is important to check.
• To move a Bending Line, click and drag on each vertex.
• A Bending Line can be removed by clicking and holding on one of the vertices, then pressing Delete on the keyboard.
• Bending Lines cannot be applied to the edge of a board cutout. If your board requires this, switch to Rigid-Flex Advanced mode.