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). As well as overlapping flex regions, the Advanced mode also brings: visual definition of the substacks, easier definition of the rigid and flexible board regions, bends on nested cutouts, custom-shaped splits, and support for bookbinder-type structures. The required mode is selected in the Layer Stack Manager, more on this below.
As the name suggests, a flexible printed circuit is a pattern of conductors printed onto a flexible insulating film. Rigid-flex is the name given to a printed circuit that is a combination of both flexible circuit(s) and rigid circuit(s), as shown in the image.
Flexible circuit technology was initially developed for the space program to save space and weight. It is popular today as it not only saves space and weight - making it ideal for portable devices such as mobile phones and tablets - it can also reduce packaging complexity, improve product reliability, and reduce cost.
Flexible circuits are normally divided into two usage classes: static flexible circuits, and dynamic flexible circuits. Static flexible circuits (also referred to as use A), are those that undergo minimal flexing during assembly and service. Dynamic flexible circuits (also referred to as use B), are those that are designed for frequent flexing,such as a disk drive head, a printer head, or as part of the hinge in a laptop screen. This distinction is important as it affects both the material selection and the construction methodology. There are a number of layer stackup configurations that can be fabricated as rigid-flex, each with its own electrical, physical, and cost advantages.
Designing a flex or rigid-flex circuit is very much an electromechanical process. Designing any PCB is a three-dimensional design process, but for a flex or rigid-flex design, the three-dimensional requirements are much more important. Why? Because the rigid-flex board may attach to multiple surfaces within the product enclosure, with the attaching and folding process often happening during product assembly. Delivering a working electromechanical design requires close and constant collaboration between the mechanical and electrical engineering teams. The traditional approach to confirm that the folded board fits within its enclosure has been to create a mechanical mockup - known as a paper doll cut out. By its very nature, it's difficult to achieve the accuracy and realism required with this approach.
A board with two rigid regions connected by a flexible region in the ECAD PCB editor and in MCAD.
Altium is helping to solve this challenge with CoDesigner, a sophisticated mechanical-to-electronic design interface technology. CoDesigner allows the engineers to pass the board shape and component changes back and forth between the ECAD and MCAD design domains directly from within the ECAD and MCAD design software.
A printed circuit board is designed as a series of layers stacked on top of one another. For a traditional rigid printed circuit board, the board shape defines the board in the X-Y plane, and the stack of layers defines the board in the Z plane. The X-Y board shape is defined in the main PCB editing window, and the layers are configured in the Layer Stack Manager. In a rigid-flex PCB, there is more than one zone or Region in the finished printed circuit board, and each of those Regions can use a different set of layers.
To design a rigid-flex board, you need to:
To support the complex structures present in a modern rigid-flex printed circuit board, the Z plane editor - the Layer Stack Manager, provides different display modes for editing the structure of your board. Select the Design » Layer Stack Manager command to open the Layer Stack Manager, where you can enable the required rigid-flex mode, and create and align the Substacks needed in your rigid-flex design.
When the Layer Stack Manager opens, it will show the current board layer Stackup. For a new PCB, this will be a simple two-layer board. To enable the features needed to design a rigid-flex board, open the Tools » Features sub-menu or click the Features button to select either the standard Rigid-Flex mode (also referred to as RF1), or the Rigid-Flex (Advanced) mode (also referred to as RF2).
Select the command to enable the required rigid-flex mode.
A quick way to check which rigid-flex mode is being used for a board is to switch to Board Planning Mode (1 shortcut) and have a look at the Active Bar.
There are two rigid-flex design modes available in Altium's PCB design software. The original, or standard mode, referred to as Rigid-Flex (or rigid-flex 1), supports rigid-flex designs that include: single or multiple rigid and flex stackup definitions. To use the Standard rigid-flex mode, you must be able to define the overall board as a single flat shape when viewed from above, with no overlapping regions. This is the approach used in rigid-flex 1 mode - a single, overall board shape is defined, and then split lines are placed to divide that shape into the various rigid and flexible regions. Once that is done, each region can be assigned a layer stack.
Learn more about designing a rigid-flex board in Standard mode.
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). As well as overlapping flex regions, the Advanced mode also brings: visual Z-plane definition of the substacks, independent definition of each rigid and flexible region of the board, bends on nested cutouts, custom-shaped splits, the ability to define bookbinder-type structures, the ability to include coverlay on a flex region, and support for flex-only designs.
Learn more about designing a rigid-flex board in Advanced mode.
You switch from Standard mode to Advanced mode in the Layer Stack Manager, as shown in the image above. When you choose the Rigid-Flex (Advanced) option in the Tools » Features menu, the software automatically converts the single board shape into multiple board region objects and assigns the layer stacks as required. The video below demonstrates the process.
An overview of switching from the Standard rigid-flex mode to the Advanced mode.
When trying to disable the advanced rigid-flex mode, or switch to the standard rigid-flex mode for a PCB that already uses advanced rigid-flex features, a warning dialog will open for confirmation.
A Board Region is the term used to describe each user-defined area of the board that needs a unique layer stack assigned to it - a standard requirement for a rigid-flex PCB. In the image below the board shape has been divided into three distinct Board Regions: the upper circular region, the thin center strip, and the lower circular region.
A rigid-flex board viewed in Board Planning Mode, note the board shape has been divided into three distinct Board Regions, each showing its region name and the layer stack assigned to it.
When a new board is created, it defaults to having a single Board Region. If the board design requires multiple regions, then you can either:
Board Regions are defined and edited in Board Planning Mode (View menu).
The View menu has three PCB editor working modes with easy-to-remember shortcuts, allowing you to quickly switch between:
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.
Bend Lines are defined and edited in Board Planning Mode (View menu).
Bending Lines have the following inter-related properties:
The relationship between the Bend Angle, Radius and width can be expressed as:
In the PCB panel’s Layer Stack Regions mode, its three main regions change to reflect the following (in order from the top):
While using the Layer Stack Regions mode of the PCB panel, change to the Board Planning Mode view through the View » Board Planning Mode menu, or use the 1 shortcut.
A board can split into distinct regions (Stackup Regions) that are assigned specific layer stackup arrangements (Layer Stacks). Folding areas (Bending Lines) are defined in the board's flexible regions.
When a particular layer stackup name is selected in the Layer Stacks area of the PCB panel, filtering will be applied using the Layer Stack as the scope of the filter. Any board regions assigned to that stackup will therefore be listed in the panel's Stackup Regions area. In turn, any bending lines defined in a selected Stackup Region will be listed in the Bending Lines list area.
Double-clicking on a Stackup Region in the list (or double-clicking on the board region itself in the design space) opens the Board Region dialog (Standard Rigid-Flex mode) or Board Region mode of the Properties panel (Advanced Rigid
