Rigid-Flex PCB design in Allegro

 It is very similar to designing a rigid board with a minimum number of layers.  For the stackup you use the Cadence soldermask layer for what is called a "coverlay" layer on a flex circuit.  You will need to work with your flex fabricator to understand their spacing constraints and capabilities.  In between copper layers you will define your adhesive layer thickness requirements.  Many flex fabricators have good general design information on their websites.

Thanks for quick reply. In a combination of flex-rigid board, having rigid and flex sections, how do I define seperate cross sections for each of these sections? And how do I specify what section of the board is rigid and what section is flexible? Is it done in fab drawing? Does it require to be defined anywhere else?

Can you please list some of the fabricators from whose websites I can find more information.

Thanks again for your reply.

There's some great resources out there.

San Francisco Circuits has an excellent page on rigid flex boards and is a fab shop I've used multiple times in the past for some high-end projects:
Rigid Flex PCBs

PCD&F has a very informative article on rigid flex design:
PCD&F Rigid flex design article

Many other authors have great books and resources on rigid flex design as well. A search at amazon or Barnes & Noble should give you some good results.

Hello Dane & everyone,

 Came across this through a mention of our name.

 We also have a good resource in our PCB School section:
http://www.sfcircuits.com/pcb-school

Our 2nd and most recent publication is on the topic of Flexible Circuit Design & Manufacturing.

Registration is required to download the PDF resource.

Vinatronic's blog also has a good amount of resources for this