The development of FPC and PCB gave birth to a new product of Rigid-flex PCB boards (also called Flex-Rigid PCB). Flex-rigid PCB is a flexible circuit board and a rigid circuit board bonded together with laminating and other relevant technical processes. This made the Flex-rigid circuit board have both the characteristics of the FPC board and the Rigid PCB.

But Flex PCB also could add PI/FR4/SUS/Alumimum stiffeners to make some areas thicker and rigid. How to distinguish them? The main difference is the stiffeners have no any copper tracks and copper pads but only for mechnical support. And this is also the reason why Rigid-flex PCB is much more expensive than rigid PCB or Flex PCB. It's easy to make circuits on one same material, like the rigid PCB material FR4 and the flex PCB material PI. But to combind them together, it's not easy and the manufacturing processes are almost double to make the rigid-flex PCB and harder to control the PCB quality. Also rigid-flex PCB could also add stiffeners as same as flex PCB.

Advantages: 

Since the Flex-rigid PCB has both the characteristics of the FPC and the characteristics of the PCB, it can be used in some products with special requirements. It has both a certain flexible area and a certain rigid area which could save the internal space, reduce the volume of finished products and improve product performance. 

Disadvantages: 

There are many production processes for Flex-rigid PCB, which are difficult to produce and have a low yield rate. The materials and manpower are relatively large. Therefore, the prices are relatively expensive and the production cycle is relatively long.