Differences Between FPC with Stiffener & Rigid-flex PCB

FPC is widely used in PCBA Manufacturing. There Makerfabs always meet some customers confused about FPC with stiffener & Rigid-flex PCB, some detailed explanation here:

1. Definition

FPC(Flexible Printed Circuit) refers to a thin insulating polymer film having conductive circuit patterns affixed. The most advantage for FPC is flexibility, which allows it to be a good connection within a compact space or parts that need to be bent.

But it’s advantage of flexibility sometimes also becomes its own disadvantages. For example, if you need to install an IC on it, as the FPC is soft, the IC pins maybe drop from the FPC. We need a firm/ flat base for the IC soldering… That is why "stiffener" needed:

The stiffener can be FR4/ resion, and even metal, it makes a special area of the FPC firm and flat, so there would be safe for components soldering. There no traces/ pads on the stiffener, the function of this rigid part are only to strengthen the rigidity of this area. All the circuits/ traces are on the FPC. By nature, rigidized flex construction is still a flex circuit, but "stiffened" by some other material.

A rigid-flex PCB circuit is a hybrid construction of the FPC board and FR4 board, it is laminated together into a single structure. That is, both rigid and flex parts are designed with traces and they are connected, the FR4 does not act only as a stiffener, there would be circuits both on FPC and FR4 board.

2. Production & Price
It's simple for the production process of rigidized flex construction, the factory will bond stiffeners after the FPC produced. As for the cheap price, the FPC is widely used and the cost is relatively low. For the most common FPC, the starting fee only about $50 at Makerfabs(click for our FPC service).

While rigid-flex PCB is comparatively complex, they need lamination of the FPC circuit and FR4 board many times, when fabricating rigid-flex PCBs, the factory needs both rigid PCB production machines and flex PCB production machines, with more than 50 processes, the quality control will be more difficult.

Because of the production difficulty, the rigid-flex PCB is normally much more expensive than any other boards such as FR4/ FPC with stiffener…They are usually only used in quality demands projects such as military projects, satellite. While FPC more commonly used on consumer electronic products such as mobile phones, laptops.

Check this video to have a factory tour to know how's the FPC assembly process: