The difference between Rigid-flex PCB and Flex PCB with FR4 Stiffener

      When I came into PCB industry, many people may be confused about rigid-flex PCB and rigidized flex construction, they could not make a distinguish between these two, so today I decide to write a simple article to show their differences, hope via this you can know them very clearly.

I will show differences from 6 aspects below:

1.Definition

      FPC(Flexible printed circuit) refers to a thin insulating polymer film having conductive circuit patterns affixed there to and typically supplied with a thin polymer coating to protect the conductor circuits.While rigidized flex construction actually is also flexible printed circuit but it's bonded with FR4 stiffener to strengthen the rigidity when assembly.So by nature rigidized flex construction is still flex circuit.

      Rigid-flex circuits are a hybrid construction flex circuit consisting of rigid and flexible substrates which are laminated together into a single structure.From the definition, you can see rigid-flex circuit is not belong to flex circuit.

2.Circuit/wiring board design

      This is key to distinguish these two.There are no traces at all on rigid part of rigidized flex construction, even on pads. The function of this rigid part is only to strengthen the rigidity of this location.That is to say,it's just mechanical connection between these two.

      However, for rigid-flex PCB, both rigid and flex part are designed with traces and they are connected by VIA holes.That is to say,it's not mechanical connect but electrical connection for rigid- flex PCB.

3.Connection

It is becaure trace design is different that the connection is not the same. Rigidized flex construction is mechanical connection and rigid-flex PCB is electrical connection.

4.Production process

It's simple for the production process of rigidized flex construction, just bonding stiffeners for flexible circuit. While rigid-flex PCB is comparatively complex, they need many times laminations. When fabricating rigid flex PCBs, the factory need both rigid PCB production machines and flex PCB production machines.The quality control will be more difficult.

5.Price level

For the same area(size),the price of rigid-flex PCB is much higher than rigidized flex construction.Why? I think you can conclude this from the 4th aspect.

6.Application

Nowadays, rigid flex circuits are usually used in high-end electrical applications, and most are prototypes, few volumn production, such as satellite,medical devices,military,communications equipment.Rigidized flex construction are more widely used in mobile phones, laptops,sensors.