The essence of rigid flex PCB is to use FPC as one or two circuit layers of rigid PCB, and then partially route the rigidity of PCB, leaving only the flexible part.

What is a rigid flex PCB?

With the birth and development of FPC & PCB, a new product, rigid flex PCB, was born. Therefore, the rigid flex PCB is a circuit board with FPC characteristics and PCB characteristics formed by combining flexible circuit board and rigid circuit board through lamination and other processes according to relevant technological requirements. As a special interconnection technology, rigid flex PCB provides a brand-new connection way between electronic components, which can realize the two-dimensional design and manufacture of circuits, and the three-dimensional interconnection and assembly, thus reducing the assembly space and weight of electronic products. It is light, thin, short and small. The rigid flex PCB can replace connectors, reducing the number of connectors and saving costs; Repeated bending over 100,000 times can still keep the electrical performance; Can realize the impedance control of the thinnest insulating carrier plate, reduce the weight, and reduce the installation time and cost; The material has high heat resistance and better thermal diffusivity. At present, there are some shortcomings in the rigid flex PCB, such as complicated process, high manufacturing cost, and difficult to change and repair.

Material introduction of rigid flex PCB

The processing substrate material of the rigid flex PCB is the same as that of flexible printed circuit board, which is the flexible copper clad laminate (FCCL). FCCL refers to the copper clad laminate formed by bonding one or both sides of flexible insulating materials such as polyimide film or polyester film with copper foil through a certain process. Among them, the flexible copper clad laminate composed of copper foil, film and adhesive is called three-layer flexible copper clad laminate ("3L-FCCL" for short). Adhesive-free flexible copper clad laminate is called two-layer flexible copper clad laminate ("2L-FCCL" for short).

Production process of rigid flex PCB

Because the rigid flex PCB is the combination of FPC and PCB, the production of rigid flex PCB should have both FPC production equipment and PCB production equipment. First, the electronic engineer draws the circuit and shape of the flexible board according to the requirements, and then sends it to the factory that can produce the flexible board. After the CAM engineer processes and plans the relevant documents, the FPC and PCB production lines required for FPC production are arranged to produce the PCB. After these two flexible boards and rigid boards come out, according to the planning requirements of the electronic engineer, the FPC and PCB are pressed together seamlessly by a pressing machine, and after a series of details, the flexible board and the PCB are finally manufactured. A very important link should be rigid flex PCB, which is difficult and has many detailed problems. Before shipment, it is generally necessary to conduct a full inspection, because its value is relatively high, so as not to cause the loss of related interests between the supplier and the buyer.

What are the advantages of rigid flex PCB?

The rigid flex PCB has the characteristics of FPC and rigid PCB at the same time. Therefore, it can be used in some products with special requirements. It has a certain flexible area and a certain rigid area, which is of great help to save the internal space of products, reduce the volume of finished products and improve product performance.

One of the key characteristics of rigid flex PCB is its slim shape and changeable shape, which makes it an ideal solution for ultra-thin and ultra-light packaging. Although rigid flex PCB may be more expensive in design and manufacture, they do have many advantages and can solve many problems in traditional rigid board technology.

1. Compact size and flexible shape

Rigid flex PCB makes it easier to install more components in a smaller space, because they can change shapes according to specific contours. This technology will reduce the size and weight of the final product and the overall system cost. At the same time, the compact shape of rigid flex PCB makes it the best choice for thin line and high density circuit in HDI technology.

2. It can be customized for different applications

Rigid flex PCB has free packaging geometry and can be customized for many industries such as aerospace, military, medical equipment and consumer electronics. They can be customized in size and shape to suit shell design and 3D design, which provides designers with more possibilities to meet different requirements in specific applications.

3. Better mechanical stability

The stability of rigid board and the flexibility of flexible board form a stable structure of the whole package, while retaining the reliability and flexibility of electrical connection required for small space installation.

4. Better performance in harsh environment

rigid-flex PCB has high impact resistance and high vibration capability, so they can work normally in high stress environment. rigid-flex PCB uses fewer cables and connectors, which also reduces safety risks and maintenance in future use.

5. Easy to manufacture and test

rigid-flex PCB requires a small number of interconnectors and related components/parts. It is helpful to simplify the assembly operation and make the rigid-flex PCB easier to assemble and test. rigid-flex PCB is very suitable for PCB prototype.

In addition to the above advantages, other common advantages of rigid-flex PCB include high circuit density, good heat dissipation and chemical resistance, etc. In a word, rigid-flex PCB combines all the advantages of rigid board and flex board, while making up for the disadvantages. . This PCB is the best solution to design reliable and powerful circuits for smart wearable devices and other industries.

What are the disadvantages of rigid-flex PCB?

There are many production processes of rigid flex board, which are difficult to produce, low in yield and more in materials and manpower. Therefore, its price is more expensive and its production cycle is longer.

Rigid and flexible board is not cheap. Why use rigid-flex PCB?

In hardware design, cost is often not the key factor;

First, reliability: rigid-flex PCB can solve the installation reliability problem of FPC.

The FPC is connected through connectors, which brings problems of installation cost, inconvenient installation and reliability, and at the same time, it is easy to short circuit and fall off. In the design of a barrel machine that Hikvision shipped in large quantities, we saw the phenomenon of repair welding between FPC and PCB after the installation of FPC. rigid-flex PCB solves the problem of installation reliability of FPC.

Second, the comprehensive cost:

rigid-flex PCB, although the price per unit area is increased, saves the cost of connector, reduces the installation time, repair rate and repair rate, and improves the productivity and reliability. The use of products shipped in large quantities is often effective in reducing costs.

Third, effectively improve the signal quality.

Because it is not connected by a connector, the wiring continuity is better and the signal integrity is better.

Traditional IPC uses FPC and connector to connect the Sensor board with the main control board.

The rigid-flex PCB can integrate the main control board and the sensor board, which solves many problems and meets the structural design requirements of the bobbin machine.

Points for attention in the design of rigid-flex PCB:

A. It is necessary to consider the bending radius of the flexible board. If the bending radius is too small, it will be easily damaged.

B. Effectively reduce the total area and optimize the design to reduce the cost.

C. It is necessary to consider the structural problems of the three-dimensional space after installation.

D. It is necessary to consider the optimal design of the number of layers of flexible part wiring.

Application field of soft and hard integrated electronic circuit board:

The characteristics of the rigid-flexible board determine that its application field covers all the application fields of FPC in PCB.

1. The penetration rate of consumer electronic products continues to increase.

rigid-flex PCB were first used in the field of battery modules. Now, looking at all mobile phone brands around the world, it is a consensus that rigid-flex PCB are used for batteries, and it may become a long-term trend. At the same time, in order to accommodate more lenses in a smaller and smaller space, the lens module of mobile phone also begins to adopt the rigid-flex PCB, and it is gradually expanded to other mobile phone modules such as monitors. As for the lightweight and multifunctional features of wearable devices, it is naturally expected to become the next application of a large number of rigid-flex PCB.

2. The combination of soft and hard board becomes the key technology of straddle vehicle market.

The position of hard and soft boards in automotive electronics is rising steadily, which is beyond the original imagination of PCB industry. The main reason is that the technology used for mobile phone lens module was not thought of at the beginning, and it has the opportunity to extend to ADAS lens module for vehicles, and further attracted the manufacturers of vehicle components to introduce the soft and hard combination board into module products such as Guangda, thus becoming the entry brick for cutting into the high-end vehicle market.

Rigid-flex printed circuit boards (PCBs) are composite boards of rigid boards and flexible boards. Most rigid-flexible circuits are multi-layered. A rigid-flex PCB can include one/several flexible boards and rigid boards, which are connected by internal/external plated through holes.  

Why do you need to reserve the break-away line in the production of rigid-flex PCB?

The main reason for reserving the break-away line in the production of hard and soft boards is that the track of SMT mounter is used to clamp the circuit board and flow through the mounter. Therefore, when the components too close to the track edge are sucked by the suction nozzle of SMT mounter and mounted on the circuit board, the phenomenon of collision occurs, and the production cannot be completed. Therefore, in the production process of rigid-flex PCB, in order to consider the subsequent patches and plug-ins, the technological edge is usually added.