Rigid-Flex PCB - Rigid-Flex PCB for Digital Products

What is Rigid-Flex PCB?

Rigid-Flex PCB is a new type of printed circuit board that combines the durability of rigid PCB with the adaptability of flexible FPC. Among all types of circuit boards, Rigid-Flex PCB has the strongest resistance to harsh application environments, and is therefore favored by industrial control, medical, and military equipment manufacturers. iPCB is gradually increasing the proportion of Rigid-Flex PCB in overall production. The advantage of Rigid-Flex PCB is that it has excellent characteristics in both PCB and FPC, which can be folded and bent to reduce space, and can also solder complex components. Compared to ribbon cables, it has a longer lifespan, more reliable stability, and is less prone to breakage, oxidation, and detachment. It is of great help in improving product performance. The disadvantage of Rigid-Flex PCB is that it has multiple production processes, high production difficulty, low yield rate, and requires a lot of materials and manpower. Therefore, its price is relatively expensive and the production cycle is relatively long.

What are the uses of Rigid-Flex PCBs?

1. Industrial use - Industrial use includes Rigid-Flex PCB used in industrial, military, and medical applications. Most industrial components require precision, safety, and durability. Therefore, the requirements for Rigid-Flex PCB include high reliability, high precision, low impedance loss, complete signal transmission quality, and durability. But due to the high complexity of the process, the output is small and the unit price is relatively high.

2. Mobile phone - The application of Rigid-Flex PCB in mobile phones commonly includes the hinge, camera module, keypad, and RF module of foldable phones.

3. Digital electronic products - In consumer digital products, DSC and DV are representative of the development of Rigid-Flex PCB, which can be discussed in terms of performance and structure. In terms of performance, Rigid-Flex PCB can connect different PCB hard boards and components in a three-dimensional manner, so it can increase the total usable area of PCB under the same circuit density, relatively improve its circuit load capacity, and reduce the signal transmission limit and assembly error rate of contacts. On the other hand, due to the lightweight and thin nature of Rigid-Flex PCBs, they can flex wiring, which is of substantial benefit in reducing volume and weight.

4. Automobiles - The use of Rigid-Flex PCBs in automobiles commonly includes connecting the buttons on the steering wheel to the motherboard, connecting the video system screen and control panel, operating the speakers or function keys on the side doors, reversing radar imaging systems, sensors (including air quality, temperature and humidity, special gas regulation, etc.), communication systems for vehicles, satellite navigation, connecting boards for the rear seat control panel and front end controller, exterior detection systems, and more.

What are the key points of Rigid-Flex PCB processing?

The birth and development of FPC and PCB have given birth to the new product Rigid-Flex PCB. Rigid-Flex PCB is a circuit board formed by combining flexible circuit boards and rigid circuit boards through pressing and other processes according to relevant process requirements, with FPC characteristics and PCB characteristics. What is the key process for Rigid-Flex PCB processing? Pure PCB or FPC board lamination is already very mature, but one difficulty of Rigid-Flex PCB is the lamination of the bonding parts of the board. Currently, it is still a key point that various Rigid-Flex PCB manufacturers need to pay attention to.

1. It is necessary to use a vacuum transmission machine to ensure good adhesion of materials under continuous pressure and temperature, as well as good flow and exhaust of bonding materials.

2. Suitable overlay material: The metal surface of the board pressed out of too soft overlay material is prone to showing lines and patterns, which affects the appearance; Overly hard overlay materials can easily cause local under pressure and generate microbubbles.

The above are some key points of Rigid-Flex PCB processing. Rigid-Flex PCB can be used in products with special requirements, which greatly helps to save internal space, reduce finished product volume, and improve product performance. However, in the sampling of Rigid-Flex PCB, the production process is complex, the production difficulty is high, the yield rate is low, and a large amount of materials and manpower are invested. Therefore, its price is relatively expensive and the production cycle is relatively long. IPCB can provide bulk processing services for Rigid-Flex PCB samples to meet the diverse needs of customers. It can produce 2-38 layers of Rigid-Flex PCBs.

What are the process difficulties in Rigid-Flex PCB processing?

Rigid-Flex PCB is a circuit board formed by combining flexible circuit boards and rigid circuit boards through compression and other processes according to relevant process requirements, with FPC characteristics and PCB characteristics. However, the manufacturing process of Rigid-Flex PCB is quite complex, with some key technologies and difficulties that are difficult to control. Due to the different structures and materials used in FPC and hardboard, there is a significant difference in size expansion and contraction between the two. Therefore, selecting the appropriate Rigid-Flex PCB material is crucial to ensure good alignment. So, what are the process difficulties in Rigid-Flex PCB processing?

About FPC

1. Hard board PCB production equipment is used to make FPC. Due to the soft and thin material of FPC, it needs to be pulled with a traction board to pass through all horizontal lines to avoid card scrap.

2. The use of OPE punching for positioning holes and the single piece processing before lamination also have a significant impact on interlayer alignment. Due to the poor alkali resistance of polyimide materials, swelling occurs in strong alkali solutions. Therefore, during the process of blackening and browning, the temperature and time should be appropriately reduced in strong alkaline processes such as degreasing, blackening, and browning.

3. Due to the easy deformation of flexible single sheets and poor flatness before lamination, as well as the significantly lower resin flowability of the adhesive sheet used compared to the semi cured sheet used for rigid board lamination, in order to ensure good bonding between the adhesive sheet and the single sheet and embed it into the fine line spacing, we choose to use materials with good coverage as laminating liner materials, such as polypropylene film, polytetrafluoroethylene (PTFE), silicone rubber sheet, etc., which can improve the lamination quality of flexible boards.

About PCB

Whether it is substrate lamination or simple semi cured sheet lamination, it is important to ensure that the warp and weft directions of the glass cloth are consistent. During the lamination process, attention should be paid to eliminating thermal stress and reducing warping.

2. Rigid-Flex PCB compression expansion and contraction control. Due to the poor stability of FPC material during expansion and contraction, priority should be given to the production of FPC and laminated PI cover film, and the hard board part should be made based on their expansion and contraction coefficients.

3. For the processing of flexible windows, there are usually two methods: first milling and then milling. However, flexible processing needs to be carried out according to the structure and thickness of the Rigid-Flex PCB itself. If the flexible window is milled first, the precision of the milling should be ensured, and it should not affect welding or bending too much.

iPCB specializes in one-stop services including PCB and PCBA, component procurement, SMT surface mount processing, assembly and testing. The product has passed UL safety certification, ISO13485 medical device quality management system certification, ISO9001 international quality system certification, and IATF16949 international automotive electronics quality system certification. PCB products involve multiple fields such as automotive electronics, medical equipment, industrial control, aerospace, communication equipment, etc.