Rigid-flex PCB combines the stability of rigid PCB and flexibility of flexible PCB and into an integral design, it is an innovative structure of printed circuit board. However, the design of rigid-flex PCB is much more difficult than traditional PCB. In the meantime, there are many points need to be noticed, especially the connection area between rigid PCB and flexible PCB, the circuit layout and design of vias, must strictly follow the requirement of design rules.

Advantages and Disadvantages about Rigid-Flex PCB

Advantages

Since the rigid-flex PCB has the features of rigid PCB and flexible PCB, it can be used in the products which have special requirement, it can;

• Flexible shape and size: using rigid-flex PCB is much easier to assemble more components in smaller internal space, since it can change appearance based on the specific outline. Rigid-flex PCB is helpful to lower the final product size and weight and save the whole system cost.
• High density layout: Rigid-flex PCB can realize higher circuit density within limited space to improve the performance and function of circuit.
• Stability and reliability: rigid part offers stable support for the circuit and ensures the stability and reliability. The flexible part can suit various shape and dimension packaging and increase the reliability of circuit board.
• More design freedom: rigid-flex PCB allows PCB designer has more freedom in the design process, the shape and dimension of PCB can be changed freely as per the requirement to meet the demand of different application scenarios.

Disadvantages

• High Manufacturing difficulty: the manufacturing procedure of rigid-flex PCB is relatively complex and requires special equipment and technology, the manufacturing difficulty is high, which may cause longer lead time and high cost.
• Hard to repair: since rigid-flex PCB is the combination of rigid PCB and flexible PCB, the difficulty of maintenance and repair is increased, once the malfunction is occurred, may need more complicated repair operations.
• Pass rate is relatively low: since the manufacturing procedure is complex, the pass rate of rigid-flex PCB is kind of low, which will increase the manufacturing cost and influence the lead time.
• Reliability is affected by the environment: The environment factor has a big influence on the reliability of rigid-flex PCB, for example, the temperature, humidity, etc. Under harsh environment, the performance of rigid-flex PCB will be influenced.

Key Points to Choose Rigid-Flex PCB

1. Reliability: rigid-flex PCB effectively solves the reliability issue of FPC, avoids installation inconvenience, short circuit, falling off, etc. caused by connector connection.
2. Comprehensive cost: though the unit area cost of rigid-flex PCB is pretty high, but it can save the connector cost, reduce assembly time and repair rate, improve manufacturability and reliability. In mass production situation, the comprehensive cost may be lower.
3. Better signal quality: without connectors, the circuit continuity is better, as well as signal integrity.

What issues should be paid attention to when designing rigid-flex PCB?

Reinforcement

Before design the PCB, the designer needs to make sure whether it is necessary to design the board to be rigid-flex PCB. If the rigid part is only for reinforcement purpose, the board can be designed to be flexible PCB and reinforcement board, since the cost for such structure is lower than rigid-flex PCB.

Stackup

The laminated structure should be designed to be symmetrical as much as possible, and the flexible layer should be designed in the middle position, which can increase the flexibility of the product, reduce the processing difficulty, and thus reduce the processing cost.

Symmetrical Structure(suggested)

Asymmetric (not recommended)

Through Hole Location

The designer better avoids locating through holes in the flexible area, or the through hole will influence the flexibility and increase the processing cost.

Pad Location

The designer better avoids locating pads in the flexible area, or the pads will influence the flexibility and increase the processing cost.

Hole Spacing

If there should be a through hole on the rigid PCB, the spacing between the through hole and the edge of rigid and flexible PCB should be as least 2mm, if possible, the spacing should be wider, since the coverlay should cover flexible PCB and also have some spacing from the holes.

• The bending radius of FPC should be considered to avoid damaged.
• The total area of finished rigid-flex PCB should be as small as possible, optimize the design to lower manufacturing cost.
• The three-dimensional structure after assembled should be considered.
• The layer count of flexible PCB should be reasonably designed.
• The length of FPC should be more than 3mm.

In this article, we have discussed in detail rigid-flex PCB, advantages and disadvantages, and precautions of rigid-flex boards. As an important innovation in the field of electronic engineering, rigid-flex PCBs fully reflect the advantages of software and hardware collaborative design, and can effectively improve system performance, reduce costs, and shorten development cycles. With the continuous advancement of technology, rigid-flex boards will play a key role in more fields, driving the industry towards higher integration and greater intelligence. In the future, we look forward to further unleashing the potential of rigid-flex boards and injecting new impetus into the development of the industry through continuous technology optimization and application exploration.

Jerico PCB has been deeply involved in the field of rigid-flex PCB processing for more than ten years. Our professional engineering team has rich production experience and provides seamless production support from prototype to mass production. Jerico’s own advanced factory can also cooperate with the product development cycle to ensure flexible lead time. We are happy to discuss any of your projects and bring more added value to your business.

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