What is a rigid-flex circuit board?

In the 21st century, various innovative designs have emerged and gained popularity among consumers, including folding electronic designs and various wearable applications. However, these advancements pose a challenge for traditional rigid PCB, as they are not suitable for flexible form factors. On the other hand, flexible PCB lack the sturdiness required for certain applications. To address this, the combination of rigid-flex PCB offers an effective solution. In this article, TechSparks will delve into the details of this circuit type to help you better understand its application and benefits in the ever-evolving world of electronic design.

What is rigid flex PCB

Rigid flex printed circuit board

As the name suggests, a Rigid-Flex PCB is a unique circuit board type that integrates both rigid and flexible circuits into a single structure, combining the advantages and characteristics of both circuit types. This design allows the PCB to be folded and bent while maintaining a certain level of robustness. The manufacturing process for rigid flex PCB board involves producing rigid and flexible circuits separately. Subsequently, FPC connectors, embedded connections or flex-pin connections, or adapter boards are utilized to connect the individual components into a cohesive unit. This intricate process ensures the seamless integration of rigid and flexible elements, providing a reliable and versatile PCB solution for various applications.

Let’s consider the example of a folding mobile phone. By utilizing a combination of rigid and flexible PCB, the circuit design can allocate the flexible part for the screen area and the rigid part for the main board area. When the mobile phone is folded, the screen part can bend while the rigid part remains stable, maintaining electrical connections and functionality.

Advantages of rigid-flex PCB board

Among the various PCB types, rigid flexible PCB is indeed considered more expensive. However, electronics manufacturers are still willing to use it due to its ability to address numerous issues associated with traditional circuit technology. One of the main features is its thin form factor and adaptable shape, making it an ideal solution for ultra-thin and lightweight applications. Let’s delve into the advantages of rigid flex PCB:

  • Lightweight and Compact: Unlike using multiple circuit boards that require numerous connecting wires and connectors, rigid flex circuit board enables seamless integration and eliminates the need for additional connections. Its flexible nature allows for easy layout adjustments according to the device’s shape and size, optimizing the internal space and reducing overall weight.
  • Stable Mechanical Properties: Industries like aerospace, military, and medical demand high PCB reliability. Rigid + flexible structure offers a balanced approach by utilizing flexible circuits to absorb vibrations and shocks, while rigid circuits provide structural integrity. This combination ensures stable mechanical properties without compromising on weight or volume.
  • Resistance to Harsh Environments: In electronics, in addition to physical impact, resistance to chemical corrosion is also a part we need to pay attention to. The flexible part employs high-performance materials such as polyimide (PI) and polyester film, offering excellent UV and radiation resistance. Meanwhile, the rigid part is typically composed of glass fiber reinforced epoxy resin, providing superior resistance to chemicals and oils.
  • Increased Design Flexibility: Rigid-flex printed circuit board allows for innovative and creative designs that can conform to non-traditional shapes and contours. This design flexibility opens up new possibilities for product development and leads to improved aesthetics and ergonomics.

Application of rigid-flexible PCB

Medical Instruments: In the medical field, various devices are required to be used inside the patient’s body during operations, such as endoscopes comprising a flexible tube with a light and lens. Procedures like biopsies, effusion drainage, foreign body removal, and widening narrow passages pose challenges to the size and electrical performance of the device. Rigid-flexible board offer solutions to these issues, ensuring compact design and reliable electrical performance. They are also used in ETC (electrothermal cautery) devices, temperature control circuit boards, portable blood pressure monitors, and other medical equipment.

Medical Instruments Rigid-flex PCB

Automotive Applications: In the automotive industry, circuit boards in electronic control units (ECUs), digital control units (DCUs), air conditioning systems, and electric components must withstand the mechanical shocks and vibrations experienced during vehicle operation.Rigid flex printed circuit boards are preferred for such applications, as they are made of durable FR-4 material with additional copper foil layers for better performance in high-temperature environments.

Automotive Applications Rigid-flex PCB

Wearables: Wearable devices, such as smartwatches and fitness trackers, demand compact and lightweight circuit boards that can adapt to body movements. Rigid flex PCB boards provide the necessary flexibility and lightweight design for wearables. They can be ergonomically shaped to bend and fold without compromising their electrical integrity. This allows for increased circuit density, ensuring the devices remain lightweight and user-friendly.

Wearables Rigid-flex PCB

Gaming Equipment: Gaming equipment requires PCB that can withstand mechanical shocks and frequent bending or folding. Rigid-flex circuit offer superior protection against mechanical shock damage compared to standard rigid circuit boards. Their reduced layer count and enhanced bending capability make them ideal for gaming consoles and accessories that are subject to rigorous usage. Circuit board ensure reliable performance even during intense gaming sessions.

Gaming Equipment Rigid-flex PCB

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