Rigid flex PCBs merge the benefits of rigid and flexible circuit boards and provide outstanding design freedom. Their ability to bend, twist, and fit into compact spaces makes them indispensable in modern electronics. In this article, we will take a deep look at the advantages, applications, and challenges of rigid flex PCB.
What Is a Rigid Flex PCB?
A rigid flex PCB integrates flexible and rigid circuit boards into a single unified PCB design, combining the advantages of both types. This hybrid structure is engineered to achieve higher component density, improved space efficiency, and superior performance.
Rigid flex PCB boards provide the necessary rigidity needed to support components, the flexible part can bend or fit into compact spaces. They are often utilized in 3D designs, enabling them to operate in bent or twisted configurations. Their lightweight and thin profile makes them ideal for applications with stringent space and weight constraints, like medical devices or compact electronic systems.
Why Choose Rigid Flex PCBs?
Rigid flex printed circuit boards combine the advantages of both types of PCBs. Below, we highlight some of their key benefits.
Compact Size and Reduced Weight
Rigid flex PCB can bend or fold to fit into tight spaces, significantly enhancing space efficiency. Compared to rigid PCBs, they reduce the need for wiring harnesses and board-to-board connectors, thereby lowering component count and interconnect requirements. Thanks to the ultra-thin flexible materials and their ability to support high-density connections, rigid flex PCBs not only reduce package size but also lower overall weight.
Enhanced Reliability and Longevity
Rigid flex PCB reduces the use of connectors, thus reducing potential failure points, and improving the reliability of the overall system. The rigid flex PCB can withstand mechanical stress, vibration, and temperature fluctuations, adapt to harsh environments, and ensure long-term stable operation.
Increased Design Flexibility
Rigid flex circuits can meet a variety of complex design challenges with their excellent flexible design. By combining rigid and flexible substrates, rigid flex circuits can be designed to meet highly complex configuration requirements, support controlled impedance, high-layer count design, and effectively reduce interconnections.
Support for High-Density Applications
Rigid flex PCBs eliminate traditional interconnect hardware, freeing up space and enhancing connection density. Rigid boards are used to place high-density surface mount (SMT) components, while flexible boards interconnect these rigid areas, forming a 3D structure. This design improves space utilization and enhances circuit integration.
Lower Assembly Costs
Although rigid flex PCB manufacturing is more complex, the assembly process requires fewer components and manual steps, helping to reduce overall costs.
What Challenges Arise in Designing Rigid Flex Circuit Boards?
Designing a rigid flex PCB presents some challenges. Below, we’ll explore the key challenges in PCB design that must be addressed to ensure optimal performance.
Intricate Design Guidelines
PCB designers must understand the electrical and mechanical specifications of the two sections, like bend radius, material requirements, and layer stack-up.
Bend Radius Considerations
For the flex section of a rigid flex design, figuring out the proper bend radius is essential. The bend radius directly affects the functionality and dependability of the board. If the design doesn’t meet the required bend radius, it can cause signal integrity issues and mechanical failures.
Choice of Materials
The physical properties of various materials will influence the final bendability, thermal expansion, reliability, etc. Improper selection of flexible PCB materials can result in a board that lacks the required bendability.
Connector Positioning
In the transition area between rigid and flexible parts, improper connector placement can lead to mechanical stress concentrations, significantly increasing the risk of solder joint cracking and structural failure.
Layer Transition
The transition of signal layers between the rigid and flexible parts is a critical challenge. Misalignment or improper layer transitions can lead to impedance mismatch and signal integrity issues such as signal reflection or degradation.
Assembly and Manufacturing
The manufacturing and assembly of rigid flex PCB are more complex than a single type of circuit board. Designers need to thoroughly consider the PCB layout and assembly methods of components during the design phase.
Mechanical Reliability
The main challenge in designing flexible parts is to ensure that they can maintain mechanical reliability under repeated bending and flexing. Especially in wearable or foldable devices, flexible parts need to be durable enough to avoid material fatigue, fractures, or performance degradation due to continuous stress.
Applications of Rigid Flex PCB Boards
The application range of rigid flex PCB is very wide. Here, we will list some applications in various fields.
Medical
In medical devices, rigid flex PCB is particularly suitable for medical devices with limited space due to its thin, light and flexible features. Its excellent reliability also meets the strict requirements of medical devices.
Common applications include:
- Portable monitoring equipment
- Ultrasonic diagnostic equipment
- Implantable medical devices (Cochlear implants, Pacemakers)
Military
The anti-vibration and anti-shock properties of rigid flex PCBs as well as their excellent space utilization meet the stringent requirements of military equipment. These PCBs withstand the extreme and harsh environments typical of military applications, ensuring reliability in critical systems.
Common applications include:
- Radar systems
- Navigation equipment
- Communications equipment
- Weapon control systems
- Surveillance or tracking systems
Aerospace
In the aerospace field, rigid flex PCBs can maintain stability under extreme conditions while providing flexible three-dimensional space layout solutions.
Common applications include:
- Radio communication systems
- Environmental and climatic test chambers
- Various sensors
- Avionics systems
- Control tower systems
Automotive
The vibration resistance, reliability, and three-dimensional spatial layout of rigid flex PCB meet the special needs of automobiles.
Common applications include:
- Instrument panel
- In-vehicle infotainment system
- LED lighting system
- Various sensor modules
- Air conditioning system
- Electronic control module
- Transmission control device
Consumer Appliances
The ultra-thin and lightweight structure of rigid flex PCBs meets the miniaturization needs of portable devices, while their design flexibility enables diverse form factor solutions for wearable devices.
Common applications include:
- Smartphones
- Laptops
- Wearable devices (Smart bracelets, Wireless headphones, Wearable photography equipment)
Last Words
Rigid flex PCB provides solutions for compact, reliable, and high-performance electronic designs required by various industries. If you’re seeking professional rigid flex PCB manufacturing, UnityPCB is your trusted partner. With nearly 20 years of expertise in PCB production, UnityPCB is dedicated to providing high-quality solutions tailored to your needs. Contact us today to have a quote.
