The Ultimate Guide to Rigid Flex PCB: Everything You Need to Know


Table of Contents:   What is a Rigid Flex PCB?   Typical Layup of a Rigid Flex PCB?   Key Benefits of Using Rigid Flex PCBs Space SavingsEnhanced ReliabilityDesign FlexibilityEase of Assembly and MaintenanceLightweight ConstructionCost Savings   Applications of Rigid Flex PCBs Wearable TechnologyLaptops and TabletsDrones and RoboticsAutomotive SensorsMedical Equipment   How to Select a Reliable Rigid Flex PCB Manufacturer   Conclusion

The world of electronics is rapidly evolving. Every year, devices become smaller, faster, and more powerful. This presents unique design and manufacturing challenges that standard printed circuit boards (PCBs) cannot meet. Rigid-flex PCBs, came into being to offer an innovative solution that combines the stability of rigid PCBs with the dynamic flexibility of flex circuits, to meet the unique requirements for multifunction, light-weight, movability and bendability.

A rigid flex PCB is a circuit board that combines rigid and flexible materials in one single circuit board. While rigid sections provide mechanical support and mounting stability, flexible sections allow for dynamic movement and three-dimensional configuration. The rigid parts are made of FR-4 material, and the flex regions are made of polyimide flexible copper laminates.

Rigid-flexible PCBs can be bent, folded, or twisted to fit various device shapes and 3D assembly and usage requirements. This potent hybrid technology combines the functionality of multiple PCBs into a single, compact unit that offers tremendous design flexibility.

Let’s explore why rigid-flex circuit boards are the top choice for various advanced electronic devices which need three-dimensional assembly or usage.

 Typical Layup of a Rigid Flex PCB?

We know rigid-flex circuit boards are produced by FR-4 material and polyimide material, but are they laminated together? Here we take a typical 4-layer rigid-flex PCB as an example: 

  • Inner layers (copper layers 2 and 3) are flexible layers; these two layers will exist on the entire PCB
  • Layers 1 and layer 4 are rigid layers; these two layers only exist on rigid section
  • All these four layers are laminated together with non-flow prepreg
  • Flexible parts are protected by overlayer (normally also polyimide material)
  • Rigid parts are protected by a solder mask
  • Surface finishes are done on the whole PCB

Rigid flex PCBs offer several unique advantages that make them an attractive choice for modern, compact electronic devices:

Space Savings

The ability of rigid-flex PCBs to fold, bend, and twist allows them to fit into extremely tight spaces where a regular rigid PCB won’t work. This helps minimize the overall size of electronic devices.

  • Can be stacked vertically or folded into complex 3D shapes
  • Helps condense electronics into smaller packages
  • Vital for wearable tech, medical devices, etc., where space is limited

Additionally, rigid-flex PCBs eliminate the need for external connectors and lengthy wires acting as interconnects between PCBs. This further saves precious real estate inside electronic enclosures.

Enhanced Reliability

The rigid and flexible sections are integrated into the identical PCB with rigid-flex PCBs, avoiding the need for board-to-board connectors. This reduces the number of potential failure points in electronic parts connections.

  • Fewer connectors mean fewer solder joints prone to cracking or breaking
  • The integrated construction eliminates interconnection failures between separate PCBs
  • Can withstand vibration, shock, and repeated flexing better than connectors

By removing connectors, rigid flex PCBs also minimize signal degradation and electromagnetic interference (EMI) that can affect signal integrity.

Design Flexibility

Rigid-flex PCB opens up new electrical design and layout possibilities. Some ways rigid flex PCBs enable greater design flexibility include:

  • Circuits can be partitioned over multiple strict areas connected by flexible sections
  • Components can be mounted on several parts of the identical PCB, more functions can be achieved in a small area
  • The relaxed site allows previously impossible 3D configurations
  • Perfect for unconventional or dynamically moving designs

For designers, this means the ability to accommodate more complex circuit requirements within smaller spaces. With intricate stacking and bending abilities, rigid flex PCBs unlock new avenues for innovation compared to standard PCB solutions.

Ease of Assembly and Maintenance

Because rigid flex PCBs condense what may earlier require multiple rigid and flexible PCBs onto a single PCB board, they significantly simplify device assembly.

  • Reduces cables and connectors that need mounting
  • Fewer parts mean reduced assembly time and cost
  • Testing is much easier and quick since only need to test once
  • It is easier to isolate and access details during repairs

Furthermore, the lack of cables or wire harnesses makes maintenance, troubleshooting, and repairs much more accessible. The condensing of the electronics onto a single unified circuit board creates a modular system that can be diagnosed and serviced rapidly. This is especially relevant for mission-critical equipment where uptime is paramount.

Lightweight Construction

Rigid-flex PCBs eliminate bulky connectors, fasteners, and structural components needed to stack or join several ordinary PCBs into functioning devices. The result is a lighter-weight product, which is critical in some industrial areas.

  • Greatly aids weight reduction efforts in aircraft and aerospace applications
  • Important for portable and wearable consumer electronics where every gram matters
  • Vital in reducing the energy consumption of electric vehicles through lower mass

The reduced mass is an often overlooked but substantial benefit in various use cases spanning defense, automotive, industrial, and consumer device segments. With consumer preferences shifting towards lighter and compact form factors, rigid flex PCBs facilitate weight savings.

Cost Savings

At first glance, the fabrication of rigid flex printed circuit boards requires specialized polyimide materials and complex processes that may appear more expensive than traditional PCB technologies. However, viewed holistically from a total cost perspective encompassing everything from design, part sourcing, assembly, testing, and repairs over a product’s entire lifecycle, employing rigid flex circuit board technology reduces overall costs significantly.

  • Design consolidation translates to fewer components to source
  • Lower assembly time due to fewer parts translates to labor cost savings
  • Higher reliability lowers servicing and warranty costs
  • More significant economies of scale over time bring down initial fabrication costs

Therefore, despite the perception of being pricier, rigid flex PCBs offer noteworthy cost reduction opportunities from a big-picture standpoint. The reliability benefits lead to dramatically lowered failure rates and reduced repairs over the operating lifetime of the products. And as more sector adoption accrues, the cost efficiencies will compound. 

Rigid Flex PCB

The advantages outlined above make rigid flex PCBs an extremely versatile technology suitable across domains like consumer electronics, telecom, automotive, aerospace, industrial machinery, and medical devices. Some examples include:

Wearable Technology

Smart glasses, smart bracelet smart watches, head mounted displays, health monitoring patches, athletic biosensors, etc., all require dense electronics packaged into ergonomic and dynamic form factors. Rigid flex printed circuit board technology integrates electronics into the necessary 3D contours while saving space. The flexible regions can comfortably match the contours around wrists, arms, and heads; besides they are very lightweight which is suitable for long wearing.

Laptops and Tablets

Portable computing devices require compact stacking and layering of circuit boards and durable interconnections between them to survive constant opening/closing and twisting motions. Rigid flexible PCB construction ideally satisfies both needs. Millions of flex cycles can be sustained over product lifetimes.

Drones and Robotics

Remote-controlled drones and autonomous robots need ultra-lightweight and rugged circuit boards that endure vibrations while occupying the least space possible. Rigid flex PCBs check all boxes due to low weight and flexibility. The technology is impacting everything from hobbyist quadcopters to military reconnaissance drones.

Automotive Sensors

The expanding array of cameras, radar, ultrasonic sensors, and actuation electronics enabling modern automotive autonomy and safety features demand proven reliable and space-saving PCB solutions. Rigid flex printed circuit board integration proves an ideal choice to embed electronics conformally across vehicle interiors and exteriors.

Medical Equipment

Medical devices have long relied on rigid flex PCBs owing to the need for biocompatible and compact circuit boards in life-saving implantable devices like pacemakers, in addition to increasing electronics integration in large equipment like MRI scanners and CT scanners. As medical devices become more complex, rigid flexible PCBs are indispensable.

The common themes tying all these use cases together are bendability, miniaturization, reliability, and ingenious enclosures – requirements perfectly aligned with the fundamental merits of the rigid flex circuit board technology. And as electronics get infused into every facet of life, the applicability of the technology will only expand.

To fully capitalize on the benefits of rigid flex PCBs on your devices, partnering with a competent rigid flexible PCB manufacturer is key. Look for the below signs of excellence when selecting a rigid flex PCB manufacturing partner:

  • Rich expertise in manufacturing of rigid-flex circuit boards
  • Advanced in-house engineering capabilities DFM, prototyping, and testing
  • Advanced equipment to fabricate multilayer rigid flex printed circuit board configurations
  • Experienced and skilled workers in rigid flex PCBs production
  • Strict quality control to meet the IPC standards and customer’s requirements
  • Excellent team in supply chain and material inspection
  • International certifications like UL, ISO9001, ISO13485., etc
  • Competitive and transparent pricing structured around value
  • Great and professional customer service team

While the merits of the technology are well established, realizing a successful product depends heavily on an experienced manufacturing partner. Rigid flex PCB fabrication requires mature production techniques and robust quality control. Partnering early in the design stages with a qualified manufacturer paves the path to overcoming technical challenges smoothly.

Rigid flex PCB technology pushes the limits of electronic device engineering across crucial performance metrics from bendability, size, weight, and reliability to cost and manufacturability tradeoffs. As electronic products become more capable, compact, and ubiquitous across everyday life, embracing innovative technologies like rigid flex PCBs serves well to meet fast-evolving market demands and gain a competitive edge. Any engineering organization should actively evaluate where rigid flexible PCBs can enrich their next-generation product roadmap.