1 / 5
Buy China Rigid Flex PCB Suppliers - Single, Double-Sided & Multi-Layer Flex Circuit Factory Supplier, Factory
Product Description
What is Rigid Flex PCB?
Rigid-Flex PCB (Rigid-Flex Printed Circuit Board) is a hybrid circuit board that combines the characteristics of rigid PCBs and flexible PCBs (flex PCBs) into a single integrated structure. It integrates rigid sections (for stable mounting of components) and flexible sections (for bending, folding, or dynamic movement) without the need for additional connectors, making it widely used in electronic devices that require compact design, reliability, and space optimization.
Core Components & Structure
A typical rigid-flex PCB consists of three key parts, layered and bonded together through specialized processes:
Rigid sections: Made of traditional rigid substrate materials (e.g., FR-4, a glass-reinforced epoxy resin). These parts provide mechanical stability to support electronic components (such as chips, resistors, capacitors) and ensure structural integrity.
Flexible sections: Composed of flexible substrates (common materials include polyimide, PI, or polyester, PET). These parts are thin, lightweight, and can be repeatedly bent, folded, or twisted, allowing the board to adapt to irregular shapes or dynamic environments.
Interconnect layers: The rigid and flexible sections share internal conductive copper layers (signal traces, power lines, ground planes) that are seamlessly connected. This eliminates the need for wires, connectors, or solder joints between separate rigid and flex boards, reducing failure risks.
Key Advantages
Compared to standalone rigid PCBs or flex PCBs, rigid-flex PCBs offer distinct benefits:
Space & weight savings: They can be folded to fit into tight, complex enclosures (e.g., foldable phones, wearables), reducing the overall size and weight of electronic devices.
Enhanced reliability: Fewer connectors and solder joints mean fewer potential points of failure (e.g., loose connections from vibration or aging), which is critical for high-reliability applications like aerospace equipment.
Simplified assembly: Integrating multiple rigid and flex parts into one board streamlines the manufacturing process, reducing assembly time and human error.
Improved performance: Continuous copper traces minimize signal loss and electromagnetic interference (EMI), ensuring stable signal transmission—essential for high-frequency devices.
Common Applications
Rigid-flex PCBs are indispensable in industries where space, reliability, and flexibility are paramount:
Consumer electronics: Foldable smartphones, smartwatches, laptops, cameras, and earbuds (e.g., the hinge area of foldable phones uses flexible sections to connect rigid display and battery boards).
Aerospace & defense: Satellites, aircraft avionics, and military equipment (they withstand extreme temperatures, vibration, and space constraints).
Automotive: In-vehicle infotainment systems, sensor modules, and advanced driver-assistance systems (ADAS) — adapting to the curved or confined spaces of car interiors.
Medical devices: Portable monitors, implantable devices (e.g., pacemakers), and diagnostic equipment (offer biocompatibility, miniaturization, and durability).
The Types of Rigid Flex PCB
The classification dimensions of Rigid-Flex PCB are numerous. The core classification can be based on structural form, flexible area characteristics, number of layers, and adaptability to application scenarios. Different categories correspond to different process difficulties and usage requirements.
Classified by Structural Form
This is the most commonly used classification method. The core basis is the connection mode and layout characteristics of the rigid and flexible areas, which directly determine the installation compatibility of the PCB.
Single flexible zone rigid-flex PCB: The entire board has only one continuous flexible zone, with both ends or one end connected to the rigid board. It has a simple structure and low cost, and is the most common basic model in consumer electronics.
Multi-flexible zone rigid-flex PCB: Contains two or more independent flexible zones and forms a complex structure through the series connection of multiple rigid boards. Suitable for equipment that requires multi-directional bending and decentralized layout.
Three-dimensional rigid and flexible combined PCB: The flexible area can achieve bending and twisting in three-dimensional space, while the rigid area is distributed in different spatial planes. Mostly used in equipment with extremely compact space and irregular shapes.
Classified by Characteristics of Flexible Regions
Static rigid-flex combined PCB: The flexible area is only bent and shaped once during assembly, maintaining a fixed form during subsequent use. The core requirement is structural stability after shaping.
Dynamic rigid-flex PCB: The flexible area needs to withstand long-term and repeated bending and twisting, requiring extremely high fatigue resistance. Typical applications include printer paper feed mechanisms and wearable device opening/closing components.
Classified by Number of Line Layers
Single-layer rigid-flex PCB: Contains only one layer of conductive copper foil. Simplest structure and lowest cost, suitable for low-complexity circuits such as simple toy control boards.
Double-layer rigid-flexible combined PCB: Consists of two layers of conductive copper foil with interlayer conduction achieved through vias. Widely used as a peripheral module for smartphones and tablet computers.
Multi-layer rigid-flex PCB (≥4 layers): Composed of alternating superposition of rigid and flexible layers with power, ground, and signal layers inside. Suitable for high-end electronics such as satellite circuit boards and precision medical detection mainboards.
Classified by Special Function Adaptation
High-frequency rigid-flex PCB: Adopts flexible substrates with low dielectric constant and low loss (such as PTFE-modified polyimide). Suitable for 5G equipment, radar systems, and satellite communication equipment.
High-temperature resistant rigid-flex PCB: Made of high-temperature resistant materials (such as special PI), operating stably within -55°C to 200°C or wider. Widely used in aero engine peripherals and industrial high-temperature sensors.
High-density interconnect (HDI) rigid-flex PCB: Uses micro-vias and fine line width/spacing technologies to enhance line density and reduce board size. Suitable for smartwatches and implantable medical devices.
How to Design Rigid Flex PCB?
The design and production of rigid-flex combined PCBs need to take into account both the structural stability of rigid PCBs and the bending adaptability of flexible PCBs. During the design stage, potential risks in subsequent production and use should be avoided.
Key Points of Design
▶ Structural and Layout Design
Clear rigid/flex boundary: A transition zone (usually 0.5–1mm) should be reserved at the boundary to prevent components, vias, and copper foils from crossing. Edges of the flexible zone need to be rounded (radius ≥1mm) to reduce stress concentration.
Flexible zone bending planning: The minimum bending radius of inner copper foil should be ≥10× the flexible substrate thickness; outer copper foil ≥15×. Avoid overlapping and bending in the flexible zone to prevent long-term circuit damage.
Reasonable component layout: Heat-generating components should be concentrated in the rigid area and away from the flexible area. Heavy-duty components need to be fixed in rigid areas with reserved heat dissipation space and fixing holes.
▶ Line and Layering Design
Line direction adapted to bending: In the flexible zone, line direction should be horizontal (parallel to bending direction). Minimum line width/spacing should be ≥0.1mm in the flexible area.
Stacking structure optimization: For multi-layer boards, the flexible layer should adopt a symmetrical structure to prevent warping. Rigid core materials are prohibited in the flexible zone; adhesive should be flexible materials (such as acrylic).
Via and grounding design: Metallized vias are prohibited in the flexible zone. All vias must remain in the rigid zone, at least 1mm from the flexible zone boundary. Use "microstrip line" or "ribbon line" structures for high-frequency scenarios.
▶ Material Selection
Flexible substrate: For dynamic bending, choose polyimide (PI) with good fatigue resistance. For static scenarios, polyester (PET) with lower cost can be selected. High-frequency equipment should use PI substrates with low dielectric constants (such as PTFE-modified PI).
Copper foil and covering film: For flexible areas, rolled copper foil (good ductility and bending resistance) is preferred; for rigid areas, electrolytic copper foil can be used. The flexible zone surface should be covered with a flexible PI film, extending 0.2–0.3mm beyond the copper foil.
Key Points of Manufacturing
▶ Substrate Pretreatment and Lamination Process
Substrate cleaning: The surface of the flexible PI substrate is prone to adsorbing impurities. Remove oil stains and oxide layers through plasma cleaning or chemical treatment to enhance copper foil adhesion. Rigid FR-4 substrates need drying and dehumidifying to prevent air bubbles during lamination.
Precise lamination: Temperature, pressure, and time need to be controlled. Bonding parameters of the flexible zone and rigid zone should be set differently. The stepwise lamination method is adopted — first laminate the flexible layer, then laminate with the rigid layer to ensure tight interlayer bonding.
▶ Circuit Fabrication and Etching Control
High-precision exposure: Flexible substrates are prone to stretching. Use special fixtures for fixation during exposure. Adopt UV parallel light exposure to ensure line pattern accuracy — control line width error in the flexible zone within ±0.02mm.
Etching process optimization: Use alkaline etching solution for the copper foil in the flexible zone at a slightly lower etching speed than the rigid zone to prevent line breakage. Clean immediately after etching to avoid residual liquid from corroding the substrate.
▶ Cutting and Forming Processes
Flexible zone contour cutting: Processed by laser cutting (CO₂ laser or UV laser) with a smooth cut and no burrs, avoiding base material tearing. Laser power needs to be controlled to prevent damage to internal circuits.
Rigid zone forming: Formed by CNC milling with edges deburred and chamfered. The boundary between rigid and flexible zones needs secondary grinding to ensure a smooth transition and reduce stress concentration during bending.
▶ Post-Processing and Quality Inspection
Surface treatment: Rigid areas can undergo tin spraying, gold plating, and OSP to enhance soldering performance. The flexible zone surface is only protected by a covering film — high-temperature treatments such as tin spraying are prohibited to prevent base material deformation.
Full-process inspection: Inspect interlayer adhesion (peel test) and line conductivity (flying probe test) during production. Finished products undergo bending tests (dynamic bending simulates tens of thousands of cycles) and high/low temperature environment tests.
| RIGID FLEXIBLE PCB CAPABILITY | |||
|---|---|---|---|
| Category | Parameter | Standard | Advanced |
| RIGID FLEX PCB | Flex layers | Lamination structure ≤4L；Book structure ≤10L | Lamination structure ≤4L；Book structure ≤12L |
| Max. Panel Size (shipping) | 210MM × 480MM | 460MM × 480MM | |
| FPC dielectric thickness | 2MIL、3MIL、4MIL | 1MIL | |
| PTH rigid-flex transition area | ≤1.2MM | ≤1.0MM | |
| Pattern spacing, rigid area to rigid-flex transition area | ≥1.2MM | ≥0.9MM | |
| Rigid-Flex Structure | Typical structure、Flying tail structure、Multi-flex book structure、Two-flex lamination structure、Single-sided asymmetric structure、Asymmetric structure etc. | ||
Send Inquiry
Frequently Asked Questions
1
What is the main difference between a rigid-flex PCB and a standard flexible PCB?
A standard flexible PCB consists entirely of flexible substrate material and is designed for bending or dynamic movement throughout the entire board. A rigid-flex PCB, on the other hand, combines both rigid sections (typically FR-4 substrate) and flexible sections (typically polyimide) into a single integrated structure. The rigid sections provide stable mounting platforms for components, while the flexible sections allow the board to bend, fold, or adapt to complex enclosures — offering the best of both worlds in one unified design.
2
How many times can a rigid-flex PCB be bent without failure?
The number of bending cycles a rigid-flex PCB can withstand depends heavily on the design and materials used. For static applications (bent once during assembly and held in position), the board is designed for long-term fixed use. For dynamic applications requiring repeated bending — such as printer mechanisms or wearable devices — a well-designed rigid-flex PCB using rolled copper foil and high-quality polyimide substrate can typically withstand tens of thousands to hundreds of thousands of bending cycles without failure, provided the minimum bending radius specifications are respected during design.
3
What materials are commonly used for the flexible substrate in rigid-flex PCBs?
The most commonly used flexible substrate material is Polyimide (PI), which offers excellent thermal resistance, mechanical flexibility, and fatigue resistance — making it ideal for both static and dynamic bending applications. For cost-sensitive and static applications, Polyester (PET) is sometimes used. For high-frequency applications such as 5G equipment, radar systems, and satellite communications, PTFE-modified polyimide substrates with low dielectric constants and low signal loss are preferred. The choice of material depends on the operating environment, frequency requirements, and expected mechanical stress.
4
Are rigid-flex PCBs more expensive than traditional rigid PCBs?
Yes, rigid-flex PCBs generally have a higher unit manufacturing cost compared to standard rigid PCBs due to the complexity of combining multiple material types, specialized lamination processes, laser cutting, and more stringent quality control requirements. However, when considering the total system cost, rigid-flex PCBs often provide significant savings by eliminating the need for separate connectors, cables, and assembly steps that would be required if using multiple individual boards. They also reduce field failure rates, which lowers long-term maintenance and warranty costs — making them highly cost-effective for demanding applications.
5
Can components be mounted on the flexible sections of a rigid-flex PCB?
Generally, it is not recommended to place components on the flexible sections of a rigid-flex PCB. The flexible sections are designed for bending and movement, and mounting components on them can lead to solder joint cracking, component damage, or delamination when the board is flexed. Best design practice dictates that all electronic components — especially heavy, heat-generating, or vibration-sensitive ones — should be placed on the rigid sections, which provide the mechanical stability needed for reliable soldering and long-term component integrity.
6
What industries benefit most from using rigid-flex PCBs?
Rigid-flex PCBs are widely adopted across industries where space constraints, reliability, and complex form factors are critical. The key industries include: Consumer Electronics (foldable smartphones, wearables, cameras), Aerospace & Defense (satellites, avionics, military hardware requiring resistance to extreme temperatures and vibration), Automotive (ADAS systems, infotainment modules, sensor arrays in confined spaces), and Medical Devices (implantable devices like pacemakers, portable diagnostic equipment, and miniaturized monitors requiring biocompatibility and long-term durability). The HDI variant is particularly valuable in ultra-miniaturized medical and wearable applications.
