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OEM China Suppliers of Rigid Flex PCB, Double-Sided & Multi-Layer Flex Circuit Factory Company, Pricelist
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 boards, reducing failure risks.
Key Advantages
Space & Weight Savings
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), 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) — adapt 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 of Rigid-Flex PCB covers structural form, flexible area characteristics, number of layers, and 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.
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. Used in laptop screen cables, headphone circuit boards. Simple structure, low cost — the most common basic model in consumer electronics.
Multi-Flexible Zone Rigid-Flex PCB: Contains two or more independent flexible zones forming complex structures through series connection of multiple rigid boards. Suitable for industrial sensor modules and multi-camera mobile phone lens modules.
Three-Dimensional Rigid-Flex PCB: The flexible area achieves bending and twisting in three-dimensional space. Used in UAV fuselage control boards and car instrument panel integrated circuit boards to maximize three-dimensional space utilization.
Classified by Flexible Region Characteristics
The main distinction is whether the flexible part can be repeatedly bent to adapt to static installation or dynamic working scenarios.
Static Rigid-Flex PCB: The flexible area is only bent and shaped once during assembly, maintaining a fixed form during subsequent use. Core requirement is structural stability after shaping. Example: foldable phone frame connections.
Dynamic Rigid-Flex PCB: The flexible area must withstand long-term repeated bending and twisting, requiring extremely high fatigue resistance. Typical applications include printer paper feed mechanisms and wearable device opening/closing components — must meet no-failure after tens of thousands of bends.
Classified by Number of Layers
Similar to ordinary PCBs, classified by the number of conductive circuit layers. More layers = higher integration and more complex processes.
Single-Layer Rigid-Flex PCB: Contains only one layer of conductive copper foil. Simplest structure, lowest cost. Suitable for low-complexity circuits such as simple toy control boards and small remote control connection lines.
Double-Layer Rigid-Flex PCB: Consists of two layers of conductive copper foil with interlayer conduction through vias. Widely used as peripheral modules for smartphones and tablet computers, balancing cost and practicality.
Multi-Layer Rigid-Flex PCB (≥4 layers): Composed of alternating rigid-flexible-rigid layers with power, ground, and signal layers inside. High integration for complex signal transmission and power management. Used in aerospace satellite circuit boards and medical precision detection mainboards.
Classified by Special Function Adaptation
Specialized types designed for extreme environments or special needs, with additional customized requirements for materials and processes.
High-Frequency Rigid-Flex PCB: Uses 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℃ to 200℃ or wider. Used in aero engine peripheral equipment and industrial high-temperature sensors.
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 such as pacemaker auxiliary circuit boards.
How to Design Rigid Flex PCB?
The design and production of rigid-flex PCBs must balance structural stability of rigid PCBs with bending adaptability of flexible PCBs. The following are the key design points:
Structural and Layout Design
Clear rigid/flexible boundary: Reserve a transition zone (0.5–1mm) at the boundary. Edges of the flexible zone need to be rounded (radius ≥1mm) to reduce stress concentration. Prevent components, vias, and copper foils from crossing the boundary.
Bending radius planning: Minimum bending radius of inner copper foil ≥ 10× flexible substrate thickness; outer copper foil ≥ 15×. Avoid overlapping and bending in the flexible zone to prevent long-term compression damage.
Component layout: Heat-generating components (chips, resistors) should be concentrated in rigid areas, away from flexible areas. Heavy-duty components must 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, prefer horizontal line direction (parallel to bending direction). Minimum line width/spacing ≥ 0.1mm. Avoid dense thin lines and sharp-angled lines in the flexible area.
Stacking structure optimization: For multi-layer boards, the flexible layer should adopt a symmetrical structure (e.g., "rigid – flex – flex – rigid") to prevent warping. Use flexible adhesive materials (such as acrylic) in the flexible zone.
Via and grounding design: Metallized vias are prohibited in the flexible zone. All vias must remain in the rigid zone and be at least 1mm from the flexible zone boundary. In high-frequency scenarios, use microstrip or ribbon line structures.
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, use rolled copper foil (good ductility and bending resistance). For rigid areas, electrolytic copper foil can be used. The flexible zone surface should be covered with a flexible covering film (PI film), with edges extending 0.2–0.3mm beyond the copper foil.
Key Points of Manufacturing
The production of rigid-flex PCBs integrates the processes of rigid and flexible PCBs, requiring additional control over the connection links between rigidity and flexibility. The core points are as follows:
Substrate Pretreatment and Lamination Process
- Substrate cleaning: The surface of 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 dehumidification to prevent air bubbles during lamination.
- Precise lamination: Control temperature, pressure, and time with different bonding parameters for flexible and rigid zones. Use stepwise lamination — first laminate the flexible layer, then bond with the rigid layer to ensure tight interlayer bonding.
Circuit Fabrication and Etching Control
- High-precision exposure: Use special fixtures to fix flexible substrates during exposure to prevent line deviation. Use ultraviolet parallel light exposure machines to control line width error in the flexible zone within ±0.02mm.
- Etching process optimization: Use alkaline etching solution for the flexible zone copper foil. Etching speed is slightly lower than the rigid zone to prevent excessive etching. Clean immediately after etching to avoid residual liquid corroding the substrate.
Cutting and Forming Processes
- Flexible zone contour cutting: Process by laser cutting (CO₂ laser or UV laser) for smooth cuts without burrs, avoiding tearing caused by mechanical cutting. Control laser power to prevent damage to internal circuits.
- Rigid zone forming: Use CNC milling with deburring and chamfering. The boundary between rigid and flexible zones needs secondary grinding to ensure 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 protected only 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 Capability | Advanced Capability |
|---|---|---|---|
| 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. | ||
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Frequently Asked Questions (FAQ)
What is the main difference between a rigid-flex PCB and a standard flexible PCB?
A standard flexible PCB (FPC) consists entirely of flexible substrate material and is designed purely for bending and folding. A rigid-flex PCB combines both rigid sections (typically FR-4) and flexible sections (typically polyimide) into a single integrated board. The rigid sections provide stable mounting platforms for components, while the flexible sections enable bending and routing through confined spaces — eliminating the need for separate connectors or cables between boards.
How many times can a rigid-flex PCB be bent without failure?
This depends on the design type and materials used. Static rigid-flex PCBs are designed for one-time bending during assembly and are not intended for repeated flexing. Dynamic rigid-flex PCBs, however, are engineered to withstand tens of thousands to hundreds of thousands of bending cycles. Key factors affecting bend life include the minimum bending radius, copper foil type (rolled copper is preferred for dynamic applications), flexible substrate material, and the line routing direction in the flex zone.
What materials are commonly used for the flexible substrate in rigid-flex PCBs?
The most common flexible substrate material is Polyimide (PI), which offers excellent thermal stability, chemical resistance, and fatigue resistance — making it ideal for both static and dynamic applications. For lower-cost or static applications, Polyester (PET) may be used. For high-frequency applications such as 5G equipment and radar systems, PTFE-modified polyimide substrates with low dielectric constants are preferred to minimize signal loss and interference.
Can components be placed in the flexible zones of a rigid-flex PCB?
Generally, it is not recommended to place components in the flexible zones, especially for dynamic bending applications. Components mounted on flex areas can crack solder joints or damage the substrate during repeated bending. Heavy, heat-generating, or mechanically sensitive components (chips, connectors, large capacitors) should always be placed in the rigid sections. In some static applications, very small, lightweight components may be placed near the edge of a flex zone, but this requires careful design review and testing.
What industries most commonly use rigid-flex PCBs?
Rigid-flex PCBs are widely used across multiple high-demand industries. In consumer electronics, they are found in foldable smartphones, smartwatches, laptops, and cameras. In aerospace and defense, they are used in satellites, avionics systems, and military equipment due to their ability to withstand extreme conditions. The automotive industry uses them in ADAS sensors and infotainment systems. Medical devices such as pacemakers, portable monitors, and implantable devices also rely on rigid-flex PCBs for their miniaturization, biocompatibility, and durability.
What are the key quality inspection steps for rigid-flex PCBs during manufacturing?
Quality inspection for rigid-flex PCBs involves multiple stages throughout production. During manufacturing, interlayer adhesion is verified using peel tests, and circuit conductivity is checked using flying probe tests. Dimensional accuracy of the flex zone contour is verified after laser cutting. For finished products, bending cycle tests simulate real-world dynamic use (tens of thousands of cycles for dynamic boards). High and low temperature environment tests (thermal cycling) verify stability across operating temperature ranges. Visual inspection and automated optical inspection (AOI) are also performed to detect surface defects, line breaks, and solder joint issues.
