ODM China Rigid Flex PCB Suppliers - Single & Double-Sided, 4-16 Layer Complex Multi-Layer Factory Solutions Supplier, Company
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:
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.
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 (e.g., parts that need to open/close or vibrate).
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
They can be folded to fit into tight, complex enclosures (e.g., foldable phones, wearables), reducing the overall size and weight of electronic devices.
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.
Integrating multiple rigid and flex parts into one board streamlines the manufacturing process, reducing assembly time and human error.
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:
The Type of Rigid Flex PCB
The classification of Rigid-Flex PCBs covers structural form, flexible area characteristics, number of layers, and special function adaptation. Different categories correspond to different process difficulties and usage requirements.
This is the most commonly used classification method. The core basis is the connection mode and layout characteristics of the rigid and flexible areas.
The entire board has only one continuous flexible zone, with both ends or one end connected to the rigid board. The flexible zone is mainly used to achieve "folding" or "turning" functions. Simple structure and low cost — the most common basic model in consumer electronics.
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, such as industrial sensor modules and lens module circuit boards for multi-camera mobile phones.
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, such as UAV control boards and car instrument panel circuits.
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.
The flexible area needs to withstand long-term and repeated bending and twisting, requiring extremely high fatigue resistance and copper layer adhesion. Typical applications include printer paper feed mechanisms and wearable device opening/closing components — must meet no-failure requirements after tens of thousands of bends.
Contains only one layer of conductive copper foil. Simplest structure, lowest cost, suitable for low-complexity circuits such as simple toy control boards.
Consists of two layers of conductive copper foil with interlayer conduction via vias. Takes into account both cost and practicality — widely used as peripheral modules for smartphones and tablets.
Usually composed of alternating superposition of "rigid layer – flexible layer – rigid layer". High integration with power, ground, and signal layers inside. Suitable for high-end devices such as satellite circuit boards and medical precision detection mainboards.
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.
Made of high-temperature resistant materials (such as special PI), operable within -55°C to 200°C or wider. Widely used in aero engine peripherals and industrial high-temperature sensors.
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 need to take into account both structural stability and bending adaptability. During design, potential risks in subsequent production and use must be addressed in advance.
Clear rigid/flex boundary: Reserve a transition zone (0.5–1mm) at the boundary to prevent components, vias, and copper foils from crossing the boundary. Edges of the flexible zone should be rounded (radius ≥1mm) to reduce stress concentration.
Flexible zone bending planning: In dynamic bending scenarios, the minimum bending radius of the inner copper foil should be ≥10× the flexible substrate thickness, and ≥15× for outer copper foil. Avoid overlapping and bending in the flexible zone.
Component layout: Heat-generating components (chips, resistors) should be concentrated in the rigid area, away from the flexible area. Heavy components (interfaces, sensors) must be fixed in rigid areas with reserved heat dissipation space and fixing holes.
Line direction: In the flexible zone, prefer horizontal lines (parallel to bending direction) to reduce tensile/compressive damage. Minimum line width/spacing ≥0.1mm recommended for flexible areas.
Stacking structure: Multi-layer boards should use symmetrical structure (e.g., "rigid – flex – flex – rigid") to prevent warping. Adhesive in flexible zones should be flexible materials (e.g., acrylic).
Via and grounding: Metallized vias are prohibited in the flexible zone — all vias must remain in the rigid zone, at least 1mm from the flex boundary. Use independent ground layers to reduce signal interference.
Flexible substrate: For dynamic bending, choose polyimide (PI) for fatigue resistance; for static scenarios, polyester (PET) is a lower-cost option. High-frequency equipment should use low dielectric constant PI substrates.
Copper foil and covering film: Rolled copper foil (better ductility) is preferred for flexible areas; electrolytic copper foil for rigid areas. Flexible zone surfaces should be covered with PI film, extending 0.2–0.3mm beyond the copper foil edge.
Key Points of Manufacturing
The production of rigid-flex PCBs integrates the processes of both rigid and flexible PCBs, and requires additional control over the connection links between rigidity and flexibility.
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 to be dried and dehumidified to prevent air bubbles during lamination.
Precise lamination: Temperature, pressure, and time need to be controlled. Bonding parameters for the flexible zone and rigid zone should be set differently to prevent deformation or delamination. Use stepwise lamination — first laminate the flexible layer, then combine with the rigid layer.
High-precision exposure: Flexible substrates are prone to stretching — use special fixtures for fixation during exposure to prevent line deviation. UV parallel light exposure machines ensure line pattern accuracy; control line width error in flexible zones within ±0.02mm.
Etching process optimization: Use alkaline etching solution for flexible zone copper foil. Etching speed should be slightly lower than in the rigid zone to prevent line breakage. Clean promptly after etching to avoid residual liquid corrosion.
Flexible zone contour cutting: Process flexible zone contours by laser cutting (CO₂ or UV laser) for smooth, burr-free cuts. Control laser power to prevent damage to internal circuits.
Rigid zone forming: Use CNC milling for rigid zone forming with deburring and chamfering. The rigid-flex boundary needs secondary grinding to ensure a smooth transition and reduce stress concentration during bending.
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. | ||||
