Famous China Rigid Flex PCB Suppliers - Single & Double-Sided, 4-16 Layer, Complex Multi-Layer Factory Solutions Supplier, Factory
Product Description
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.
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.
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.
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), 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.
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.
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. The flexible zone is mainly used to achieve "folding" or "turning" functions, such as the flat cable connecting the laptop screen to the main unit. 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, such as industrial sensor modules and lens module circuit boards for multi-camera mobile phones.
Three-Dimensional Rigid-Flex 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, such as UAV fuselage control boards and integrated circuit boards in car instrument panels.
Static Rigid-Flex 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. Example: the frame of a foldable phone connected to the circuit board.
Dynamic Rigid-Flex PCB
The flexible area needs to withstand long-term and repeated bending, twisting, and other dynamic actions, requiring extremely high fatigue resistance and copper layer adhesion. Typical applications include printer paper feed mechanism circuit boards and opening/closing components of wearable devices, which must endure tens of thousands of bends without failure.
Contains only one layer of conductive copper foil. Simplest structure and lowest cost. Suitable for low-complexity circuits such as simple toy control boards and small remote control connection lines.
Two layers of conductive copper foil with interlayer conduction achieved through vias. Widely used as a peripheral module for smartphones and tablet computers, balancing cost and practicality.
Usually composed of alternating superposition of "rigid layer – flexible layer – rigid layer". Has a high degree of integration and can achieve complex signal transmission and power management. Suitable for high-end electronics such as satellite circuit boards in aerospace and precision detection mainboards in medical equipment.
High-Frequency Rigid-Flex PCB
Adopts flexible substrates with low dielectric constant and low loss (such as PTFE-modified polyimide), reducing attenuation and interference during signal transmission. Suitable for 5G equipment, radar systems, and satellite communication equipment.
High-Temperature Resistant Rigid-Flex PCB
Flexible substrate and adhesive are made of high-temperature resistant materials (such as special PI), operating stably within -55°C to 200°C or even wider. Widely used in peripheral equipment of aero engines and industrial high-temperature sensors.
HDI (High-Density Interconnect) Rigid-Flex PCB
By using micro-vias and fine line width/spacing technologies, it enhances line density and reduces board size. Suitable for miniaturized devices such as smartwatches and implantable medical devices (e.g., pacemaker auxiliary circuit boards).
The design and production of rigid-flex 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. In the production stage, special process links need to be controlled to ensure reliability and consistency.
Rigid/Flex Zone Boundary: A transition zone (usually 0.5–1mm) should be reserved at the boundary between the rigid zone and the flexible zone to prevent components, vias, and copper foils from crossing the boundary and to avoid cracking due to material differences during bending. The edges of the flexible zone need to be rounded (radius ≥1mm) to reduce stress concentration.
Flexible Zone Bending Planning: The minimum bending radius of the inner copper foil should be ≥10× the thickness of the flexible substrate; for outer copper foil ≥15×. Static bending only requires one-time shaping. Avoid overlapping and bending in the flexible zone to prevent long-term compression from damaging the circuit.
Component Layout: Heat-generating components (chips, resistors) should be concentrated in the rigid area and far away from the flexible area. Heavy-duty components (interfaces, sensors) need to be fixed in rigid areas with reserved heat dissipation space and fixing holes.
Line Direction: In the flexible zone, line direction is preferred to be horizontal (parallel to the bending direction) to reduce tensile/compressive damage to the copper foil during bending. Minimum line width/spacing ≥0.1mm is recommended in the flexible area.
Stacking Structure: For multi-layer rigid-flex PCBs, the flexible layer should adopt a symmetrical structure (e.g., "rigid layer – flexible layer – flexible layer – rigid layer") to prevent warping. Rigid core materials are prohibited in the flexible zone; adhesive should be flexible materials such as acrylic.
Via & Grounding Design: Metallized vias are prohibited in the flexible zone. All vias must remain in the rigid zone and be at least 1mm away from the flexible zone boundary. Set up independent ground layers to reduce signal interference.
Flexible Substrate: For dynamic bending scenarios, choose polyimide (PI) with good fatigue resistance. For static scenarios, polyester (PET) with lower cost can be selected. High-frequency equipment should select PI substrates with low dielectric constants (such as PTFE-modified PI).
Copper Foil & 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 surface of the flexible zone should be covered with a flexible covering film (PI film), with the edge extending 0.2–0.3mm beyond the copper foil for protection and insulation.
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 adhesion between copper foil and substrate. 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 with different bonding parameters for the flexible and rigid zones. Stepwise lamination is adopted — first the flexible layer is laminated, then laminated with the rigid layer to ensure tight interlayer bonding.
High-Precision Exposure: Flexible substrates are prone to stretching. Special fixtures should be used for fixation during exposure to prevent line deviation. UV parallel light exposure machines are adopted to ensure line pattern accuracy, especially controlling line width error in the flexible zone within ±0.02mm.
Etching Process Optimization: Alkaline etching solution is used to treat copper foil in the flexible zone. The etching speed is slightly lower than that in the rigid zone to prevent excessive etching from causing line breakage. After etching, clean promptly to avoid residual liquid from corroding the substrate.
Flexible Zone Contour Cutting: The flexible zone contour is processed by laser cutting (CO₂ laser or UV laser), with smooth cuts and no burrs, avoiding base material tearing caused by mechanical cutting. Laser power needs to be controlled to prevent damage to internal circuits.
Rigid Zone Forming: The rigid zone can be 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.
Surface Treatment: Rigid areas can undergo tin spraying, gold plating, and OSP surface treatments 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: During production, interlayer adhesion (peel test) and line conductivity (flying probe test) need to be inspected. Finished products must undergo bending tests (dynamic bending simulating tens of thousands of cycles) and high/low temperature environment tests to ensure stability and reliability.
| 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. | ||
