China China Suppliers Rigid Flex PCB Factory - Single & Double-Sided, 4-16 Layer Complex Multi-Layer Options Suppliers, Company
Product Description
What is Rigid Flex PCB?
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.
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
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, 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:
Foldable smartphones, smartwatches, laptops, cameras, and earbuds. The hinge area of foldable phones uses flexible sections to connect rigid display and battery boards.
Satellites, aircraft avionics, and military equipment — withstanding extreme temperatures, vibration, and space constraints.
In-vehicle infotainment systems, sensor modules, and ADAS — adapting to curved or confined spaces of car interiors.
Portable monitors, implantable devices (e.g., pacemakers), and diagnostic equipment — offering biocompatibility, miniaturization, and durability.
The Types of Rigid Flex PCB
The classification of Rigid-Flex PCBs spans multiple dimensions — structural form, flexible area characteristics, number of layers, and application-specific adaptability. Below are the mainstream classification methods and detailed explanations.
📐 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 flat cables, some 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 a complex structure through series connection of multiple rigid boards. Suitable for industrial sensor modules and multi-camera mobile phone lens modules requiring multi-directional bending and decentralized layout.
Three-Dimensional Rigid-Flex PCB: The flexible area achieves bending and twisting in three-dimensional space, with rigid areas distributed in different spatial planes. Used in UAV fuselage control boards and car instrument panel integrated circuit boards to maximize three-dimensional space utilization.
🔄 Classified by Flexible Region Characteristics
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 connection boards.
Dynamic Rigid-Flex PCB: The flexible area withstands long-term 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 foldable watch opening/closing components, needing to meet no-failure requirements after tens of thousands of bends.
🔢 Classified by Number of Line Layers
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 controls.
Double-Layer Rigid-Flex PCB: Two layers of conductive copper foil with interlayer conduction through vias. Takes into account both cost and practicality — widely used as peripheral modules for smartphones and tablets.
Multi-Layer Rigid-Flex PCB (≥4 layers): Composed of alternating "rigid layer – flexible layer – rigid layer" superposition with power, ground, and signal layers inside. High integration for complex signal transmission and power management. Used in satellite circuit boards and medical equipment precision 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), reducing attenuation and interference. Suitable for 5G equipment, radar systems, and satellite communication equipment.
High-Temperature Resistant Rigid-Flex PCB: Flexible substrate and adhesive made of high-temperature resistant materials (such as special PI), operating stably within -55°C to 200°C or wider. Used in aero engine peripheral equipment 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 such as pacemaker auxiliary circuit boards.
How to Design Rigid Flex PCB?
The design and production of rigid-flex PCBs must account for 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 proactively avoided.
Structural and Layout Design
- Clear rigid/flex zone boundary: A transition zone (usually 0.5–1mm) should be reserved at the boundary to prevent components, vias, and copper foils from crossing the boundary and to avoid cracking due to material differences during bending. Flexible zone edges need to 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 outer copper foil ≥15×. Avoid overlapping and bending in the flexible zone to prevent long-term compression from damaging the circuit.
- Rational component layout: Heat-generating components (chips, resistors) should be concentrated in the rigid area, away from the flexible area. Heavy-duty components (interfaces, sensors) 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, line direction should be horizontal (parallel to the bending direction) to reduce tensile/compressive damage to the copper foil. Avoid dense thin lines and sharp-angled lines in the flexible area. Minimum line width/spacing ≥0.1mm recommended.
- Stacking structure optimization: For multi-layer boards, the flexible layer should adopt a symmetrical structure (e.g., "rigid – flex – flex – rigid") to prevent warping. Rigid core materials are prohibited in the flexible zone; adhesive should use 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. In high-frequency scenarios, "microstrip line" or "ribbon line" structures can be adopted to optimize signal transmission.
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 select 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 covering film (PI film), with edges extending 0.2–0.3mm beyond the copper foil for protection and insulation.
Key Points of Manufacturing
The production of rigid-flex PCBs integrates the processes of both rigid and flexible PCBs, requiring additional control over the connection links between rigidity and flexibility. The core points are as follows:
- 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 the 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. Bonding parameters of the flexible zone and the rigid zone should be set differently to prevent deformation of the flexible substrate or delamination of the rigid zone. Use stepwise lamination — first laminate the flexible layer, then laminate with the rigid layer to ensure tight interlayer bonding.
- High-precision exposure: Flexible substrates are prone to stretching. Use special fixtures for fixation during exposure to prevent line deviation. Adopt UV parallel light exposure machines 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. The etching speed is slightly lower than in the rigid zone to prevent excessive etching from causing line breakage. Clean promptly after etching to avoid residual liquid corroding the substrate.
- Flexible zone contour cutting: Process the flexible zone contour by laser cutting (CO₂ laser or UV laser), with a smooth cut and no burrs, avoiding tearing of the base material caused by mechanical cutting. Control laser power to prevent damage to internal circuits.
- Rigid zone forming: Form the rigid zone 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, inspect interlayer adhesion (peel test) and line conductivity (flying probe test). 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.
| 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 PCB | Rigid-Flex Structure | Typical structure, Flying tail structure, Multi-flex book structure, Two-flex lamination structure, Single-sided asymmetric structure, Asymmetric structure, etc. | |
