Famous China Suppliers Rigid Flex PCB Factory - Single, Double-Sided, 4-16 Layer Complex Multi-Layer Solutions Manufacturers, Quotes
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:
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:
-
📱
Consumer Electronics Foldable smartphones, smartwatches, laptops, cameras, and earbuds — the hinge area of foldable phones uses flexible sections to connect rigid display and battery boards.
-
🛸
Aerospace & Defense Satellites, aircraft avionics, and military equipment — withstand extreme temperatures, vibration, and space constraints.
-
🚗
Automotive In-vehicle infotainment systems, sensor modules, and ADAS — adapt to the curved or confined spaces of car interiors.
-
🏥
Medical Devices 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 covers structural form, flexible area characteristics, number of layers, and special function adaptation. Different categories correspond to different process requirements and application scenarios.
How to Design Rigid Flex PCB?
The design and production of rigid-flex PCBs must consider both the structural stability of rigid PCBs and the bending adaptability of flexible PCBs. Below are the detailed design key points:
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. 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 flexible substrate thickness; outer copper foil ≥15×. Avoid overlapping and bending in the flexible zone to prevent long-term compression from damaging the circuit.
Reasonable component layout: Heat-generating components should be concentrated in the rigid area and away from the flexible area. Heavy-duty components must be fixed in rigid areas with reserved heat dissipation space and fixing holes.
Line direction: In the flexible zone, lines should run parallel to the bending direction to reduce tensile/compressive damage during bending. Minimum line width/spacing ≥0.1mm in flexible areas.
Stacking structure: 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.
Via and grounding design: Metallized vias are prohibited in the flexible zone and must remain in the rigid zone at least 1mm from the boundary. In high-frequency scenarios, microstrip line or ribbon line structures can be adopted to optimize signal transmission.
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 (e.g., PTFE-modified PI).
Copper foil & covering film: For flexible areas, rolled copper foil (with good ductility and bending resistance) is preferred. The surface of the flexible zone should be covered with a flexible PI film, with the edge extending 0.2–0.3mm beyond the copper foil for protection and insulation.
Key Points of Manufacturing
- 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: Temperature, pressure, and time must be controlled with different bonding parameters for flexible and rigid zones. The stepwise lamination method is adopted — first laminate the flexible layer, then bond with the rigid layer to ensure tight interlayer bonding.
- High-precision exposure: Flexible substrates are prone to stretching. Use special fixtures during exposure to prevent line deviation. UV parallel light exposure machines ensure line pattern accuracy — control line width error in the flexible zone within ±0.02mm.
- Etching process optimization: Use alkaline etching solution for the flexible zone copper foil at a slightly lower etching speed than the rigid zone to prevent line breakage. Clean immediately after etching to avoid residual liquid corroding the substrate.
- Flexible zone contour cutting: Processed by laser cutting (CO₂ or UV laser) for smooth, burr-free cuts, avoiding tearing from mechanical cutting. Laser power must be controlled to prevent damage to internal circuits.
- Rigid zone forming: CNC milling with edge deburring and chamfering. The rigid/flex boundary requires secondary grinding to ensure smooth transition and reduce bending stress concentration.
- Surface treatment: Rigid areas can undergo tin spraying, gold plating, and OSP to enhance soldering performance. Flexible zone surfaces are protected only by covering film — high-temperature treatments like tin spraying are prohibited to prevent substrate deformation.
- Full-process inspection: During production, inspect interlayer adhesion (peel test) and line conductivity (flying probe test). Finished products undergo bending tests (dynamic bending simulates tens of thousands of cycles) and high/low temperature environment tests.
| 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. | ||
