ODM Flexible PCB China Suppliers | Lightweight, Thin, and Bendable Connection Solutions from Top Factory Manufacturers, Manufacturer
Product Description
The Main Functions Are Reflected In
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Realize three-dimensional wiring: It can be bent and folded inside the device, greatly enhancing space utilization and design freedom.
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Promoting the miniaturization of devices: Its thin and light characteristics are the key for smartphones and wearable devices to achieve lightness and portability.
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Enhance system reliability: Reduce connectors and solder joints to be more durable in vibrating and bending environments.
Far-Reaching Impact
It has directly given rise to innovative product forms such as foldable screen mobile phones and wearable devices, and has become an indispensable cornerstone for the high-end development of fields such as automotive electronics, medical equipment, and aerospace. Flexible PCBS have profoundly transformed the design concepts and industrial landscape of electronic products by endowing them with "flexibility" and "deformability" capabilities.
What is Flexible PCB (FPC)?
Flexible PCB, whose full name is flexible printed circuit board, is commonly known as "soft board". You can imagine it as a kind of "flexible electronic circuit" or "circuit cloth". It is a "relative" of the common green, hard computer motherboard (rigid PCB) we often see, but the core material is completely different.
- The material is soft: Substrate is flexible plastic film such as polyimide — heat-resistant and repeatedly bendable.
- Bendable and foldable: Can be bent, wound and folded in three dimensions to adapt to irregular spaces.
- Thin and light: Much thinner and lighter than rigid PCBs.
- Smartphones / Foldable phones: Flat cables connecting screen, camera, buttons and battery.
- Wearable devices: Smartwatches, bracelets and health patches fitting body curves.
- Notebook computers: Linking the motherboard and screen.
- Automotive electronics: LED headlights, central control screens, sensors.
- Precision medical equipment: Endoscope capsules, pacemakers.
- Aerospace: Satellites and aircraft — reducing weight and adapting to complex layouts.
Normal Types of Flexible PCB
How to Design Flexible PCB?
Flexible PCB design needs to take into account the characteristics of flexible substrates, mechanical reliability and electrical performance. The core design points can be decomposed into the following core dimensions.
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1Base Material and Structure Selection
- Substrate selection: Commonly used PI (polyimide) base material (temperature resistance -200℃ to 260℃, excellent bending resistance), supplemented by PET (low cost, poor temperature resistance). PI material is preferred for the covering film.
- Thickness matching: The thickness of the flexible substrate (such as 25μm, 50μm PI) should be combined with the bending radius and load-bearing requirements. Electrolytic copper is preferred; recommended thickness is 12μm or 18μm. Thick copper (≥35μm) should be avoided.
- Structural design: Single layers are suitable for simple wiring; multi-layers require an additional bonding layer. For high-frequency/high-bending scenarios, glue-free flexible boards (Rigid-Flex) are preferred. The junction between rigid and flexible zones should be chamfered (≥0.3mm).
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2Wiring and Layout Design
- Routing rules: Line width in the flexible zone ≥0.1mm, line spacing ≥0.1mm. Right-angle/acute angle routing is prohibited — use arc transitions (fillet radius ≥0.1mm). Wiring in the bending area should be parallel to the bending direction.
- Layout optimization: Components are not allowed in the flexible area; place in the rigid area at least 1mm from the flexible zone edge. Multi-layer wiring should be symmetrically distributed to reduce inter-layer stress.
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3Bending and Reliability Design
- Bending radius control: Minimum bending radius ≥5× the total thickness of the flexible board. For dynamic bending scenes, increase to 10× the total thickness. Dynamic bending life of a common flexible board is approximately 100,000 times.
- Stress relief: Grid-shaped copper sheets (instead of solid copper) in the bending area reduce stretching/compression. Polyimide reinforcing ribs (25–50μm thickness) can be added in high-stress areas.
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4Pad and Hole Position Design
- Pad specification: No pads in the flexible zone. If welding is required, add a rigid reinforcing plate (FR-4 or stainless steel) covering ≥0.5mm outside the pad. Use rectangular pads with rounded corners (radius ≥0.1mm).
- Hole position design: Through holes are prohibited in the flexible zone. Metallized via hole diameter ≥0.2mm, copper plating thickness on hole walls ≥8μm. Positioning hole edges should be chamfered.
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5Manufacturing and Process Compatibility
- Covering film design: Must completely cover the flexible area traces. Distance between the window edge and traces ≥0.1mm. Recommended covering film thickness in the bending area is 25μm.
- Process limitations: Cold bending (at room temperature) is required; hot bending is strictly prohibited. Bending angle should not exceed 180°. For the flexible zone surface, OSP or nickel-gold plating is preferred; avoid tin spraying.
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6Electrical Performance Supplement
- Impedance control: For high-frequency flexible boards (5G and RF scenarios), impedance calculation (50Ω, 100Ω differential) is required. Impedance deviation in the bending area must be controlled within ±10%.
- Grounding design: Design a complete grounding layer to reduce electromagnetic interference. The grounding layer should be as continuous as possible and avoid disconnection in the bending area.
Core Summary: The core of flexible PCB design lies in "adapting to bending characteristics, distributing stress, and ensuring dual reliability of electrical and mechanical aspects". It prioritizes following the basic principles of "wide traces, arc transitions, component placement far from the bending area, and matching the bending radius", while adjusting the substrate and structure selection in combination with application scenarios (static/dynamic bending, high frequency/large current).
Flexible PCB Manufacturing Processes and Controls
The manufacturing process of flexible PCBs is one of the most delicate and complex fields in electronic manufacturing. The core difficulty lies in dealing with extremely thin, soft, deformable and environmentally susceptible materials.
I. Detailed Explanation of Core Manufacturing Process Flow
- Cutting and cleaning: Cut the roll-shaped PI substrate and copper foil in a constant temperature and humidity environment. Clean immediately to remove oil stains and particles.
- Dry film application / photoresist coating: Apply a single layer of photosensitive resist (dry film) onto the copper foil.
- Exposure and development: Expose the film with a line pattern to ultraviolet light, then develop to protect the required line pattern and wash away unexposed resist.
- Etching: Use chemical solutions (such as acidic copper chloride) to etch away unprotected copper to form fine copper circuits. The control requirements for the etching factor are extremely high.
- Film removal and cleaning: Remove the resist layer protecting the circuit to obtain the exposed inner circuit pattern.
- Surface treatment: Micro-etching or chemical treatment is carried out on the copper circuit to enhance adhesion with the covering layer.
- Coating alignment and lamination: Align the PI covering film with the inner circuit through a precise optical alignment system, then perform hot-pressing curing. No bubbles, no wrinkles, and precise alignment are essential.
- Drilling: Use a drilling rig with high rotational speed and low feed rate, along with specially designed covers and pads, to prevent burrs, nail heads or material tearing.
- Pre-treatment and electroless copper plating: Remove drilling dirt, activate with plasma or potassium permanganate solution, then deposit a thin layer of chemical copper on the hole wall to provide a conductive substrate for subsequent electroplating.
- Outer layer pattern transfer: Through film application, exposure, development, pattern electroplating, and etching, form the outer layer circuits and through-hole connections.
- Solder mask and surface treatment: Apply flexible solder mask ink; pads undergo surface treatment such as chemical nickel-gold, OSP or electroplated hard gold.
- Shape processing: Cut out final shape through precision die punching or CNC milling. Mold clearance and milling cutter parameters must be strictly controlled.
- Electrical testing and final inspection: Conduct 100% open and short circuit electrical tests (flying probe tests), visual inspection, dimensional measurement, and reliability spot checks.
II. Four Core Control Dimensions Running Through the Entire Process
All conveying rollers and mechanical hands must achieve minimum or zero tension transmission. Any excessive stretching leads to permanent deformation, inaccurate alignment, dimensional deviations, and microcracks.
Key processes (exposure, lamination, covering) must be carried out in an environment with a cleanliness level of 1,000 or higher. Tiny dust particles can cause circuit notches, short circuits or open circuits.
Maintain constant temperature and humidity (e.g., 22±2°C, 50±5%RH). All hygroscopic materials must be baked before use to prevent plate cracking, delamination and bubbles during high-temperature processes.
Design symmetrical stacked structures. Adopt slow cooling after lamination. Carry out stress release baking when necessary to prevent the finished board from warping and curling.
The Application of Flexible PCBs in 2026
Looking ahead to 2026, the application of flexible PCBs (FPCs) and rigid-flex boards will become more extensive and in-depth. The core driving forces come from innovation of equipment forms, the demand for performance improvement, and the explosion of emerging markets.
- Folding/curling/stretching screen devices: FPCs serve as the "neural network" for hinges and screens in more diverse foldable forms.
- AR/VR devices: Key to achieving high-density wiring and sensor integration in thin and light helmets and smart glasses.
- New wearable devices & "electronic skin": Smart bracelets/watches integrating more health sensors; flexible patches for health monitoring entering the consumer market.
- Intelligent cockpits and displays: Large-sized, irregular-shaped automotive displays extensively employing rigid-flex panels and FPCs.
- ADAS and autonomous driving: Lightweight FPCs for cameras, millimeter-wave radars and lidar sensors around the vehicle body.
- Battery management system: FPC replacing traditional wiring harnesses in battery packs for more accurate monitoring and higher integration.
- Implantable and ingestible devices: Micro-implantable devices for cardiac monitoring and nerve stimulation requiring highly integrated flexible/rigid-flex circuits.
- High-end wearable medical devices: Hospital-grade continuous vital sign monitoring patches with FPCs as the core for comfort, accuracy and wireless connectivity.
- 5G-Advanced/6G and millimeter-wave devices: Flexible circuits using LCP substrates as preferred solutions for millimeter-wave antenna modules and high-speed connectors.
- Advanced packaging and chip interconnection: FPC technology applied to chip-level interconnection in 2.5D/3D packaging or fan-out packaging rewiring layers.
- Bionic and collaborative robots: Flexible sensors and circuits integrated into robot "fingers" and "skin" for sensitive touch and adaptive grasping.
- Structural electronics integration: FPC integrated with structural components — the product casing itself becomes part of the circuit for ultimate space savings.
- Technology integration: FPC integrating with sensors, antennas, heat dissipation films, and light-emitting components — becoming a "multi-functional system module".
- Material innovation: Popularization of high-end substrates such as LCP and modified PI for higher frequencies, greater heat resistance and better bending performance.
- Market penetration: FPC rapidly penetrating from high-end models to mid-range consumer electronics and mainstream vehicle models.
By 2026, flexible PCBs will become a fundamental and transformative technology that defines the form of the next generation of electronic products, enhances system performance, and empowers emerging intelligent scenarios.
Conclusion
Flexible PCB (FPC) is a silent revolution in electronic interconnection technology. It is not only a material that makes electronic devices "softer" and "thinner", but also a fundamental enabling technology that drives product innovation, enhances system performance, and gives rise to brand-new application scenarios. Its future development will continue to follow the direction of "thinner and lighter, more reliable, higher frequency and speed, and higher integration", deeply embedded in every key electronic node of the intelligent society, and its importance will increase day by day.
