China China Flexible PCB Suppliers: Lightweight, Bendable & Foldable Solutions from Top Factory Manufacturers, Companies
Product Description
The Main Functions Are Reflected In
It can be bent and folded inside the device, greatly enhancing space utilization and design freedom.
Its thin and light characteristics are the key for smartphones and wearable devices to achieve lightness and portability.
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.
- ▶ Material is soft: Substrate is flexible plastic film (polyimide), heat-resistant and repeatedly bendable.
- ▶ Bendable and foldable: Can be bent, wound and folded in three dimensions.
- ▶ Thin and light: Much thinner and lighter than rigid PCBs.
- ▶ Smartphones / foldable phones — flat cables for screens, cameras, buttons
- ▶ Wearable devices — smartwatches, bracelets, health patches
- ▶ Notebook computers — linking motherboard and screen
- ▶ Automotive electronics — LED headlights, sensors, wiring harnesses
- ▶ Precision medical — endoscope capsules, pacemakers
- ▶ Aerospace — satellites and aircraft weight reduction
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.
- Substrate selection: Commonly used PI (polyimide) base material (temperature resistance -200°C to 260°C, excellent bending resistance). For the covering film, PI material is preferred to match the bending characteristics.
- Thickness matching: Flexible substrate thickness (25μm, 50μm PI) combined with bending radius. Electrolytic copper preferred at 12μm or 18μm. Avoid thick copper (≥35μm) to reduce bending stress.
- Structural design: Single/double/multi-layer boards — multi-layers require bonding layer. For high-frequency/high-bending, glue-free Rigid-Flex is preferred. Rigid-to-flexible zone junctions should be chamfered (≥0.3mm).
- Line width/spacing: Flexible zone line width ≥0.1mm, spacing ≥0.1mm. For 1A current, line width ≥0.3mm with 18μm copper.
- Routing form: Prohibit right-angle/acute-angle routing. Use arc transitions (fillet radius ≥0.1mm). Wiring in bending area should be parallel to bending direction.
- Layout optimization: Components must not be mounted in flexible area — place in rigid area, at least 1mm from flexible edge. Symmetrical wiring for multi-layer boards.
- Minimum bending radius: Must meet "bending radius ≥5× total thickness." For dynamic bending, increase to 10× total thickness.
- Bending life: Common flexible board dynamic bending life ~100,000 times. Use bent-resistant base materials for high-reliability scenarios.
- Stress relief: Use grid-shaped copper (not solid) in bending area. Add polyimide reinforcing ribs (25–50μm) in high-stress areas.
- No pads in flexible zone: Pads only in rigid zone. If welding required in flexible zone, add rigid reinforcing plate covering ≥0.5mm outside the pad.
- Pad shape: Rectangular with rounded corners (radius ≥0.1mm). SMD pad size matches component pins with 0.05–0.1mm solder allowance.
- Through holes: Prohibited in flexible zone. Metallized via hole diameter ≥0.2mm, copper plating on walls ≥8μm.
- Covering film: Must completely cover flexible area traces. Edge-to-trace distance ≥0.1mm. Recommended thickness in bending area: 25μm.
- Bending process: Cold bending (room temperature) required. Hot bending strictly prohibited. Bending angle must not exceed 180°.
- Surface treatment: OSP or nickel-gold plating preferred. Avoid tin spraying in flexible zone.
- Impedance control: For high-frequency boards (5G/RF), impedance calculation required (50Ω, 100Ω differential). Bending area impedance deviation ≤±10%.
- Grounding design: Complete grounding layer to reduce EMI. Grounding layer must be continuous — avoid disconnection in bending area.
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. The following figure clearly summarizes its core process flow and the key points of control at each link:
- Cutting and cleaning: Cut roll-shaped PI substrate and copper foil in constant temperature/humidity environment. Clean immediately after cutting.
- Dry film application: Apply single layer of photosensitive resist (dry film) onto copper foil.
- Exposure and development: Expose film with line pattern to UV light, develop to protect required line pattern, wash away unexposed resist.
- Etching: Use chemical solutions (e.g., acidic copper chloride) to etch unprotected copper. Extreme control of etching factor required for fine line accuracy.
- Film removal and cleaning: Remove resist layer to obtain exposed inner circuit pattern.
- Surface treatment: Micro-etching or chemical treatment on copper circuit to enhance adhesion with covering layer.
- Coating alignment and lamination: Key difficulty — align PI covering film with inner circuit via precision optical alignment system, then hot-press cure. No bubbles, no wrinkles, precise alignment required.
- Drilling: Use high rotational speed, low feed rate drilling rig with specially designed covers and pads to prevent burrs, nail heads or material tearing.
- Electroless copper plating: Remove drilling dirt, activate with plasma or potassium permanganate, then deposit thin chemical copper on hole wall for subsequent electroplating.
- Outer layer pattern transfer: Film application, exposure, development, pattern electroplating, etching to form outer circuits and through-hole connections.
- Solder mask and surface treatment: Apply flexible solder mask ink; pads undergo surface treatment (chemical nickel-gold, OSP or electroplated hard gold).
- Shape processing: Final shape cut via precision die punching or CNC milling. Strict mold clearance control to prevent delamination and burrs.
- Electrical testing and final inspection: 100% open/short circuit electrical tests (flying probe). Visual inspection, dimensional measurement, reliability spot checks (bending test, solderability test).
Objective: Achieve minimum or zero tension transmission from opening to winding.
Reason: Any excessive stretching causes permanent deformation, inaccurate alignment, dimensional deviations, and microcracks.
Objective: Key processes must be carried out in cleanliness level 1,000 or higher environment.
Reason: Tiny dust particles can cause circuit notches, short circuits or open circuits.
Objective: Maintain constant temperature/humidity (e.g., 22±2°C, 50±5%RH). All hygroscopic materials must be baked before use.
Reason: Moisture absorption causes plate cracking, delamination and bubbles during high-temperature processes.
Objective: Balance stress of each material layer in design and process.
Measures: Symmetrical stacked structures; slow cooling after lamination; stress release baking when necessary; prevent finished board warping.
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, demand for performance improvement, and explosion of emerging markets.
-
1. Consumer Electronics — The Core of the Form Revolution
Foldable/curling/stretching screen devices will see more diverse forms (three-fold, rollable). AR/VR devices pursue ultimate lightness. "Electronic tattoos" or flexible health patches will start entering the consumer market. -
2. Automotive Electronics — "Blood Vessels" of Intelligence and Electrification
Large-sized irregular automotive displays will use rigid-flex panels. ADAS cameras, millimeter-wave radars and lidar require lightweight FPCs. FPC replacement of traditional wiring harnesses in BMS battery packs will increase significantly. -
3. Medical and Healthcare — In-Depth from Diagnosis to Treatment
Micro-implantable devices for cardiac monitoring and nerve stimulation require highly integrated flexible/rigid-flexible circuits. Hospital-grade continuous vital sign monitoring patches will become more widespread. -
4. Communication and Computing — Cornerstone of Performance Upgrade
5G-Advanced/6G millimeter-wave devices require extremely low signal loss. Flexible circuits using LCP substrates will become preferred for millimeter-wave antenna modules. FPC will be more widely applied to chip-level interconnection in 2.5D/3D packaging. -
5. Robots and Human-Machine Interaction
Flexible sensors and circuits integrated into robot "fingers" and "skin" will provide sensitive touch and adaptive grasping. FPC will integrate with structural components to form "structural electronics" — the product casing itself becomes part of the circuit.
- ▶ Technology integration: FPC integrates with sensors, antennas, heat dissipation films, and light-emitting components — becoming a "multi-functional system module."
- ▶ Material innovation: Higher frequencies, greater heat resistance, and better bending performance driving popularization of LCP and modified PI substrates.
- ▶ Market penetration: With cost optimization and process maturation, FPC will rapidly penetrate from high-end to mid-range consumer electronics and mainstream vehicle models.
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.
