Flexible PCB Manufacturer in China: Single & Double Layer FPC

A flexible PCB (FPC) is a thin circuit built on polyimide film instead of rigid FR4, allowing it to bend, fold, or flex inside a product. It is used when a connection needs to move, fit a tight space, or reduce connector count between sub-assemblies. Common applications include wearable devices, camera modules, medical probes, and foldable consumer electronics.

What to Specify When Quoting a Flexible PCB

Before a flexible PCB manufacturer can quote accurately, confirm the specs that drive material choice and fatigue life:

• Layer count. Single-layer FPC is the lowest cost and most flexible; double-layer supports crossover traces; four-layer flex is used only when routing density justifies the stiffness and cost, similar to a rigid multilayer PCB.
• Base PI thickness. 12.5µm or 25µm PI is standard for tight-radius dynamic flex; 50µm PI is used for static-flex applications where stiffness helps assembly.
• Copper type and thickness. RA (rolled-annealed) copper is required for dynamic flex; ED (electro-deposited) copper is cheaper but cracks under repeated bending. 18µm (1/2oz) and 35µm (1oz) are the most common weights.
• Bend radius and flex cycles. Static flex needs 6× total thickness; dynamic flex needs 10–20×. A wearable hinge design should target ≥100,000 cycles.
• Coverlay vs. LPI solder mask. Polyimide coverlay is better for tight or dynamic bends; LPI is cheaper and finer-resolution but less flexible.
• Termination. 0.5mm or 1.0mm ZIF connectors are standard; confirm the contact thickness (0.2mm or 0.3mm) matches the connector.

Most FPC specialists are clustered in the Pearl River Delta near Shenzhen and Dongguan, where connector supply chains and quick-turn lamination shops are dense.

Common Pitfall: Confusing FPC with FFC

Buyers often request an FPC quote when their mechanical design only needs an FFC cable. FFC is a flat ribbon of parallel conductors laminated in PET film — it cannot route arbitrary signals, carry components, or have vias. FPC is a true etched circuit on polyimide that supports complex routing and assembly. They may share the same ZIF connector footprint, but the cost and capability gap is large. Confirm with your mechanical team whether the flex region needs arbitrary trace routing or just a straight bus before sending drawings to a factory.

Typical Buyer Profile

A UK audio startup building a foldable headphone with a pivoting headband is a typical case. The design routes audio and control signals through a dynamic-flex FPC that bends every time the headphone folds. The FPC uses 25µm PI, 18µm RA copper, polyimide coverlay, and a 0.5mm ZIF connector. The target is 100,000 fold cycles with no intermittent opens. The team needs 200 prototype pieces in 10–12 days, then 2,000 pieces per month for a crowdfunding fulfillment run.

Sourcing notes from the floor

We visited an FPC factory in Shenzhen last year and checked copper grain structure and coverlay adhesion. During the audit we saw dynamic-flex samples that cracked within 20,000 cycles because the factory used ED copper instead of rolled-annealed copper to save cost. The most common spec mismatch is a 0.5mm ZIF connector spec paired with a 0.3mm contact thickness, which damages the latch on insertion. Real-world MOQ/price is often 100 pieces at $0.50–5.00, with multilayer or impedance-controlled flex at the top. Certification gotcha to watch: UL 94V-0 must cover the exact polyimide and adhesive combination, not just the base film.

Recommended Next Steps

Send the factory a mechanical drawing showing the installed bend radius and a stackup table listing PI thickness, copper weight, coverlay material, and adhesive type. For products sold into the EU or US, request RoHS and UL documentation for the coverlay and base polyimide. Request a cross-section microsection on first articles to confirm the stackup matches your drawing. If the design also includes rigid sections, read our PCB assembly in China guide to understand how rigid-flex sourcing differs from pure FPC.

Flex Circuit Board Bend Radius Design Rules

The minimum bend radius is the single most critical FPC design parameter in custom FPC fabrication. Violating it causes conductor fatigue fractures — often intermittent failures that are difficult to diagnose in field returns. When choosing a flexible PCB manufacturer in China (FPC), our sourcing service helps you specify the correct polyimide substrate and material stack for your application, whether it’s a PCB assembly project or a wearable device with dynamic flex PCB requirements. See our PCB assembly guide for more on specifying and sourcing printed circuit boards from China.

The IPC-2223 design guideline for static flex (bent once during assembly, not repeatedly) specifies a minimum bend radius of 6× the total FPC thickness. For dynamic flex (repeatedly bent during operation, e.g., a flip-phone hinge or wearable band), minimum bend radius is 10–20× the total FPC thickness.

Practical calculation: a single-layer FPC with 25µm PI base + 35µm copper + 25µm coverlay = 85µm total. Minimum static bend radius: 6 × 0.085mm = 0.51mm. Minimum dynamic bend radius: 10 × 0.085mm = 0.85mm.

Using 50µm PI instead of 25µm approximately doubles the minimum bend radius requirement. For tight-radius applications (wearable devices, compact camera hinges), specify the thinnest adequate PI thickness. Over-specifying material thickness to “be safe” often creates a design that physically cannot be folded to the required radius.

ZIF vs. FFC Connector Pitch Compatibility

ZIF (Zero Insertion Force) connectors are the most common FPC termination method. Key parameters:

Pitch. 0.5mm and 1.0mm are standard. 0.3mm is possible but significantly increases FPC manufacturing difficulty and connector cost. Confirm the connector pitch matches both the FPC contact pitch and the PCB footprint on the host board.

Contact thickness. ZIF connectors specify the FPC contact thickness they accept: either 0.2mm or 0.3mm total FPC thickness at the contact area. A mismatch causes unreliable connection or connector damage. The FPC coverlay and stiffener thickness at the contact area must match the connector specification.

FFC vs. FPC. FFC (Flat Flexible Cable) is a parallel conductor ribbon cable — conductors embedded in a PET film, no PCB. FPC (Flexible Printed Circuit) is a true circuit board on PI film with etched conductors and optional components. They use the same connector footprints at 0.5mm and 1.0mm pitch, but FPC allows arbitrary trace routing and component mounting. Confirm which type your application requires.

Static Flex vs. Dynamic Flex Material Selection

Static flex. Bent once or a few times during product assembly (e.g., connecting a display to a PCB inside an enclosure). Standard PI base material (25–50µm) is adequate. Standard rolled-annealed copper (RA copper) at 35µm (1oz) is the default.

Dynamic flex. Bent continuously during operation (e.g., printer head cable, wearable hinge). Requires:

• RA (Rolled Annealed) copper — not ED (Electro-Deposited) copper. RA copper has a grain structure aligned with the rolling direction that gives 3–5× better fatigue life than ED copper.
• Thinner PI base (12.5–25µm) to reduce bending stiffness
• Possible use of adhesiveless copper laminate to eliminate the adhesive layer, which is a common fatigue initiation site
• Finite bend radius compliance — confirm with your mechanical design team that the actual installed bend radius exceeds the minimum dynamic flex design rule

Coverlay vs. Solder Mask Trade-off

Polyimide coverlay. Laminated PI film with adhesive, punched or laser-cut to expose pads. Better flexibility and adhesion to PI base material. Standard for FPC with dynamic flex requirements. Minimum hole-to-hole spacing: 0.5mm (for punching) or 0.1mm (for laser cutting).

Liquid Photoimageable (LPI) solder mask. Screened or spray-applied, photo-developed. Finer feature resolution than punched coverlay. Lower cost for complex pad geometries. Reduced flexibility compared to PI coverlay — not recommended for tight dynamic flex applications.

For wearables and consumer FPC with bend radius below 5mm and any dynamic flex cycling, PI coverlay is the correct choice. LPI is adequate for rigid-flex PCBs where the flex section has a large bend radius. Our inspection service can verify copper grain structure (RA vs. ED), coverlay adhesion, and bend radius compliance on production samples.