What Is Flexible PCB?

Flexible printed circuit boards, also called Flexible PCBs or Flex PCBs, derive their name for their ability to enable the circuitry to be designed to fit the electronic device or product, as opposed to building the device to conform to the circuit board. Flex boards are characterized by a distinctly patterned printed circuitry and component arrangement highlighted by a malleable base material.

At PCBAndAssembly, we specialize in the fabrication and assembly of flexible PCB products for use in the manufacturing of medical devices and various types of telecommunication and industrial equipment. Our custom PCB manufacturing capabilities allow us to develop and produce a top-performing flex PCB that meets your unique requirements. We can also work with you to produce a custom flex PCB prototype that will significantly improve your prospects of a successful project outcome. For detailed capabilities, please refer to the following form.

Feature	Capability
Quality Grade	Standard IPC 2
Number of Layers	1 – 8layers
Order Quantity	1pc – 10000+pcs
Build Time	2days – 5weeks
Material	DuPont PI, Domestic Shengyi PI
Board Size	Min 6*6mm, Max 406*610mm
Board Thickness	0.1mm – 0.8mm
Copper Weight (Finished)	0.5oz – 2.0oz
Min Tracing/Spacing	3mil/3mil
Solder Mask Sides	As per the file
Solder Mask Color	Green, White, Blue, Black, Red, Yellow
Solder-stop coating—Soldermask oil	Green, White, Blue, Black, Red, Yellow
Solder-stop coating—Coverlay	PI and PET film
Silkscreen Sides	As per the file
Silkscreen Color	White, Black, Yellow
Surface Finish	HASL – Hot air solder leveling Lead – free HASL – RoHS ENIG – RoHS Immersion Tin – RoHS OSP – RoHS
Min Annular Ring	4mil
Min Drilling Hole Diameter	8mil
Min. hole size—Drilling (PTH)	0.2mil
Min. hole size—Punching (NPTH)	0.5mil
Tolerance of dimension	±0.05mm
Other Techniques	Peelable solder mask Gold fingers Stiffener (only for PI/FR4 substrate)

Stiffener Integration

We integrate FR4 stiffeners from 0.075 to 3.2 mm and polyimide stiffeners from 0.025 to 0.225 mm, with adhesive widths controlled to 1.5 ± 0.5 mm and minimum copper clearance of 0.3 mm.

On high-cycle flex designs, these are commonly used for ZIF connectors, edge contacts, and mechanical reinforcement zones.

Stiffener design and placement follow IPC-2223 guidelines for mechanical reinforcement and pad stability in dynamic flex zones.

Surface Finishes & Solderability

We offer ENIG, Lead-Free HASL, OSP, Immersion Tin, and Immersion Silver finishes for all flex PCB builds. Surface treatments are applied to exposed copper for solderability, oxidation resistance, and electrical contact durability.

ENIG is preferred for high-density designs and gold finger edge connections; OSP is ideal for prototype runs and flat SMT pads. Selective finish combinations such as ENIG + OSP are available for mixed-performance zones.

Peelable mask can be combined with coverlay for selective solder areas, ZIF connectors, or rework zones. All finishes conform to IPC-455x series standards for surface coatings and meet RoHS-compliant lead-free assembly requirements.

Impedance Control & Signal Integrity

All flexible printed circuit boards can be manufactured with impedance control:

• •Single-ended: ± 5 Ω (≤50 Ω), ±10% (>50 Ω)
• •Advanced builds: ± 3 Ω (≤50 Ω), ±8% (>50 Ω)

These tolerances (as precise as ±3 Ω) are validated through TDR testing and reflect industry-leading control for RF, sensor, and high-speed signal designs. For controlled impedance in RF, medical, and sensor applications.

Testing & Reliability

All flex PCBs undergo AOI, Flying Probe, ICT, and FCT to ensure circuit continuity and electrical performance.

Structural reliability is validated through X-ray inspection, micro-section analysis, peel strength testing, and thermal shock simulation.

We also perform impedance testing on controlled line widths to confirm ±3 Ω or ±5% targets for matched-line designs.

Turnkey Flex PCB Assembly

PCBAndAssembly provides full flex PCB assembly, including SMT, through-hole, and mixed technology builds.

We support BGA (down to 0.2 mm pitch), QFP (0.15 mm), and fine-pitch component placement with ±30 μm accuracy at CPK ≥1.

Assembly capabilities include conformal coating, box builds, and component sourcing from Mouser, Digi-Key, Arrow, and Avnet. Board sizes range from 50 × 50 mm to 610 × 508 mm.

Cable Assembly & Integration

We manufacture RF, coaxial, ribbon, overmolded, and waterproof cable assemblies for flex integration.

Custom wire harnesses are available for automotive, medical, aerospace, and robotic applications.

All cable assemblies are thoroughly tested and can be delivered as part of complete electromechanical builds or standalone units.

What is the Cost of Flexible PCBs?

On average, flexible PCBs can range from $0.50 to $5.00 per square inch for standard designs and materials. However, this cost is not fixed and can vary based on several factors. The factors that influence the price include necessary assembly labor, prevailing labor rates, and the time required for assembly. Additionally, overhead manufacturing expenses and the design complexity of the board play significant roles in determining the final cost. To get a more accurate cost estimate, please use our free pcb quote form.

What Materials are Used in Flex PCBs?

Flex PCBs are constructed using high-performance materials selected for electrical stability, mechanical flexibility, and thermal resistance. Core layers include polyimide substrates, copper foil, adhesives (if used), and coverlay for insulation.

Flexible Polyimide Substrates: Polyimide films (0.5 to 4 mil), such as Shengyi SF305, serve as the base substrate in laminated flex stackups. These materials

DuPont, Pyralux Material Options: Pyralux LF (Low-Flammability): Acrylic-based laminate with or without adhesive and copper. Not UL-rated; suitable for low-heat or non-critical builds.

Copper Foil: Rolled-annealed (RA) copper is preferred for dynamic flex zones; electro-deposited (ED) for static or low-cycle designs.

Adhesive Systems: Acrylic or epoxy adhesives (12 to 25 μm) are used between copper and substrate in laminated builds.

Coverlay Film: Shengyi SF305C is a laser-cut polyimide coverlay used to insulate exposed copper areas and reinforce mechanical flex zones.

What’s the Difference Between Flex and Rigid PCBs?

Flex PCBs are constructed entirely from flexible materials like polyimide, allowing the full board area to bend, fold, or twist during use. Rigid-flex PCBs combine one or more rigid layers with integrated flexible layers, enabling 3D routing between rigid sections while limiting flexibility to defined areas within the stackup.

Feature	Flex PCB	Rigid-Flex PCB
Core Construction	Manufactured from a flexible polyimide substrate, which is between 0.5 to 4 mil thick, with optional adhesive or adhesiveless layers.	A hybrid structure combining rigid PCB cores (FR4 or BT resin) with laminated flex layers between or across zones.
Layer Configuration	Available in single-sided, double-sided, and up to 10-layer flex circuits with coverlay for insulation.	Supports advanced stackups (e.g. 2+N+2) with mixed rigid and flexible layers. Includes via-in-pad, buried/blind vias, and impedance-controlled regions.
Mechanical Behavior	Designed for continuous bending, folding, and tight bend radius installations. Optimized for dynamic motion.	Typically, flex-to-install or limited dynamic flex. Rigid sections maintain mechanical stability for connectors or component loads.
Assembly	Built for lightweight, connector-free signal routing. Assembled with SMT or through-hole components in flex zones.	Allows direct mounting of components on rigid zones, while flex areas route signals. Reduces interconnect failure by eliminating jumpers and connectors.
Use Cases	Ideal for wearables, foldable devices, sensors, cameras, and medical implants with space or motion constraints.	Common in aerospace, medical instrumentation, military electronics, and 3D-assembled modules requiring structural rigidity.
Fabrication Complexity	Lower complexity: fewer lamination steps, simpler tooling, faster build times.	Higher complexity: sequential lamination, multicore alignment, and more extensive DRC for rigid/flex interaction.
Cost Factors	Lower cost per unit for most builds. Ideal for prototype and volume production where board flexibility is a core requirement.	Higher cost due to material stackup, rigid zone fabrication, and tighter registration tolerances. Best suited for integrated, high-reliability systems.

How to Reduce PCB Production Costs

• Minimize flexible layers, as rigid laminates are more cost-effective.
• Reduce overall layers to lower the need for additional materials.
• Limit controlled impedance requirements to necessary values only.
• Opt for flexible copper thickness, approximately 1/3 oz.
• Purchase FPCBs in bulk to reduce unit cost.

Why Choose a Flexible PCB Made from China?

China’s flex PCB industry offers many advantages, such as the combination of high quality with cost-effectiveness. Chinese manufacturers like PCBAndAssembly use advanced tech and skilled labor.