FPC — Flex Printed Circuit — is structurally closer to a PCB than to flat cable. Copper patterns are etched onto polyimide base, with Coverlay film covering the traces, vias connecting layers, and surface finishes like ENIG applied to exposed pads. The process is similar to rigid PCB manufacturing with flexibility as the main difference. If your design needs circuit patterns, component soldering pads, or multilayer routing, this is the right page. For simple parallel-conductor ribbons, see our standard FFC page instead. MOQ typically 100 sets plus photomask NRE; prototypes from 5 pieces with higher per-unit cost.
FPC Construction — Layer by Layer
FPC is built from the inside out. Understanding the layers helps decide what spec fits your application:
- Base layer (polyimide film). Typically 12.5, 25, or 50 µm thick. Thicker base = more durable, less flexible. Thinner base = more flexible, fits tighter bends.
- Copper layer. Etched to the specified trace pattern. Thickness options: 1/3 oz (12 µm), 1/2 oz (18 µm), 1 oz (35 µm), 2 oz (70 µm). Current-carrying capacity scales with thickness.
- Coverlay (or solder mask). Protective film laminated over the etched copper. Standard green, black (for cosmetic panels), white (for LED applications), or clear (for visual inspection). Openings exposed for component pads.
- Stiffener. Rigid material bonded behind component mounting areas or connector interfaces. Options: PI, FR4, stainless steel (for extreme rigidity).
- Surface finish on exposed pads. ENIG (Electroless Nickel Immersion Gold) is the default for solderable pads. OSP (Organic Solderability Preservative) is cheaper but shorter shelf life. Hard gold plating for edge connectors and wear surfaces.
Each layer choice interacts with the others. For FPCs that bend repeatedly, thinner PI base with 1/3 oz copper and PI Coverlay gives the best flex life. For FPCs that carry high current, 2 oz copper with rigid stiffener is the typical combination.
Layer Count — Single, Double, Multi, Rigid-Flex
- Single-layer (1L). One copper layer on one side of PI base, Coverlay on top. Simplest, cheapest, most flexible. Covers most wearables, simple display drivers, and single-function flexes.
- Double-layer (2L). Copper on both sides of PI base, connected through vias. Typical for camera modules, OLED drivers, and boards that need crossing signals.
- Multi-layer (3L to 8L). Multiple copper + PI layers pressed together. High-density signal routing for smartphone mainboards, 5G antenna modules, and complex wearables. Requires more precise tooling and tighter impedance control.
- Rigid-flex. Hybrid construction with rigid sections (like a normal PCB) bonded to flexible sections. Used in foldable devices, military electronics, premium medical devices, and applications where connectors add failure points.
Layer count drives cost and lead time significantly. A single-layer FPC is 3-5x cheaper than a 4-layer version at the same area. We recommend starting with the lowest layer count that meets the design — it’s common for designers to over-specify and discover during layout that 2 layers suffice.
Our FPC Manufacturing Capabilities
| Parameter | Range |
|---|---|
| Layer Count | 1 to 8 layers (rigid-flex up to 10 layers total) |
| Minimum Line Width / Space | 50 µm / 50 µm (standard); 40 µm with extra cost |
| Copper Thickness | 1/3 oz (12 µm), 1/2 oz (18 µm), 1 oz (35 µm), 2 oz (70 µm) |
| PI Base Thickness | 12.5, 25, 50, 75 µm |
| Coverlay Thickness | 12.5, 25 µm PI with adhesive |
| Minimum Hole (via) Diameter | 0.15 mm (drilled), 0.1 mm (laser) |
| Surface Finish | ENIG, OSP, hard gold, immersion tin |
| Impedance Control | ± 10% for differential and single-ended signals |
| Board Thickness | 0.1 mm to 1.0 mm (rigid-flex stack) |
| Maximum Panel Size | 250 × 300 mm (standard), larger on request |
| Compliance | RoHS, REACH, UL 94V-0 for Coverlay |
| MOQ | 100 sets standard; 5-10 for prototype |
Tooling (photomask + drill program) is a one-time NRE charge. For prototypes and small runs, this typically ranges 1,500-5,000 USD depending on layer count. Once tooling exists, repeat runs amortize the cost quickly.
Typical FPC Applications
5G smartphone antenna modules. FPC is the standard carrier for 5G sub-6 GHz and mmWave antenna arrays. Multi-layer construction (4L or 6L) with impedance-controlled transmission lines, ENIG finish, and specific bend-test requirements. This is one of our growing volume categories.
Smartphone camera and periscope modules. Dual-layer FPC carrying MIPI CSI-2 differential pairs from image sensor to main board. See our MIPI cable page for related signal-integrity considerations. Periscope zoom modules add precision-bend FPCs that survive auto-focus actuator motion.
Smartwatch and wearable mainboards. Single-layer and double-layer FPC with tight space constraints. The curved profile of a smartwatch body means the mainboard is often FPC rather than rigid PCB. Includes wireless charging coil integration.
OLED display drivers. Tail flex carrying control signals and power from the OLED panel to the mainboard. Tight pitch (40-60 µm trace/space), fine line width, and impedance control for high-speed display data.
LED flexible panels and light strips. 2 oz copper for current-carrying capability, white Coverlay to maximize reflectance, high density of LED mounting pads. Single-layer is typical; some architectural lighting uses double-layer for data control lines.
Medical wearables and patches. CGM (continuous glucose monitor) sensors, ECG patches, thermal patches, digital pills. Biocompatible Coverlay, flexible construction conforming to skin, often rigid-flex hybrid for the processor section. See our medical cable assembly page for medical compliance context.
Automotive HMI and instrument clusters. Rigid-flex for dashboard displays, steering wheel button controls, and overhead console lighting. PI-only construction for temperature resilience. AEC-Q200 material sourcing on automotive programs.
EV battery module FPC. Replacing traditional wire-harness cell sampling with FPC assemblies. A single FPC can carry 30+ sampling lines through a battery pack, saving weight and improving consistency. We’re seeing this approach grow rapidly in new EV platform designs.
Rigid-Flex Hybrid Construction
Rigid-flex combines the component-mounting capability of rigid PCB with the folding capability of flex. Used when a design needs to:
- Fit around corners or into non-planar enclosures without the reliability penalty of connectors at the bend point.
- Replace cable-connector assemblies with a single integrated board. Each eliminated connector is one less failure mode.
- Achieve higher reliability in aerospace, medical implant, or defense applications where connector mate/demate cycles would be a concern.
- Reduce assembly labor — one rigid-flex board replaces several rigid boards plus interconnecting harnesses.
Typical rigid-flex stackup: 2-layer rigid + 2-layer flex + 2-layer rigid (totaling 4-6 effective layers). Higher complexity versions go to 8-10 layers. Lead time runs 3-4 weeks for first article because of the press-bond cycle complexity.
FFC vs FPC — Decision Matrix
| Consideration | Standard FFC | Custom FPC |
|---|---|---|
| Circuit pattern | Parallel only | Any pattern, multilayer |
| Tooling (NRE) | None | 1,500-5,000 USD |
| Per-piece cost | Low | 5-20x higher |
| MOQ | 500 pieces / 1,000 m raw | 100 sets |
| Prototype lead time | 5-7 days | 2-3 weeks |
| Design change cost | Very low | Requires new photomask |
| Component mounting | Not supported | Full SMT compatible |
If your design works as pure signal routing with parallel conductors, standard FFC is faster and cheaper. For anything else — circuit patterns, component pads, vias, multilayer — FPC is the answer.
Why SZFRS for Custom FPC Work
Prototype-to-production scaling. We handle small prototype runs (5-10 pieces) through volume production (50,000+ sets per month) on the same program. Prototype tooling scales into production without re-engineering.
Impedance control. For 5G antenna, MIPI, and differential signal FPC, we provide ± 10% impedance control with TDR verification on first articles. Stackup engineering done in-house to meet impedance targets before production release.
Rigid-flex experience. Complex rigid-flex builds with 6-10 layers handled regularly. The press-bond cycle and inner-layer registration challenges require trained operators — not every FPC house handles this.
DFM review at quote stage. We review submitted Gerber files for manufacturability issues before quoting — trace-to-copper-edge clearance, via-to-pad ratio, stiffener placement. Catching issues upfront prevents rework during first article.
SMT assembly on FPC. For programs needing populated FPC (components mounted on the flex), we handle through qualified SMT assembly partners. Common for camera modules, wearable mainboards, and LED panels.
IPC-6013 Class 2/3 compliance. IPC-6013 is the FPC-specific standard (equivalent to IPC-A-600 for rigid boards). Class 2 default, Class 3 for aerospace and medical. See our quality and certifications page for full compliance scope.
Frequently Asked Questions
What design files do you need to quote FPC?
Gerber RS-274X files plus drill file (Excellon format), stackup specification, and assembly drawing if components are involved. ODB++ is also accepted. Without stackup spec, we quote based on our standard stackup for the layer count — for impedance-critical designs, stackup must be customer-specified.
How much does FPC tooling (NRE) cost?
Typical range 1,500-5,000 USD depending on layer count, panel size, and precision requirements. Single-layer prototype tooling toward the lower end; 6-layer rigid-flex toward the higher end. NRE is one-time; repeat orders skip the tooling cost.
Can you handle impedance-controlled FPC for 5G and high-speed applications?
Yes. ± 10% impedance control is standard for 5G antenna, MIPI camera, and high-speed display drivers. TDR (Time Domain Reflectometry) testing on first article for impedance verification. For tighter tolerance (± 5%), we work case-by-case with additional process controls.
Can you build rigid-flex boards?
Yes. Standard rigid-flex up to 8 layers total (mixed rigid and flex sections). More complex 10-layer builds handled with extended lead time. For truly complex designs (12+ layers, tight impedance, buried vias), we discuss feasibility at quote stage.
Do you support SMT component assembly on FPC?
Yes, through qualified SMT assembly partners. We produce the bare FPC, then route to assembly for component placement, reflow soldering, and testing. Common for camera modules, wearable boards, and LED panels. Tell us the BOM at quote stage so we plan assembly capacity.
What’s your minimum order quantity for custom FPC?
Standard production MOQ is 100 sets. Prototype batches of 5-10 pieces available with higher per-unit cost. For programs expecting 10,000+ sets in production, we sometimes waive the NRE charge or offer favorable pricing in exchange for volume commitment.
What’s the lead time for FPC prototype and production?
Prototype lead time 2-3 weeks for single-layer and double-layer; 3-4 weeks for multi-layer; 4-5 weeks for rigid-flex. Production lead time (repeat orders) 10-14 days for most builds, longer for complex rigid-flex. Quote includes tooling status — new tooling vs existing tooling makes a significant difference.
Do you ship FPC worldwide?
Yes. FPC ships light and flat, so air freight is cost-effective even for volume. Europe, US, India, Southeast Asia, and Middle East destinations regular. DDP, DAP, or EXW per preference; NDAs signed for pre-release product designs.
Related FFC/FPC and Related Products
- FFC/FPC Overview — full category overview.
- Standard FFC — parallel-conductor flat flexible cable for simpler designs.
- MIPI Cable — MIPI CSI-2 and DSI interconnect for camera and display.
- Medical Cable Assembly — ISO 13485 medical device interconnect.
- Custom Manufacturing — OEM, ODM, overmolding, and value-added services.
Ready to Quote Your FPC Project?
Send us Gerber files, stackup specification, and expected volume. For early-stage designs without complete files, send a description and we provide a preliminary quote with assumed stackup. NDAs executed within 24 hours for pre-release products.