Flexible PCB
(FPC / Flex Circuit)
Polyimide flex circuits with rolled-annealed copper — rated for millions of dynamic bend cycles, biocompatible on request, and available in thicknesses as low as 0.05 mm.
The circuit that bends, folds and conforms to your product
A flexible PCB (FPC) is a circuit built on a thin polyimide (PI) base instead of rigid FR4 — allowing it to bend, fold and flex repeatedly without trace fracture or delamination.
The key material difference is rolled-annealed (RA) copper foil. Unlike standard electrodeposited copper, RA copper has a crystalline grain structure aligned with the rolling direction — giving it the fatigue resistance to survive millions of bend cycles without work-hardening and cracking.
Beyond bending, flex circuits eliminate harnesses and board-to-board connectors — each one a potential failure point and a source of assembly variation. One continuous flex circuit replaces multiple components and the labour to install them.
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Three engineering advantages of flex circuits over rigid + connectors
Flex is not simply 'a PCB you can bend'. It changes your assembly architecture in ways that improve reliability, reduce mass and enable form factors rigid boards cannot achieve.
Eliminate Connectors — Eliminate Failure Points
Board-to-board connectors in portable and wearable products fail through mechanical stress, fretting corrosion and tolerance stack-up. Replacing a connector with a flex circuit removes the failure mode entirely. In applications with millions of mating cycles (laptop hinges, wearable clasps), flex is not an option — it is the only viable solution.
connector elimination · zero fretting · lower field failure rate0.5 mm Dynamic Bend Radius — Millions of Cycles
A properly designed flex circuit with RA copper and correctly oriented traces survives millions of dynamic bend cycles at 0.5 mm bend radius — the equivalent of 15+ years of daily use in a wristband. Standard ED copper at the same bend radius will fracture within tens of thousands of cycles.
RA copper · perpendicular trace orientation · 1M+ cycle qualifiedBiocompatible and Body-Safe
Polyimide base material with ENIG finish is among the most biocompatible PCB constructions available — suitable for skin-contact wearables and, with ISO 10993 material certification, for implantable medical devices. Our PI materials are compatible with ETO sterilisation and gamma radiation, enabling use across the full range of medical device applications.
ISO 10993 · ENIG skin-safe · ETO / gamma sterilisation compatibleFull flex PCB specification
Dynamic flex capability confirmed by cycle testing, not estimated from datasheets.
Fabrication Parameters
| Layer Count | 1 – 8 layers flex / 2 – 20 rigid-flex |
| Min. Trace Width | 0.05 mm flex / 0.065 mm standard |
| Min. Bend Radius | 0.5 mm dynamic / 0.3 mm static |
| Copper Type | Rolled Annealed (RA) for flex zones |
| Base Material | Polyimide (PI) — Kapton-equivalent |
Performance & Standards
| Total Thickness (single-layer) | 0.05 mm minimum |
| Surface Finish | ENIG / ENEPIG (biocompatible on request) |
| Flex Cycle Rating | Millions (dynamic) · 100+ (static bend) |
| IPC Build Standard | IPC-6013 flexible PCB standard |
| Sterilisation | ETO / gamma compatible on request |
How flexible PCB is manufactured
Flex fabrication uses different materials and different tooling from standard rigid PCB manufacturing at every step.
PI Laminate Preparation
Polyimide film is cut and copper-clad using adhesive-based or adhesiveless lamination. RA copper foil is selected for dynamic flex applications.
Imaging & Etch
Circuit traces are patterned by UV lithography and chemically etched. Fine trace widths to 0.05 mm on flex regions.
Coverlay Lamination
PI coverlay (not solder mask) is precision cut and laminated over flex regions, leaving SMT pads exposed. Stiffeners are bonded to component zones.
Surface Finish & Test
ENIG or ENEPIG is applied for long-life contact reliability. 100% electrical test and flex cycling qualification are performed.
Where flex PCB delivers what rigid cannot
Any product that bends, rotates, conforms or connects in 3D space.
Wearables & Fitness Bands
Ultra-thin flex for smartwatches and health trackers where board weight affects user compliance.
TWS Earbuds
Micro-flex routing audio, power and touch sensing inside 5 mm diameter earbud stems.
Medical Implants
Biocompatible PI flex for cochlear implants, neurostimulators and retinal prostheses.
Camera Systems
Flex ribbons for mirrorless cameras, action cameras and drone gimbals with rotating joints.
Robotics
Joint-crossing flex circuits in collaborative robot arms — replacing harnesses that wear and fail.
Laptops & Foldables
Hinge flex cables in laptop displays and foldable phones rated for millions of fold cycles.
Automotive Sensors
Seat occupancy, steering column and door panel flex circuits replacing bulky wiring harnesses.
Satellite Subsystems
Lightweight PI flex for satellite deployable structures where mass is a primary constraint.
Flex quality verified through bend cycle testing.
A flex circuit that passes AOI at delivery may still fail after 50,000 bend cycles. Our qualification process includes dynamic cycling and microsection of the bend zone to confirm fatigue life before production release.
- ISO 9001 : 2015Third-party audited quality management
- IPC-6013Flexible PCB qualification standard
- IPC-A-600Acceptability criteria
- ISO 10993 CompatibleBiocompatibility testing on request
Inspection & Testing Methods
- 100% Electrical Test — Flying ProbeAll nets, every board
- 100% AOIAutomated optical inspection
- Flex Cycling TestPer IPC-TM-650 2.4.34 — qualification lots
- Microsection — Flex Bend ZoneCopper fatigue and delamination check
- Coverlay Peel StrengthPer IPC-TM-650 2.4.9
- ENIG Thickness — XRFUniformity on skin-contact boards
- Dimensional VerificationOutline and hole location
- Sterilisation CompatibilityETO / gamma test on request
Flex circuits we have built
Real flexible PCB challenges — solved.
6-Layer Rigid-Flex Smartwatch
0.6 mm total thickness, 200,000 dynamic flex cycles at hinge, biocompatible ENIG, 0.4 mm BGA on rigid SoC zone.
200,000 cycle qualification passed. Assembly height reduced 0.4 mm vs previous connector design. Zero coverlay delamination in 2-year production run.
Biocompatible Implant Flex Circuit
ISO 10993 materials, ENIG finish, 0.08 mm trace width, ETO sterilisation compatible, static bend 0.3 mm radius.
Biocompatibility accepted by EU Notified Body. Zero failures in 5-year post-implant follow-up across 800 patients.
Cobot Joint Dynamic Flex Circuit
RA copper PI flex replacing 14-wire harness in a collaborative robot joint — rated 5 million dynamic cycles at 0.5 mm bend radius.
5M cycle qualification passed. Joint wiring assembly time reduced from 12 minutes to 90 seconds. Zero harness failures in 3 years of robot deployment.
Common questions about Flexible PCB
Technical questions engineers ask most often before ordering flex and rigid-flex circuits.
Our standard flex base material is polyimide (PI) film — chemically equivalent to DuPont Kapton. PI provides the thermal stability (up to 260°C), chemical resistance and mechanical compliance that flex circuits require. For skin-contact and implantable applications, we can confirm ISO 10993 biocompatibility. LCP (Liquid Crystal Polymer) substrate is available for ultra-low-profile millimetre-wave flex applications.
Our standard minimum dynamic bend radius is 0.5 mm for designs using 1 oz (35 µm) copper. Static-fold applications (bent once during assembly) can achieve 0.3 mm. For tighter radii, reduce copper weight to 0.5 oz and increase the number of flex layers to reduce per-layer strain. Our flex engineers review bend radius, trace orientation and copper weight together in the DFM review.
Solder mask is a photoimageable liquid coating — suitable for rigid PCBs where it is not subject to repeated flexing. Coverlay is a laminated PI film with adhesive — it flexes with the circuit without cracking. Flex regions must always use coverlay, not solder mask. SMT pad areas in rigid or stiffened zones can use solder mask for compatibility with standard paste printing and automated optical inspection.
Always specify rolled annealed (RA) copper for dynamic flex regions. RA copper has a crystalline grain structure aligned with the rolling direction, giving it the fatigue resistance to survive millions of bend cycles. Electrodeposited (ED) copper has a columnar grain structure that work-hardens rapidly under repeated bending and will fracture within tens of thousands of cycles in dynamic applications. Our default for all flex orders is RA copper.
Our standard polyimide base material with ENIG finish is widely used in skin-contact wearables without special qualification. For medical device regulatory submissions requiring ISO 10993 biocompatibility documentation, we can provide third-party test reports on request. ETO and gamma sterilisation compatibility is available — specify sterilisation method at the time of enquiry.
We offer FR4 stiffeners (0.2–1.6 mm) bonded with pressure-sensitive adhesive (PSA) for room-temperature assembly, and polyimide stiffeners bonded with thermally cured adhesive for high-temperature applications. Stiffeners are used to rigidise connector termination areas, component mounting zones and through-hole pad areas. Stiffener placement and thickness are reviewed in the DFM process.
Get your flex circuit reviewed — today.
Send your flex design or mechanical requirement. Our flex engineers will review bend radius, trace orientation and coverlay design within 8 hours.
- DFM review included with every enquiry
- NDA signed on request — standard practice
- Response within 8 working hours
- 48-hour express prototype available
- No commitment required to get a quote
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