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.
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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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.
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 rateA 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 qualifiedPolyimide 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 compatibleDynamic flex capability confirmed by cycle testing, not estimated from datasheets.
| عدد الطبقات | 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 |
| نوع النحاس | مدلفن صلب ملفوف (RA) للمناطق المرنة |
| المادة الأساسية | Polyimide (PI) — Kapton-equivalent |
| Total Thickness (single-layer) | 0.05 mm minimum |
| تشطيب السطح | ENIG / ENEPIG (biocompatible on request) |
| تصنيف الدورة المرنة | Millions (dynamic) · 100+ (static bend) |
| معيار البناء IPC | IPC-6013 flexible PCB standard |
| Sterilisation | ETO / gamma compatible on request |
Flex fabrication uses different materials and different tooling from standard rigid PCB manufacturing at every step.
Polyimide film is cut and copper-clad using adhesive-based or adhesiveless lamination. RA copper foil is selected for dynamic flex applications.
Circuit traces are patterned by UV lithography and chemically etched. Fine trace widths to 0.05 mm on flex regions.
PI coverlay (not solder mask) is precision cut and laminated over flex regions, leaving SMT pads exposed. Stiffeners are bonded to component zones.
ENIG or ENEPIG is applied for long-life contact reliability. 100% electrical test and flex cycling qualification are performed.
Any product that bends, rotates, conforms or connects in 3D space.
Ultra-thin flex for smartwatches and health trackers where board weight affects user compliance.
Micro-flex routing audio, power and touch sensing inside 5 mm diameter earbud stems.
Biocompatible PI flex for cochlear implants, neurostimulators and retinal prostheses.
Flex ribbons for mirrorless cameras, action cameras and drone gimbals with rotating joints.
Joint-crossing flex circuits in collaborative robot arms — replacing harnesses that wear and fail.
Hinge flex cables in laptop displays and foldable phones rated for millions of fold cycles.
Seat occupancy, steering column and door panel flex circuits replacing bulky wiring harnesses.
Lightweight PI flex for satellite deployable structures where mass is a primary constraint.
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.
Real flexible PCB challenges — solved.
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.
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.
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.
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.
Send your flex design or mechanical requirement. Our flex engineers will review bend radius, trace orientation and coverlay design within 8 hours.
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