How to manufacture wearables in China — factory selection, FPC sourcing, battery certification (UN 38.3, IEC 62133-2), and FCC/CE/UKCA compliance.
Wearables are harder to manufacture than generic consumer electronics. Not marginally harder — structurally harder, because three problems compound on each other: FPC complexity drives yield loss, multi-jurisdiction certification adds 3–5 months to your timeline, and battery transport rules create logistics constraints that most first-time buyers don't discover until they're ready to ship.
This guide covers all three, plus design-for-assembly considerations that separate a 0.4% defect rate from a 6% one. If you're considering sourcing wearables from China, read this before you contact a single factory.
1. Finding factories that actually do FPC
Flexible printed circuits (FPC) are the wiring harness inside every modern wearable. The strap connects to the body unit. The body unit connects the display, sensor array, and battery. In a smartwatch with a 40mm case, there may be three or four FPCs, each with tolerances measured in tenths of a millimeter; even smaller formats like fitness band OEM production depend on the same precision flex assembly.
The problem: almost every PCB factory in Shenzhen claims FPC capability. Most of them are lying — or, more precisely, most of them mean "we can source FPC from a subcontractor and pass it to you." That is not FPC capability. That is procurement. These factories have no control over FPC yield, bend radius consistency, or connector seating.
How to tell the difference:
Ask for FPC yield data on a comparable product. A real FPC manufacturer can give you the scrap rate for their last 5,000-unit run: something in the 1–3% range for a simple two-layer FPC, 3–8% for a multi-layer rigid-flex. A factory sourcing FPC from a subcontractor cannot give you this data. They don't have it.
Ask about layer count capability and bend radius tolerance. A two-layer FPC is standard. A six-layer FPC with a bend radius under 2mm requires specialist equipment. If the salesperson has to go ask the engineer, that's fine. If the salesperson has no idea what you're asking, move on.
Ask whether they use ZIF (zero insertion force) connectors or non-ZIF. ZIF connectors are standard in wearable assembly because they allow precise, repeatable connector seating without applying force to the flex. Factories defaulting to non-ZIF connectors are adding a mechanical stress point into every unit.
Red flag to watch for: factories showing FPC samples that are actually rigid-flex hybrids. Rigid-flex combines a rigid PCB zone with a flexible interconnect zone — it is a different and more expensive product. If a factory shows you rigid-flex samples when you asked about FPC, they either misunderstood your requirement or are showing you the most impressive thing they have, which is not what you need.
The factories worth qualifying for wearable FPC work are concentrated in Shenzhen's Bao'an and Longhua districts, and in Dongguan's Tangxia area. These areas have the equipment density and labor pool for precision FPC assembly, and are where most smartwatch OEM manufacturing capacity is based. A factory audit visit should include a walk past the FPC assembly line — you want to see IPC-trained operators and a microscope inspection station.
2. Battery certification is non-negotiable
Every wearable with a lithium cell requires battery certification. This is not optional and it is not something to defer. Two certifications are relevant:
UN 38.3 (transport safety) is required for any shipment involving air freight — which includes virtually every consumer product shipment from China. UN 38.3 testing covers altitude simulation, thermal test, vibration, shock, external short circuit, impact/crush, overcharge, and forced discharge. The full criteria are codified in the UNECE UN 38.3 test requirements (Manual of Tests and Criteria, Part III, Section 38.3). The test applies to the specific cell model and configuration you are shipping.
IEC 62133-2 (product safety for portable sealed secondary lithium cells) is required for CE marking in the EU under the Low Voltage Directive, and is the battery safety standard referenced by most other regional certifications. See the IEC 62133 standard page for the current edition. If your cell is not IEC 62133-2 certified, you cannot CE-mark your product without testing it yourself.
The fraud pattern to watch for: factories providing "battery certification summaries" — a one-page document with a logo from SGS or Intertek and a pass/fail result. These summaries are easily forged and widely circulated for popular cell models. The real test report runs 60–150 pages. It names the specific cell model, the tested cell capacity (in mAh, matching your spec), the lab ID of the accredited facility, and the test dates.
When you receive a battery certification from a factory, verify it by:
- Checking that the cell model on the report exactly matches the cell in your BOM
- Checking that the issuing lab is accredited: SGS, Intertek, TÜV Rheinland, Bureau Veritas, or UL are the recognized names
- Checking the test date — UN 38.3 reports don't expire, but if a report is from 2019 and the cell was reformulated in 2022, the report doesn't cover your cell
- Calling the lab's certificate verification line with the report number — most accredited labs offer this service
Timeline reality: if your cell model is not pre-certified, allow 3–4 weeks for UN 38.3 testing and 6–8 weeks for IEC 62133-2 before your product can ship. This is calendar time, not working days. Plan this into your launch schedule before you finalize your design with a specific cell model.
Pre-certified cells do exist. Many Shenzhen battery suppliers carry cells with existing UN 38.3 and IEC 62133-2 reports. Using one of these cells can save 6–8 weeks. Ask about this in your initial supplier conversations.
3. Multi-region certification strategy
Most hardware startups certify for their home market first, then add regions later. For wearables with BLE or WiFi, this sequential approach is expensive in time: FCC, then CE, then UKCA, then TELEC adds up to 4–5 months of serial waiting. The parallel approach takes 8–10 weeks. Health-focused devices such as wearable health monitor OEM builds carry the heaviest certification load, since any clinical claim pushes them into the medical device pathway on top of the radio approvals below.
FCC (United States): Wearables require FCC Part 15B (unintentional radiator, for the device itself) and Part 15C (intentional radiator, for the BLE/WiFi radio) — the full requirements are in FCC Part 15. If you use a pre-certified BLE module (common examples: Nordic nRF52840, Espressif ESP32-C3 in module form), Part 15C is handled by the module's existing FCC ID and you only need to certify Part 15B for your integration. This is faster and significantly cheaper.
Cost estimate: $3,000–5,000 for FCC testing at a recognized lab. Timeline: 4–6 weeks with a pre-certified module, 8–10 weeks if you're certifying the radio yourself.
CE (European Union): Wearables with BLE or WiFi fall under the Radio Equipment Directive (RED, 2014/53/EU), not just the Low Voltage Directive. RED requires testing against radio, EMC, and safety standards. RoHS 2 compliance is a separate declaration — it covers restricted substances in the physical product, and your factory needs to provide substance test reports or declarations of conformity for all components.
Cost estimate: €2,000–4,000 for RED testing. Timeline: 4–6 weeks at an accredited EU notified body.
UKCA (United Kingdom): Post-Brexit, the UK requires its own declaration of conformity separate from CE. The technical requirements are currently identical to CE, which means the same test data can be used to generate both declarations. You do need a UK-based responsible person to hold the declaration on file. Cost is typically £1,500–2,500 in lab fees.
MIC/TELEC (Japan): If you plan to sell in Japan, the Giteki mark is required for any device with a radio transmitter. BLE modules need their own Japanese radio type approval unless the module itself already holds a Giteki mark (which some modules from major suppliers do). This is a separate certification process from FCC and CE — it does not accept FCC test data. Budget ¥250,000–400,000 (approximately $1,600–2,600) and 8–12 weeks.
The parallel approach in practice: submit to FCC, CE/RED, and UKCA simultaneously after your design is frozen. Use the same test sample set. The lab submissions happen in parallel, the test reports come back in parallel, and you have all three declarations within 8–10 weeks of submission. The only serial dependency is that IEC 62133-2 battery testing should complete before you submit for CE, because the battery safety test is part of the CE technical file.
Critical note on test samples: certification labs require production-representative samples — the same PCB layout, same antenna, same enclosure as your final product. If you change the PCB layout after certification, even to fix a trace width issue, you may need to re-test. Freeze your design before you submit. Our factory audit process includes a design review checkpoint specifically to catch layout changes that would invalidate certification.
4. Design-for-assembly considerations
Wearable assembly introduces failure modes that don't exist in a standard consumer electronics product. These are the ones we see most often during quality inspection:
Silicone strap hardness: Shore A hardness for skin-contact silicone should be specified in your drawings. The typical range for wearable straps is 40A–60A — soft enough to be comfortable, firm enough to hold shape. Most factories default to whatever Shore A their current silicone supplier stocks. If you don't specify it, you will get inconsistency between production runs as factories switch suppliers. Specify 50A±5A in your component spec and require a shore hardness certificate with each batch.
Waterproofing: IP67 means the device survives 1 meter of water for 30 minutes. IP68 means it survives beyond 1 meter (the specific depth must be stated by the manufacturer — it is not standardized). Many factories quote IP68 in their marketing without testing to that standard. Request the pressurized water test records for the test samples: the report should show test pressure (IP67 = 1.0 bar gauge, IP68 depth-equivalent), duration, and pass/fail result for each sample tested. If the factory cannot produce these records, they have not tested to the standard they're quoting.
Display bonding: two adhesive methods are common. OCA (optically clear adhesive) is a pre-formed adhesive film applied under controlled conditions — it gives better optical clarity and no air bubbles, but requires investment in bonding equipment and a clean assembly area. LOCA (liquid optically clear adhesive) is applied as a liquid and UV-cured — simpler to apply but more prone to voids and yellowing over time. For fitness devices and mid-range consumer wearables, LOCA is acceptable. For devices positioned as premium, specify OCA and verify that the factory has the equipment.
Hinge durability for folding/band designs: if your device has a hinge or buckle that opens and closes, specify the open/close cycle count in your purchase order. Consumer grade minimum: 10,000 cycles. Fitness-use minimum: 50,000 cycles. Require fatigue test records from the factory before the first production run. Factories that cannot provide these records have not run the test.
5. Quality checkpoints specific to wearables
Standard electronics QC catches soldering defects and functional failures. Wearable QC needs to add four checkpoints:
Golden sample review: before production starts, establish a signed-off golden sample set — typically 5–10 units — that represents the approved standard for every attribute: color, Shore A hardness, display brightness, strap texture, button force. Every production unit is compared against this, not against a written specification. Written specs leave too much room for interpretation.
FPC alignment check: the most common wearable assembly defect is misaligned or partially seated FPC connectors. A visual check at 10× magnification, combined with an electrical continuity test at the FPC connection points, catches this defect before the device is closed up. Without this check, the defect makes it into the finished unit and only presents as an intermittent fault after 100–200 flex cycles. Our incoming quality inspection process includes this as a mandatory checkpoint for all wearable orders.
Battery swell test: charge and discharge the battery 50 times under controlled conditions before approving shipment. A battery that will swell under normal use will typically show measurable expansion within 50 cycles. This test eliminates swelling batteries before they reach your customers — and before they generate the kind of product liability exposure that ends small hardware companies.
Drop test: IEC 60068-2-31 specifies a 30 cm drop onto a hard surface from 6 faces. Run this on 10 units from each production run before final QC approval. The drop test reveals enclosure joint failures, display delamination, and hinge damage that aren't visible before impact. Specify this test in your quality agreement before production, not as an afterthought.
Manufacturing wearables in China is achievable — but it requires more preparation than standard electronics sourcing. The factories are there. The certification labs are there. The supply chain for FPC, batteries, and display modules is denser in Shenzhen and Dongguan than anywhere else in the world.
The gap is in knowing which factories are genuinely capable, verifying that certification documents are real, and building the quality checkpoints into the contract before production starts.
If you want a partner who can handle factory qualification, audit the FPC line, coordinate parallel certification, and run the quality inspections described above, our Sourcing & Supplier Matching and Quality Inspection services cover the full wearable production cycle. For a concrete example of this process, see how a US fitness tech startup took a smartwatch from sample to 3,000-unit production while achieving dual FCC/CE certification. You can also review our factory audit checklist to understand what we look for on-site — or contact us to discuss your specific wearable project.
