How A 3-in-1 Wireless Charger Is Made: Inside The Production Line, Station by Station

Most wireless charger listings state the output and stop there. It’s the least informative number in the whole specification, because almost any coil will hit 15W for thirty seconds. What separates a charger that survives a two-year retail warranty from one that generates returns gets decided upstream — in how the coil is wound, how the ferrite and magnet ring are bonded, and how long the finished unit is run under load before anyone puts it in a box. This article walks the line station by station, using photographs taken during a production run in Dongguan, Guangdong in April 2025, and explains what each inspection gate is there to catch.

01

What arrives before the line starts

A 3-in-1 charger has roughly forty distinct part numbers, but six of them account for nearly all of the field failures. These are the ones that get incoming inspection rather than a paperwork check.

02

Eight stations, four gates: the build sequence

Original graphic. The build sequence is schematic — station order is accurate, spacing and timing are not to scale.

Stations 01–02  /  winding the coil and bonding the magnetics

Coils are machine-wound from Litz wire, then the leads are stripped and tinned by hand. Every coil is measured for inductance and DC resistance before it goes any further, because a coil that’s two turns short will still look perfect and will still charge a phone — it just does it at lower efficiency and higher temperature, and nobody discovers that until the units are in a warehouse overseas. That’s Gate A, and it’s the cheapest inspection on the entire line.

Wound transmit coils staged in trays with leads tinned, ready for the inductance check.

Ferrite shield discs in blister trays, staged alongside coils for the bonding station. Ferrite is brittle, so it ships in trays rather than loose.

Stations 03–04  /  PCBA and coil-to-board

The board carries the wireless power controller, the switching stage and the USB-C protocol decoder that negotiates 9V, 12V or 15V from the customer’s adapter. It comes off SMT with automated optical inspection and an in-circuit test — Gate B — before anything is soldered to it. Only then does the coil-and-ferrite stack join the board, along with the flexible circuit and the NTC thermistor. On a 3-in-1 this is the fiddliest operation on the line: three coils, a hinge and a cable all have to route through a housing under 15 mm thick.

Coil, ferrite and flexible printed circuit subassemblies staged at the coil-to-board station.

Stations 05–08  /  housing, ageing, electrical test, pack-out

Housings close over a folding hinge on the YW10 and YW11, or over a retractable USB-C reel on the YW13 and YW14. From there every unit — not a sample — goes onto a powered ageing rack and runs under load. This is where the second-order defects surface: a cold solder joint that passed ICT, a coil that shifted during shell closure, a thermal path that was fine at room temperature and isn’t fine after forty minutes. Units that pass ageing move to the electrical bench, where input voltage, current and delivered power are read on a multi-port meter and logged against the work order.

Original graphic. Power path is schematic; rated outputs are taken from GREENPORT specification sheets for YW10 / YW11 and YW13 / YW14.

Two things on that diagram are worth pausing on. The protocol decode stage decides whether the charger ever reaches its rated output — hand a 25W-capable unit a 5V adapter and it behaves like a 5W one, which is why the adapter in the box is part of the specification and not an afterthought. And the inverter drives all three coil positions from one power budget, so the ageing rack has to load the unit the way a customer will, with a phone on the main coil rather than a single low-power receiver.

Powered ageing rack. Every unit is run under load, not a sample.

Electrical bench. Voltage, current and power read per port, logged against the work order.

Pack-out is the station buyers ignore and returns data doesn’t. Missing cables, the wrong plug type for the destination market and cartons sealed before the accessory kit went in are packing-line errors, not electrical ones. Every packing operation on our line runs against a printed work instruction naming the exact accessory set and the sealing sequence, so nobody is reconstructing it from memory between orders.

Packing-line work instruction posted at the station: carton fold, accessory insertion, seal. The accessory list is fixed per work order.

03

Where 3-in-1 units actually fail

Group the failure modes by station and a pattern appears. Electrical defects are caught cheaply and early. Mechanical and thermal defects are caught late or not at all, and those are the ones that come back as warranty claims six to twelve months after shipment.

04

Qi, Qi2 and Qi2 25W: the distinction buyers get wrong

The version numbers matter too, because they set the power ceiling. The Qi2 Magnetic Power Profile launched at 15W. The v2.2.1 specification released by the WPC in 2025 and branded Qi2 25W lifts that ceiling to 25W and is optimised around modern USB-C adapters, which is why our second-generation retractable models specify a higher input range than the first generation.

Source: Wireless Power Consortium, History of the Qi Specifications. Qi2 25W corresponds to Qi v2.2.1, launched July 2025.

Qi registration certificates, an FCC test report and a RoHS declaration of compliance displayed at the plant. Registrations are held per model — ask for the QI-ID that matches the model you are quoting.

05

The GREENPORT 3-in-1 range: two formats, two generations

Everything above describes how we build four models across two families. The families differ in the mechanism, not the electronics philosophy: one folds flat and carries no cable, the other carries a retractable USB-C cable so the charger doubles as a wired 27W supply. Within each family there is a first-generation standard version and a second-generation version built to the Qi2 magnetic profile.

Round and square share a bill of materials and a test programme; the difference is the shell tool and how the product photographs on a shelf. That matters commercially, because a buyer can carry both shapes in a range without doubling the qualification work.

Housing panels and coil modules staged on the line before shell closure. Standard finish is black; custom colour and logo are handled at this stage.

06

Frequently asked questions

Can all three coils run at full rated power at the same time?

Not automatically. The rated figures — 15W or 25W phone, 2.5–3W watch, 5W earbuds — are per-output maxima, and the controller allocates power against the negotiated input and the current thermal state. If your use case requires simultaneous full-rate charging of all three, treat it as a separate requirement to confirm rather than an assumption from the datasheet.

Will these charge through a phone case?

Within the rated 3–5 mm coupling distance, yes. Thicker cases, cases with metal plates and cases with card pockets all reduce coupling. A card left between the phone and the coil will also trigger foreign-object detection and stop charging, which is correct behaviour rather than a fault.

What adapter should ship in the box?

A PD adapter that can supply the model’s rated input. The folding YW10 and YW11 want 9V/2A upward; the retractable YW13 and YW14 want a supply that can reach 15V/3A to hit both the 25W wireless and 27W wired figures. Undersizing the adapter is the most common reason a charger tests slower in the field than on the bench.

How do I verify your Qi certification myself?

Look up QI-ID 24629 for the YW10 or 24633 for the YW11 in the WPC public product database. You don’t need to contact us to do it. Any supplier claiming Qi certification can give you a QI-ID; if they can only send a scan of a certificate, ask why.

Do you support OEM colour, logo and packaging?

Yes. Colour and logo are set at housing assembly, and the accessory kit and carton artwork are fixed per work order at pack-out. Custom colour affects tooling and shell lead time rather than the electronics, so quote it separately from the electrical specification.

Which model should a first order start with?

If the buyer is price-sensitive and the channel is gifting or travel retail, start with the folding YW10 or YW11 — they are also the two already certified on the public record, which shortens the compliance conversation. If the channel is consumer electronics retail where the Qi2 mark carries weight on the shelf, start with the Qi2.2 YW13 or YW14 and accept the higher landed cost. Round versus square is a merchandising decision, not a technical one — the electronics are identical.

Sources

• History of the Qi Specifications, Wireless Power Consortium

• Qi Wireless Charging standards overview, Wireless Power Consortium

• WPC Logos and Licensed Products guidelines, Wireless Power Consortium, 18 December 2024

• Ushering in the New Wireless Charging Era with Qi v2.1, Granite River Labs (WPC authorised test lab)