The defect that matters most on a wireless charger is usually created before the product reaches the end of the line. A coil placed a fraction of a millimetre off centre passes a visual inspection and fails a customer, and the step that controls it is an assembly fixture rather than a test. The order of the steps below is what keeps the fixture in control of the result.
Wireless charger assembly: the order the steps have to happen in
Eight steps, and each one has a check that has to pass before the next begins.
Incoming verification, board assembly, coil and magnet assembly, housing closure, functional test at the alignment position, aging, final inspection and packaging, with traceability closing the loop. The sequence is fixed by dependency: the coil cannot be positioned before the board is, and the delivered power cannot be tested before the housing is closed.
Brands often focus on the test steps, because those are the ones that produce the numbers they see. On this product the assembly steps decide those numbers, which is why the checks after each step matter more than the final test alone.
Prerequisites before the line starts
Four documents and two fixtures, and the line should not start without them.
The frozen mechanical and electrical revision, the approved component list for the coils, magnets, shielding and power stage, the test plan with its limits per surface, and the packaging and label specification. The two fixtures are the coil positioning fixture and the electrical test fixture with its adapter. A line that starts without the coil fixture produces a first batch whose variation will only appear when customers start reporting slow charging.
Step 1: incoming verification of coils, magnets and boards
Verify the components that decide the coupling before they are built in.
Coil geometry and inductance, magnet grade and polarity, shielding dimensions and board revision. Polarity is the item that is easiest to miss: a magnet placed the wrong way round produces a unit that still charges and holds the phone poorly, which is a complaint that takes a long time to trace. The check is a measurement against the approved list, recorded per lot rather than per batch.
Step 2: board assembly and the coil fixture
The coil position is the single most important tolerance in the whole assembly.
The board is assembled and tested first, then the coil is positioned by the fixture against the same datum the enclosure uses. The check after this step is the measured coil centre against that datum, on a sample taken across the shift rather than at the start. Adjusting the fixture is a process change; adjusting the coil by hand is a batch-specific repair that will not survive the next batch.
Step 3: magnet, shield and housing assembly
Concentricity between the coil and the magnet array is what the customer experiences as consistent charging.
The shield goes behind the array, the array goes around the coil, and the housing closes over both. The check is the measured concentricity, taken on finished assemblies rather than on sub-assemblies, because the closure can move the parts. This is also the step where the thermal path is completed: the gap between the coil stack and the surface has to match the revision, since a larger gap reduces coupling and a smaller one changes the temperature rise.
Step 4: functional test at the alignment position
The test measures the delivered power where the customer will actually place the device.
Every unit is tested at the alignment position with a reference receiver, and the limit is set from the characterisation data rather than from a nominal figure. On a multi-coil pad the test includes each active region, and on a stand it includes the resting position for the heaviest supported phone. A unit that passes at the centre and fails at the edge is a mechanical unit, not an electrical one, and the test is what makes that visible before shipment.
| Step | Check | Pass condition | What forces a restart |
|---|---|---|---|
| 1 Incoming | Coil, magnet and board verification per lot | Within the approved specification | An unapproved substitution |
| 2 Board and coil | Coil centre against the datum | Inside the position tolerance | A fixture that has drifted |
| 3 Array and housing | Concentricity and stack gap | Inside the mechanical revision | A closure that moves the parts |
| 4 Functional test | Delivered power at the alignment position | Inside the limit per surface | A limit set without characterisation data |
| 5 Aging and final | Temperature rise, appearance, packaging | Inside the stated conditions | A late artwork or accessory change |
Step 5: aging, final inspection and packaging
Aging exposes the units that would have failed in the customer’s first week.
The aging plan states which units are run at load, for how long and at what ambient, and the final inspection covers appearance, marking and the accessory set. Packaging closes the mechanical side: the carton, the insert and the accessories have to protect the coil stack during transport, because a drop test failure usually shows up as a coupling problem rather than as visible damage.
Traceability: what the record has to link
A traceable unit can be tied to the parts, the fixture and the test.
The record links the serial or the lot to the component lots, the coil fixture used, the operator station and the functional test result. That link is what allows a complaint to be answered with a cause instead of a replacement, and it is also what allows a batch to be narrowed when a component issue appears months later. Without it, every complaint becomes a full production investigation.
The four mistakes that force a restart
Four process decisions send a batch back to the beginning.
Starting without the coil fixture; substituting a coil, magnet or shield without an approval; setting the functional limit from a nominal figure rather than from characterisation data; and changing the artwork or the accessory set after the packaging proof. Each one is cheap to prevent and expensive to correct, because the correction requires the batch to be re-tested rather than re-labelled.
FAQ
Which step in wireless charger assembly causes the most complaints?
Coil and magnet placement. Both are mechanical tolerances that a visual inspection cannot see and a functional test only detects if the limit was set from characterisation data. The fixture and the recorded measurement are what keep the step in control. Coil and magnet placement are mechanical tolerances that a visual inspection cannot see and a functional test only detects if the limit came from characterisation.
Some factories say every unit is tested. Is that enough?
It depends on what the test measures. A continuity or power-on check confirms the unit works; it does not confirm the delivered power at the alignment position. The test that matters is the one taken with a reference receiver where the customer places the device. A continuity or power-on check confirms the unit works but not the delivered power at the alignment position with a reference receiver.
Is aging necessary on a wireless charger?
Where the plan requires it, yes, because it exposes thermal and contact issues that appear in the first week of use. The plan should state which units are aged, at what load and for how long, and the result should be recorded rather than summarised. The plan should state which units are aged, at what load and for how long, and the result should be recorded rather than summarised.
How is a batch traced when a customer reports a fault?
Through the record that links the unit or lot to the component lots, the fixture used and the test result. Where that link does not exist, the only available action is to replace units, and the cause is never established. Without the link that ties the unit to its component lots and test result the only available action is to replace units and the cause is never established.
Next step
Send the product specification, the markets and the expected quantity to Wecent Group through the contact page. The reply sets out the assembly sequence for the product, the fixture and test plan behind it and the records that travel with each shipment. Related reading: our charger factory, the factory floor and wireless charger applications. External references: WPC knowledge base, IEC standards, USB Power Delivery specification, UL standards and certification, TUV testing services and ETSI standards.
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