The submission came back with an EMC result two decibels above the limit and a note that the sample had been tested with the coil active, which is how the product is used. Nothing in the design was unsafe and nothing in the file was wrong; the margin had simply never been measured during development. Five failures account for most of the returns on this product, and each one is cheaper to find before submission than after.
Wireless charger certification: the five failures that send a submission back
EMC margin at the coil frequency, foreign object behaviour, thermal evidence from the wrong assembly, marking that describes a different product, and an unapproved substitution.
Each produces a different kind of failure notice, and each is confirmed by a specific measurement rather than by an opinion. The order below follows the frequency: the first two account for the majority of returns on wireless charging products.
Failure 1: EMC above the limit at the coil frequency
The switching frequency of the coil and its harmonics are the emissions this product is most likely to exceed.
The margin depends on the coil geometry, the shielding, the switching design and the enclosure, and it is normally established during development with a pre-scan rather than discovered in the certification laboratory. Confirm it by measuring emissions with the coil active at full load, in the shipping enclosure, with the intended receiver in place. A pre-scan taken on an open board without the housing understates the result, because the housing and the receiver change the field.
Failure 2: foreign object behaviour outside the defined threshold
This is a safety function, and a submission tests the behaviour rather than the intention.
The product has to refuse to charge when an object that is not a device is present, and to charge normally when it is not. Confirm it with the objects the market actually encounters: a card holder on the back of a case, keys, coins and a metal-bodied accessory. Where the threshold is set too sensitively the product fails on ordinary use; where it is set too loosely it fails on the safety test. Both are corrected in development, not in the laboratory.
Failure 3: thermal evidence produced on the wrong assembly
A temperature rise measured on a prototype does not describe a production unit.
The evidence has to come from the shipping enclosure, at a stated ambient, at full load, with the intended receiver and case. Where the derating threshold is part of the design, the test has to show where it engages. Confirm it by repeating the measurement on a production-representative assembly, and record the ambient and the load with the result, because a figure without them cannot be compared with anything.
Failure 4: the marking and the file describing different products
Documentation failures are slower to fix than technical ones.
The label, the model designation, the ratings, the applicant named in the file and the revision identifier all have to describe the same product. Confirm it by laying the artwork, the report and the bill of materials side by side before submission, and by checking that the revision identifier appears in all three. A one-line label change after the report is issued reopens the file and can require a re-test where the change touches the tested parameters.
Failure 5: an unapproved component substitution
A substitution made for supply reasons can invalidate the construction that was tested.
The coils, the magnets, the shielding, the switching devices and the control circuit are all part of the tested configuration. Confirm it by comparing the approved component list with what the line actually receives, per lot rather than per batch. Where a substitution is necessary, it is assessed against the tested construction and, depending on the parameter it touches, may need a partial or full re-test.
| Failure | How it appears | How to confirm it | What the fix changes |
|---|---|---|---|
| EMC at the coil frequency | A margin above the limit with the coil active | Pre-scan in the shipping enclosure at full load | Shielding, coil or switching design |
| Foreign object behaviour | Fails to refuse, or refuses in normal use | Test the objects the market encounters | The detection threshold and its test |
| Thermal evidence | A figure without an ambient, load or assembly | Repeat on a production-representative unit | The measurement, not always the design |
| Marking and file | The report, label and product disagree | Compare artwork, report and bill of materials | The documentation and artwork revision |
| Component substitution | The tested construction is no longer what ships | Compare the approved list with lots received | An assessment, and possibly a re-test |
Pre-compliance: one day of measurement against three weeks of schedule
A pre-scan is a schedule instrument rather than a formality.
Measuring emissions, thermal behaviour and foreign object response on a representative unit, before the submission is booked, converts an unknown into a plan. Where a margin is thin, the fix is a design change that can be made while the tooling is still open; where it is comfortable, the submission proceeds without a surprise. The cost of the measurements is small compared with a failed submission, which restarts the queue position at the laboratory rather than the design work.
FAQ
Some suppliers say a wireless charger never fails EMC. Is that realistic?
It is a claim about their products rather than about the category. A wireless charger is a switching product with a coil that radiates, so emissions are a normal part of its assessment and the margin depends on the design and the enclosure. A wireless charger is a switching product with a coil that radiates, so emissions are a normal part of its assessment.
Can a failed submission be appealed?
The result is a measurement against a limit, so the route is to change the design or the configuration and re-measure rather than to argue the figure. That is why a pre-scan before booking the submission is cheaper than a re-test afterwards. The result is a measurement against a limit, so the route is to change the design or the configuration and re-measure rather than to argue the figure.
Who pays for a re-test after a component substitution?
It follows the agreement between the brand and the factory. Where the substitution was made to keep a production date, the commercial conversation is easier when the assessment requirement was written into the supply terms before the substitution happened. It follows the agreement between the brand and the factory, and the conversation is easier when the assessment requirement was written into the supply terms beforehand.
Does the certification expire?
A file describes a product revision, so it stops describing the product when that revision changes. Maintaining the file means keeping the tested revision and the shipped revision identical, not re-registering a product on a calendar. A file describes a product revision, so it stops describing the product when the revision changes, and maintaining it means keeping the tested and shipped revisions identical.
Next step
Send the configuration, the test results you already hold and the markets to Wecent Group through the contact page. The reply identifies which of the five failures the evidence suggests, states the measurement that confirms it and describes how the pre-scan is run before a submission is booked. Related reading: wireless charger applications, our charger factory and the factory floor. External references: WPC knowledge base, Wireless Power Consortium, IEC standards, EU EMC Directive 2014/30/EU, UL standards and certification and TUV testing services.
{“@context”:”https://schema.org”,”@type”:”FAQPage”,”mainEntity”:[{“@type”:”Question”,”name”:”Some suppliers say a wireless charger never fails EMC. Is that realistic?”,”acceptedAnswer”:{“@type”:”Answer”,”text”:”It is a claim about their products rather than about the category. A wireless charger is a switching product with a coil that radiates, so emissions are a normal part of its assessment and the margin depends on the design and the enclosure.”}},{“@type”:”Question”,”name”:”Can a failed submission be appealed?”,”acceptedAnswer”:{“@type”:”Answer”,”text”:”The result is a measurement against a limit, so the route is to change the design or the configuration and re-measure rather than to argue the figure. That is why a pre-scan before booking the submission is cheaper than a re-test afterwards.”}},{“@type”:”Question”,”name”:”Who pays for a re-test after a component substitution?”,”acceptedAnswer”:{“@type”:”Answer”,”text”:”It follows the agreement between the brand and the factory. Where the substitution was made to keep a production date, the commercial conversation is easier when the assessment requirement was written into the supply terms before the substitution happened.”}},{“@type”:”Question”,”name”:”Does the certification expire?”,”acceptedAnswer”:{“@type”:”Answer”,”text”:”A file describes a product revision, so it stops describing the product when that revision changes. Maintaining the file means keeping the tested revision and the shipped revision identical, not re-registering a product on a calendar.”}}]}