Qi2 Wireless-Charging Coil BOM: Resonance, Ferrite and EMI-Control Components

Meta description: Build a Qi2 wireless-charging coil BOM with the coil, ferrite, resonance capacitors and EMI controls matched to your mechanical stack-up and certification plan.

TL;DR: A Qi2 wireless-charging coil is not a standalone commodity. Its electrical behavior is set by the coil geometry, ferrite, resonance capacitors, shielding, alignment, enclosure stack-up and control design. Source the matched assembly around your target power, available area and certification plan; do not substitute only by coil diameter or inductance label.

Qi2 has turned a familiar accessory category—chargers, stands, battery packs, in-car mounts and desk products—into a more disciplined BOM problem. The Wireless Power Consortium describes Qi v2.0 as including a Magnetic Power Profile (MPP), so magnetic alignment becomes part of both the user experience and the engineering stack-up (WPC announcement).

For buyers and hardware teams, the real question is: can we source a coil, ferrite and resonant network that behaves correctly inside our finished mechanical assembly? The answer is never guaranteed by an isolated coil sample.

Contents

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1. Why the coil BOM must be designed as a system
2. The six variables that alter performance
3. A practical RFQ and alternate-approval workflow
4. What Qi2 certification does—and does not—mean
5. FAQ

Why the coil BOM must be designed as a system

A wireless-power receiver or transmitter relies on magnetic coupling between coils. The surrounding ferrite shapes the magnetic field and can reduce unwanted coupling into nearby metal; the resonance capacitors tune the network; shielding and EMI parts help manage noise; and the controller supervises communication, foreign-object detection and power transfer.

Murata’s noise-suppression example for wireless-power modules discusses the receiver coil together with series/parallel capacitors and shows suppression measures on coil, supply and ground paths (Murata). TDK also supplies WPC/Qi-compliant transmitter coil modules, a useful reminder that a qualified assembly is more than wound copper (TDK).

That is why sourcing begins with the system envelope, not a photo of a round coil.

The six variables that alter coil performance

1. Coil geometry and inductance

Outer diameter, inner diameter, turns, conductor construction and inductance affect coupling and resonant design. A coil that physically fits may still shift the intended resonant point or produce a different field pattern.

2. Ferrite and nearby metal

Ferrite thickness, material and position influence coupling, loss and heating. A steel back plate, battery, camera assembly or decorative metal ring can change the behavior dramatically. Keep the final stack-up in the validation plan.

3. Resonance capacitors

The capacitor value, tolerance, AC stress, dielectric stability and ESR are part of the tuned power path. Replacing a capacitor from “same µF” stock without considering those parameters can move resonance and raise temperature. Use the controller/reference-design guidance, then validate at expected alignment and load conditions.

4. Alignment and gap

Magnetic alignment can improve the repeatability of user placement, but it does not remove all tolerance. Coil-to-coil gap, off-axis position, case thickness and magnet arrangement affect coupling and thermal behavior. Engineering discussions about long-distance Qi modifications repeatedly return to distance, alignment and heat as the limiting practical variables (discussion).

5. EMI and protection components

Ferrite beads, common-mode control, decoupling and transient protection must suit the actual noise path. Do not add parts simply because another charger uses them: their placement and value are coupled to the layout and controller.

6. Thermal path and materials

Losses appear in the coil, ferrite, resonant network, switching stage and nearby metal. Include ambient temperature, case materials, adhesive, gap and allowable surface temperature in qualification. A coil that runs cool on an open bench can be unacceptable in a thin enclosed mount.

A Qi2 wireless-charging coil RFQ that works

Provide these fields:

• Receiver or transmitter role; target Qi/Qi2 profile and certification objective
• Target power range, controller MPN and reference design if available
• Coil drawing: outer/inner dimensions, height, lead length, connector and allowed keep-outs
• Mechanical stack-up: case thickness, ferrite area, nearby metal, magnet arrangement and maximum air gap
• Required inductance/tolerance and matching capacitor requirements
• Temperature, quantity, date-code and traceability requirements
• Whether a prequalified coil module or a custom assembly is acceptable

This prevents a supplier from quoting a physically similar but electrically unsuitable coil. It also enables a transparent answer when an exact part is unavailable: a candidate can be marked “engineering sample needed,” not mislabeled as drop-in.

Certification is a system outcome

The WPC’s Qi2 announcement describes the certification rollout and the MPP architecture; it does not mean every magnetic-looking charger, coil or accessory is Qi2 certified. Certification depends on the specified system, including the relevant controller/implementation and test process. Do not advertise a finished product as Qi2 certified until the applicable program has confirmed it.

Likewise, a coil supplier’s Qi/WPC-compliant module can be a strong starting point, but the final product still needs the proper electrical, thermal, EMC and certification review. Make that boundary explicit in supplier and marketing communications.

Frequently asked questions

Can I replace a Qi2 charging coil with one of the same diameter?

Not safely without validation. Diameter alone does not define inductance, Q, field distribution, lead arrangement, ferrite interaction or resonant-network compatibility. Compare the mechanical drawing and electrical data, then validate the alternate in the completed stack-up and controller design.

Does magnetic alignment guarantee the same charging result for every phone?

No. Alignment improves repeatability, but phone geometry, case thickness, coil position, power negotiation, thermal protection and the charger implementation still affect performance. Validate representative devices and use only claims supported by your actual product test and certification status.

What should an independent distributor verify for a coil assembly?

For an exact MPN, request manufacturer identity, drawing, lot/date code, packaging and any stated compliance documents. For an alternate, provide the candidate’s full electrical/mechanical data and mark it as requiring customer engineering approval; a distributor should not imply Qi2 certification from appearance or magnet presence.

Conclusion: source the stack-up, not just the coil

Qi2 wireless-charging coil sourcing is a system task: the coil, ferrite, resonant capacitors, EMI parts, controller and mechanical stack-up must work together. Put those constraints in the RFQ, retain documentation and validate alternates in the final product. That is the shortest route to a stable, defensible charger BOM.

Have a Qi2 charger, stand or in-car mount BOM to quote? Send Cosolvic your coil envelope, target power and controller details. We can help source specified components and present documented candidates clearly for engineering review.

Related reading

• Power-inductor miniaturization: Murata and TDK guide
• MLCC capacitor sourcing guide
• How to prepare a BOM for quotation

For parts headed into production, who verifies them before they ship matters as much as the part itself. How Cosolvic operates covers our inspection process, counterfeit refund policy, and why we work as an independent distributor rather than a franchise reseller.

Sources

• Wireless Power Consortium: Qi v2.0 / Qi2 certification announcement, accessed July 25, 2026.
• TDK: WPC/Qi transmitter coil modules, accessed July 25, 2026.
• Murata: Noise suppression for wireless-power-supply modules, accessed July 25, 2026.

Editorial quality check

• Direct answer, systems-level decision checklist, RFQ tool, FAQ and CTA: Pass.
• Avoids asserting certification, phone compatibility or power performance without system evidence: Pass.
• Primary keyword placement and source coverage: Pass.