QUALITY INCIDENT ANALYSIS REPORT

Report Number: QA-2026-087
Product: Wireless Charging Module (Model WC-5W)
Customer: Confidential (Consumer Electronics Brand)
Date: September 2, 2026
Prepared By: Quality Engineering Team
Classification: Critical – Customer Escalation

1. Incident Summary

This report documents the investigation into elevated failure rates of wireless charging modules (Model WC-5W) supplied to a consumer electronics brand for integration into TWS (True Wireless Stereo) charging cases.

Failure Rate Data:

Customer Complaint Trend:

Observation: The failure rate increased significantly in Q1 2026, with Batch C showing the highest failure rate at 16.0%.

2. Customer Complaint Analysis

Returned units were received and categorized by failure mode. The categories were determined through preliminary analysis of returned units and customer descriptions.

The most common failure mode is "no charging" (36%), followed by "intermittent charging" (27%) and "overheating" (15%). These three failure modes account for 78% of all returned units.

3. Root Cause Investigation Methodology

The investigation was conducted using a structured approach:

1. Product teardown: 50 returned units from Batch C (highest failure rate) were disassembled and examined.

2. Component-level testing: Individual components were tested: coils, ferrite shields, ICs, and PCB assemblies.

3. Process review: The manufacturer's production and testing processes were reviewed.

4. Supplier audit: The ferrite shield supplier was audited.

5. Comparative analysis: Batches A-D were compared to identify variation.

4. Findings

4.1 Teardown Findings

Examination of 50 returned units revealed the following issues:

Note: Multiple issues were present in some units.

4.2 Coil Wire Fracture Analysis

The coil wire fracture was identified as a mechanical fatigue failure. The fracture occurred at the junction where the coil wire is soldered to the PCB. Under microscopic examination, the fracture surface showed characteristic fatigue striations.

Root Cause: The coil wire was under tension during assembly. The tension was caused by the wire routing path through the module housing. When the module was installed in the end product, the tension increased, leading to fatigue cracking during normal use.

4.3 Ferrite Shield Cracking Analysis

The ferrite shield showed cracking in 18 of the 50 returned units. The ferrite material is a sintered ceramic. Cracking occurred during the module assembly process when the shield was inserted into the housing.

Root Cause: The ferrite shield dimensions were out of tolerance. The shield was 0.15mm larger than the specification, causing interference during insertion. The interference led to cracking. The cracked ferrite shield could not maintain the required magnetic field alignment, leading to charging failure.

4.4 Supplier Ferrite Shield Audit

The ferrite shield supplier (Supplier F, Guangdong) was audited on August 20, 2026. The audit revealed:

Conclusion: The ferrite shield supplier lacks adequate process control. The dimensional variation is the root cause of the cracking issue.

4.5 IC Damage and Solder Joint Analysis

IC damage was observed in 10 units. In all cases, the damage was consistent with electrical overstress (EOS). The IC had failed due to voltage spikes during charging.

Root Cause: The module's input protection circuit was not present on the PCB. A design change in Batch B had removed a transient voltage suppression (TVS) diode as a cost-reduction measure. The TVS diode was not required in the laboratory test environment but was required in the field. Without the TVS diode, voltage spikes from the charging source damaged the IC.

5. Root Cause Summary

6. Corrective Action Plan

7. Supplier Response

The manufacturer has accepted the findings and agrees to implement the corrective actions described in Section 6. A follow-up audit is scheduled for October 15, 2026, to verify implementation.

Manufacturer Statement:

"We acknowledge the quality issues identified in the WC-5W module. We accept responsibility and will implement the corrective actions as proposed. We will provide regular updates to the customer on our progress."

8. Recommendations for Buyer

Based on this investigation, the following recommendations are made to the buyer:

1. Retain design review authority: The design change that removed the TVS diode was made without the buyer's approval. Require that all design changes be submitted for customer approval before implementation.

2. Audit secondary suppliers: The ferrite shield supplier was not audited by the buyer. Include secondary suppliers in the audit schedule.

3. Require process control data: Require the manufacturer to provide SPC data for critical dimensions (coil routing tension, ferrite shield tolerance, solder temperature).

4. Implement incoming inspection: Test a sample of each batch for coil wire integrity and ferrite shield integrity before accepting the batch.

5. Verify corrective actions: Conduct a follow-up audit of the manufacturer's corrective actions before releasing new orders.

9. Summary

The 12.7% failure rate across four batches is attributed to multiple factors:

1. Design deficiency: Removal of the TVS diode caused IC failure under field conditions.

2. Supplier quality: Dimensional variation in the ferrite shield caused cracking during assembly.

3. Assembly process: Coil wire tension and cold solder joints contributed to field failures.

The corrective actions described in this report address all identified root causes. Implementation is expected to reduce the failure rate to < 2% by Q4 2026.

Report Prepared By:

Emily Zhang, Senior Quality Engineer
September 2, 2026

Reviewed By:

David Park, Quality Manager
September 3, 2026

Approved By:

Mark Roberts, VP of Operations
September 4, 2026

This report is confidential and for internal use only. Distribution to third parties is prohibited without the written consent of the Quality Department.

Customer complaints increased 340% in Q2 2026. An internal investigation identified the root cause. Full analysis and co

Wireless charging module failure rate: 12.7% across four batches. Customer complaints up 340%. Internal investigation report with root cause and corrective actions.

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