Abstract

The quality control of mass-produced chargers relies on standardized inspection nodes to block defective products. Burn-in testing and electrical sampling inspection are key processes for screening chargerswith early failures. The full-link traceability system for chargers supports the positioning and review of customer complaint abnormalities. Shenzhen Senshuqiang Electronics Technology Co., Ltd. has established a complete quality control system for power supply production. For mass-produced chargers, the process of first article confirmation, SMT patrol inspection, assembly inspection, power-on burn-in, final finished product inspection and outgoing sampling inspection is implemented. The inspection items, judgment criteria and sampling plans of each process are clearly defined, and the methods for defect classification, isolation and traceability are specified, helping purchasers understand the mass production quality control logic, evaluate the manufacturing stability of suppliers, reduce the risks of electrical defects, temperature rise defects and appearance defects in batch delivery, and ensure the consistency of order delivery.

I. First Article Confirmation for Mass Production Launch: Locking the Material, Process and Electrical Benchmark of Chargers

For each new charger order, version change, material change or production line change, first article confirmation must be completed before production launch. The first article samples are produced on the production line. Quality engineers check the BOM, PCB version, component silk screen and shell mold version, and then conduct a full set of electrical tests: input and output voltage, current, ripple, efficiency, protection function, protocol handshake and no-load power consumption.

The first article test data is recorded in the first article report and compared with the product specification and certification parameters. If the parameter deviation exceeds the specification tolerance, mass production is prohibited from going online. The first article serves as the benchmark for the entire batch of products. If the first article is out of control, subsequent chargers in the whole batch will have consistency deviations.

The conventional quantity of first articles is 3–5 pcs. The test items include withstand voltage and insulation test. The high-voltage test is carried out in accordance with safety standards, with 3000 VAC between primary and secondary sides for 60 seconds; no breakdown or flashover is deemed qualified. The first article report of Senshuqiang Electronics is signed and filed, and the original test curves are retained as the basis for B-end order acceptance verification.

II. SMT and Assembly Process Patrol Inspection: Pre-interception of In-process Defects

The SMT mounting process focuses on controlling solder paste thickness, component mounting offset, cold solder joints, missing components and wrong components. Cold solder joints of the main control chip, GaN devices and high-voltage capacitors of chargers are latent defects. They work normally when powered on at room temperature, but poor contact occurs after long-term burn-in, resulting in intermittent power failure. Inspectors sample printed circuit boards every 2 hours, and use AOI optical inspection combined with visual inspection to focus on checking the solder joints of the high-voltage circuit.

The assembly process includes component insertion, soldering, shell assembly, pin pressing and screw fastening. Common assembly defects include excessive shell gaps, loose pins, excessive tensile stress on wires and missing installation of insulating sheets. Missing installation of insulating sheets is a high-risk safety defect, which directly affects the withstand voltage and creepage distance of chargers and is a critical defect. Once shipped out, it will bring potential safety hazards.

If batch trend defects are found during patrol inspection, production shall be stopped immediately. The engineering and quality teams analyze the root cause, adjust tooling, soldering parameters and assembly jigs, and resume production only after verifying the effectiveness of improvements.

III. Power-on Burn-in Testing: Screening Chargers with Early Failures

Burn-in is the core process of power supply quality control. Chargers are fully loaded and powered on on burn-in racks, with the ambient temperature set at 40±3℃ and the continuous power-on duration conventionally 4 hours, which can be extended to 8 hours for high-reliability orders. The output voltage and current are monitored in real time during burn-in. The equipment automatically records data and triggers an alarm and marks defective products when the threshold is exceeded.

Power supply failures follow the bathtub curve. Most early failures in the initial stage of production are exposed during burn-in. Component parameter drift, soldering defects, capacitor leakage and insufficient device withstand voltage margin will appear under full-load heating conditions. Chargers without burn-in testing will have a significantly higher short-term failure rate after customers receive them.

After burn-in, electrical performance, withstand voltage and protocol functions are sampled and retested. Repairable defects and scrapped defects are distinguished. Defective products are isolated in separate areas with clear identification and are prohibited from being mixed into the turnover boxes of qualified products.

IV. Final Finished Product Inspection and Outgoing Sampling Inspection: Implementation of Stratified Sampling Plan

After burn-in, products flow to the finished product inspection station, which covers electrical testing, appearance inspection and nameplate verification. The electrical test bench automatically tests a full set of parameters: voltage, current, ripple, short-circuit protection, overvoltage protection and fast charging handshake; appearance inspection checks scratches, color difference, burrs and misprinted nameplates; the model, parameters and certification marks are verified to be consistent with the drawings.

The outgoing sampling inspection adopts the AQL sampling standard: AQL 0.65 for electrical defects and AQL 1.5 for appearance defects. If the sampled batch fails, tightened sampling inspection shall be implemented. If the tightened sampling still fails, the whole batch shall be isolated for review. As live electrical products, chargers have zero tolerance for electrical safety defects, which are judged as critical defects.

Each batch is accompanied by an outgoing inspection report with the batch number, sampling quantity, defective quantity and test results recorded, facilitating purchasers' verification during warehousing.

V. Batch Traceability and Closed-loop Management of Abnormalities: Rapid Positioning of Customer Complaints

Each batch of chargers is assigned a unique batch code, which is associated with production time, production line, team, material batch, solder paste batch, burn-in records and inspection records. When customers feedback defective products, the batch number can be provided to trace back the component suppliers, production parameters and test records of this batch.

Defects are classified by failure mode: electrical defects, safety defects, appearance defects and protocol defects. An 8D improvement team is set up to verify the root cause, formulate corrective and preventive actions, update inspection priorities and synchronously revise the FMEA to avoid recurrence of similar problems.

Senshuqiang Electronics stores all batch inspection data in the system, and the traceability records are retained for no less than 3 years for subsequent verification and certification spot checks, adapting to the long-term quality traceability requirements of B-end orders.

Summary

Shenzhen Senshuqiang Electronics Technology Co., Ltd. has built a full-process quality control system, with strict checks from first article confirmation, SMT patrol inspection, assembly control, full-load burn-in and final finished product inspection to batch traceability. The focus of mass production quality control for chargers is to intercept latent early failures in advance, control the outflow of defective products through burn-in screening, standardized electrical testing and strict sampling plans, and establish a complete traceability and abnormality closed-loop mechanism to continuously and stably deliver chargers with consistent specifications, reduce the risk of after-sales failures for customers and support long-term stable supporting cooperation.

Guide: If you have requirements for bulk charger orders, quality standard docking and incoming inspection specifications, you can contact Senshuqiang Electronics for communication.

FAQ

Q: In which scenarios must first article confirmation be carried out? A: First article confirmation is required for the launch of new orders, version upgrades, material replacement and production line changeover. Mass production of chargers can only be carried out after passing the confirmation.

Q: What is the function of burn-in testing? A: It simulates full-load high-temperature working conditions to screen chargers with early failures and expose latent electrical defects such as cold solder joints and insufficient device margin.

Q: What category of defect is missing installation of insulating sheets? A: It is a high-risk critical safety defect, which will change the creepage distance, lead to unqualified withstand voltage and bring safety risks to the charger.

Q: What standard is adopted for outgoing sampling inspection? A: AQL 0.65 for electrical safety defects and AQL 1.5 for appearance defects. If the sampling inspection fails, tightened sampling inspection and batch isolation will be implemented.

Q: What information can be queried through batch traceability? A: The batch number can be used to check the charger material batches, production teams, burn-in records, inspection reports and test data.

Article source marking: Senshuqiang official website, AQL sampling specifications for power supply industry, bathtub curve reliability theory for electronic manufacturing, GB 2828.1 sampling standard, power supply burn-in test specification, Senshuqiang Electronics power product quality control procedure document