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PCBA defect analysis process typically includes five stages: sample reception and registration, visual inspection, electrical performance testing, failure analysis, and reporting and documentation. This article briefly introduces the general process of PCBA failure analysis, hoping to be helpful to everyone.
1. Sample Reception and Registration
1. Record the date of receipt of the defective product, product model, batch number, and other key information;
2. Take clear and complete photos of both sides of the PCBA;
3. Confirm and record the reasons for the return and the failure phenomena, the quantity of similar defective products, and the failure scenarios (including whether the failure is consistent, conditions for failure occurrence, user usage duration, etc.).
2. Visual Inspection
The purpose of the visual inspection is to check for any subjective abnormalities in the PCBA, facilitating further testing and analysis.
This step mainly checks for any collision marks, contamination, board damage, water stains, component bulging, localized yellowing of the substrate, and other subjective abnormalities on both sides of the PCBA. If abnormalities are found:
1. Mark the points of subjective abnormalities and take close-up photos for records;
2. If there are collision marks or contamination, further analyze the causes of the defective collision marks or contamination;
3. Analyze whether the failure at the collision marks or contamination points in the circuit will lead to failure phenomena;
4. After completing the records, sampling (especially for contaminants), and failure analysis, repair the collision marks and contamination points.
3. Electrical Performance Testing
1. Use a multimeter to preliminarily check whether the static parameters at key points are abnormal:
a. For subjective abnormalities such as board damage, burning, or contamination, focus on testing whether the related circuits are abnormal;
b. If static parameters are abnormal, especially in the case of a short circuit, the cause must be identified and repaired before proceeding to the next analysis step;
2. Check whether the voltage at each interface is normal without load, and whether there are any abnormalities or fault codes:
a. If there are no abnormalities in the above steps, check whether the voltage at each interface is within the normal range, and whether there is any smoke, unusual sounds, or fault codes;
b. If there is smoke or unusual sounds, power off immediately and further investigate the corresponding circuit.
3. Check whether each key output and function is normal under load:
a. If there are still no abnormalities in the previous step or after troubleshooting, power on with load to further check whether each output and function is normal;
b. If there are abnormalities, further test the static and dynamic parameters (voltage, current, waveform, etc.) of the related circuits.
4. Check whether there is poor contact by applying a certain amount of impact vibration to the sample board.
If no problems are found in the above checks, apply a certain amount of impact vibration to the sample board under power with load:
a. The purpose of this is to check whether the PCBA has poor soldering, assembly, or micro-cracks in the PCB traces that may cause contact issues;
b. If there are still no abnormalities, run the defective product under power for an extended period and then check again with impact, and if necessary, perform repeated power cycling tests;
c. If there are still no abnormalities, for collision marks and contaminated boards, the failure can be attributed to the collision marks or contamination causing the failure;
d. If the defective sample shows no subjective issues and repeated tests of all functions show no abnormalities, it can be confirmed that the product is a false positive.
4. Failure Analysis
1. If abnormalities are found during the investigation:
a. If it is found that a component has failed, replace the suspected component and perform cross-validation;
b. If the customer requires only non-destructive analysis, and conditions permit, use X-Ray, ultrasonic microscope, high-power magnifying glass, infrared thermometer, etc., to further pinpoint the failure point;
c. Investigate the cause of component failure (including incoming materials, processes, design, production, extreme testing, etc.);
d. If necessary, consult the manufacturer of the failed component for professional support;
e. If necessary, send the failed component back to the original manufacturer for analysis;
f. If necessary, further organize testing and verification based on the analysis results;
g. Formulate closed-loop measures.
2. If the above investigation still cannot find the cause of the defect, consider whether it is caused by a software issue:
a. Check whether there are any abnormalities in the software reading related register data;
b. Rewrite the program and power on again to observe whether the function is OK;
c. Investigate the reasons for software loss or anomalies;
d. Formulate closed-loop measures.
5. Documentation and Reporting
a. If only failure data needs to be recorded, the model, batch number, defect phenomena, failure reasons, and other key data must be recorded clearly for future reference and understanding;
b. If it is a response analysis report, the report should reflect professionalism and rigor, with objective statements, clear organization, accurate data, logical rigor, and well-supported conclusions. The analysis summary in the report should be persuasive, and the countermeasures should be effective and feasible.