In the PCBA manufacturing process, testing is a critical component of quality control. However, in actual production, false positive results are not uncommon. False positives not only delay delivery schedules, increase rework costs, but may also lead to incorrect handling of good products, thereby reducing production efficiency. Therefore, optimising the PCBA testing process and reducing false positive rates are key measures for manufacturers to enhance their quality management standards.
1、Analysis of Common Causes of False Positives and False Negatives in Testing
False positives (classifying good products as defective) and false negatives (classifying defective products as good) are the two main types of false results in testing. The causes of these false results include:
Poor contact of test fixtures: Insufficient probe spring force, positional deviation, or severe oxidation can lead to inaccurate measurements;
Incomplete test program logic: Unreasonable test logic settings that ignore the product’s normal tolerance range;
Unstable testing conditions: fluctuations in voltage, temperature, or equipment status can cause inconsistent test results;
Inexperienced operators: incorrect execution of test steps or misinterpretation of test prompts.
If these issues are not optimised and prevented, they will directly impact the yield rate and shipment quality of PCBA manufacturing.
2、Reasonably designing test program logic
The test program is the core of the judgement criteria, and whether the program logic is scientifically set directly determines the false positive rate. When writing test scripts, it is essential to thoroughly understand product characteristics to avoid ‘one-size-fits-all’ judgement criteria.
It is recommended to establish independent test processes and standards for different functional modules, such as communication, analogue, digital, and power modules, which should be tested separately. Numerical judgements should set upper and lower limit ranges rather than absolute values, while retaining raw test data for subsequent analysis and correction.
3、Optimise fixture structure and contact materials
Test fixtures are the most common source of false positives in physical contact processes. To reduce false positives, select probe materials with high durability, low resistance, and stable elasticity. Customise probe layouts based on product characteristics to ensure uniform contact and accurate positioning.
Additionally, fixtures should be regularly cleaned and maintained, especially for high-frequency workstations in mass production. It is recommended to clean or replace probes after producing a certain batch to ensure contact reliability.
4、Enhance the stability of the test environment
PCBA testing processes have certain environmental requirements. Factors such as temperature, humidity, and unstable power supply voltage can all affect test results. To reduce misjudgments caused by external interference, it is recommended to control the temperature and humidity of the test area, use a regulated power supply, and provide good anti-static and anti-interference protection measures for the test workstations.
For RF or high-frequency signal testing, it is even more important to consider the construction of a shielded environment to eliminate external signal interference on the results.
5、Strengthen personnel training and anomaly identification capabilities
Even the most comprehensive testing process relies on the correct execution by operators. Training should cover testing steps, identification of common anomalies, and equipment alarm logic to enhance frontline personnel’s understanding of testing results.
Additionally, an experience data analysis system can be introduced. When a product consistently displays the same error message, the system can alert that it may be due to fixture issues or parameter misconfiguration, helping personnel quickly determine if it is a misjudgment and reduce losses caused by human error.
The testing process in PCBA manufacturing is not static but should be continuously optimised as product complexity increases and customer quality requirements rise. By reasonably designing test procedures, upgrading fixture structures, stabilising test environments, and strengthening personnel training, not only can misjudgment rates be effectively reduced, but overall test efficiency and customer satisfaction can also be improved. Continuously optimising the test process is a long-term effort that every PCBA manufacturing company striving for high-quality delivery must invest in. Only by doing so can a company stand out in intense market competition and win more trust and cooperation opportunities.
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