NDF means No Defect Found, that is, no defect found. This term is used when a product returns with a failure complaint, but does not show any evident defect in the tests performed. This scenario is often associated with false negatives, which occur when a test releases a defective unit without detecting it.
False negatives and NDFs are clear signs that the testing system is not capturing all real failures.
🧩 Common causes of NDFs and false negatives
| Cause | Technical explanation |
|---|---|
| Incomplete testing | The testing system does not cover all functions of the product |
| Environmental conditions | The failure only occurs at specific temperature, vibration, or humidity |
| Intermittency | Failure occurs in a random condition that is difficult to reproduce |
| Weak validation criteria | Wide tolerance or incorrect logic allows defective units to be released |
| DUT or operator error | Product poorly connected, improperly handled, or poorly tested |
⚠️ Impacts for the company
- Increase in rework and reverse logistics costs
- Difficulty in diagnosis and overload of repair centers
- Loss of customer trust and impact on brand image
- Lack of reliable data for continuous improvement and corrective actions
🔧 How AJOLLY Testing helps reduce NDFs and false negatives
AJOLLY Testing designs benches, sequences, and testing processes focusing on validation robustness, repeatability, and traceability, minimizing the chance of false negatives and NDF cases.
🛠️ Complete test coverage
- Functional verification of digital, analog signals, sensors, and communication
- Simulation of real use conditions (temperature, load, protocol)
- Creation of SILVER units to consistently repeat intermittent failures
📊 Advanced diagnostics
- Capture of execution logs with waveform, response, and time
- Integration with failure dashboards and DUT history
- Support for assisted manual test modes for technical debugging
📁 Validation and traceability
- Tests with validated repeatability (R&R) and statistical criteria (CPK, FPY)
- Recording by serial number and product revision
- Automatic alerts for failure recurrence or retest
With AJOLLY Testing, you transform NDFs and false negatives into actionable technical knowledge, improving quality, efficiency, and confidence in your process.