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Aiming at the problem of solder joint intermittent fault reproduction, an intermittent fault reproduction method based on sweep frequency vibration test is proposed. Firstly, the dynamic model is constructed for intermittent fault mechanism analysis, and the environmental factors that affect intermittent faults are obtained. Then, sweep frequency vibration test is used to perform intermittent fault reproduction, and intermittent fault signals are obtained for intermittent fault detection.

For intermittent fault diagnosis, it is important to extract fault features. An intermittent fault feature extraction method based on wavelet transform is proposed. Firstly, the stress-intensity model is used to describe the fault process of intermittent faults, analysing the main part of intermittent fault signal characteristics. Considering the randomness and suddenness of intermittent faults, wavelet transform is used to extract intermittent fault features based on the advantages of wavelet transform in signal mutation and singularity detection. By extracting signal energy through the wavelet coefficients, intermittent fault features are obtained, which can be used to identify and isolate the intermittent faults. Finally, by a simulating circuit, transient intermittent fault response characteristics are obtained by simulation in the circuit, and the features are extracted by wavelet transform for the intermittent fault location. Results show that the intermittent fault features can be extracted by the wavelet transform, and the features can be used for intermittent fault diagnosis.

Aiming at intermittent fault detection problem that caused by solder joint under vibration stress, induced mechanism of solder joint intermittent fault is analysed and the detection method of solder joint intermittent fault number is studied. Firstly, theoretical analysis of the solder joint intermittent connection fault under vibration stress is conducted. Relationships between vibration stress parameters and intermittent faults are described. Dynamic characteristics of the solder joint are interaction between contact interface and vibration stress. However, within a finite time, dynamic parameter amplitude does not depend on the contact interface morphology, and the contact resistance is proportional to the acceleration, displacement and frequency. Next, the detection of solder joint intermittent connection fault is studied. Stimulus signal is selected and a detection algorithm is proposed. A continuous monitoring circuit detects the intermittent fault and DSP processor calculates the number of intermittent faults. Finally, a case study is conducted and a circuit board is used to test the intermittent fault detection method. Voltage change is detected by oscilloscope and the described method simultaneously. Test result shows the number of intermittent faults can be recorded correctly.

For the crack intermittency detection in circuit board, a detection method based on time domain reflectometry is proposed. And a time domain signal feature is extracted, the time domain signal feature is highly sensitive to the defect. Firstly, in order to analyze the change trend of time domain signal under intermittent disconnection. The influence of conductor crack on the physical parameters is analyzed. The physical parameters include AC/DC resistance, inductance and capacitance. And then the principle of signal reflection is described. The ringing phenomenon that caused by signal reflection is used for crack intermittency detection. Therefore the maximum, minimum and peak-peak values of time domain signal are used to detect intermittent disconnection. At last solder joint equivalent circuit is used to verify the effectiveness of the method. When the intermittent disconnection happened in circuit board, the time domain reflection phenomenon is observed clearly. The maximum, minimum and the peak-peak values of output voltage signal are changed greatly, simulation result shows that the high frequency signal is sensitive to intermittent disconnection, and the proposed method is effective.

To study the failure modes that can't be injected in the testability test, an equivalent fault selection method is presented in the paper. The principle and types of the equivalent fault in testability test are explained according to the characteristics of fault propagation. By introducing switch element in the fault-test dependency model, an equivalent fault analytical model is formed. The method was applied to select equivalent fault injection sample in testability test. The effects of fault injection between equivalent fault and original fault were compared and the method of equivalent fault selection is proved to be feasible.