Research On The Failure Mechanism And Reliability Of Electrical Contacts At High Frequency

Connectors,playing a connecting role,are the basic component of the communication system,which are widely used in various fields,including aerospace,new energy vehicles,communication and data transmission,medical treatment,and so on.In the wake of development in 5G,6G technology,and the increase of frequency and signal transmission rate,the connectors should meet higher demands in terms of performance and quality.Of particular interest are applications where the connectors are often exposed to the atmospheric environment or operated in other complex and severe circumstances,which degrade the contact surface by contamination or corrosion,resulting in low reliability and deteriorated performance.This poses new requirements and challenges to the environmental adaptability and reliability of connectors.The failure mechanism and reliability of electrical contact for high frequency are investigated in the thesis.The research is composed of four contents,including the impacts of electrical contact failure on the features of time and frequency domains,the effects of electrical contact failure on signal transmission,the characteristics of electromagnetic radiation caused by electrical contact failure,and the prediction of reliability under different environmental stresses for connectors,which are implemented with the methods of the combination of theoretical modeling,simulation,and experimental testing.The investigation explores a series of reliability problems caused by electrical contact failure from the comprehensive multi-level perspective.The study results provide a reference for the selection and optimal design of radio frequency connector,and also could be used in the other components with electrical contact parts.The research provides important theoretical and practical application value.The main contributions and innovations of this thesis are as follows:1.The relationship between the electrical contact failure characteristics and macroscopic time and frequency domain parameters was established from the point of microscopic failure physics and equivalent circuit model,and the effects of contact surface performance degradation on the radio frequency signal transmission were investigated.An equivalent circuit model with a degraded contact surface was developed based on the structure,size,material,and other characteristics of the actual faulty connector.An accelerated testing method was designed to obtain the faulty connectors samples with different degradation levels.The micro-morphology features of the connector contact surfaces with different degradation degrees were analyzed,and the generation mechanism each parameter in the equivalent circuit model was explored.The results of reflected voltage and the impedance in the time domain,the transmission impedance and scattering parameters in the frequency domain were measured using the network analyzer,respectively.Simulation studies for fresh and degraded connectors were conducted,combined with the experimental results to analyze the effect of the contact surface degradation on the parameters in the time and frequency domains.2.The influence mechanism of electrical contact failure on analog and digital modulation signals was revealed from the perspective of signal transmission.Based on the mechanism of electrical contact failure and transmission line theory,the equivalent models of the degraded contact surface and the faulty connector were developed.The approaches of theoretical modeling and circuit simulation were used to explore the impact of contact degradation on the time domain waveform and phase for the AM and FM signals,the bit error rate,and error vector amplitude for QPSK,?/4-DQPSK signals,respectively.The accelerated testing was performed to obtain degraded connector samples.A measured platform consisting of a signal source and an oscilloscope was built to test the output waveforms.The experimental results are agreement with the simulation results.Moreover,the impact mechanism and influence regularities of contact degradation on the signal transmission are explored from the view of theory and measurement.3.The electromagnetic leakage signal caused by contact failure was investigated from the perspective of the electromagnetic field,and the relation model between the contact failure features and the electromagnetic radiation characteristics of the interconnected device was established.An equivalent model was developed to analyze the impact of contact failure on high frequency parameters.Meanwhile,the inner conductor of the connector was modeled as the leakage source,and the radiated electromagnetic field generated by the leakage source in the time domain was derived according to the actual physical size of the connector and the tensor calculation method.Combining with the transfer function of the near-field probe,the analytical expression of the electromagnetic leakage signal was obtained.The mechanism of electromagnetic leakage caused by loose contact was explained from the view of theoretical calculation and experimental test.A near-field probe was used to measure the leakage signal caused by loose contact.The measured results for a specific loose contact condition were consistent with the theoretical analysis.The results elaborated that the approaches of theoretical modeling and experimental test can better explain the electromagnetic radiation mechanism caused by electrical contact failure.4.A performance prediction method suitable for evaluating the reliability of electrical connectors was proposed based on the failure mechanism of electrical contacts.The behavior degradation parameters,including contact resistance and high frequency scattering parameters,were selected to evaluate the reliability of the connectors.For the lifetime prediction,considering the influence of multiple stresses of temperature and particle concentration for the first time,the reliability was conducted.The uniform design method was adopted to design the accelerated testing plan and then conduct the testing.The contact resistance values were measured,which were applied to estimate the unknown parameters in the reliability function.The reliable lifetime of the connectors under the multiple environment stresses including temperature and particulate contamination could be predicted for electrical connectors.For the prediction of high frequency characteristics,the high frequency scattering parameters of slight and severe degradation levels were selected as the training and testing data.The prediction of connector parameters at high frequency under different degradation levels was conducted using the BP and Elman neural network algorithm.MSE was adopted as the criteria for prediction accuracy,and the accuracy of two neural networks were compared.