Study On Insulation Breakdown And Electrical Aging Characteristics Of Printed Circuit Board Under Continuous Square Impulse Voltage

The insulation reliability level directly affects the safe and stable operation of the printed circuit board(PCB).With the high density,high integration and multi-function of electronic devices,the line width,line spacing and spacing between PCB interconnects become more and more subtle,which brings severe test to the PCB interline and interlayer insulation.On the other hand,PCB in avionics products always faces harsh environment such as electromagnetic radiation,high temperature,low pressure and so on.Therefore,it is necessary to further study the insulation characteristics of PCB,so as to provide some theoretical basis for insulation design and protection of PCB.The main contents are as follows:(1)This paper designed four PCB electrode models according to the actual insulation problems of PCB.The model includes PCB parallel interconnect model(model a),PCB interconnect corner model(model b),PCB interconnect and pad model(model c),and PCB adjacent layer interconnect orthogonal model(model d).Then,the simulation analysis of the four model are conducted by Ansys,the simulation results show that the model of the electric field distortion of a and d reached the maximum at the bottom angle of trapezoidal copper electrode film,and the distortion of the electric field in the model b appears at the angle of the electrode bottom at the corner of the electrode,what's more,the field intensity distortion at the edge of the weld plate in model c is obviously larger than the field strength of the electrode interconnects.(2)The short-time durability characteristics of PCB is studied,the results show that the breakdown voltage of model a,b,c,and d increase with the insulation distance and decreases with the pulse duty ratio,pulse repetition frequency.On the other hand,the breakdown voltage of model a,b and c decrease with the increase of temperature,and with the decrease of air pressure,the breakdown voltage of the three PCB models were first decreased and then increased,when repeat the test on same PCB,it still retains the insulation ability.The breakdown voltage of model d changes little with the increase of temperature at first and then decreases linearly.Moreover,the breakdown voltage does not change with the change of air pressure.After repeated breakdown test,the insulation capacity is basically lost after the first breakdown for model d.(3)The surface morphology after PCB breakdown is analyzed qualitatively and quantitatively by SEM and XPS.The analysis shows that the insulation breakdown between the electrodes of PCB electrode model a,b and c consists of two processes,which are the surface discharge and the carbonization of insulating polymers to form carbonization channel.The heat energy produced in the discharge process and the impact of electron emission will cut off the molecular chain of the PCB insulated polymer to a certain extent,and the accumulation of heat energy occupies the leading role.Moreover,the factors such as temperature,air pressure and electrode type have great influence on the breakdown of insulation between PCB electrodes.(4)The accelerated life test of the PCB electrode model a is carried out at standard atmospheric pressure and low pressure,respectively.In the statistical test,the failure data can well accord with the double parameter weibull distribution,then,the weibull characteristic failure time of PCB is obtained by the maximum likelihood estimation.Based on this,the Fallou,Ramu,and Crine life models of PCB are obtained through the multiple linear regression analysis.The experimental verification shows that the Fallou model has superior fitting performance to the insulation life of the electrode model a both at standard atmospheric pressure and low pressure.