Study On Interaction Mechanism Of Dust Characteristic Parameters And Multi-Environmental Factors On Electrochemical Migration Of Circuit Board

With the development of miniaturization and integration of electronic devices,electrochemical migration(ECM)has become one of the factors that affect the insulation reliability of printed circuit boards(PCB).Dust affects the characteristics and mechanism of ECM by changing the surface humidity,temperature and electric field distribution of PCB.With the air pollution becoming more and more serious in China,dust has become an important factor affecting PCB insulation failure.Based on the extraction of the characteristic parameters of natural dust,the influence mechanism of dust and other environmental factors on ECM is studied,which plays a guiding role for PCB reliability research.The dust can be divided into two parts:soluble and insoluble.Sodium chloride is taken as the representative of soluble salt,and the concentration is taken as its characteristic parameter;quartz is taken as the representative of insoluble particles,and the covering density is taken as its characteristic parameter.Firstly,the insulation failure mechanism of insoluble particles coverage density on PCB surface was studied by dispersing particles and thermal humidity bias test,combined with the analysis of ECM dendrite morphology and element components detection.On this basis,the change of influence mechanism of insoluble particle coverage density on ECM in the presence of soluble salt pollution was studied.Then,the influence performance of soluble salt on ECM failure under the coverage of insoluble particles was studied.Finally,through two orthogonal experiments,influence significance and characteristics of two dust characteristic parameters,temperature,relative humidity and bias voltage on the ECM failure of PCB were studied.The research results show that the capillary adsorption of insoluble particles on water and the physical hindrance to the growth of dendrites are superimposed,which causes the time to failure(TTF)of ECM is firstly shortened and then prolonged with the increase of particle coverage density,and the turning point is 350μg/cm2.In the presence of high concentration of soluble salt,the water absorption capacity of soluble salt and the conductivity of solution are significantly enhanced,which is greater than the degree of hindrance of insoluble particles on the growth of dendrites under high coverage density,so that TTF presents a monotonically decreasing law of negative power function with the increase of particle coverage density.The water absorption and conductivity of soluble salts increase with the increase of concentration,resulting in a negative power function decrease of TTF.When insoluble particles are involved,different coverage density only affects the range of change of TTF.The interaction of dust characteristic parameters(insoluble particle coverage density,soluble salt concentration)and multiple environmental factors(temperature,relative humidity,bias voltage)shows that compared with the characteristic parameters of soluble salt concentration and insoluble particle coverage density of dust accumulated for about 3 years,high temperature,high humidity and high bias voltage have a greater impact on the ECM failure of PCB.But in the normal temperature and humidity environment,the effect of natural dust cannot be ignored.Under the combined action of five factors,TTF showed a first decrease and then increase relationship with 350μg/cm2 as turning point as the increase of insoluble particle coverage density.However,soluble salt concentration and simulated natural dust pollution all show a negative power function trend of TTF,indicating that trace amount of soluble salt plays a significant role in dust pollution.