Atmospheric Corrosion Behavior And Mechanism Of Tin Under External Electric Field

The corrosion of electronic materials is not only a key issue in the reliability of electronic systems,but also a fundamental problem of corrosion science under the coupling effect of electricity and electrochemistry.Withrapid development of electronic industry,the miniaturization of electronic components continuously increases,the distance of electronic components further reduces,electronic materials become thinner,electric field gradient gets greater,which makes electronic components more sensitive to corrosion.Tin andits alloys are important electronic interconnect materials,so the study of tin corrosion mechanism is of significant practical meaning and theoretical value.Based on the array electrode technology,the atmospheric corrosion behavior of pure tin in the applied electric field was studied by electrochemical method and SEM/EDS characterization.The main research work and results are as follows:1.The effect of direct current electric field?DCEF?on the tin corrosion behavior has been studied.In the same direct current electric field,the corrosion rate near the positive plate is the largest.This can be explained as follows:Firstly,since the pH of thin electrolyte layer?TEL?near the positive plate is acidic,the oxide film on tin surface can be dissolved.Secondly,aggressive Cl^-ions gather in the positive plate,accelerating the destruction of oxide film on tin surface.Thirdly,tin ions(Sn²⁺and Sn⁴⁺),produced in the corrosion processes,can migrate out from the tin surface.Under these three combined effects,the corrosion rate of tin near the positive plate is the largest.The corrosion rate in the middle of DCEF is the least.This can be explained as follows:OH^-ions,produced by the reduction reaction in the cathode,migrate to the positive plate under the electrode field.Tin ions,produced by the anodic dissolution,migrate towards negative plate.Consequently,they meet in the intermediate position and form tin hydroxide depositing at the surface of tin electrode,which hinders the corrosion processes.The corrosion rate of tin near the negative plate is lower than that of tin near the positive plate,and faster than that of tin in the middle of DCEF.This can be ascribed to the fact that OH^-ions restrain the cathodic process of corrosionand Sn?OH?₄ can be dissolved in the alkaline environment.From positive plate to negative plate,the corrosion potential shifts negatively.This can be attributed to the restrain of cathodic process of corrosion caused by OH^-produced in the negative plate of DCEF.In addition,under DCEF,the corrosion rate increases with the increase of the electric field intensity,and the corrosion potential negatively shifts.The increase of the corrosion rate of tin may be explained by the fact that with the increase of the intensity of the DCEF,the acidity of TEL near the positive plate increases,the removal of the corrosion product accelerates and the Cl^-ions aggregation intensifies.With the increasing electric field,the positive shift of the tin corrosion potential may be attributed to the significant acceleration of the tin cathodic process.2.The effect of alternating current electric field?ACEF?on the tin corrosion behavior has been studied.Under alternating current electric field,the corrosion potential shifts positively because ACEF plays a dominant role in the cathodic process.The situation of the square wave electric field is more obvious,which indicates that the square wave electric field is more obvious for the cathodic process.the corrosion extent of tin under square wave electric field is more severe than that under sinusoidal wave electric field,which can be explained that the duration under the maximum disturbance potential for the square wave ACEF is longer than that for the sinusoidal wave ACEF.The corrosion rate of tin separately increases with increasing amplitude and frequency of ACEF.When the amplitude is constant,the higher the frequency,the greater the disturbance effect of the ACEF on the system,resulting in the greater the degree of damage to the oxide film.When the frequency is constant,the larger the amplitude,the greater the leakage current,and leakage current can destruct the integrity of surface oxide film.Under ACEF,the contribution of leakage current to tin corrosion rateis much greater than that of electric field gradient.Electric field gradient merely accelerates the migration of ions,while leakage current not only accelerates the migration of ions,but also causes the damage and dissolution of tin surface film.3.The effect of bias in different electric fields on the tin corrosion behavior has been studied.In the same electric field,the corrosion rate of tin increases with increasing bias voltage.This could be explained that increasing bias voltage promotes the anodic dissolution of tin.Under the same bias voltage,the corrosion rate of tin in the space electric field is greater than that of tin in the electric field,because the presence of leakage current promotes the corrosion of tin.Under the same bias voltage,the order of tin corrosion rate in the different electric field is as follows,square wave ACEF>sinusoidal wave ACEF>DCEF>blank.This can be explained that the value of leakage current is different in the different electric field,and the order of leakage current in the different electric field is as follows,square wave ACEF>sinusoidal wave ACEF>DCEF>blank.In the different electric field,the contribution of leakage current to tin corrosion rate is much greater than that of electric field gradient.Electric field gradient merely accelerates the migration of ions,while leakage current not only accelerates the migration of ions,but also causes the damage and dissolution of tin surface film.The contribution of the electric field gradient to the corrosion rate in the DCEF is larger than that of ACEF,which is attributed to the directional migration of ions in the DCEF.