Failure Mechanism of Electromigration in Solder Joint
In advanced electronic products,electromigration-induced failure is one of the mostserious problems in fine pitch flip chip solder joints because the design rule in devices requires highcurrent density through small solder joints for high performance and miniaturization.The failuremode induced by electromigration in the flip chip solder joint is unique,owing to the loss of underbump metallurgy (UBM) and the interfacial void formation at the cathode contact interface.In thisstudy,Electromigration of flip chip solder joints has been investigated under a constant density of2.45×104 A/cm2 at 120℃.The in-situ marker displacements during the electromigration test wasmeasured and found to show a rough linear change as a function of time.Scanning electronmicroscopic images of the cross section of samples showed the existence of voids at the interfacebetween Al interconnection and under bump metallurgy.The void movement was matched with themarker displacements during the electromigration test,and voids moved to the cathode interfacebetween Al interconnection and under bump metallurgy in the downward electron flow (from chip tosubstrate) joint.The mechanism of electromigration-induced void migration and failure in the flipchip are discussed.During electromigration,a flux of atoms is driven from the cathode to the anode ora flux of vacancies in the opposite direction.It can lead to two possible mechanisms of voidmigration.First,if we regard the void as a rigid marker of diffusion,it will be displaced towards thecathode by the atomic flux in the electromigration,Second,if we consider surface diffusion on thevoid surface,electromigration will drive atoms on the top surface of the void to the bottom surface ofthe void,and consequently the void will move towards the cathode.
solder joint flip chip electromigration current crowding
Y.D, Lu X.Q.He Y.F.En X.Wang
Key Laboratory of Specially Functional Materials,Ministry of Education,College of Materials Science National Key Laboratory for Reliability Physics and Its Application Technology of Electrical Compone Key Laboratory of Specially Functional Materials,Ministry of Education,College of Materials Science
国际会议
成都
英文
2008-08-04（万方平台首次上网日期，不代表论文的发表时间）