焦耳热作用下共晶锡铋焊点电迁移特性

电迁移可以引发芯片内部互连金属引线(单一元素)中的原子或离子沿电子运动方向移动.但是,在共晶锡铋焊点中,组成的元素为锡和铋而非单一元素.由于铋原子和锡原子在高电流密度下具有不同的迁移速率,因此共晶锡铋钎料具有独特的电迁移特性.实验中采用的电流密度为104A/cm2,同时焦耳热会引发焊点温度从25升高至49℃,富铋相在此温度下会发生明显粗化,除此之外,铋原子会首先到达正极界面处并形成坚硬的阻挡层,使得锡原子的定向运动受到阻碍,最终,富锡相会,凸起,其与负极界面问会有凹谷形成.

Effects of Joule Heating on the Electromigration Properties of Eutectic SnBi Solder Joints

Electromigration could induce the movement of atoms/ions towards the direction of electron flow in pure metal line in chips.However,in the eutectic SnBi solder joints,the constituted elements are Sn and Bi.Due to the different drift velocity of Bi atoms and Sn atoms under high current density,the electromigration properties of eutectic SnBi are unique.With a current density of 1E4A/cm2 and the Joule heating effect,the temperature of solder joints increased from 25 to 50℃,and the Bi-rich phases grew bigger during current stressing due to the high ambient temperature (49℃).In addition,Bi atoms initially arrived at the anode side and eventually formed a barrier layer to inhibit the movement of Sn atoms towards the anode side.Sn-rich phase bulged,and a valley formed along the interface at cathode side.