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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,其与负极界面间会有凹谷形成.
Electromigration can cause atoms or ions in the metal interconnects (single elements) within the chip to move in the direction of electron motion, but the eutectic tin-bismuth solder joints consist of tin and bismuth rather than a single element.Because bismuth Atom and tin atoms have different migration rates at high current density, so eutectic tin bismuth solder has unique electromigration characteristics. The current density used in the experiment is 104 A / cm2, while Joule heat will cause the solder joint temperature to rise from 25 In addition, the bismuth atoms reach the positive electrode interface first and form a hard barrier layer, which hinders the directional movement of the tin atoms. At last, Tin rich phase will be raised, with the negative electrode interface will have a valley between the formation.