Cu/SAC305/Cu焊点界面Ag和Sn扩散差异性研究

Study on the Diffusion Difference of Ag and Sn at Cu/SAC305/Cu Solder Joint Interface

电子元器件不断向小型化发展,电流密度也随之增大,因此焊点中的电迁移问题日益严重。电迁移现象的本质是元素扩散,为解决该问题并提升焊点的可靠性,必须深入研究焊点中的元素扩散过程。焊点通电时伴随着焦耳热,因此需综合考虑电效应和热效应。为解耦电迁移过程中的电流效应和热效应,分别进行了电流密度为1.04×10^(4)A/cm^(2)、温度为120℃的通电测试以及120℃下的热扩散测试。实验结果显示,两种条件下Cu基体内Ag和Sn扩散行为存在差异,并且观察到了Cu_(6)Sn_(5)金属间化合物(IMC)。从化学亲和力的角度计算发现,Cu-Sn的化学亲和力约为Cu-Ag的4倍,这表明Cu-Sn间更容易发生化学反应,从而阻碍Sn在Cu基体中的扩散。最后,通过分子动力学模拟得出,DAg/DSn比值为2.788~7.386。

As electronic components continue to move towards miniaturization and current density increases,the problem of electromigration in solder joints is becoming more and more serious.The essence of electromigration is diffusion of elements.To address this issue and enhance the reliability of solder joints,it is necessary to deeply study diffusion process of elements in solder joints.When the solder joint is energized,Joule heating occurs,so it is necessary to consider both electrical effect and thermal effect comprehensively.In order to decouple the current effect and thermal effect during electromigration process,electrical tests are conducted at a current density of 1.04×10^(4)A/cm^(2)and a temperature of 120℃,as well as thermal diffusion tests at 120℃.Experimental results show that there are differences in the diffusion behavior of Ag and Sn in Cu matrix under two conditions,and Cu6Sn5 intermetallic compound(IMC)has been observed.From the perspective of chemical affinity,it is found that the chemical affinity of Cu-Sn is about 4 times that of Cu-Ag,which indicates that the chemical reaction between Cu-Sn is more likely to occur,thus preventing the diffusion of Sn in the Cu matrix.Finally,the D_(Ag)/D_(Sn) ratios range from 2.788 to 7.386 by molecular dynamics simulations.