关键词: 封装技术, Cu/SAC305焊点, 扩散, 金属间化合物, 化学亲和力, 分子动力学模拟

Abstract: 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 1.04×10⁴ A/cm² 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.

Key words: packaging technology, Cu/SAC305 solder joint, diffusion, intermetallic compound, chemical affinity, molecular dynamic simulation