基于分子动力学的Cu3Sn/Cu界面元素扩散行为数值模拟

文中采用修正的嵌入原子势函数(modified embedded atomic method, MEAM)的分子动力学模拟，研究了无铅焊点中Cu3Sn/Cu界面元素的扩散过程，对界面元素的扩散行为进行了分析计算，获得了界面各元素的扩散激活能，根据元素扩散的经验公式得出界面过渡区的厚度表达式. 结果表明, 扩散过程中主要是铜晶格中Cu原子向Cu3Sn晶格中扩散. 其中，铜晶格内原子以较慢的速率扩散，但可以深入Cu3Sn晶格内部，Cu3Sn中原子以较快的速率扩散，但难以进入铜晶格内部. 结合阿伦尼乌斯关系和爱因斯坦扩散定律，计算得到界面处铜晶格原子的扩散激活能为172.76 kJ/mol，界面处Cu3Sn晶格中Cu原子扩散激活能为52.48 kJ/mol，Sn原子扩散激活能为77.86 kJ/mol.

Numerical simulation of diffusion behavior of Cu3Sn/Cu interface based on molecular dynamics

In this paper, the diffusion process of Cu3Sn/Cu interface in lead free solder joints was investigated using molecular dynamics (MD) technique with the modified embedded atomic method (MEAM) potentials. The diffusion behavior of different atoms was analyzed and the diffusion activation energies was obtained. In addition, the thickness of diffusion transition zone was acquired based on the empirical equation of diffusion. The simulation results indicate that the Cu atoms predominantly diffuse into the Cu3Sn side in the process of diffusion. The Cu atoms diffuse slowly but deeply diffuse into the interior of Cu3Sn, whereas the atoms of Cu3Sn diffuse with high rate but hardly diffuse into the interior of Cu. Based on the Arrhenius relation and equation of Einstein, the diffusion activation energies of Cu lattice atoms at interface is 172.76 kJ/mol, and the Cu and Sn atoms in Cu3Sn lattice are 52.48 and 77.86 kJ/mol, respectively.