基于价电子理论的Ag-Sn金属间化合物形成机理  

Formation Mechanism of Ag-Sn Intermetallic Compounds Based on the Empirical Electron Theory

作　　者：马立民[1,2] 齐楚晗 王乙舒 MA Limin;QI Chuhan;WANG Yishu(College of Materials Science and Engineering,Beijing University of Technology,Beijing 100124,China;Key Laboratory of Advanced Functional Materials,Ministry of Education,Beijing University of Technology,Beijing 100124,China)

机构地区：[1]北京工业大学材料科学与工程学院,北京100124 [2]北京工业大学新型功能材料教育部重点实验室,北京100124

出　　处：《北京工业大学学报》2021年第6期655-662,共8页Journal of Beijing University of Technology

基　　金：北京市自然科学基金资助项目(2172006);北京市青年拔尖人才支持计划资助项目(CIT&TCD201804007)。

摘　　要：SnAgCu焊点中的金属间化合物(intermetallic compounds,IMCs)Ag_(3)Sn脆性大且电阻高,对焊点可靠性具有重要影响,有必要明确其形成过程和相变机制以控制其生长.采用固体与分子经验电子理论(empirical electron theory,EET)研究Ag-Sn系统中的主要扩散元素及原子运动路径,应用自洽键距差(self-consistent bond length difference,SCBLD)法计算了Ag-Sn系统内参与反应相的价电子结构及可能形成的固溶体的结合能,根据结合能变化趋势从价电子层面描述出Ag_(3)Sn在焊点内部的形成过程.研究结果表明:Ag-Sn系统中的主要扩散元素为Sn,Sn原子进入Ag晶胞形成固溶体,固溶体内原子重新排布,形成结合能更高、排布更均匀的共价键,造成晶格膨胀,位于(110)晶面和面心位置的Ag原子随之向外扩张,形成了同样具有良好对称性的Ag_(3)Sn,与前人研究Ag-Sn系统扩散的实验结果相符.Ag_(3)Sn in SnAgCu solder formed by Ag and Sn has a pivotal role in reliability of solder joints due to its brittle nature and high resistivity.Therefore,it is necessary to confirm the phase transformation process and mechanism of Ag_(3)Sn to control its growth.The domain diffusion element and atom movement pathway in Ag-Sn system was investigated by using the empirical electron theory(EET)of solids and molecules,which clearly described the formation of Ag_(3)Sn from the aspect of electron level.The valence electron structures of Ag,Sn,Ag_(3)Sn and probable solid solutions in Ag-Sn system have been calculated by self-consistent bond length difference(SCBLD)method.Results show that the domain diffusion element is Sn in Ag-Sn system.Sn atoms first come into Ag unit cell to form solid solution.Atoms in solid solution units rearrange to form new covalent bonds that have higher cohesive energy and well-distributed in units.The new covalent bonds cause lattice to expand,which leads to movement of Ag atoms in solid solution.Ag_(3)Sn with good symmetry forms,which verifies former studies about Ag-Sn system diffusion.

关 键 词：经验电子理论(EET) 相变 扩散 金属间化合物(IMCs) 自洽键距差(SCBLD)法 结合能 

分 类 号：TG401[金属学及工艺—焊接]