AuSn20共晶电沉积中锡可控析出的配体作用机制及设计原则

During AuSn20 eutectic soldering, its melting point will greatly increase, when tin doped quantity is under 20 wt%. It will lead to packaging failure.In this project, the AuSn20 eutectic will be prepared by electrodeposition. The effect of Au(I) and Sn(II) complex structure on electrochemical overpotential will be investigated in the process. In addition, the kinetic characteristics on gold and tin generation processes will be obtained. On the basis of above research, the complexes crystal suiting for AuSn20 electrodeposition will be synthesized by hydro-thermal method. The structure and molecular orbital characteristic of weak Au(I)-strong Sn(II) type complex will be analyzed by single crystallogram and density functional theory on the molecular level. The relationship between ligands structure and kinetic will be discussed. Finally, the ligands screening model for AuSn20 electrodeposion will be built. Furthermore, the effect of electrostatic field on molecular orbital characteristic will be considered. The purpose is to adjust the ligands screening model for the presence of electrostatic field. Finally, the new weak Au(I)-strong Sn(II) type complex will be designed according to screening model. Then, a highly efficient complex system will be explored. It will be applied to quantitative control tin doping amount in 20 wt% in the alloy. Those research approach can make up for the current deficiency of complexing agent screening depending on experience, which obtained by single electrochemical method. The project can enrich the preparation method for AuSn20 eutectic and research approach for composition quantitative control. It can provide theoretical foundation and technical support for alloy material electrodepositon engineering. Undoubtedly, it has important theoretical significance and actual value.

AuSn20共晶钎焊过程中，锡含量低于20wt%，其熔点将显著升高,导致封装失效。本项目采用电化学沉积法制备AuSn20共晶，通过研究合金析出过程中，Au(I)和Sn(II)配合物构型对电化学极化的影响，获得合金组分析出的宏观动力学特征。在此基础上，利用水热法合成适合AuSn20沉积的配合物晶体，结合单晶衍射和密度泛函手段，从分子角度定量分析弱Au(I)强Sn(II)型配合物的分子轨道特征，阐明配体结构与微观动力学间的构效关系，建立配体筛选模型。同时，研究电场存在下配合物分子轨道的变化规律，校正筛选模型。据此，设计出新型配体，开发高效的络合体系，达到控制合金中锡含量20wt%。这一研究方法弥补了目前络合剂筛选以经验为主体，单纯依托电化学研究存在的缺陷。本项目可以丰富和发展AuSn20共晶的制备方法和成分控制的研究方法，具有重要的理论意义和实际价值。

AuSn20是目前稳定性最高的，导热性最好的，不需要助焊剂的高可靠特殊焊料。课题组针对AuSn20.共晶展开一系列研究工作。由于EAu与ESn两者偏差较高，课题组通过电沉积的方式获得了AuSn20共晶。课题组研究如何通过络合剂拉低ESn与EAu相互匹配，从而形成共沉积。从工程角度来说，实现了AuSn20的三个指定，分别在指定位置上，获得指定含量和指定厚度的AuSn20共晶，并实现工业化。课题组将AuSn20共晶中的锡去除，获得纳米多孔金结构，是目前的超材料所使用的重要材料，可用于传感器电极使用。目前已针对此问题发表了9篇SCI文章。.课题组通过加入焦磷酸型配体，可实现将ESn拉负，与EAu共沉积，通过量化化学模拟拉负情况，从而实现金锡共沉积的溶液体系的筛选。获得的金锡比例在金含量78%-82wt%，熔点范围低于300℃。通过去合金法，获得了纳米多孔金材料结构，孔洞尺寸可控制在80nm-100nm之间，可作为传感器电极使用。.目前课题组已经实现以下成果：两种电位不同的金属实现共沉积，并从理论上证明通过络合剂加入大幅度改变沉积电位的方法可行。金锡重量比例80:20可以实现共沉积，可获得的AuSn和Au5Sn复合的共晶材料。去合金后可获得纳米多孔金的结构，这种超材料结构可用于电催化，传感器，水电解等多个领域。.本项目丰富和发展了AuSn20共晶和多孔金的制备方法和成分控制的研究方法，具有重要的理论意义和实际价值。