纳米相强化低Ag含量Sn-Ag-Zn系无铅焊点界面反应机理及可靠性的研究

In this project, a series of low Ag content Sn-Ag-Zn lead free solders were studied. the series of lead free solders have nanoscale enhancing particles, uniform and fine microstructure. their melting properties and mechanical properties are better than the SAC305 solder, and the lower cost. But due to the interfacial reaction, their wettability on Cu substrate is poor. At the other hand, Sn-Ag series lead free solder is easy to produce brittle interface during soldering of precious metal substrate, while the doping of Zn can inhibite the formation of brittle IMCs. But The usage of Sn-Ag-Zn solder on substrates other than Cu is rarely reported. Therefore, in this project, the interfacial reaction between the novel solders and various substrate materials, the relationships between the interfacial reaction and the wetability and the interfacial strength are researched. The interfacial reaction is controlled to improve the wettability and the interfacial strength. At last, the reliability test is introduced to study the practicability of the novel solder joints. Due to the complexity of microelectronic soldering, one or a series of lead-free solder can not meet all needs of the microelectronic manufacturing, the results of this project will provide more alternatives for the microelectronics manufacturing industry.

本课题以一组优化配比的低Ag含量Sn-Ag-Zn无铅焊料为研究目标，该系列焊料具有纳米尺度的增强颗粒、细致均匀的微观组织，其熔融性能和机械性能超过SAC305焊料，同时成本更低。但由于界面反应问题，该系列焊料与Cu焊盘的润湿性变差。另一方面，Sn-Ag系无铅焊料在焊接贵金属焊盘时容易产生脆性的焊点界面，而Zn的适当添加可抑制脆性IMC的生成，但关于Sn-Ag-Zn焊料在Cu以外的基板上的运用还鲜见报道。因此，本课题将系统研究新型焊料与各种焊盘材料的界面反应以及界面反应对润湿性和界面强度的影响，并且通过控制界面反应来提高焊料与基板的润湿性和界面强度，最后引入可靠性测试来研究新型焊点的实用性。由于微电子焊接的复杂性，一种或一类无铅焊料不可能满足所有微电子制造的需要，本研究的结果将为微电子制造行业提供更多的备选方案。

在本项目的前期研究中，本项目组研发出一种具有纳米相强化的Sn-Ag-Zn系无铅焊料。相比Sn-Ag-Cu无铅焊料，该新型焊料具有更好的力学性能和熔融性能，但是润湿性较差。本课题旨在改善Sn-Ag-Zn无铅焊料性能、提高可靠性、研究其强化机理和界面反应机理。研究主要包括下面三个方面：1、Sn-Ag-Zn-x焊料第四组元强化及强化机理的研究；2、Sn-Ag-Zn-x焊料与多种焊盘的焊点界面反应及对润湿性影响的研究； 3、Sn-Ag-Zn/Cu焊点可靠性试验。研究取得了一系列成果，其中主要成果有：1、明确了Sn-Ag-Zn焊料的强化机理和界面反应机理，成果汇集成为专著《低Ag含量Sn-Ag-Zn系无铅焊料》；2、发现Sn-Ag-Zn/Cu焊点抗电迁移能力远高于Sn-Ag-Cu/Cu焊点；3、发现Sn-Ag-Cu/Cu焊点中存在Sn的逆向电迁移和相关失效机理，这一发现对微电子领域有重要意义；4、发现Pr、Sm掺杂可全面提高Sn-58Bi焊料的综合性能。