应用于先进电子封装的低熔点高熵合金焊料焊接性与可靠性研究

Nowadays, the electronic packaging technology is becoming highly complicated and integrated to satisfy the demanding requirements on the performance of electronic products from the customers. According to the trend, the development of materials in electronic packaging is facing some challenges, for example, the control of intermetallic compound thickness in microbumps and the substrate warpage issue in huge packages. These issues will be relieved by the low reflow temperature. This project proposes to apply high entropy alloy (HEA) as low melting point solder so as to get a low reflow temperature. The melting point of HEA with different components will be studied and the relation between them will be explained. To apply the HEA as a solder, the wetting ability will also be studied. Moreover, the intermetallic compound growth kinetics will be studied after HEA reacts with Cu substrate in the reflow and the entropy effect on the pre-factor in Arrhenius equation will be made clear. Finally, reliability tests, including the electromigration test will be done. The effect of sluggish diffusion in HEA on the diffusion of atoms during reliability tests will be investigated. Based on the research of these topics, the HEA that can be applied to electronic packaging industry will be selected. This research can provide a solution to the challenges that will be faced in advance packaging technology.

芯片封装技术正通过复杂化、高集成化来满足消费者对于电子产品性能日益苛刻的要求。这带给封装相关的材料科学一系列挑战，如焊点小型化过程中微凸点的金属间化合物生长动力学控制以及大尺寸封装翘曲度问题等。本项目提出采用低熔点高熵合金作为低温焊料，从而降低回流焊接时的温度来解决上述挑战性问题。本项目将系统研究不同组分的高熵合金和熔点之间的关系，研究其作为低温焊料的焊接性能，探寻高熵合金组分和结构及其熔点和焊接性能之间的科学关联。更进一步，研究高熵合金对金属间化合物反应动力学的影响，明确高熵合金在回流过程中的“熵变”对阿伦尼乌斯公式指前因子的作用。最后通过电迁移等可靠性测试，研究高熵合金扩散迟缓效应对电迁移的影响。通过对这些科学问题的研究，筛选出适用于封装工业焊接用的低温焊料，为先进封装所面临的问题和挑战提供一种解决途径。

本项目制备出以SnBiIn为主体的一系列高熵低温焊料，完成了焊料焊接性能的研究，并深入研究了高熵效应对金属间化合物生成速率的影响。高熵低温焊料展示出有利于焊接可靠性的独特性质，如超低的金属间化合物生长速率，良好的润湿性等。在此基础上，本项目通过大规模收集多元共晶数据，利用机器学习筛选出一系列四元共晶，成功设计并制备出低温共晶高熵合金。此外，本项目成功探索出适用于该低温共晶高熵合金的生产工艺，此种创新性制备颗粒的工艺技术，可以打破目前工业界焊膏颗粒尺寸5至15微米的束缚，实现超小粒径均匀光滑焊膏颗粒的制备，成功研发出有产业化前景的低温焊接技术。在本项目基础上，申请人开始尝试推广该技术在大尺寸高性能芯片生产制造中的产业化。