有限晶粒Sn基微焊点组织遗传性及晶粒生长调控原位研究

With continuous downsizing of interconnection in advanced packaging technology, Sn-based micro solder joints may consist of a few number of Sn grains after soldering. The electrical, thermal and mechanical properties of the micro solder joints show a strong anisotropy, which play a significant effect on the service performance and reliability of packaging devices. Thus, effective structure control measures are needed to control grain orientation in micro solder joints. In doing so, based on the principle of structure heredity of metallic materials and our latest research findings on solidification behavior of micro solder joints, this project will study the structure heredity and grain growth control of Sn-based micro solder joints by using XAFS and X-ray real-time imaging technologies. The correlation between the local structure of liquid Sn-based solders and structure heredity will be established. Thus, the mechanism and rules of structure heredity of micro solder joints will be revealed. Then, the control mechanism on the preferred growth of Sn grains will be clarified from the viewpoint of the effect of temperature gradient on local structure. A relational model between the direction of temperature gradient and the c-axis of Sn grain will be established. Finally, the heredity of Sn grain orientation features in multiple soldering processes will be clarified. Therefore, the heredity of beneficial structure will be realized among different packaging levels. The research findings of this project will lay the theoretical and practical foundation for optimizing and developing interconnection technology of advanced packaging, improving the reliability of interconnects, and realizing beneficial structure control and heredity of Sn-based micro solder joints with limited Sn grains.

先进封装微互连尺寸持续减小，导致所用Sn基微焊点可能仅由数个Sn晶粒构成，微焊点的电、热及力学性能呈现强烈的各向异性，严重影响封装器件的服役性能与可靠性，亟需建立有效的组织调控手段以控制微焊点的晶粒取向。本项目基于金属材料组织遗传性基本原理，结合申请人在微焊点凝固行为研究方面的最新发现，拟利用同步辐射XAFS技术及实时成像技术，进行Sn基微焊点组织遗传及晶粒生长调控研究。探索液态Sn基钎料的局域结构与组织遗传之间的相关性问题，揭示Sn基微焊点组织遗传的机理与规律；阐明温度梯度影响局域结构来调控Sn晶粒择优生长的机制，建立温度梯度方向与Sn晶粒c轴的关系模型；明确多次钎焊过程中Sn基微焊点晶粒取向特征的遗传控制机制，实现有益取向特征在不同封装层次之间的遗传。研究成果将为优化和开发先进封装互连技术、提高互连可靠性、实现有限晶粒Sn基微焊点有益组织控制与遗传奠定理论和实践基础。

先进封装微互连尺寸持续减小，导致所用Sn基微焊点可能仅由数个Sn晶粒构成，微焊点的电、热及力学性能呈现强烈的各向异性，严重影响封装器件的服役性能与可靠性，亟需建立有效的组织调控手段以控制微焊点的晶粒取向。本项目首先研究了微焊点在多次回流过程中Sn晶粒取向的调控，获得了Sn晶粒取向具有遗传性的回流条件，包括回流温度区间、冷却速度以及保温时间，通过原位技术手段优化回流工艺，利用温度梯度获得的具有特殊SRO/MRO团簇结构的微焊点组织，在特定的回流条件下对后续多次回流过程中的微观组织和取向进行调控，获得具有特定择优取向的微焊点组织，实现在多次回流过程中Sn晶粒的择优生长控制，为开发高可靠性微互连焊点的制备技术提供理论和实践指导。同时，深入研究了(001)Cu/Sn/Cu、(011)Cu/Sn/Cu微焊点在温度梯度下冷端界面IMC的择优生长行为，揭示了在温度梯度下以及等温条件下单晶Cu基体上界面IMC形貌转变及取向保持机制，获得了界面IMC与单晶Cu基体的位向关系，阐明了冷、热端界面IMC生长动力学，建立了温度梯度下界面IMC择优生长模型，实现了对界面IMC晶粒取向的调控。研究成果将为优化和开发先进封装互连技术，提高互连可靠性，实现有限晶粒Sn基微焊点有益组织控制与遗传，改善微焊点各向异性等问题，奠定理论和实践基础。共发表学术论文11篇，其中SCI收录期刊论文6篇，EI收录国际学术会议论文5篇；授权中国发明专利7项；培养博士研究生毕业1名，在读博士研究生1人，硕士研究生毕业4人。