GOALI: Effects of Processing and Microstructure on the Fracture Properties of Microelectronic Lead Free Solder Joints under Dynamic Loading Conditions

技术：焊点是封装中的机械和电气互连，在跌落过程中特别容易发生故障。因此，焊料在高应变率下的断裂行为是一个至关重要的设计参数。大多数手持设备在使用过程中都会经历热机械循环，因此焊点很可能存在低周疲劳裂纹，这些裂纹在拉伸和剪切载荷的共同作用下扩展。因此，在预裂焊点上，液滴只是一种混合模式、高加载率的断裂测试。因此，获得焊点的断裂韧性数据至关重要，不仅可以预测焊点在使用过程中的生存能力，而且还可以作为设计参数，可以通过材料和工艺参数进行调整，以提高寿命。在这项工作中，PI将进行一项全面的实验计划，以产生对快速加载条件下几个微观结构和测试变量对焊点断裂的作用的基本力学见解。这项研究的结果将是通过更好地控制工艺、微观结构和几何参数，设计出在跌落条件下具有更高断裂韧性的微电子焊点。另一个结果将是将通过这项工作开发的实验方法转移到该行业。这项工作将对微观结构对动态断裂的作用产生新的力学见解具有重要的基础意义，这是第一次研究快速加载条件下焊点的断裂力学。其次，通过生成重要焊点系统的断裂韧性数据，并将测试方法传递给行业，这项工作将具有实际意义。第三，这项工作将具有高技术意义，通过开发断裂机制图，可以用于新型连接方案的设计和可靠性评估，因为它们是为了满足新兴的芯片/封装互连体系结构而开发的。非技术性：随着移动电子产品在日常生活中的普及(如移动电话、个人数字助理、mp3播放器和手持计算机)，电子包装在跌落条件下承受冲击载荷的能力已成为最重要的可靠性问题。这项工作的更广泛影响在于其与移动电子设备可靠性的技术相关性，移动电子设备几乎涉及现代生活的方方面面，并且是整个微系统行业当前非常感兴趣的话题。在整个项目中，PI将与其Goali合作伙伴(英特尔)以及飞思卡尔半导体密切合作，以确定/解决新出现的相关问题。除了培训研究生和博士后，PI还将通过当地的充实计划聘请夏季高中生实习生参与该项目，并聘请高中/中学科学教师在夏季在他们的实验室工作，并协助他们开发与本研究一般领域相关的课程模块。

TECHNICAL: Solder a joint, which serve as mechanical and electrical interconnects in a package, are particularly prone to failure during a drop. Therefore the fracture behavior of solders at high strain rates is a critically important design parameter. Most handheld devices undergo thermo-mechanical cycling during service, and therefore, solder joints are likely to have existing low-cycle fatigue cracks, which propagate under a combination of tensile and shear loading. Therefore, a drop simply serves as a mixed mode, high loading rate fracture test on a pre-cracked solder joint. Hence it is critical to obtain fracture toughness data on solder joints, not only to predict survivability during service, but also to serve as a design parameter which may be adjusted through material and process parameters to improve life. In this work, PIs will conduct a comprehensive experimental plan to generate fundamental mechanistic insight into the role of several microstructural and test variables on the fracture of solder joints under rapid loading conditions. The outcome of this study will be the ability to design microelectronic solder joints with greater fracture toughness under drop conditions via better control of processing, microstructural and geometrical parameters. An additional outcome will be the transfer of experimental approaches developed through this work to the industry. The work will be of substantial fundamental importance in generating new mechanistic insights into the role of microstructure on dynamic fracture, being the first-ever study of fracture mechanics of solder joints under rapid loading conditions. Secondly, the work will be of practical importance by generating fracture toughness data on important solder joint systems, and by transferring the testing methodologies to the industry. Thirdly, the work will be of high technological significance by developing fracture mechanism maps, which can be utilized in the design and reliability assessment of new types of joining schemes as they are developed to meet emerging chip/package interconnection architectures. NON-TECHNICAL: With the proliferation of mobile electronics in everyday life (e.g., cellular phones, personal digital assistants, mp3 players and handheld computers), the ability of electronic packages to sustain impact loading under drop conditions has become a paramount reliability concern. The broader impact of the work lies in its technological relevance to the reliability of mobile electronic devices that touch upon nearly all facets of modern life, and is a topic of substantial current interest to the entire micro-systems industry. Throughout the project, PIs will work closely with their GOALI partner (INTEL) as well as Freescale Semiconductor to identify/address issues of emerging relevance. In addition to training graduate students and post-docs, PIs will hire summer high school student interns to work on the project through a local enrichment program, and hire high/middle school science teachers to work in their laboratory during summer and assist them in developing lesson modules relevant to the general area of this research.