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

技术：焊接接头，作为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组合下扩展。因此，跌落只是作为一种混合模式，高加载速率断裂测试预开裂焊点。因此，获得焊点断裂韧性数据至关重要，不仅可以预测使用过程中的生存能力，还可以作为设计参数，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将进行一个全面的实验计划，以产生基本的机械洞察的作用，几个微观结构和测试变量的快速加载条件下的焊点断裂。这项研究的结果将是通过更好地控制加工、微观结构和几何参数，设计在跌落条件下具有更大断裂韧性的微电子焊点的能力。另一项成果将是将通过这项工作制定的实验方法转让给工业界。这项工作将产生新的微观结构对动态断裂的作用机理的见解，是有史以来第一次研究快速加载条件下的焊点断裂力学的实质性的根本重要性。其次，通过生成重要焊点系统的断裂韧性数据，并将测试方法转移到工业中，这项工作将具有实际意义。第三，这项工作将具有很高的技术意义，通过开发断裂机制图，这可以被用于设计和可靠性评估的新类型的连接方案，因为它们是开发，以满足新兴的芯片/封装互连架构。非技术性：随着日常生活中移动的电子产品的激增（例如，蜂窝电话、个人数字助理、MP3播放器和手持计算机），电子封装在跌落条件下承受冲击载荷的能力已经成为最重要的可靠性问题。这项工作更广泛的影响在于它与移动的电子设备的可靠性的技术相关性，这些设备几乎涉及现代生活的所有方面，并且是整个微系统行业当前感兴趣的主题。在整个项目中，PI将与GOALI合作伙伴（INTEL）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将聘请暑期高中学生实习生通过当地的丰富计划在项目上工作，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的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.