EAGER: Fracture of Microelectronic Lead Free Solder Joints under Dynamic Loading Conditions

技术摘要：随着移动电子产品在日常生活中的普及，电子封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。因此，焊料在高应变速率下的断裂行为是一个至关重要的设计参数。提出了一种动态条件下弹塑性粘接接头混合模态断裂韧性测试方法。进一步提出，该方法可用于对焊点断裂的几个微观组织/工艺和测试变量的作用产生基本的机制见解，包括焊垫光面、老化、界面金属间结构、应变速率、模态混合和电迁移效应的影响。通过开发一种新的动态关节断裂测试方法，这项工作将具有重要的技术意义，最终将转移到工业中。其次，这项工作将对微观结构在动态断裂中的作用产生新的机制见解，并通过开发断裂机制图，可用于设计新兴芯片/封装互连架构的新连接方案具有重要的基础意义。移动电子产品，如pda， MP3播放器和超便携笔记本电脑在使用过程中经常掉落，因此以稳健的方式构建构成系统大脑的电子封装非常重要。构成这些封装重要部分的微小焊点在跌落条件下极易断裂，因此，高应变率下焊点的断裂行为是一个至关重要的设计参数。在提出的工作中，将开发一种新的方法，用于在跌落条件下对焊点进行断裂测试，并用于获得有关如何设计高度坚固可靠的无铅焊点的知识，这些焊点将比现有的焊点更耐跌落。这将导致更可靠的电子产品和更长的使用寿命。

TECHNICAL ABSTRACTWith the proliferation of mobile electronics in everyday life, the ability of electronic packages to sustain impact loading under drop conditions has become a paramount reliability concern. Therefore, the fracture behavior of solders at high strain rates is a critically important design parameter. A new methodology is proposed for mixed-mode fracture toughness testing of elasto-plastic adhesive joints under dynamic conditions. It is further proposed that this methodology be used to generate fundamental mechanistic insight into the role of several microstructural/process and test variables on the fracture of solder joints, including the effects of solder pad finish, aging, interfacial intermetallic structure, strain rate, mode-mixity and electromigration effects. The work will be of substantial technological importance by developing a new dynamic joint fracture testing methodology which will be eventually transferred to industry. Secondly, the work will be of substantial fundamental importance in generating new mechanistic insights into the role of microstructure on dynamic fracture, and by developing fracture mechanism maps that can be utilized in the design of new joining schemes for emerging chip/package interconnection architectures.NON-TECHNICAL ABSTRACTMobile electronics such as PDAs, MP3 players and ultra-portable laptops are often dropped during use, making it important to build the electronic packages which constitute the brains of the system in a robust fashion. The tiny solder joints that constitute an important part of these packages are highly susceptible to fracture under drop conditions, and therefore, the fracture behavior of solders at high strain rates is a critically important design parameter. In the proposed work a new methodology will be developed for fracture testing of solder joints under drop conditions, and used to gain knowledge about how to design highly robust and reliable lead-free solder joints which will be much more resistant to drops than those currently available. This will lead to more reliable electronics with longer usable lifetimes.