Mechanical Shock and Vibration Fatigue Behavior of Environmentally-Benign PB-Free Solders in Electronic Packaging

技术：随着人们越来越重视开发环保的电子封装，无铅合金受到了极大的关注。这些合金的机械性能非常重要，因为焊点必须在热机械疲劳、蠕变、机械冲击和振动疲劳下保持其机械完整性。后者已成为行业中日益严重的问题。相对较低的循环应力可以应用于电子封装，特别是在汽车和飞机应用中，这会导致等温疲劳。与这个问题有关的基本问题很少受到注意。迄今为止，对机械冲击的理解主要是经验性的。典型的测试包括从给定的高度将模块掉落在地面上，并测量电阻和定性外观以确定组件是否失效。在机械冲击期间，对包装中的应力和应变状态的理解基本上是不存在的。此外，金属间化合物厚度和焊料组织对机械冲击和振动疲劳的影响还没有得到真正的研究。迫切需要一种模拟机械冲击下应力状态的方法。pi将对Sn-3.5 ag -0.7 cu和Sn- ag焊料的机械冲击和振动疲劳行为进行深入的研究和分析，并与纯Sn焊料进行比较。该计划将：(i)使用一种新颖、复杂的系统来量化机械冲击和振动疲劳行为，该系统能够在单个和多个焊点以及批量焊点上应用逼真且可控的应变速率（10/s或更高）；（ii）使用高速相机和数字图像相关（DIC），通过聚焦离子束（FIB）微加工的基准标记，测量小长度焊点的应变分布和演变；（iii）了解焊料/接头界面金属间厚度和焊料微观结构与机械冲击和振动疲劳抗力之间的关系；（iv）在机械冲击和振动过程中建立焊点变形模型，使用多尺度数值技术，以获得对焊料变形的微观结构和几何影响的基本理解。非技术：由于这些材料的环保性质，无铅焊料非常重要。该研究项目将对无铅焊料的机械冲击和振动疲劳损伤有深入的了解。它还将为半导体行业提供对这些材料的高应变率变形的定量理解。该研究项目将包括大学和工业之间的大量互动。虽然在过去的几年里，对士兵的研究已经得到了广泛的开展，但对这一领域学生的教育却没有得到同样的重视。一个综合教育推广计划，结合：(a)对新硕士发展的贡献？在亚利桑那州立大学的电子封装计划，(b)面向学生的项目活动，和(c)工业推广，计划。

TECHNICAL: With the increasing focus on developing environmentally-benign electronic packages, Pb-free alloys have received a great deal of attention. The mechanical behavior of these alloys is extremely important because solder joints must retain their mechanical integrity under thermo-mechanical fatigue, creep, and mechanical shock and vibration fatigue. The latter has become an increasing problem in the industry. Relatively low cyclic stresses may be applied to electronic packages, particularly in automotive and aircraft applications, which results in isothermal fatigue. Fundamental issues related to this problem have received very little attention. To date, the understanding of mechanical shock is largely empirical. Typical testing involves dropping the modules on the ground, from a given height, and measuring the electrical resistance and qualitative appearance to determine whether the component has failed. An understanding of the stress and strain state in the package during mechanical shock is largely non-existent. Furthermore, the role of intermetallic thickness and solder microstructure on mechanical shock and vibration fatigue has not really been examined. A methodology for modeling the stress state under mechanical shock is urgently required. PIs will conduct a thorough study and analysis of the mechanical shock and vibration fatigue behavior of Sn-3.5Ag-0.7Cu and Sn-Ag solders with a comparison to pure Sn. The program will: (i) quantify the mechanical shock and vibration fatigue behavior using a novel, sophisticated system that enables application of realistic and controlled strain rates (10/s or higher) on single and multiple solder joints, as well as bulk solder, (ii) measure the strain distribution and evolution in a small-length scale solder joint, with fiducial marks micromachined by Focused Ion Beam (FIB), using a high speed camera and digital image correlation (DIC), (iii) understand the relationships between intermetallic thickness at the solder/joint interface and solder microstructure with mechanical shock and vibration fatigue resistance, (iv) model deformation of solder joints during mechanical shock and vibration, using multi-scale numerical techniques, to obtain a fundamental understanding of microstructural and geometric effects on solder deformation. NON-TECHNICAL: Pb-free solders are of importance because of the environmentally-benign nature of these materials. The research program will yield a thorough understanding of mechanical shock and vibration fatigue damage in Pb-free solders. It will also provide the semiconductor industry with a quantitative understanding of high strain rate deformation in these materials. The research program will include substantial interaction between university and industry. While research on solders has been extensive over the last several years, education of students in this area has not received the same attention. An integrated education outreach program that combines: (a) contributions to the development of a new Master?s in Electronic Packaging Program at ASU, (b) project-oriented activities for students, and (c) industrial outreach, is planned.