GOALI - The Effect of Changing to Pb Free Solders on Manufacturing Processes: Evolution of Solder Joint Microstructure

这个GOALI项目是与通用仪器公司合作的，旨在研究向无铅焊料过渡将如何影响电子封装的制造过程。焊点可靠性的综合处理至少需要三个主要的研究工作：(1)对焊点微观结构（晶粒尺寸/结构、相区、金属间化合物）的基本理解，包括在任何给定的热历史中任何给定时间预测微观结构的能力。(2)发展本构关系，量化变形特性作为温度、应变速率和详细微观结构的函数。(3)开发损伤函数，量化给定温度、应变/应力（或其综合函数，如延性耗尽）和微观结构下的损伤进程。原则上，在描述了这些关系之后，建立无铅焊点的力学行为和可靠性的预测能力相对简单，尽管需要广泛的力学建模。这种能力将允许预测特定焊料组件的加速测试结果，以及对实验结果的解释和对使用条件的推断。然而，如果没有能力预测关节历史上微观结构的重要方面的变化，上述努力2和3最多只能是半经验的，并且对于外推的目的来说非常值得怀疑。特殊的并发症是损伤进展的影响和热失配引起的变形的（通常是循环的）影响。这个项目解决了与环保制造相关的重要问题，特别强调了制造电子产品。预计材料行为的基本知识和这种材料替代的处理将取得进展。本科生和研究生通过研究和教育部分直接参与，并通过工业合作得到加强。

This GOALI project is a collaboration with Universal Instruments Corporation to study how a transition to lead (Pb)-free solders will affect manufacturing processes for electronic packaging. A comprehensive treatment of solder joint reliability requires at least three major research efforts: (1) Development of a fundamental understanding of solder joint microstructure (grain size/structure, phase regions, intermetallics), including the ability to predict microstructure at any given time during any given thermal history. (2) Development of constitutive relations which quantify deformation properties as functions of temperature, strain rate, and detailed microstructure. (3) Development of damage functions that quantify the progression of damage for given temperature, strain/stress (or integrated functions thereof such as ductility exhaustion) and microstructure. In principle, after characterizing these relations, establishing a predictive capability for the mechanical behavior and reliability of Pb free solder joints is relatively straightforward, although extensive, mechanical modeling is required. This capability would allow the prediction of accelerated test results for specific solder based assemblies, as well as the interpretation of experimental results and extrapolation to service conditions. However, without the ability to predict the variation of important aspects of the microstructure over the history of the joint, efforts 2 and 3 above become at best semi-empirical and highly questionable for purposes of extrapolation. Particular complications are the effects of the progress of damage and the (often cyclic) effects of the thermal mismatch induced deformations. This project addresses significant issues related to environmentally benign manufacturing, with specific emphasis on manufacturing electronics. It is expected that advancements in fundamental knowledge of material behavior and processing of this material substitution will be made. There is direct involvement of undergraduate and graduate students through both research and an educational component, strengthen by the industrial collaboration.