Mechanisms of Cyclic Loading Induced Microstructure Evolution and Damage in High-Sn Alloys

高锡合金循环加载引起显微组织演变和损伤的机制

• 批准号: 1206474
• 负责人: Peter Borgesen
• 金额: $ 42万
• 依托单位: SUNY at Binghamton
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2017-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206474&HistoricalAwards=false
• 关键词: Mechanisms; Cyclic; Loading; Induced; Microstructure

TECHNICAL SUMMARY:Ongoing changes in the electronics industry provide for an urgent need for a quantitative understanding of the behavior of SnAgCu solder alloys in both isothermal and thermal cycling. This kind of materials system is, however, also of considerable scientific interest in its own right. The tetragonal Sn crystal structure provides for extremely anisotropic properties, and the addition of a few percent of Ag leads to cyclic twinning structures with unique properties and behavior. This has particular consequences for overall sample dimensions well below a millimeter. Notably, thermomechanical properties vary strongly with various aspects of the microstructure and its evolution over time. The goal of the proposed research is to establish a quantitative understanding of the evolution of fatigue damage in high-Sn alloys with a few percent Ag and Cu under cyclic loading. Recent work has led to the formulation of a general hypothesis involving direct causal links between dislocation generation and recovery, the build-up of dislocation cell structures, the thermal and strain enhanced grain growth and coarsening of secondary precipitates, the formation and rotation of sub-grains, and the eventual initiation and growth of cracks. It is anticipated that much of this picture will apply to a number of other precipitate hardened metals as well. A systematic study will be conducted to validate and, if necessary, improve upon or revise the above hypothesis. Experimental efforts will focus on the in-depth characterization of dislocation cell structures and eventual sub-grains in selected high-Sn alloys before and after carefully designed combinations of thermomechanical loading. Cycling with varying amplitudes will be particularly effective for the characterization of the underlying mechanisms. Microstructure studies will rely heavily on cross polarized microscopy, scanning electron microscopy, electron backscatter diffraction, focused ion beam sectioning and transmission electron microscopy. NON-TECHNICAL SUMMARY:Electronics are serving critical roles in ever more aspects of modern life and of the general functioning of society, and the premature failure of a microelectronics product may have consequences ranging from economical to loss of life. The inexpensive availability of many electronics products may have tremendous consequences in areas ranging from military preparedness and public safety to education, social services and the development of poorer countries around the world. The long term life of a product is most often limited by wear out of the solder joints that connect components to each other or to a printed circuit board. As the industry is forced to transition even high reliability products to environmentally friendly lead free solders there is an urgent need for a level of understanding of damage and failure mechanisms that has yet to be established. This is the focus of the proposed research. Results will help the industry design and manufacture more durable, reliable electronics at lower costs. Graduate and undergraduate students, including a number of minority students, will be trained on state of the art equipment and conduct experiments both at the university and in the laboratory of industrial partner Universal Instruments. At Universal Instruments the students will work closely with Ph.D. level industry engineers. Students will present results at regular meetings of a large industry consortium, as well as at regional conferences and at major scientific conferences. They will also publish their work in peer reviewed journals. Results and experiences will furthermore contribute to the ongoing development of undergraduate and graduate level courses.

技术摘要：电子行业的持续变化规定，迫切需要对等温和热循环中SNAGCU焊合金的行为进行定量理解。但是，这种材料系统本身也具有相当大的科学兴趣。四方SN晶体结构提供了极端各向异性的特性，并且增加了几个Ag的Ag导致具有独特性能和行为的环状孪生结构。这对远低于毫米的总体样品维度具有特殊的后果。值得注意的是，热力学特性随着微观结构的各个方面及其演变而随着时间的流逝而差异很大。拟议的研究的目的是确定对循环载荷下的Ag和Cu的高SN合金中疲劳损伤演变的定量理解。最近的工作导致了一般假设的制定，该假设涉及脱位产生与恢复之间的直接因果关系，位错细胞结构的积累，热和应变增强的谷物生长以及二级沉淀物的结块，亚晶粒的形成和旋转，以及裂纹的最终启动和生长。 预计这张图片的大部分也适用于许多其他沉淀的硬金属。将进行一项系统的研究以验证并在必要时进行改进或修改上述假设。实验努力将集中于在精心设计的热力学负载组合之前和之后，在选定的高SN合金中的位错细胞结构和最终子细粒的深入表征。具有变化幅度的循环对基本机制的表征特别有效。显微结构研究将在很大程度上依赖于交叉极化显微镜，扫描电子显微镜，电子反向衍射，聚焦离子束分段和透射电子显微镜。非技术摘要：电子产品在现代生活和社会一般职能的越来越多的方面起着关键作用，微电子产品的早产失败可能会产生从经济性到生命损失的后果。许多电子产品的廉价可用性在从军事准备和公共安全到教育，社会服务以及世界各地贫穷国家的发展等领域可能会产生巨大后果。产品的长期寿命通常受到将组件彼此或印刷电路板连接的焊接接头的磨损限制。由于该行业被迫将高可靠性产品转换为环保的无铅焊料，因此迫切需要了解尚未确定的损害和故障机制。这是拟议研究的重点。结果将有助于行业设计和制造更耐用，可靠的电子产品，成本较低。包括少数族裔学生在内的研究生和本科生将在大学和工业合作伙伴环球乐器实验室进行最先进的设备和行为实验培训。在环球乐器中，学生将与博士密切合作。水平行业工程师。学生将在大型行业财团以及区域会议和主要科学会议的定期会议上介绍结果。他们还将在同行评审的期刊上发布其作品。结果和经验将进一步有助于本科和研究生水平课程的持续发展。