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：电子行业不断发生的变化迫切需要定量了解 SnAgCu 焊料合金在等温和热循环中的行为。然而，这种材料系统本身也具有相当大的科学意义。四方锡晶体结构提供了极其各向异性的特性，添加百分之几的银会产生具有独特特性和行为的循环孪晶结构。这对于远低于一毫米的总体样品尺寸具有特殊的影响。值得注意的是，热机械性能随微观结构的各个方面及其随时间的演变而变化很大。本研究的目标是定量了解含少量银和铜的高锡合金在循环载荷下的疲劳损伤演变。最近的工作已经形成了一个一般性假设，涉及位错产生和恢复之间的直接因果关系、位错单元结构的形成、热和应变增强的晶粒生长和二次析出物的粗化、次位错的形成和旋转。晶粒，以及裂纹的最终产生和扩展。 预计该图的大部分内容也适用于许多其他沉淀硬化金属。将进行系统研究来验证并在必要时改进或修正上述假设。实验工作将集中于在精心设计的热机械载荷组合之前和之后，对选定的高锡合金中位错单元结构和最终亚晶粒的深入表征。不同振幅的循环对于表征潜在机制特别有效。微观结构研究将在很大程度上依赖于交叉偏光显微镜、扫描电子显微镜、电子背散射衍射、聚焦离子束切片和透射电子显微镜。非技术摘要：电子产品在现代生活和社会一般功能的越来越多方面发挥着关键作用，微电子产品的过早失效可能会造成从经济损失到生命损失等一系列后果。许多电子产品价格低廉，可能会对从军事准备和公共安全到教育、社会服务和世界各地较贫穷国家的发展等领域产生巨大影响。产品的长期寿命通常受到将组件相互连接或连接到印刷电路板的焊点磨损的限制。由于行业被迫将高可靠性产品过渡到环保无铅焊料，因此迫切需要对尚未建立的损坏和故障机制有一定程度的了解。这是拟议研究的重点。结果将帮助行业以更低的成本设计和制造更耐用、更可靠的电子产品。研究生和本科生，包括一些少数民族学生，将接受最先进设备的培训，并在大学和工业合作伙伴环球仪器公司的实验室进行实验。在环球仪器公司，学生将与博士密切合作。级行业工程师。学生将在大型行业联盟的定期会议以及区域会议和主要科学会议上展示研究结果。他们还将在同行评审的期刊上发表他们的作品。成果和经验将进一步促进本科和研究生课程的持续发展。