GOALI: Microstructural Evolution and Damage Nucleation Mechanisms during Thermomechanical Cycling in the Sn Phase of Lead-free Solder Joints

目标：无铅焊点锡相热机械循环过程中的微观结构演变和损伤成核机制

• 批准号: 1006656
• 负责人: Thomas Bieler
• 金额: $ 42万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1006656&HistoricalAwards=false
• 关键词: GOALI; Microstructural; Evolution; Damage; Nucleation

TECHNICAL SUMMARY: As the electronics industry converts to lead-free solder worldwide, fundamental research on the physical and mechanical metallurgy (mechanisms of deformation, recovery, recrystallization) of tin (Sn) lags far behind its implementation. The substitution of Sn-based solders for Sn-Pb solder has led to failures in modes and locations never encountered before, and the fundamental cause of these failures is still not understood. Hence, lead-free solder joints lack a physically based (rational) foundation for reliability prediction. As the electronics infrastructure transitions to lead-free solder, high reliability products will become increasingly vulnerable. The research objectives of this program are to identify rules for operation of slip systems, hardening characteristics and recovery processes that can be implemented into crystal plasticity finite-element constitutive models. This analytical capability, combined with statistically large amounts of experimental characterization, will enable identification of fundamental microstructural evolution mechanisms and their interrelationship with dislocation generation and recovery in Sn based solders. A second major objective is to establish a database of observations on damaged and undamaged joints that also quantifies how locally active slip systems are correlated with crystal orientations, orientation gradients, grain boundaries, and recrystallization mechanisms so that interrelationships between these variables can be discovered. Success will be enabled by analytical capabilities present in the PI's group at MSU leveraged with Cisco's ability to provide high quality specimens manufactured in a repeatable industrially relevant process, augmented by the information gained in related research and development efforts. Insights gained will assist constitutive model development, and identify criteria that govern microstructural evolution and damage nucleation. These models will allow designers to evaluate worst-case microstructures in worst-case solder joint locations computationally, which cannot be done empirically.NON-TECHNICAL SUMMARY: Historically, more than half the failures in electronic systems can be traced to solder joints. Because fundamental research on the metallurgy of tin (the basis for lead-free solder) lags far behind its implementation, this failure rate will increase as the worldwide electronics industry transitions to environmentally friendly lead-free solder. At present, manufacturing decisions are based upon costly empirical studies that are limited to the product and service conditions tested. In this project undergraduate and graduate students will work together with industrial partners at Cisco Systems, Inc., to develop specimens, experiments, and analyze data that will enable physically-based 3-D material models to be built. Students and the PIs will work at Cisco via internships, and 2-4 weeks faculty visits in summers to develop synergistic research thrusts at the interface between industrial product development and basic science. Existing collaborations with colleagues at Max-Planck-Insititut fur Eisenforschung in Dusseldorf will contribute to analysis and modeling capabilities. These results will be publicized in archival journals, conferences, workshops, and K-12 outreach to help the public gain appreciation for how materials engineering affects electronic system reliability, and hence, modern life (why do electronics quit working?). As models are developed, they will be evaluated by electronic system design engineers at Cisco in order to establish the ability to computationally predict the likelihood of damage in particular designs.

技术摘要：随着全球电子行业转向无铅焊料，锡（Sn）的物理和机械冶金（变形、回复、再结晶机制）的基础研究远远落后于其实施。用锡基焊料替代锡铅焊料导致了以前从未遇到过的模式和位置​​的故障，并且这些故障的根本原因仍然不明确。因此，无铅焊点缺乏可靠性预测的物理（理性）基础。随着电子基础设施向无铅焊料过渡，高可靠性产品将变得越来越脆弱。该项目的研究目标是确定滑移系统的运行规则、硬化特性和恢复过程，这些规则可以应用于晶体塑性有限元本构模型。这种分析能力与统计上大量的实验表征相结合，将能够识别基本的微观结构演化机制及其与锡基焊料中位错产生和恢复的相互关系。第二个主要目标是建立一个关于受损和未受损接头的观察数据库，该数据库还可以量化局部活跃滑移系统如何与晶体取向、取向梯度、晶界和再结晶机制相关，以便发现这些变量之间的相互关系。密歇根州立大学 PI 团队的分析能力将有助于取得成功，并利用思科提供在可重复的工业相关流程中制造的高质量样本的能力，并通过相关研发工作中获得的信息进行增强。获得的见解将有助于本构模型的开发，并确定控制微观结构演化和损伤成核的标准。这些模型将允许设计人员通过计算来评估最坏情况焊点位置的最坏情况微观结构，而这无法凭经验完成。非技术摘要：从历史上看，电子系统中一半以上的故障都可以追溯到焊点。 由于锡冶金学（无铅焊料的基础）的基础研究远远落后于其实施，随着全球电子工业向环保无铅焊料过渡，这种故障率将会增加。目前，制造决策基于昂贵的实证研究，这些研究仅限于所测试的产品和服务条件。在该项目中，本科生和研究生将与思科系统公司的工业合作伙伴合作，开发样本、进行实验并分析数据，从而构建基于物理的 3D 材料模型。学生和 PI 将通过实习在思科工作，并在夏季进行 2-4 周的教师访问，以在工业产品开发和基础科学之间开展协同研究。与杜塞尔多夫马克斯普朗克研究所同事的现有合作将有助于提高分析和建模能力。这些结果将在档案期刊、会议、研讨会和 K-12 宣传活动中公布，以帮助公众了解材料工程如何影响电子系统可靠性，进而影响现代生活（为什么电子设备会停止工作？）。随着模型的开发，思科的电子系统设计工程师将对其进行评估，以便建立通过计算预测特定设计损坏可能性的能力。