High Reliability Interconnects: New Methodologies for Lead-free Solders

高可靠性互连：无铅焊接的新方法

• 批准号: EP/R018863/1
• 负责人: Christopher Gourlay
• 金额: $ 165.61万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FR018863%2F1
• 关键词: Reliability; Interconnects; New; Methodologies; Lead

The reliability of electronics depends to a large degree on the reliability of the solder joints that interconnect the circuitry. Most solder joints contain tin as the majority phase to enable soldering at a temperature tolerable to the electronic components, but the tin must then operate at up to ~80% of its melting point due to resistance heating in service. As a percentage of melting point, this is as demanding as a turbine blade in an aeroengine and there is a similar ongoing desire to increase the operation temperature.In service, the joints regularly cycle between ~50 and 80% of melting point due to cycles of resistance heating and natural cooling, which causes thermal expansion and contraction of all phases and, therefore, thermal fatigue due to the mismatch in the coefficient of thermal expansion (CTE) at interfaces. Joints can also experience shock impacts, vibration and surges in current density, all of which must be withstood to ensure successful operation.Solder joints contain only up to a few tin grains and are highly heterogeneous with anisotropic properties. Therefore, to understand and predict the performance of solder joints it is necessary (i) to link mechanical measurements to the microstructure and crystallographic orientations in the joint and (ii) to develop crystal-level deformation and damage models that explicitly account for the evolving microstructure and link through to component and PCB-level models of thermal cycling, shock impact etc. Furthermore, to capitalise on the understanding generated by such an approach, it is necessary to develop the capability to reproducibly create the microstructures and orientations during the soldering process that are predicted to give optimum performance in service. To deliver this vision, we bring together expertise in controlling solidification kinetics in solder alloys, in-situ micromechanical measurement of crystal slip and slip transfer across interfaces, defect nucleation and growth, and micromechanical modelling at the crystal and microstructure level and at the component and board-level. With this team, we seek a step change improvement in the understanding, prediction and manufacturing of solder joints that are optimised for high reliability in high value UK industry and in the consumer electronics industry.The work addresses using solidification processing to generate single crystal and structurally representative units (e.g. intermetallic crystals (IMCs) with the desired facets, beta-Sn micro-pillars, or BGA joints with a single known beta-Sn orientation etc.). These are to be studied in carefully instrumented micromechanical tests to extract key material properties, and mechanistic understanding of defect nucleation at the crystal level. The properties and defect nucleation mechanisms are to be implemented in crystal plasticity models and, where necessary, discrete dislocation plasticity models to provide validated quantitative prediction of solder performance under thermo-mechanical and impact loading. The models are then to be exploited to design solder microstructures for optimal performance. The work will then develop methods to manufacture these optimum microstructures within the soldering process, building on recent advances in microstructure control made by the team. These optimised joints will then be tested and modelled such that optimally designed, high reliability joints may ultimately be achieved.

电子产品的可靠性在很大程度上取决于连接电路的焊点的可靠性。大多数焊点都含有锡作为主要相，以便在电子元件可以承受的温度下进行焊接，但由于在使用中电阻加热，锡必须在高达其熔点的80%的温度下工作。作为熔点的百分比，这与航空发动机中的涡轮叶片一样苛刻，并且有类似的持续期望提高操作温度。在使用中，由于电阻加热和自然冷却的循环，接头在熔点的~50和80%之间有规律地循环，这导致所有阶段的热膨胀和收缩，因此，由于界面热膨胀系数（CTE）的不匹配，导致热疲劳。接头还会受到冲击、振动和电流密度激增，所有这些都必须经受住，以确保成功运行。焊点只含有少量锡粒，具有高度的非均质性和各向异性。因此，为了理解和预测焊点的性能，有必要(i)将机械测量与接头中的微观结构和晶体取向联系起来；（ii）开发晶体级变形和损伤模型，明确地解释微观结构的演变，并将热循环、冲击冲击等组件和pcb级模型联系起来。此外，为了利用这种方法产生的理解，有必要开发在焊接过程中可重复创建微结构和方向的能力，以预测在服务中提供最佳性能。为了实现这一愿景，我们汇集了以下方面的专业知识：控制焊料合金的凝固动力学，晶体滑移和跨界面滑移转移的原位微力学测量，缺陷成核和生长，以及晶体和微观结构水平以及组件和电路板水平的微力学建模。通过这个团队，我们寻求在理解，预测和制造焊点方面的逐步改进，这些焊点针对高价值英国工业和消费电子行业的高可靠性进行了优化。该工作涉及使用凝固处理来生成单晶和结构上具有代表性的单元（例如具有所需facet的金属间晶体（IMCs）， β - sn微柱或具有单一已知β - sn取向的BGA接头等）。这些都将在仔细的仪器微力学测试中进行研究，以提取关键的材料特性，并在晶体水平上对缺陷成核的机理进行理解。性能和缺陷成核机制将在晶体塑性模型中实现，必要时，可以在离散位错塑性模型中实现，以提供热机械和冲击载荷下焊料性能的有效定量预测。然后利用这些模型来设计焊料微结构以获得最佳性能。接下来的工作将基于团队在微观结构控制方面的最新进展，开发出在焊接过程中制造这些最佳微观结构的方法。然后将对这些优化后的接头进行测试和建模，从而最终实现优化设计的高可靠性接头。

项目成果

Nucleation and growth of Ag3Sn in Sn-Ag and Sn-Ag-Cu solder alloys

• DOI: 10.1016/j.actamat.2023.118831
• 发表时间: 2023-03-16
• 期刊: ACTA MATERIALIA
• 影响因子: 9.4
• 作者: Cui, Y.;Xian, J. W.;Gourlay, C. M.
• 通讯作者: Gourlay, C. M.

Role of Bi, Sb and In in microstructure formation and properties of Sn-0.7Cu-0.05Ni-X BGA interconnections

Bi、Sb 和 In 在 Sn-0.7Cu-0.05Ni-X BGA 互连微结构形成和性能中的作用

• DOI: 10.23919/icep.2019.8733493
• 发表时间: 2019
• 作者: Belyakov S

In-situ electron backscatter diffraction of thermal cycling in a single grain Cu/Sn-3Ag-0.5Cu/Cu solder joint

• DOI: 10.1016/j.scriptamat.2019.09.003
• 发表时间: 2019-07
• 期刊: Scripta Materialia
• 影响因子: 6
• 作者: Tianhong Gu;Yilun Xu;C. M. Gourlay;T. Ben Britton

Advances in Electronic Interconnection Materials

电子互连材料的进展

• DOI: 10.1007/s11837-018-3267-4
• 发表时间: 2018
• 期刊: JOM
• 影响因子: 2.6
• 作者: Gourlay C

Twin boundary fatigue crack nucleation in a polycrystalline Nickel superalloy containing non-metallic inclusions

• DOI: 10.1016/j.jmps.2022.104785
• 发表时间: 2022-01-19
• 期刊: JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
• 影响因子: 5.3
• 作者: Bergsmo, Alexander;Xu, Yilun;Dunne, Fionn P. E.
• 通讯作者: Dunne, Fionn P. E.