{"title":"Characterization and degradation of β-Sn particles in thermal aged Pb-rich solder joint for low-temperature co-fired ceramic (LTCC) applications","authors":"Jin-Hong Liu, Zhe Zhu, Qiang-Qiang Nie, Jun-Fu Liu, Peng He, Shu-Ye Zhang","doi":"10.1007/s12598-024-02923-2","DOIUrl":null,"url":null,"abstract":"<div><p>High-lead solder joints are still playing an indispensable role in military and space applications. Nevertheless, in-depth characterization of high-lead solder joints and the underlying degradation mechanisms remain unexplored. This research first performed aging tests on Sn10Pb90 solder joints, the shear strength at room and elevated temperatures gradually reduced, and the resistance increased. Here, a two-layered Ni–Sn intermetallic compound (IMC) structure was identified using transmission electron microscopy (TEM), which could be attributed to the change of Sn content in the solder. Moreover, the internal annealing twin of a Sn particle was discovered, which could be attributed to creeping induced by thermal expansion coefficient (CTE) difference between Sn and Pb. Detailed analysis of partial and whole annealing twins was conducted through high-resolution TEM (HRTEM). Finally, four degradation mechanisms were proposed. Thickening of the IMC layer would result in increased brittleness and resistivity. For particle coarsening, apart from diminishing the ductility and toughness of the solder joint, it would also accelerate the creeping rate by weakening the phase boundary strength. Regarding voids and cracks induced by phase boundary sliding, wedge-shaped cracking and pore-shaped cracking were discovered and their formation was analyzed. Most importantly, the consumption of Sn resulted in a depletion of wettable layer, leading to the formation of Pb streams and isolated IMC islands, also known as the spalling and delamination of IMCs. Pb diffusion followed a spiral path, which was mutually influenced by orientation misfit and concentration gradient. A technique to prevent cracking was proposed. This research is expected to provide significant technical references for high-lead solder joints.</p><h3>Graphical abstract</h3>\n<div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":749,"journal":{"name":"Rare Metals","volume":"43 10","pages":"5346 - 5361"},"PeriodicalIF":9.6000,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Rare Metals","FirstCategoryId":"88","ListUrlMain":"https://link.springer.com/article/10.1007/s12598-024-02923-2","RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
High-lead solder joints are still playing an indispensable role in military and space applications. Nevertheless, in-depth characterization of high-lead solder joints and the underlying degradation mechanisms remain unexplored. This research first performed aging tests on Sn10Pb90 solder joints, the shear strength at room and elevated temperatures gradually reduced, and the resistance increased. Here, a two-layered Ni–Sn intermetallic compound (IMC) structure was identified using transmission electron microscopy (TEM), which could be attributed to the change of Sn content in the solder. Moreover, the internal annealing twin of a Sn particle was discovered, which could be attributed to creeping induced by thermal expansion coefficient (CTE) difference between Sn and Pb. Detailed analysis of partial and whole annealing twins was conducted through high-resolution TEM (HRTEM). Finally, four degradation mechanisms were proposed. Thickening of the IMC layer would result in increased brittleness and resistivity. For particle coarsening, apart from diminishing the ductility and toughness of the solder joint, it would also accelerate the creeping rate by weakening the phase boundary strength. Regarding voids and cracks induced by phase boundary sliding, wedge-shaped cracking and pore-shaped cracking were discovered and their formation was analyzed. Most importantly, the consumption of Sn resulted in a depletion of wettable layer, leading to the formation of Pb streams and isolated IMC islands, also known as the spalling and delamination of IMCs. Pb diffusion followed a spiral path, which was mutually influenced by orientation misfit and concentration gradient. A technique to prevent cracking was proposed. This research is expected to provide significant technical references for high-lead solder joints.
期刊介绍：
Rare Metals is a monthly peer-reviewed journal published by the Nonferrous Metals Society of China. It serves as a platform for engineers and scientists to communicate and disseminate original research articles in the field of rare metals. The journal focuses on a wide range of topics including metallurgy, processing, and determination of rare metals. Additionally, it showcases the application of rare metals in advanced materials such as superconductors, semiconductors, composites, and ceramics.
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