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July 2015 • SMT Magazine 11 boundaries. This is a problem in metals, which contain trace impurities that are transformed into liquid phases that can "wet" the grain boundaries. For tin whisker to occur, when g.b. plays a predominant role, low angle grain boundaries may become the initiating sites for whiskers due to their low energy. Low energy sites (e.g., low energy grain boundaries or recrystallized grains) serve as the foundation for whiskers. Whiskers often (although not always) originate at the intersection of grain boundaries on the surface or in the bulk of the deposit, not from the substrate interface. When there are more g.b. intersections on the surface, more whiskers will result. However, high angle grain boundar- ies are favored diffusion pathways that can be critical to sustain whisker growth. Tin material needs to transport to a whisker grain by either the surrounding grain boundary network or by lattice diffusion. This movement into the whis- ker grain pushes the free surface of the whisker grain upward, growing the whisker structure. The movement of high angle grain boundaries has implications for recrystallization and grain growth while sub-grain boundary movement influences recovery and the nucleation of re- crystallization. Discussions will continue in Part 3 and Part 4 of this series. SMT smt ProsPeCts & PersPeCtives THE THEORy BEHIND TIN WHISKER PHENOMENA, PART 2 continues Dr. Hwang, an international busi- nesswoman and speaker, and busi- ness and technology advisor, is a pioneer and long-standing contribu- tor to SMT manufacturing since its inception, as well as to the lead-free electronics implementation. among her many awards and honors, she is inducted to the WiT international Hall of fame, elected to the na- tional academy of engineering, and named an r&D-Stars-to-Watch. Having held senior execu- tive positions with lockheed Martin Corp., Sher- win Williams Co., SCM Corp, and iEM Corp., she is currently ceo of H-Technologies group, providing business, technology and manufactur- ing solutions. She serves as Chairman of Assess- ment board of DoD army research laboratory, Commerce Department's Export Council, various national panels/committees, international lead- ership positions, and the board of fortune 500 nYSE companies and civic and university boards. She is the author of 450+ publications and sev- eral textbooks, and an international speaker and author on trade, business, education, and social issues. Her formal education includes four academic degrees as well as Harvard business School Executive program and Columbia univer- sity corporate governance program. for further info, visit To read past col- umns, click here. Despite their ubiquity in consumer electron- ics, rare-earth metals are, as their name suggests, hard to come by. Mining and purifying them is an expensive, labor-intensive and ecologically devastating pro- cess. researchers at the university of pennsylvania have now pioneered a process that could enable the efficient recycling of two of these metals, neodymium and dysprosi- um. These elements comprise the small, powerful magnets that are found in many high-tech devices. in contrast to the massive and energy-inten- sive industrial process currently used to separate rare earths, the penn team's method works near- ly instantaneously at room temperature and uses standard laboratory equipment. Sourcing neodymium and dysprosium from used electronics rather than the ground would increase their supply at a fraction of the financial, human and environ- ment cost. The research was led by eric J. Schelter, assistant professor in the Department of chemistry in penn's School of Arts & Sciences, and graduate student justin bog- art. it was published in angewandte chemie, international edition. Research Simplifies Recycling of Rare-Earth Magnets

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