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May 2015 • SMT Magazine 11 Dr. Hwang, an international busi- nesswoman, speaker, and busi- ness and technology advisor, is a pioneer and long-standing contributor to SMT manufactur- ing 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 national academy of engineer- ing, and named an r&D-Stars-to-Watch. Having held senior executive positions with lockheed Martin Corp., Sherwin Williams Co., SCM Corp, and ieM corp., she is currently ceo of H-Tech- nologies group, providing business, technol- ogy and manufacturing solutions. She serves as chairman of assessment board of DoD army research laboratory, commerce Department's export council, various national panels/commit- tees, international leadership positions, and the board of Fortune 500 nYSE companies and civic and university boards. She is the author of 450+ publications and several textbooks, and an inter- national speaker and author on trade, business, education, and social issues. Her formal educa- tion includes four academic degrees as well as Harvard Business School Executive program and columbia university corporate governance pro- gram. for further info, visit To read past columns, click here. THE THEORy BEHIND TIN WHISkER PHENOmENa, PaRT 1 continues sMt prospeCts & perspeCtives of tin whisker under accelerated conditions, as well as in real-life services, tin whisker calls for a deeper treatment of crystal lattice at atomic level. This goes to the heart of theories of physi- cal metallurgy in crystal nucleation and grain growth from a high energy state to a low energy or stress-free state. The mechanisms by which tin whiskers oc- cur have been studied over the years through different approaches and concepts, namely, the recrystallization process and stress relief mechanism. And despite the fact that some test results are at variation with the observations, the loosely termed "internal stress" is deemed primarily responsible for the metal whisker for- mation and growth. As such, the factors that can contribute to internal stress of the tin plat- ing and the conditions that impart additional residual stress to the plating layer during and after plating deposition are the right places to be deliberated. Nonetheless, tin whisker is more than a clas- sical recrystallization and it is more than a clas- sical stress relief phenomena. It is the product of a multi-faceted process. One plausible theory of tin whisker growth can be postulated through considering the combination and confluence of several key metallurgical processes, which will be outlined in Parts 2–4 of this series. SmT A paper published in ACS nano ("Tuning Thermal Transport in ultrathin Silicon Membranes by Surface nanoscale engineering") and led by researchers from the Max planck institute for polymer research (ger- many), the catalan institute of nanoscience and nanotechnol- ogy (iCn2) at the campus of the universitat autònoma de barce- lona (uAB) (Spain) and the VTT Technical research centre of fin- land (Finland) describes how the nanometre-scale topology and the chemical composi- tion of the surface control the thermal conductivity of ultrathin silicon membranes. The work was funded by the european project Membrane-based phonon engi- neering for energy harvesting (MErging). The paper describes how thermal conductivity of ul- trathin silicon membranes is controlled to large extent by the structure and the chemical composition of their surface. a detailed understanding of the connections of fabrication and processing to structural and thermal properties of low-dimensional nanostruc- tures is essential to design mate- rials and devices for phononics, nanoscale thermal management, and thermoelectric applications. Flat Silicon Channels Hinder Heat Conduction

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