Issue link: https://iconnect007.uberflip.com/i/339176
July 2014 • SMT Magazine 29 TIN WHISKERS: CAPSulIzATIoN continues 4. BAE Systems/Celestica study. 5. S. Meschter, P. Snugovsky, J. Kennedy, Z.Bagheri#, and E. Kosiba, "SERDP Tin Whis- ker testing and Modeling: High temperature/ Humidity Conditions", ICSR Toronto, Ontario 2013. 6. S. Sakuyama & M.Kutami, "Substitute Ma- terials for Complete Elimination of hazardous Substances – Study of Whisker growth on lead- free Plating", Fujitsu Sci. Tech. J., 41. 2. (2005). 7. NASA Goddard Space Flight Center report. upcoming Appearances Dr. Hwang will present a lecture on "Tin Whiskers – What is Important to Know" at SMT International Conference/Exhibition, on Sep- tember 28 in Chicago, IL. fEATURE reason that tin whisker appears to be elusive. Seeking an absolute prevention is hardly a practical task. Based on the scientific principles as well as the decades' field service performance, a tin-lead reference material containing lead in the range of 3% to 37% is indispensable. And this defines tin-whisker-resistance. As to which preventive approach to take, it is the priority setting in the order of importance and effectiveness by assessing the design and specific application. For whisker-sensitive ap- plications, with practical importance in mind, steps to be taken in descending priority steps are: step one is not to use pure tin; step two is to select an effective composition of tin-based al- loy; steps three, four or five, if needed, are to be selected from the above list with the assessment based on the specific system. There are a number of SAC alloy compo- sitions and the number of the compositions is looming. A specific composition of an SAC should be specified (e.g., SAC105 has different mechanical behavior and physical phenomena from SAC305). Lead-free solder comprises a wide array of alloy systems not to mention that each alloy system can be modified in numerous ways. The bottom line is that an alloy, SAC or other, does not represent the material world of lead-free un- less a sufficient testing scheme comprising rep- resentative materials is designed and the rep- resentative tests are conducted to validate the "representation." In whisker phenomenon, the physical met- allurgy engaged in the process is complex and intricate—a compositional shift and /or an addi- tion of extraneous elements to a base alloy system can change its whisker propensity enormously. Tin whisker propensity under a study should be concluded with a specific alloy composition—the clarity is the name of the game. SMT References 1. (ISBN: 9780901150400) "Environment- Friendly Electronics—Lead Free Technology", Electrochemical Publications, LTD, Great Brit- ain, 2001, Page 697. 2. Courtesy of Lucent Technologies. 3. Courtesy of George Milad, Uyemura In- ternational. Dr. Hwang, a pioneer and long- standing contributor to SMT manufacturing since its inception as well as to lead-free develop- ment and implementation, has helped improve production yield and solved challenging reliability issues. Among her many awards and honors, she is inducted into the WiT international Hall of fame, elected to the national Academy of Engineering, and named an R&D-Stars-to- Watch. Having held senior executive positions with Lockheed Martin Corp., Sherwin Wil- liams Co., SCM Corp, iEM Corp., she is cur- rently CEo of H-Technologies group provid- ing business, technology and manufacturing solutions. She has served on U.S. Commerce Department's Export Council, various national panels/committees, and the board of fortune 500 nySE companies and civic and university boards. She is the author of 400+ publications and several textbooks, and an international speaker and author on trade, business, educa- tion, and social issues. Her formal education includes four academic degrees (Ph.D., M.S., M.A., and B.S.) as well as Harvard Business School Executive Program and Columbia Uni- versity Corporate governance Program. To read past columns, click here. for further in- formation, go to: www.jenniehwang.com.