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60 SMT Magazine • February 2015 Conclusions The increased copper content in the area of whisker base can be related to the presence of intermetallic compounds (in particular the pres- ence of Cu6 Sn5). The increased oxygen con- tent is caused by the presence of tin oxides on the surface of the solder, particularly at such a high content of oxygen—the presence of SnO2. Both, increased copper and oxygen contents at the whisker base are strongly related to whisker growth. acknowledgments This work has been supported by the Na- tional Science Centre under project no. N N515 503940. SMT references 1. D. Pinsky, M. Osterman, S. Ganesan, IEEE Trans. Comp. Package Technol. 27, 427 (2004). 2. G.T. Galyon, IEEE Trans. Electron. Pack- age Manuf. 28, 17 (2005). 3. K.N. Tu, Phys. Rev. B 49, 2030 (1994). 4. K. Kanaya, S. Okayama, J. Phys. D, Appl. Phys. 5, 43 (1972). 5. C. Chiavari, C. Martini, G. Poli, D. Prand- straller, J. Mater. Sci. 41, 1819 (2006). Figure 3: eDS spectra of the samples of Sn99.3Cu0.7ni, after 3000 h exposure at 87% rH and 60°C soldered on (A) niAu sublayer and (b) directly on Cu layer. Andrzej Czerwinski (phD, DSc) is associate professor and head of Department of Materials and Semiconductor Structures research, institute of electron Technology, Warsaw, poland. agata Skwarek (phD) is an assis- tant professor in the Department of Microelectronics in the institute of electron Technology (Krakow Division), poland. Mariusz pluska (phD) and Jacek ratajczak (phD) are assistant professors with the Department of Materials and Semiconductor Structures research, institute of electron Technology, Warsaw, poland. Krzysztof Witek (M.Sc. eng.) works in the institute of electron Technology (Krakow Division), poland as manager of implementation and production Department. Feature TIN WHISKer GrOWTH ON THe SurFaCe OF TIN-rICH Lead-Free aLLOyS continues