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SMT-July2014

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30 SMT Magazine • July 2014 Abstract Tin-rich solders are widely applied in the electronic industry in the majority of mod- ern PCBs. Because the use of lead-tin solders has been banned in the European Union since 2006, the problem of the bridging of adjacent conductors due to tin whisker growth (limited before by the addition of Pb) has been reborn. In this study, tin alloys soldered on glass-epoxy laminate (typically used for PCBs) are consid- ered. Scanning ion microscopy with focused ion beam (FIB) system and energy-dispersive X-ray spectroscopy (EDXS) were used to determine correlations between spatial non-uniformities of the glass-epoxy laminate, the distribution of intermetallic compounds and whisker growth. Introduction Tin whiskers are crystals growing from tin or tin-alloy surface that are a threat to the reliabil- ity of electronic circuits because of short circuits (due to the bridging of adjacent conductors), increased electromagnetic radiation or device littering [1,2] . The phenomenon can occur in tin- rich solders, but the addition of lead to the tin alloy inhibits whisker growth. In the twentieth century, the most popular solder was Pb37Sn63 eutectics. However, since July 2006, when the Restriction of Hazardous Substances (RoHS) Di- rective was adopted by the European Union, the amount of Pb in solders has been limited to 0.1 wt.%. The application of tin-rich lead-free solders in the PCB assembly process has reintro- Whisker Growth in Tin Alloys on Glass-epoxy Laminate fEATURE by A. Czerwinski, A. Skwarek, M. Płuska, J. Ratajczak, K. Witek inSTiTUTE of ELECTRon TECHnoLogy

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