SMT007 Magazine

SMT-Feb2015

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56 SMT Magazine • February 2015 by a. Skwarek, K. Witek, M. Pluska and a. Czerwinski inSTiTuTe OF eleCTrOn TeCHnOlOgY Tin Whisker Growth on the Surface of Tin-Rich Lead-Free Alloys Feature The introduction of lead-free technology into electronics has intensified concern over tin whiskers phenomenon. Tin whiskers are crystals growing from the alloy surface as the result of compressive stress relaxation. This paper presents the dependence of tin whisker growth on copper and oxygen surface content. The observations and measurements were done using scanning electron microscopy with en- ergy-dispersive X-ray spectroscopy. The results show that whisker growth is strongly related to increased copper and oxygen surface content in whisker neighborhood. Introduction Soldering is one of the oldest processes known to mankind. The proper solder joint is created by producing the metallic bond be- tween the soldered elements and solder. In the 20 th century, the most popular solder was Pb- 37Sn63 eutectics. From July 2006, the use of Pb in solders is banned in the European Union as a consequence of RoHS directive. Actually, most of the lead-free alloys are based on Sn, contain- ing in their composition also Ag, Cu, and small additions of Ni, Co, Ge or Sb. The introduction of tin-rich lead free solder has renewed the con-

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