Thin film metallic glass as an underlayer for tin whisker mitigation: A room-temperature evaluation

Introduction of underlayer is one of the mitigation methods commonly used for the suppression of the Sn whiskering phenomenon in electronic packaging. The presence of a proper underlayer prevents the intermetallic compound formation resulting from a Cu/Sn interaction believed to be the major driving force of Sn whisker growth. Ni as an underlayer has been widely studied and industrially accepted. However, Ni underlayer suffers from its polycrystalline grain structure where grain boundaries can potentially act as a diffusion path for the Cu/Sn interaction to take place. In this study, a 100-nm-thick Zr46Ti26Ni28 thin film metallic glass (TFMG) is introduced to block the Cu/Sn interaction. Samples with and without TFMG underlayer were aged at room temperature for up to 33 days in ambient atmosphere. No Sn whisker is observed in the sample with TFMG underlayer after aging. In contrast, Sn whiskers are found in the absence of the underlayer and the whisker density increases with increasing aging time. It is found that TFMG underlayer plays an important role in effectively suppressing Sn whisker growth. (C) 2013 Elsevier B.V. All rights reserved.