Analysis of tin whisker growth on lead-free alloys with Ni presence under thermal shock stress

This paper presents the results of whiskers formation after thermal shocks on various tin-rich materials used in electronics: Sn100, Sn99Cu1, Sn97Cu3, Sn99.3Cu0.7Ni, Sn99.3Cu0.7AgNiGe and Sn99Ag0.3Cu0.7NiGe. Alloys plated over an Ni/Au sublayer were compared with those plated directly over a Cu layer. Scanning electron microscope (SEM) imaging was applied to determine whisker densities, lengths and types. Different degrees of susceptibility to whisker formation were found for all the investigated alloys subjected to 1500 shocks in a cyclic temperature range of −45 °C to +85 °C. Although the whisker growth rates for the alloys plated over an Ni/Au sublayer were lower than for the alloys plated directly over a Cu layer, all the materials tested were more or less prone to whisker formation.