Risk of whiskers formation on the surface of commercially available tin-rich alloys under thermal shocks

Whisker-Like Formations in Sn-3.0Ag-Pb Alloys

“…As a result of research, the risk of the occurrence of whiskers has been significantly reduced. The pure tin surface is one of the most favorable ones for whiskers [4,5], but they can also grow on tin-based alloys in various conditions [5,6]; however, this phenomenon has been observed on gold, silver and aluminum surfaces too [7]. For example, whisker growth can be caused by pressure [8][9][10].…”

“…For example, whisker growth can be caused by pressure [8][9][10]. The application of tin matte coating (by large grains with C content below 0.05%) helps to reduce the risk of the formation of whiskers, also avoiding pure Sn coating, the use of porosity-free coating of Ni, or a heat treatment of the surface [3,5]. Some of the typical formations of whiskers are shown in Fig.…”

“…There is no need of electric field or specific atmosphere (whiskers grow even in vacuum) for whisker growth because the main conditions of the growing process are the compressive stress, oxide layer and the deformation of the microstructure [2,5,6]. Therefore, the phenomenon is often associated with the grain structure.…”

“…It has also been proved that the presence of lead (from 1wt%) provides uniform grain structure which blocks the whisker formation [4]. It is experienced that on Sn-Ag coatings there is no risk of whisker growth [6], but thermal shock cycles resulted in whisker formations on the surface of Sn-3.0Ag-0.5Cu solder alloy [5].…”

Effect of current load on corrosion induced tin whisker growth from SnAgCu solder alloys

“…Skwarek et al found that commercially used tin-rich alloys Sn/Cu [8] and Sn/Ag/Cu can already develop tin whiskers under thermal shock tests [9,10], however the length of developed whiskers was only in the range of 10-20 µm which are not dangerous for the microelectronics. Horváth et al found that high tin content SnCu solder alloys (Cu1-5wt%) can produce tin whiskers under corrosive climate [11].…”