Publications Details

Dynamic Recrystallization Model for Whisker and Hillock Growth

Vianco, Paul T.; Neilsen, Michael K.

Tin (Sn) whiskers are not a recent development. Studies in the late 1930’s investigated thin filaments that grew spontaneously from Sn coatings used for the corrosion protection of electronic hardware. It was soon recognized that these Sn filaments, or whiskers, could create short circuits in the same electronic equipment. Figure 1a illustrates whisker growth in the hole of a printed circuit board having an immersion Sn surface finish. The engineering solution was to contaminate the Sn with > 3 wt.% of lead (Pb). The result was that whisker growth was replaced with hillock formation (Fig. 1b) that posed a minimal reliability concern to electrical circuits. Today, Pb-containing finishes are being replaced with pure Sn coatings to meet environmental restrictions on Pb use. The same short-circuit concerns have been raised, once again, with respect to Sn whiskers.