Electrical Contacts, Proceedings of the Annual Holm Conference on Electrical Contacts, September 2005: pp. 121-126.The room temperature spontaneous growth of low
melting point metal whiskers, such as Sn, poses a serious
reliability problem in the semiconducting industry; a problem
that has become acute with the introduction of Pb-free solder
technology. Recently it was shown that the driving force is most
probably a reaction between oxygen and the sprouting metal. [1]
The resulting volume expansion creates a compressive stress that
pushes the whiskers up. The model proposed explains
observations on In and Sn whiskers as well as many past
observations. Herein further evidence is presented for, and
discussion of, the proposed model. Stresses, calculated using
finite element modeling, are reasonable and in line with
measured values. Based on this work, a potential solution to the
whisker problem is in principle simple: either slow or prevent the
diffusion of oxygen into the soft metal or, more practically and
effectively, work with larger grained solder, which should reduce
the magnitude of the compressive stresses
