Driving force and mechanism for spontaneous metal whisker formation

Physical Review Letters, 93(20): pp. 206104-1—206104-4. Retrieved September 19, 2006 from http://www.mse.drexel.edu/max/pdf%20references/drexel_pdfs/papers/WhiskesPRL_2004.pdf. DOI: http://dx.doi.org/10.1103/PhysRevLett.93.206104The 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 technology. To date, this 50+ year old problem has resisted interpretation. Herein we show that the driving force is essentially a reaction between oxygen and the sprouting metal. The resulting volume expansion creates a compressive stress that pushes the whiskers up. The model proposed explains our observations on In and Sn whiskers and many past observations. The solution is in principle simple: diffusion of oxygen into the metal must be prevented or slowed down. This was demonstrated by coating the active surfaces with a polymer coating

On the spontaneous growth of soft metallic whiskers

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

Elasto-viscoplasticity of isotropic porous metals

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1992.Includes bibliographical references (leaves 287-297).by Antonios I. Zavaliangos.Ph.D