錫真正ホイスカ成長における鉛の抑制作用とホイスカ成長機構

抄録

It is said that lead in electroplated tin film suppresses whisker growth. But mechanism of this suppression has not been clarified. In this paper, role of lead on the whisker growth suppression has been examined by means of X-ray micro analysis, Auger electron spectroscopy and scanning electron microscopy of electroplated Sn/Pb films and Pb/Sn films on brass (Cu60%, Zn40%) substrates. As a result, the followings have been known: (1) Lead suppresses the formation of zinc oxide in spite of small oxide formation energy of zinc oxidation. (2) Extrusion grows on the electroplated tin film surface in preference to whisker. It is also assumed that lead plays a role of zinc oxidation suppression on the whisker. Because of no oxide film, growth of whisker embryo is accompanied with radial direction growth in addition to axial, and extrusion growth results. (3) On the base of acceralation effects by zinc and suppression effects by lead on whisker generation, an "oxide film defect model" has been proposed to explain the whisker generation and growth mechanism.