Effect of current density and electrolyte concentration on hillock growth from pure bright Sn electrodeposits

Abstract

The effect of current density and Sn methane sulfonate concentration on hillock density, columnar grain size, crystallographic texture, and residual stress of bright Sn electrodeposits is measured. Correlation was found between hillock density and the ratio of the applied current density to the transport limited current density. When the ratio exceeds unity no hillocks are observed. As the transport limited current is approached and exceeded, the columnar grain size decreases from 1.4 to 0.7 mu m and the preferred orientation (fiber texture) rotates toward the [001] direction. Possible explanations are presented for how these factors reduce hillock growth. Because hillock and whisker growth are related phenomena, electrodeposition beyond the limiting current may be a possible whisker mitigation strategy.