Gery R. Stafford, Maureen E. Williams, Jae W. Shin, Kil-Won Moon, William J. Boettinger, Carlos R. Beauchamp
Tin(Sn)-lead(Pb) alloys have been used extensively for surface finishing of electronic components in part because Pb was found to be effective in retarding Sn whisker growth in electrodeposits. Altough whiskers appear to be a local response to the existence of residual compressirve stree in the electrodeposited film, questions remain as to the dominent source of stress and the precise growth mechanism. Using both deflection measurements of plated cantilever beams and x-ray diffraction methods (sin^2Psi), we have determined the in-place residual stress in Sn, Sn-Cu, and Sn-Pb alloys electrodeposited from both bright- and matte-finish MSA based electrolytes. Stress measurements were made soon after deposition, and as a function of time. The appearance of hillocks and/or whiskers following plating is influenced by several factors such as intrinsic grwoth stress, stress induced by Cu_6Sn_5 formation at the Sn-Cu interface, and the deposit microstructure.
, Williams, M.
, Shin, J.
, Moon, K.
, Boettinger, W.
and Beauchamp, C.
Whisker Formation in Pb-Free Surface Finishes, Journal of the Electrochemical Society
(Accessed December 11, 2023)