Impression stress relaxation of Sn3.5Ag eutectic alloy

The reliability of microelectronic interconnections depends on hot deformation of solders. In this work, we studied the localized stress relaxation of Sn3.5Ag eutectic alloy using the impression testing in the temperature range of 393-488 K. By incorporating the effect of internal stress in the analysis, we obtained the strain rate-stress exponent of 6.59. The activation energy for the stress relaxation is in the range from 38.6 to 43.8 kJ/mol, which compares well with the estimated activation energy of dislocation pipe diffusion, 46 kJ/mol, in pure tin. This suggests that a single mechanism of dislocation climb limited by dislocation pipe diffusion might be the controlling mechanism for the localized stress relaxation of the Sn3.5Ag eutectic alloy.