Influence of Thermomechanical Processing on Micromechanical Properties of SN-0.7CU Solder Alloy via Nanoindentation Approach

Abstract

Sn-based solder alloys are commonly utilized in electronic packages as an interconnection. In this study, nanoindentation was used to explore the impact of thermomechanical processing on the micromechanical characteristics of Sn-0.7Cu solder alloy. Bar-shaped Sn-0.7Cu solder alloy was cut into 9 cubic-shaped samples with dimension of 6 mm (l) X 6 mm (w) X 10 mm (h). First, cubic-shaped Sn-0.7Cu solder alloys was heat-treated for 20 minutes at temperatures of 30°C, 90°C, and 150°C, followed by compression until the thickness reduced to 40% and 80% and quick quench in water medium. As a control, solder alloys without compression process are employed. The result shows that thermomechanical-processed samples with 80% thickness reduction have the least hardness changes along temperature increment. These values were 6.46 MPa (from 30℃ to 90℃) and 23.73 MPa (from 90℃ to 150℃), respectively. The smaller gap of values when temperature increased were obtained through formation of new recrystallize grains which also referred as grain refinemet. The reduced modulus for thermomehanical-procesed sample with 80% thickness reduction sample also showed the same trend as the hardness value. The value dropped from 56.22 GPa to 42.12 GPa before rising slightly to 48 GPa as the temperature increased. The change of reduced modulus values were lower when compared to control and thermomechanical-processed sample with 40% thickness reduction samples. The findings demonstrate that as the temperature rises, thermomechanical processing with an 80% thickness reduction stabilizes the micromechanical properties of the Sn-0.7Cu solder alloy.