Ab initio-aided CALPHAD thermodynamic modeling of the Sn-Pb binary system under current stressing.
Soldering is an ancient process, having been developed 5000 years ago. It remains a crucial process with many modern applications. In electronic devices, electric currents pass through solder joints. A new physical phenomenon--the supersaturation of solders under high electric currents--has recently been observed. It involves (1) un-expected supersaturation of the solder matrix phase, and (2) the formation of unusual "ring-shaped" grains. However, the origin of these phenomena is not yet understood. Here we provide a plausible explanation of these phenomena based on the changes in the phase stability of Pb-Sn solders. Ab initio-aided CALPHAD modeling is utilized to translate the electric current-induced effect into the excess Gibbs free energies of the phases. Hence, the phase equilibrium can be shifted by current stressing. The Pb-Sn phase diagrams with and without current stressing clearly demonstrate the change in the phase stabilities of Pb-Sn solders under current stressing.
1] Department of Materials Science and Engineering, National Cheng Kung University, Tainan city 70101, TAIWAN [2] Promotion Center for Global Materials Research, National Cheng Kung University, Tainan city 70101, TAIWAN [3] Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan city 70101, TAIWAN.
Shih-kang
SK
Lin
Chao-kuei
CK
Yeh
Wei
W
Xie
Yu-chen
YC
Liu
Masahiro
M
Yoshimura