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.
Sci Rep. 2013;3:2731. doi: 10.1038/srep02731.
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.
焊接是一种古老的工艺，已有 5000 年的历史。它仍然是一个关键的工艺，有许多现代的应用。在电子设备中，电流通过焊点。最近观察到一种新的物理现象——在高电流下焊料的过饱和。它涉及（1）焊料基体相的意外过饱和，和（2）形成不寻常的“环形”晶粒。然而，这些现象的起源尚不清楚。在这里，我们根据 Pb-Sn 焊料的相稳定性变化，对这些现象提供了一个合理的解释。基于第一性原理的 CALPHAD 建模被用来将电流引起的效应转化为各相的过剩吉布斯自由能。因此，相平衡可以通过电流应力来改变。有和没有电流应力的 Pb-Sn 相图清楚地表明了电流应力下 Pb-Sn 焊料的相稳定性的变化。
