Abstract

Preventing the formation of large platelets of Ag₃Sn intermetallic compounds (IMCs) during solidification of solder joints has become a significant challenge in the design of Sn–Ag–Cu lead-free solder alloys. Large platelets of Ag₃Sn are generally considered as undesirable as their presence can create solidification defects and causes mechanical property anisotropy. In the present work, the synergetic effects of adding 0.1 wt% of Fe, Co, Te and 2 wt% Bi to Sn–3.0Ag–0.7Cu (SAC 307) solder are studied in terms of the growth of large platelets Ag₃Sn IMCs and the resulting alloy’ creep resistance as well as their thermal behavior. Although minor Fe, Co, Te and Bi alloying elements addition causes large increase in the degree of undercooling from 3.4 to 22.3 °C with maintaining the pasty range and melting temperature at the same levels, the modified SAC307–FeTeCoBi alloy exhibits considerable increase in creep resistance (~ 10 times) and large fracture life-time than SAC (307) solder at same stress levels and testing temperatures. This is attributed to the transition of Ag₃Sn IMCs from large platelets into fine needle-like morphology and formation of new (Cu,Co)₆Sn₅, FeSn₂, SnTe IMCs and Bi particles, which could provide more obstacles for dislocation movement at the interphase boundaries.

Graphic Abstract

中文翻译：

---

加入少量合金元素Fe，Co，Te和Bi控制Ag 3 Sn板的形成及其对Sn–3.0Ag–0.7Cu无铅焊料抗蠕变性的影响

摘要

防止焊点凝固过程中形成大片的Ag ₃ Sn金属间化合物（IMCs）已成为Sn-Ag-Cu无铅焊料合金设计中的重大挑战。大片的Ag ₃ Sn片通常被认为是不可取的，因为它们的存在会产生凝固缺陷并引起机械性能各向异性。在目前的工作中，研究了在大片Ag ₃的生长方面向Sn–3.0Ag–0.7Cu（SAC 307）焊料中添加0.1 wt％的Fe，Co，Te和2 wt％的Bi的协同作用。锡IMC和所得合金的抗蠕变性及其热行为。尽管少量的Fe，Co，Te和Bi合金元素的添加会导致过冷度从3.4提高到22.3°C，同时保持糊状范围和熔化温度在相同水平，但改性SAC307–FeTeCoBi合金的蠕变却显着增加。在相同的应力水平和测试温度下，其电阻（〜10倍）和比SAC（307）焊料更长的断裂寿命。这归因于Ag ₃ Sn IMCs从大血小板转变为细针状形态，并形成了新的（Cu，Co）₆ Sn ₅，FeSn ₂，SnTe IMC和Bi粒子，它们可能为相间边界处的位错运动提供更多障碍。

图形摘要