Abstract

The effect of Co addition (0.5-2.0 wt.%) on the microstructure evolution, thermal and mechanical property of Sn-0.7Cu (wt.%) solder was investigated. The microstructure of Sn-Cu alloy was refined with the addition of Co, and CoSn₂ phase formed during solidification. The volume fraction of CoSn₂ phase increases with the increase of Co content. The melting temperature of Sn-0.7Cu-xCo alloys increases with increasing Co content. The melting range of these alloys is small (< 4°C), and decreased with the increase of Co content. The ultimate tensile strength and microhardness of Sn-Cu-xCo (x = 0.5, 1.0, 1.5, 2.0) alloys increase with the increase of the Co content. The relationships between tensile strength/microhardness and Co content of Sn-Cu-xCo alloy are established. Meanwhile, Sn-0.7Cu-1.5Co (wt.%) and Sn-0.7Cu-2.0Co (wt.%) alloys revealed an indentation size effect. Different ISE behaviors of Sn-0.7Cu-xCo alloys are mainly related to the presence of CoSn₂ phase and the volume fraction of it. The indentation creep property of Sn-Cu-xCo alloys is modified with the addition of Co. Enhanced creep property of the alloys is depended on the solid solution of Co and precipitate out of CoSn₂ phase.

中文翻译：

---

Co合金化Sn-0.7Cu无铅焊料的组织演变，热力学性能

摘要

研究了添加Co（0.5-2.0 wt。％）对Sn-0.7Cu（wt。％）焊料的组织演变，热和机械性能的影响。通过添加Co来细化Sn-Cu合金的微观结构，并在凝固过程中形成CoSn ₂相。CoSn ₂相的体积分数随Co含量的增加而增加。Sn-0.7Cu- x Co合金的熔化温度随着Co含量的增加而增加。这些合金的熔化范围很小（<4°C），并且随着Co含量的增加而降低。Sn-Cu- x Co（x 的极限抗拉强度和显微硬度= 0.5、1.0、1.5、2.0）合金随Co含量的增加而增加。建立了Sn-Cu- x Co合金的拉伸强度/显微硬度与Co含量的关系。同时，Sn-0.7Cu-1.5Co（wt。％）和Sn-0.7Cu-2.0Co（wt。％）合金显示出压痕尺寸效应。Sn-0.7Cu- x Co合金的不同ISE行为主要与CoSn ₂相的存在及其体积分数有关。Sn-Cu- x Co合金的压痕蠕变性能可通过添加Co来改变。合金蠕变性能的增强取决于Co的固溶体并从CoSn ₂相中析出。