Li Sijin, Zhu Junxian, Zhou Huiling, Liao Mingqing, Wang Fengjiang, Chen Jian
School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212000, China.
Department of Chemistry and Surface Science Western, University of Western Ontario, London, ON N6A 5B7, Canada.
Materials (Basel). 2024 Sep 3;17(17):4364. doi: 10.3390/ma17174364.
Sn-10Bi low-bismuth-content solder alloy provides a potential alternative to the currently used Sn-Ag-Cu series due to its lower cost, excellent ductility, and strengthening resulting from the Bi solid solution and precipitation. This study primarily investigates the interfacial evolution and shear strength characteristics of Sn-10Bi joints on a Ni/Au surface finish during the as-soldered and subsequent isothermal aging processes. To improve the joint performance, a 0.2 or 0.5 wt.% dopant of Zn was incorporated into Sn-10Bi solder. The findings demonstrated that a 0.2 or 0.5 wt.% Zn dopant altered the composition of the intermetallic compound (IMC) formed at the interface between the solder and Ni/Au surface finish from NiSn to Ni(Sn, Zn). The occurrence of this transformation is attributed to the diffusion of Zn atoms into the NiSn lattice, resulting in the substitution of a portion of the Sn atoms by Zn atoms, thereby forming the Ni(Sn, Zn) IMC during the soldering process, which was also verified by calculations based on first principles. Furthermore, a 0.2 or 0.5 wt.% Zn dopant in Sn-10Bi significantly inhibited the Ni(Sn, Zn) growth after both the soldering and thermal aging processes. Zn addition can enhance the shear strength of solder joints irrespective of the as-soldered or aging condition. The fracture mode was determined by the aging durations-with the brittle mode occurring for as-soldered joints, the ductile mode occurring for aged joints after 10 days, and again the brittle mode for joints after 40 days of aging.
Sn-10Bi低铋含量焊料合金因其成本较低、延展性优异以及铋固溶体和析出强化作用，为当前使用的Sn-Ag-Cu系列提供了一种潜在的替代方案。本研究主要考察了在焊接态及随后的等温时效过程中，Ni/Au表面处理的Sn-10Bi接头的界面演变和剪切强度特性。为改善接头性能，向Sn-10Bi焊料中掺入了0.2或0.5 wt.%的Zn掺杂剂。研究结果表明，0.2或0.5 wt.%的Zn掺杂剂使焊料与Ni/Au表面处理之间界面处形成的金属间化合物（IMC）的成分从NiSn转变为Ni(Sn, Zn)。这种转变的发生归因于Zn原子扩散到NiSn晶格中，导致一部分Sn原子被Zn原子取代，从而在焊接过程中形成了Ni(Sn, Zn) IMC，这也通过基于第一性原理的计算得到了验证。此外，Sn-10Bi中0.2或0.5 wt.%的Zn掺杂剂在焊接和热时效过程后均显著抑制了Ni(Sn, Zn)的生长。无论在焊接态还是时效状态下，添加Zn都能提高焊点的剪切强度。断裂模式取决于时效持续时间——焊接态接头为脆性模式，时效10天后的接头为韧性模式，时效40天后的接头又变为脆性模式。
