Wang Chao-Hong, Li Yue-Han
Department of Chemical Engineering, National Chung Cheng University, Chiayi 621301, Taiwan.
Materials (Basel). 2025 May 20;18(10):2379. doi: 10.3390/ma18102379.
This study investigates the interfacial reactions of FeCoNiCr and FeCoNiMn medium-entropy alloys (MEAs) with Sn and Sn-3Ag-0.5Cu (SAC305) solders at 250 °C. The evolution of interfacial microstructures is analyzed over various aging periods. For comparison, the FeCoNiCrMn high-entropy alloy (HEA) is also examined. In the Sn/FeCoNiCr system, a faceted (Fe,Cr,Co)Sn layer initially forms at the interface. Upon aging, the significant spalling of large (Fe,Cr,Co)Sn particulates into the solder matrix occurs. Additionally, an extremely large, plate-like (Co,Ni)Sn phase forms at a later stage. In contrast, the Sn/FeCoNiMn reaction produces a finer-grained (Fe,Co,Mn)Sn phase dispersed in the solder, accompanied by the formation of the large (Co,Ni)Sn phase. This observation suggests that Mn promotes the formation of finer intermetallic compounds (IMCs), while Cr facilitates the spalling of larger IMC particulates. The Sn/FeCoNiCrMn system exhibits stable interfacial behavior, with the (Fe,Cr,Co)Sn layer showing no significant changes over time. The interfacial behavior and microstructure are primarily governed by the dissolution of the constituent elements and composition ratio of the HEAs, as well as their interactions with Sn. Similar trends are observed in the SAC305 solder reactions, where a larger amount of fine (Fe,Co,Cu)Sn particles spall from the interface. This behavior is likely attributed to Cu doping, which enhances nucleation and stabilizes the IMC phases, promoting the formation of finer particles. The wettability of SAC305 solder on MEA/HEA substrates was further evaluated by contact angle measurements. These findings suggest that the presence of Mn in the substrate enhances the wettability of the solder.
本研究调查了FeCoNiCr和FeCoNiMn中熵合金（MEA）与Sn以及Sn-3Ag-0.5Cu（SAC305）焊料在250℃下的界面反应。分析了不同时效时间内界面微观结构的演变。为作比较，还研究了FeCoNiCrMn高熵合金（HEA）。在Sn/FeCoNiCr体系中，界面处最初形成一个多面体的(Fe,Cr,Co)Sn层。时效过程中，大尺寸的(Fe,Cr,Co)Sn颗粒会大量剥落至焊料基体中。此外，后期会形成一个极大的板状(Co,Ni)Sn相。相比之下，Sn/FeCoNiMn反应生成了分散在焊料中的细晶粒(Fe,Co,Mn)Sn相，并伴有大尺寸(Co,Ni)Sn相的形成。这一现象表明，Mn促进了更细小金属间化合物（IMC）的形成，而Cr则促使更大尺寸的IMC颗粒剥落。Sn/FeCoNiCrMn体系表现出稳定的界面行为-(Fe,Cr,Co)Sn层随时间无显著变化。界面行为和微观结构主要受高熵合金中组成元素的溶解、成分比例及其与Sn的相互作用控制。在SAC305焊料反应中也观察到类似趋势，界面处有大量细小的(Fe,Co,Cu)Sn颗粒剥落。这种行为可能归因于Cu的掺杂，它增强了形核并稳定了IMC相，促进了更细小颗粒的形成。通过接触角测量进一步评估了SAC305焊料在MEA/HEA基体上的润湿性。这些结果表明，基体中Mn的存在增强了焊料的润湿性。
