Purpose

This paper aims to analyze the effect of cerium addition on the microstructure and the mechanical properties of Tin-Silver-Copper (SAC) alloy. The mechanical properties and refined microstructure of a solder joint are vital for the reliability and performance of electronics. SAC305 alloys are potential choices to use as lead-free solders because of their good properties as compared to the conventional Tin-Lead solder alloys. However, the presence of bulk intermetallic compounds (IMCs) in the microstructure of SAC305 alloys affects their overall performance. Therefore, addition of cerium restrains the growth of IMCs and refines the microstructure, hence improving the mechanical performance.

Design/methodology/approach

SAC305 alloy is doped with various composition of xCerium (x = 0.15, 0.35, 0.55, 0.75, 0.95) % by weight. Pure elements in powdered form were melted in the presence of argon with periodic stirring to ensure a uniform melted alloy. The molten alloy is then poured into a pre-heated die to obtain a tensile specimen. The yield strength and universal tensile strength were determined using a fixed strain rate of 10 mm per minute or 0.1667 mm s^(−1). The IMCs are identified using X-ray diffraction, whereas the elemental phase composition and microstructure evolution are, respectively, examined by using electron dispersive spectroscopy and scanning electron microscopy.

Findings

Improvement in the microstructure and mechanical properties is observed with 0.15% of cerium additions. The tensile test also showed that SAC305-0.15% cerium exhibits more stress-bearing capacity than other compositions. The 0.75% cerium doped alloy indicated some improvement because of a decrease in fracture dislocation regions, but microstructure refinement and the arrangement of IMCs are not those of 0.15% Ce. Different phases of Cu_6 Sn_5, Ag_3 Sn and CeSn_3 and ß-Sn are identified. Therefore, the addition of cerium in lower concentrations and presence of Ce-Sn IMCs improved the grain boundary structure and resulted refinement in the microstructure of the alloy, as well as an enhancement in the mechanical properties.

Originality/value

Characterization of microstructure and evaluation of mechanical properties are carried out to investigate the different composition of SAC305-xCerium alloys. Finally, an optimized cerium composition is selected for solder joint in electronics.

中文翻译：

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为 SAC305 的微观结构和机械性能优化添加铈

目的

本文旨在分析铈的添加对锡-银-铜(SAC)合金显微组织和力学性能的影响。焊点的机械性能和精细的微观结构对于电子产品的可靠性和性能至关重要。SAC305 合金是用作无铅焊料的潜在选择，因为与传统的锡铅焊料合金相比，它们具有良好的性能。然而，SAC305 合金微观结构中块状金属间化合物 (IMC) 的存在会影响其整体性能。因此，铈的加入抑制了IMCs的生长并细化了微观结构，从而提高了机械性能。

设计/方法/方法

SAC305 合金掺杂了各种成分的 xCerium ( x = 0.15, 0.35, 0.55, 0.75, 0.95) 重量％。粉末形式的纯元素在氩气存在下通过周期性搅拌熔化以确保均匀熔化的合金。然后将熔融合金倒入预热的模具中以获得拉伸试样。屈服强度和通用拉伸强度是使用 10 mm/min 或 0.1667 mm s ^(-1)的固定应变速率确定的。使用 X 射线衍射鉴定 IMC，而使用电子色散光谱和扫描电子显微镜分别检查元素相组成和微观结构演变。

发现

添加 0.15% 的铈可观察到显微结构和机械性能的改善。拉伸试验还表明，SAC305-0.15% 铈表现出比其他组合物更高的应力承载能力。由于断裂位错区域的减少，0.75% 铈掺杂合金显示出一些改善，但微观结构细化和 IMC 排列不是 0.15% Ce 的那些。确定了 Cu_6 Sn_5、Ag_3 Sn 和 CeSn_3 和 ß-Sn 的不同相。因此，添加较低浓度的铈和 Ce-Sn IMC 的存在改善了晶界结构并导致合金微观结构的细化，以及机械性能的增强。

原创性/价值

进行微观结构表征和机械性能评估，以研究 SAC305-xCerium 合金的不同成分。最后，为电子产品中的焊点选择优化的铈成分。