Driven by the trends towards miniaturization in lead free electronic products, researchers are putting immense efforts to improve the properties and reliabilities of Sn based solders. Recently, much interest has been shown on low silver (Ag) content solder SAC105 (Sn-1.0Ag-0.5Cu) because of economic reasons and improvement of impact resistance as compared to SAC305 (Sn-3.0Ag-0.5Cu. The present work investigates the effect of minor aluminum (Al) addition (0.1–0.5 wt.%) to SAC105 on the interfacial structure between solder and copper substrate during reflow. The addition of minor Al promoted formation of small, equiaxed Cu-Al particle, which are identified as Cu3Al2. Cu3Al2 resided at the near surface/edges of the solder and exhibited higher hardness and modulus. Results show that the minor addition of Al does not alter the morphology of the interfacial intermetallic compounds, but they substantially suppress the growth of the interfacial Cu6Sn5 intermetallic compound (IMC) after reflow. During isothermal aging, minor alloying Al has reduced the thickness of interfacial Cu6Sn5 IMC but has no significant effect on the thickness of Cu3Sn. It is suggested that of atoms of Al exert their influence by hindering the flow of reacting species at the interface.
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机译：在无铅电子产品的小型化趋势的推动下，研究人员正在做出巨大的努力来改善锡基焊料的性能和可靠性。最近，由于经济原因和与SAC305（Sn-3.0Ag-0.5Cu）相比抗冲击性的提高，人们对低银（Ag）焊料SAC105（Sn-1.0Ag-0.5Cu）表现出了极大的兴趣。研究了SAC105中微量添加铝（Al）（0.1–0.5 wt。％）对回流过程中焊料与铜基板之间界面结构的影响，微量添加Al促进了小的等轴Cu-Al颗粒的形成鉴定为Cu3Al2。Cu3Al2停留在焊料的近表面/边缘处，并具有较高的硬度和模量。结果表明，少量添加Al不会改变界面金属间化合物的形态，但它们基本上抑制了界面金属的生长回流后的Cu6Sn5金属间化合物（IMC）。在等温时效中，少量的合金化Al会减小界面Cu6Sn5 IMC的厚度，但对Cu3Sn的厚度没有显着影响。建议原子o f Al通过阻碍界面处反应物种的流动而发挥其影响。
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