Sn-2Ag-2.5Zn低银含量合金焊料界面反应

Interfacial reaction of low silver content Sn-2Ag-2.5Zn alloy solder

共晶Sn-Ag-Cu无铅焊料由于成本和可靠性问题导致应用受到限制,将Sn-2Ag-2.5Zn低银含量合金焊料与不同基板焊接,研究焊接后界面反应以及随后不同时效处理条件下的组织形貌变化及可靠性。Sn-2Ag-2.5Zn焊料由直接熔炼法制成焊球,将焊球置于焊接强度测试仪中与基板加热焊接,随后将焊点置于加热炉中进行时效处理。结果表明:焊料与裸Cu基板焊接,时效处理后在界面处形成Cu_(5)Zn_(8)和Ag_(3)Sn致密双层IMC结构,双层结构相互阻隔,限制铜锡IMC的发展。焊料与电镀有Ni阻挡层Cu基板焊接,焊接界面形成薄层Ni_(3)Sn_(4)金属化合物,时效1000 h后Ni_(3)Sn_(4)的厚度约为1μm,Ni阻挡层的厚度保持在2~3μm,Ni阻挡层的阻挡效果稳定。Sn-2Ag-2.5Zn焊料在长时效处理中损耗性能优良,耐热时效处理性好,焊料连接的质量较好,界面可靠性较高,对环境污染少。Sn-2Ag-2.5Zn焊料中低银含量使得成本大幅下降,不容易形成粗大的金属间化合物Ag_(3)Sn,性能有所改善,是一种非常有应用前途的合金焊料。

The application of eutectic Sn-Ag-Cu lead-free solder is limited due to the problems of cost and reliability.To study the interfacial reaction after welding and the variation of microstructure and reliability under different aging treatment conditions,low silver content Sn-2Ag-2.5Zn alloy solder was welded with different substrates.Sn-2Ag-2.5Zn solder was directly melted into solder balls.The solder ball was then heated and welded with substrates in welding strength tester,and the solder joint was placed in the heating furnace for aging treatment.Results show that for the solder welded with bare Cu substrate,a compact double-layer intermetallic compound(IMC)structure of Cu_(5)Zn_(8) and Ag_(3)Sn was formed at the interface after aging treatment.The double-layer structure blocked each other and limited the development of copper-tin IMC.For the solder welded with Cu substrate plated with Ni barrier layer,a thin layer of Ni_(3)Sn_(4) metal compound was formed at the welding interface.After aging for 1000 h,the thickness of Ni_(3)Sn_(4) was about 1μm,the thickness of Ni barrier layer maintained at 2~3μm,and the blocking effect of Ni barrier layer was stable.The Sn-2Ag-2.5Zn solder has excellent loss property in long aging treatment and performs well during heat aging treatment,with good solder connection quality,high interface reliability,and less environmental pollution.The low silver content in Sn-2Ag-2.5Zn solder greatly reduces the cost,and it is not easy to form coarse Ag_(3)Sn IMC.With improved performance,Sn-2Ag-2.5Zn solder can be a promising alloy solder.