The influence of minor Nd additions on the microstructure and spreading characteristics of Sn-9Zn solder was investigated. The interfacial morphology and the mechanical properties of the Sn-9Zn-xNd (x=0, 0.1, 0.5) solder/Cu joints were also analyzed. The results indicate that the microstructure of the eutectic structure in Sn-Zn-Nd solder alloys is refined by the addition of minor Nd. However, adding 0.5% Nd into Sn-9Zn alloy leads to the formation of large "cross" shaped NdSn3 intermetallic compound (IMC). Under the conditions of lower soldering temperature or shorter soldering time, the addition of trace Nd in Sn-9Zn could improve the spreading properties. With the increase of soldering temperature or soldering time, the spreading property of Sn-Zn-Nd alloy is decreased because of the obvious oxidation of the solders with Nd addition. Test results also indicate that the addition of 0.1% Nd into the Sn-9Zn solder can enhance, the mechanical property of soldered joint slightly. The fracture micrographs show that plenty of small and uniform bacillary structures form in the joint. 0.5% Nd addition in Sn-9Zn could significantly reduce the mechanical properties of soldered joint because of the component segregation of Nd-rich phases in the interface.%研究Sn-9Zn中添加微量稀土元素Nd对合金显微组织和铺展性能的影响,对比分析Sn-9Zn-xNd(x=0,0.1,0 5)钎料/Cu焊点界面微观特征及力学性能.结果表明:微量Nd元素在Sn-9Zn合金中能够显著细化组织,但添加量为0 5％时合金中形成了“十字状”NdSn3金属间化合物(IMC).钎焊温度较低或时间较短时,微量Nd添加能够改善Sn-9Zn合金在Cu基板上的铺展性能;但是在温度较高或时间较长的钎焊工艺条件下,由于Nd元素的严重氧化导致钎料铺展性能明显下降.在Sn-9Zn中添加0.1％Nd,在界面处形成了均匀细密分布的“毛绒状”共晶组织,能够提高焊点结合性能;Nd添加量为0 5％时,成分偏聚引起的组织不均匀导致焊点力学性能下降.
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