微量Nd对Sn-9Zn钎料特性及焊点组织与性能的影响

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。

Influence of minor Nd additions on characteristics and microstructure,mechanical properties of Sn-9Zn solder

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.