铅锡合金表面钝化层的XPS研究

XPS research on passive layers on Pb-Sn alloys

采用X射线光电子能谱(XPS)对铅锡合金表面钝化层的组分与结构进行分析,目的是要确定钝化层中各元素的化学价态和存在形式,并试图明确锡对钝化膜导电能力的影响。结果表明:钝化膜具有分层结构,表层由SnO2,SnO,PbSO4,PbOx(1<x<2)和PbOx·Sn1-xO2组成,内层为SnO2,SnO,PbO,PbOx和PbOx·Sn1-xO2。内层钝化膜的导电性优于表层,锡能促进生成电阻远小于PbSO4和PbO的铅的过渡氧化物PbOx(1<x<2),从而提高其电导率。但是,内层的物质构成和分布并不均匀,出现了非导电区(极少量)和导电区并存的现象,而外层并没有类似情况发生。钝化膜自外向内含铅量和含锡量均呈上升趋势,含氧量呈下降趋势,锡的增值幅度随母体含锡量的减少而增大,但铅浓度的变化规律与之相反。

The composition and structure of the passive film on Pb-Sn alloys were studied by X-ray photo electron spectroscopy(XPS) in order to determine the chemical valence number and existing state of alloying elements in passive layers and to elucidate the effect of Sn content on the electronic conductivity of the passive layers. It is found that the passive film has two-layered structure with SnO_2, SnO, PbSO_4, PbO_x(1<x<2) and PbO_x·Sn_(1-x)O_2 in outer layer, and SnO_2, SnO, PbO, PbO_x and PbO_x·Sn_(1-x)O_2 in inner layer. Sn can improve the formation of PbO_x(1<x<2) which results in the increase of conductivity of the passive film. From outer layer to inner one, the contents of Sn and Pb increase and O content decreases.