SnAgCu无铅焊膏可印刷性及焊点微观结构研究

The research of printability and microstructure of SnAgCu solder paste

焊膏的印刷质量及焊点的微观结构直接影响产品的最终性能和使用效果.通过对焊膏印刷性能及焊点微观结构的研究,可以制定出合适的印刷和焊接工艺,从而提高产品的最终性能和使用效果.本文以紧耦合气雾化法制备的SnAgCu合金粉末为原料,对不同质量配比下焊膏的流变和塌陷性能以及焊点的微观结构进行研究,采用旋转流变仪和扫描电镜分别对焊膏流变性能和焊点微观结构进行测试和观察.研究结果表明:焊膏黏度随合金粉末质量分数的增加而增大,但随着角速度的增大而减小;合金粉末质量分数为87.5%时所配制焊膏黏度为256.6 Pa.s,此时焊膏可印刷性好;焊膏焊接后焊点为圆形,饱满光亮,有少量助焊剂残留,其IMC层厚度为5～10μm,成分为Cu6Sn5.

The final performance of the product was directly affected by the printing quality of the solder paste and the microstructure of the welding spot.A suitable printing and welding process were gained through the study of the solder paste printing performance and the welding spot microstructure,thereby the final product performance and the application result were enhanced greatly.In this paper,SnAgCu alloy powder which was produced by the method of close-coupled gas atomization was used as raw materials.Different solder paste was prepared by changing the mass fraction of alloyed powder,and then the rheological properties and collapse performance of the solder paste as well as the microstructure of the welding spot were studied.The rotational rheometer and scanning electron microscopy was used to examine the rheological properties of the solder paste and the microstructure of the welding spot.The result indicated that：1） The viscosity of the solder paste increased with the improving of the alloyed powder mass fraction,but the viscosity of the solder paste decreased with the increase of angular velocity.2）When mass fraction of the paste prepared by alloyed powder is 87.5%,the paste viscosity is 256.6 Pa·s.This paste is suitable for printing.3）Solder pots after welding are round,full and bright,with a small amount of flux residue.And the IMC layer thickness is 5～10 μm,composed of Cu6Sn5.