(Sn_(1-x)Zn_(x))_(57)(In_(0.78)Bi_(0.22))_(43)低熔点无铅焊料的微观结构表征

Microstructure characterization of(Sn_(1-x)Zn_(x))_(57)(In_(0.78)Bi_(0.22))_(43)low melting point lead-free solder materials

为了寻求一种应用于三维集成电路低温焊接的无铅焊料,基于多组元混合的概念设计并表征(Sn_(1-x)Zn_(x))_(57)(In_(0.78)Bi_(0.22))_(43)(x=0.10,0.15,0.20,摩尔分数,%)四元合金。采用扫描电子显微镜、X射线衍射仪和差示扫描量热仪研究合金的显微组织、热性能和润湿性。结果表明,合金由金属间化合物BiIn_(2)、In_(0.2)Sn_(0.8)和富Zn固溶体组成。随着Zn添加量的增加,BiIn_(2)和富Zn相的体积分数增加。合金的熔点低至70℃,源自低熔点金属间化合物In_(0.2)Sn_(0.8)和BiIn_(2)的形成;合金具有良好的润湿性,润湿角约为40°。在合金和Cu板的界面结合处形成一种薄而坚韧的Cu_(5)Zn_(8)层,提高焊点可靠性。研究表明,通过多组元混合概念设计合金可以有效提高焊料的焊接性能。

(Sn_(1-x)Zn_(x))_(57)(In_(0.78)Bi_(0.22))_(43)(x=0.10,0.15,0.20,at.%)quaternary alloys were designed and characterized based on the multi-principal-element mixing concept in order to develop a lead-free solder suitable for low temperature soldering in three-dimensional integrated circuit.The microstructure,thermal properties and wetting properties of the alloys were investigated using scanning electron microscope,X-ray diffractometer and differential scanning calorimeter.The results show that the alloys consist of intermetallic compounds(IMCs),BiIn_(2)and In_(0.2)Sn_(0.8),and Zn-rich solid solution.With the increase of Zn content,the volume fractions of the BiIn_(2)and Zn-rich phases increase accordingly.The alloys exhibit low melting points of about 70℃,due to the formation of the low-melting-point In_(0.2)Sn_(0.8)and BiIn_(2)IMCs.The alloys show good wetting properties with wetting angle of about 40°.At the solder joints between the alloys and Cu layer,a thin and tough Cu_(5)Zn_(8)layer is formed,which is supposed to improve the joint reliability.It is demonstrated that the welding performance of solders can be effectively enhanced by designing solders through the multi-principal-element mixing concept.