Bi对SnXCuNi焊料性能和焊点界面层组织的影响

Effect of Bi Content on Properties of SnXCuNi Solder Alloy and Interfacial Microstructure Between Solder and Cu Substrate

为了获得低成本和性能良好的无铅焊料,本文在Sn-4.1X-1.5Cu-Ni焊料中添加质量分数为0.6%的Bi元素,对其微观组织及物相成分、熔点、润湿性和剪切强度进行了分析研究,并对焊点等温时效后其界面组织进行了SEM和EDS分析。结果表明,Sn-4.1X-1.5Cu-Ni-0.6Bi焊料中主要由β-Sn、Cu6Sn5、XSn和SnBi组成,Bi的加入能有效地降低焊料的熔点和提高焊料的润湿性,焊点也保持较高的剪切强度。随着等温时效时间的延长,Sn-4.1X-1.5Cu-Ni/Cu和Sn-4.1X-1.5Cu-Ni-0.6Bi/Cu界面金属间化合物(IMC)层厚度也增加,其界面IMC的增厚主要由扩散机制控制,界面IMC主要成份为Cu6Sn5、Cu3Sn和(Cu,Ni)6Sn5。Bi能抑制等温时效过程中界面IMC的形成和生长,从而提高了焊点的可靠性,其中Sn-4.1X-1.5Cu-Ni/Cu的IMC生长速率为2.95×10-17m2/s,Sn-4.1X-1.5Cu-Ni-0.6Bi/Cu的IMC生长速率为2.78×10-17m2/s。

0.6%wt Bi was added into Sn-4.1X-1.5Cu-Ni solder alloy by producing lead-free solder at low cost and high performance. The microstructure, phase composition, melting point, wettability and characteristics of weld interface were studied. The microstructure evolution of the formation and growth of intermetallic compound （IMC） layer at the interface between solder and Cu substrate after isothermal aging were analyzed. The results show that Sn-4. 1X-1.5Cu-Ni-0.6Bi solder alloy are mainly composed ofβ-Sn, Cu6Sn5, XSn and SnBi. The addition of Bi can reduce the melting point and improve the wettability of the solder. The thickness of IMC layers in Sn-4.1X-1.5Cu-Ni/Cu system and Sn-4.1X-1.5Cu-Ni-0.6Bi/Cu system increases with increasing aging time, and their growth is mainly controlled by diffusion mechanism. The main component of the joint interface of Sn-4.1X-1.5Cu-Ni-0.6Bi/Cu system is Cu6Sn5, Cu3Sn and （Cu,Ni） 6Sn5. The addition of 0.6%wt Bi into Sn-4.1X-1.5Cu-Ni solder alloy can effectively inhibite the formation and growth of IMC during isothermal aging, which can develop solder alloy with a high reliability. The intermetallic growth rate constants for Sn-4.1X-1.5Cu-Ni/Cu is 2.95×10^-17 m^2/s, and that of Sn-4.1X-1.5Cu-Ni-0.6Bi/Cu is 2.78×10^-17 m^2/s.