Sn-Cu系无铅钎料的研究进展及发展趋势

Research Status and Development Trend of Sn-Cu Lead-free Solders

传统Sn-Pb钎料因具有熔点低、成本低廉和润湿性良好等优点,被广泛应用于电子封装领域。然而由于铅的毒性问题,各个国家及地区相继限制或禁止铅的使用,因而替代Sn-Pb的无铅钎料成为电子封装领域的重要研究课题。在众多锡基无铅钎料中,Sn-Cu系无铅钎料成本最为低廉,因此备受青睐,但该系钎料的缺点也十分明显,如熔化温度高、润湿性差等。目前,国内外研究者通过合金化、颗粒强化等方法对Sn-Cu系无铅钎料进行改性研究,并取得了较为丰富的成果,例如通过添加Ag、Ni、In、Ce、Er、Fe、Co等合金元素和稀土元素及纳米颗粒能够有效提高钎料合金的综合性能;以氢化松香为基体的辅助钎剂的使用能够大幅提高Sn-Cu钎料的润湿性能;通过控制焊点凝固参数能够有效细化钎料的内部组织等。这一系列研究成果可以为无铅钎料的进一步研究提供重要的数据参考。然而,无铅钎料的开发主要针对钎料本身性能的研究居多,对焊后形成的焊点的可靠性评估相对较少。本文综合评述了近年来国内外Sn-Cu系无铅钎料合金的研究进展,从焊点显微组织和界面组织出发,阐述了合金化、颗粒强化和焊接工艺参数优化等对焊点内部组织演化规律的影响,针对Sn-Cu系钎料的润湿性、力学性能、熔化特性等评价指标,结合配套钎剂的开发和焊点可靠性的研究,探讨了钎料改性工作的研究成果,最后简述了研究过程中存在的问题以及解决方法,展望了Sn-Cu系无铅钎料的未来发展趋势,以期为新型无铅钎料的研究工作提供理论支撑。

The traditional Sn-Pb solder was widely used in electronic packaging because of its low melting point,low cost and good wettability.However,due to the toxicity of lead various countries and regions have introduced laws to restrict or prohibit the use of lead,so the lead-free solders which were expected to replace the Sn-Pb solder have become an important research topic in the field of electronic packaging.Among many tin-based lead-free solders,Sn-Cu lead-free solders attract much attention because of the competitive prices.However,the disadvantages of Sn-Cu solders are obvious,such as the high melting temperature,poor wettability and so on.At present,researchers have studied the modification of Sn-Cu lead-free solder by alloying,particle strengthening and other methods,and have made abundant achievements,for example,adding alloying elements such as Ag,Ni,In,Ce,Er,Fe,Co,rare earth elements,nanoparticles can effectively improve the comprehensive properties of the solder alloy,the use of hydrogenated rosin-based flux can greatly improve the wettability of Sn-Cu solder,and the control of solidification parameters of solder joints can effectively refine the microstructure of Sn-Cu solder.A series of research results can provide important data reference for further research of lead-free solder.However,the development of lead-free solder mainly focuses on the properties of solder itself,and the reliability evaluation of solder joints formed after soldering is relatively insufficient.The investigation status of Sn-Cu lead-free solders in recent years are reviewed comprehensively.The influence of alloying,particle strengthening and optimization of brazing process parameters on the evolution of the internal microstructure of the solder joints are expounded from the microstructure and interfacial microstructure of solder joints.In view of the development of the matching flux and the study of the reliability of solder joints,the research results of the modification of the solders are discussed.Finally,the problems and difficulty in the research procedure of lead-free solder are analyzed and some suggestions have been introduced.The development of Sn-Cu lead-free solders is prospected,which may provide a theoretical basis for future research of novel lead-free solders.