Bi对Sn-Ag-Cu无铅钎料合金及接头组织和性能的影响

【作者】 戚琳；

【导师】 赵杰；

【作者基本信息】 大连理工大学 ， 材料学， 2004， 硕士

【摘要】 由于铅和铅的化合物对环境和人体健康的危害，国际上无铅的呼声日益高涨，随着绿色和平运动在世界范围内的兴起，公众已经意识到含铅钎料对环境的污染。近年来随着微电子、表面组装技术(SMT)的发展，研制面向21世纪的绿色钎料产品以取代传统的锡铅钎料成为钎焊工业所面临的重要课题之一。通过近十年的研发，研究者们发现：在众多无铅钎料中，SnAgCu三元共晶钎料最有可能成为SnPb铅料的替代品。SnAgCu三元共晶钎料力学性能良好，且可焊性、热疲劳性也较好，在其中加入适量的Bi可以进一步降低SnAgCu钎料的熔点，且改善其润湿性，而成为高级别电子封装中所采用的钎料，但目前关于Bi在钎料及钎料接头的存在形式及作用机制的研究工作不多。 本论文以Sn-3Ag-0.5Cu无铅钎料为研究对象，在钎料基体内加入了不同含量的Bi(0.3wt％)，通过不同温度不同时间的时效处理，研究了Bi对钎料基体显微组织、力学性能及Bi对Sn-3Ag-0.5Cu／Cu接头界面处金属间化合物的组织演变的影响，及界面处金属间化合物的生长动力学的研究。研究结果表明： 1、在Sn-3Ag-0.5Cu钎料中，加入1％-3％的Bi可以提高钎料合金的抗拉强度，而且仍能保持钎料具有较高的延伸率；Bi的加入使Sn-3Ag-0.5Cu钎料经时效后强度及延伸率相对于不含Bi的钎料稳定，这可归因于固溶强化及弥散强化作用的转换；在SnAgCuBi四元合金体系中，120℃时，Bi在Sn中的固溶度为1-2％，在170℃时Bi在Sn中的固溶度约为3-5％； 2、经过再流焊，钎料与Cu基体在界面处形成的金属间化合物呈锯齿状，随着时效时间的增加，金属间化合物形貌逐渐向大波浪型转变且逐渐趋于平缓；随时效时间的延长，三种钎料界面处金属间化合物的生长速率都增大，且金属间化合物的厚度增加；含Bi的钎料与Cu基体发生反应后，在较高温度下时效时，钎料基体中的Bi在靠近界面处发生偏聚现象；含Bi钎料接头处金属间化合物的生长速率要低于不含Bi钎料接头界面处化合物的生长速率，且随Bi含量的增加化合物的生长速率降低比较明显；含Bi钎料接头处金属间化合物的生成激活要大于不含Bi钎料接头界面处化合物的生成激活能，且随Bi含量的增加化合物的生成激活能增加明显。更多还原

【Abstract】 Legislation to limit the use of lead has been introduced in many countries because of its harmful effect to human health and environment. With the developing of the " green movement" in all the world, many people have consciousness the harm of Pb-solder. In recent years, with the development of microelectronics and Surface Mounted Technology, researching lead-free solder become one of the hot projects. Among the solders that Sn-Ag-Cu solder is recommended as the best candidate of SnPb solder. It has been indicated that addition of a mount of Bi element in Sn-Ag-Cu solder can reduce the melting point of Sn-Ag-Cu solder and increase the wettability. However, there are rare reports on the effect of Bi on Sn-Ag-Cu solder and Sn-Ag-Cu solder joints, so it is important to study the effect of Bi on Sn-Ag-Cu solder.This work choose Sn-3Ag-0.5Cu solder as experimental material, adding different amount of Bi (0-3wt%) into it. Through aging at different temperature and different time, investigation is performed on the effect of Bi on microstructures evolution and mechanical properties in Sn-3Ag-0.5Cu lead-free solder and on the microstructure evolution of Sn-3Ag-0.5Cu/Cu solder joint and the growth kinetic of IMC in solder joint. The results show that:1. The addition of Bi up to 3% increases the tensile strength and keeps a good ductibility in Sn-3Ag-0.5Cu solders, a stable mechanical properties with aging time of Bi-bearing solders is observed which may attribute to the strengthening effect of Bi from solid solution strengthening to precipitating strengthening in the solders, in SnAgCuBi system, the solubility of Bi in Sn is 1-2% in 120C, but the solubility of Bi in Sn is 3-5% in 170C.2. The morphology of IMC becomes from scallop-like to planar during aging process, and with the increase of aging time, the thickness of IMC increased in Bi-bearing soler joints, Bi accumulates at the interface with the aging temperature and aging time; the growth rate of IMC in Bi-bearing solder joints is lower than SnAgCu/Cu solder joints. With the amount of Bi increases, the growth rate of IMC decreases, the activation energy of IMC in Bi-bearing solder joints is lager than SnAgCu/Cu solder joint. With the amount of Bi increases, the activation energy of IMC increases.更多还原