【作者】 闵文锦；

【导师】 宣天鹏；

【作者基本信息】 合肥工业大学 ， 材料学， 2010， 硕士

【摘要】 随着欧盟“WEEE指令”和“RoHS指令”及美国、日本、中国等国家规定和管理办法的颁布和实施,电子产品的无铅化已在全球形成了共识。人们已经对诸多无铅钎料进行了探索,在这当中Sn-Ag-Cu系无铅钎料以其较优良的润湿性能及力学性能已被普遍认为是传统含铅钎料的最有潜力的替代者。本文研究了向Sn-3.0Ag-0.5Cu中同时掺入微量的RE(富Ce混合稀土)和P(磷)元素制备Sn-Ag-Cu-RE-P无铅钎料的工艺和方法,以期得到成本低廉、性能优良电子级无铅钎料。本文主要考察了Sn-Ag-Cu-RE-P无铅钎料的物理性能、力学性能、润湿能力以及钎焊接头的性能,重点分析了RE的添加和快速冷却工艺对Sn-Ag-Cu-RE-P无铅钎料各种性能的影响。研究结果表明,在常速冷却条件下,Sn-Ag-Cu-RE-P无铅钎料的显微组织由树枝状初晶的β-Sn和分布其间的共晶组织以及IMC(金属间化合物)Ag3Sn和Cu6Sn5组成。在快速冷却工艺条件下,Sn-Ag-Cu-RE-P无铅钎料的组织得到了极大程度的细化,树枝状初晶被细小的等轴晶代替了,Ag3Sn和Cu6Sn5的尺寸也显著减小了。RE可以细化Sn-Ag-Cu-RE-P无铅钎料的组织,它的细化作用在常速冷却条件下比在快速冷却条件下表现的更为明显。在添加RE和快速冷却工艺的共同作用下,Sn-Ag-Cu-RE-P无铅钎料的显微组织细小且分布均匀。在所研究的各冷却工艺条件下的无铅钎料中,添加微量的RE和P不会使Sn-Ag-Cu-RE-P无铅钎料产生低熔点组分,这有利于钎料在钎焊过程中形成可靠的焊点。RE和快速冷却工艺对无铅钎料的固、液相线的温度影响不大,但可以适当减小熔程,提高其流动性,无铅钎料的润湿性得到显著改善。同时,稀土会使无铅钎料的密度有所下降,说明合金具有一定的比重优势;无铅钎料的导电性稍有下降,但Sn-Ag-Cu-RE-P无铅钎料仍具有优良的导电能力。RE的介入可以显著提高Sn-Ag-Cu-RE-P电子级无铅钎料钎焊接头的剪切性能,使剪切强度提高35.84%～51.26%,最高达到44.9MPa。150℃下时效过程中Sn-Ag-Cu-RE-P无铅钎料钎焊接头中的IMC层生长主要由扩散机制决定,RE的存在可以延缓IMC层的生长。更多还原

【Abstract】 With the European“WEEE”and“RoHS”directives, the provision and the regulation made by American, Japan, China and other countries promulgated and implemented, the trend of being lead-free for electronic products has reached an agreement all over the world. Several lead-free solder with different compositions were studied by researchers, among these compositions Sn-Ag-Cu family has been commonly regarded as the most possible candidate for replacing the tradition lead-containing solder in terms of their good wettability and remarkable mechanical property. In this paper, to obtain an electronic lead-free solder with low price and good property, the preparation method and process of Sn-Ag-Cu-RE-P solder which designed by adding trace RE and P elements into Sn-3.0Ag-0.5Cu solder were studied. The physical property, mechanical property and wettability of Sn-Ag-Cu-RE-P solder along with the property of the soldered joint were mainly investigated in this paper, especially the effect of adding small amount of RE and fast cooling process on the solder.The results indicated that the microstructure of Sn-Ag-Cu-RE-P solder under common cooling process were made up ofβ-Sn dendrites and eutectic structures between them and intermetallic compounds Ag3Sn and Cu6Sn5 distributed on them. While under fast cooling process, the microstructure of Sn-Ag-Cu-RE-P solder were changed greatly that it became finer: the dendrites replaced by equiaxial structure, the sizes of Ag3Sn and Cu6Sn5 decreased notably. RE could refine the microstructure of Sn-Ag-Cu-RE-P solder and the refinement effect was more obvious under common cooling process compared with that under fast cooling process. The microstructure of Sn-Ag-Cu-RE-P solder was very fine and even by both the effect of adding RE and fast cooling process.In all the Sn-Ag-Cu-RE-P solders obtained under different cooling processes, there were no low melting point phases which do harm to reliability of the joints formed with the addition of trace RE and P elements. Adding RE and fast cooling process had little to do with the temperature of solidus and liquidus, but it can decrease melting range properly and thus improve the liquidity. Meanwhile, the density decreased which means certain low-density advantage of the solders. Though the conductivity of the solders went down slightly, the Sn-Ag-Cu-RE-P solder still had good conductivity.The addition of RE can greatly increase the shear property of the solder joint of Sn-Ag-Cu-RE-P electronic lead-free solder with its shear strength increased 35.84%～51.26%, the highest shear strength was 44.9MPa. Aging at 150℃, the growth of the IMC layer at the solder joint of Sn-Ag-Cu-RE-P solder was mainly decided by diffusion mechanisms. The existence of RE element can defer the growth of IMC layer according to the aging test results.更多还原