【作者】 谢海平；

【导师】 王来；

【作者基本信息】 大连理工大学 ， 材料学， 2005， 硕士

【摘要】 由于铅及含铅化合物对人体和环境产生危害,钎料无铅化已成为电子封装等相关焊接发展趋势。通过近十年的研发,Sn-Ag、Sn-In、Sn-Bi、Sn-Zn等无铅钎料被证明最有可能成为SnPb铅料的替代品。而在所有Sn基钎料中,Sn-Zn钎料成本较低、熔点不高以及力学性能优异而逐渐成为无铅钎料有利竞争之一,但Zn易氧化和腐蚀差缺点是钎料应用前需要解决的问题。 尽管已有研究显示加入In、Bi、Al等能提高Sn-Zn钎料这种润湿性和抗氧化性,但这种提高非常有限。而通过原有实验发现Sn-9Zn合金中加入合金化元素Cu,自由Zn会向Cu-Zn化合物转变,从而有效减少Zn的氧化。因此本文主要是研究与分析添加不同Cu合金对钎料组织和力学性能影响,并通过在Cu基板上钎焊研究其润湿反应和界面组织变化。同时为了降低钎料熔点和提高润湿性而为获得综合性能良好的无铅钎料,在（Sn-9Zn）-2Cu加入3%Bi和不同量的Ni。为了研究钎料与凸点下Ni镀层钎焊润湿性和使用可靠性,采用Sn-9Zn-3Cu与Ni基钎焊并于170℃下时效不同时间从而研究界面处的组织变化。由以上研究结果表明: 1、Cu的加入减少了Zn原子在液态钎料表面的氧化,有效的降低钎料的表面张力,使钎料与Cu之间的润湿性得到显著提高,获得了较小的润湿角。但随着Cu含量的增加,合金熔点逐渐升高。钎料的抗拉强度随着Cu含量的增加先增大后减小,SZ-xCu/Cu接头剪切强度则由于界面IMC的转变以及钎料合金自身强度的变化而导致钎焊接头剪切强度发生变化。在Cu含量不大于8%时,随着Cu的增加SZ-xCu钎料中针状富Zn相逐渐转变为Cu-Zn化合物;当Cu含量超过8%后,Cu₆Sn₅相开始出现。界面处IMC在0～1%Cu时主要为层状Cu₅Zn₈相;在2～6%Cu时,为Cu₆Sn₅相和Cu₅Zn₈相共同组成;在8%Cu时,为扇状Cu₆Sn₅相组成。 2、Bi的加入会降低SZC合金的熔点,同时又会导致熔化区间扩大和富Zn相的粗化;Ni的加入会随着含量增加逐渐消除含Bi钎料组织的粗大,但会相应地提高液相线。在Ni达1%时,钎料基体中圆棒状Cu₅Zn₈相开始转变成方块状（Cu,Ni）₅Zn₈相;Bi、Ni的加入都能有效提高钎料的可焊性。随着Ni含量的增加,润湿角逐渐减少,且在使用RMA钎剂情况下,润湿角减为一半以上;微量Bi、Ni对界面IMC组织与形貌没什么影响,但1%Ni会降低界面IMC地厚度和钎料处富Zn相的含量。 3、与Sn-9Zn不润湿Ni基板的相反是,SZ-3Cu钎料中Zn与Cu生成化合物有利避免Zn在液态钎料钎焊时的氧化,在使用RMA钎剂情况下仍然较好的在Ni基上铺Sn.Zn一Cu无铅钎料研究展,所得润湿角为67“;界面IMC NisZn21在170℃下时效I000h仍然保持完整,时效初期（SO0h以前）厚度与时间主要成抛物线关系,时效时间超过50Oh后n涯C厚度增长非常缓慢因为Zn很难由Cu一Zn化合物扩散至界面。关键词:无铅钎料;显微组织;时效;润湿性;金属间化合物n-更多还原

【Abstract】 Lead and Pb compounds have been cited by the Environmental Protection Agency (EPA) as one of the top 17 chemicals posing the greatest threat to human beings and the environment, which indicate that developing viable alternative lead-free solders for electronic assemblies and other soft soldering is a trend. Through more than 10 years study, Sn-Ag、 Sn-Zn et al are summarized as properly substitutes of Sn-Pb alloy. In all Sn-based solders, Sn-Zn is a low cost , closed melting point solder and has excellent mechanical properties, however the bad wetting and oxidation behavior which caused by active Zn element need be resolved before applying.Many elements such as In、 Bi、 Al are added to Sn-Zn alloy, but the improvement of wetting is still limited. Through previous experiments’ results discover, the Zn atom will transform into Cu-Zn compound when the alloy add Cu element that can reduce the oxidation of Zn in the surface of solder. So in this text, the microstructure 、 melting point and mechanical properties are investigated by alloying Cu element and the interfacial microstructures and wetting property of the new SZ-xCu solders with Cu substrate are also investigated. For improving the wetting property and decreasing the melting point, 3wt%Bi and (0~1)wt% Ni are added to (Sn-9Zn)-2Cu solder. The wetting reaction between (Sn-9Zn)-3Cu and under bump metallic(UBM) Ni and the effect of 170℃ thermal aging on the joint are investigated for studying the reliability of solder joint. All the results show that:1、The addition of Cu can decrease the oxidation of Zn in liquid surface, which actually lessenthe surface tension and acquire the smaller angles and elevate the melting point too. The tensile strength start increase and decrease later as the Cu contents increase and the variety of shear strength is caused by the change between IMC and solder. When the Cu content between 0-8%, the needle Zn phase change into Cu-Zn compound and the contents exceed 8%, Cu6Sn5 begin to appear, when the Cu content at 0~2%Cu ,Cu5Zn8 compounds is formed at the SZ-xCu /Cu interface and both Cu6Sn5 and Cu5Zn8 compounds is formed at 2% ~ 6%, nearly single scallop Cu6Sn5 layer was detected as the addition is beyond 8%.2、The addition of 3% Bi can decrease the melting point and Ni adding to SZC-Bi alloys willrefine the microstructures and at 1%Ni, the rod-shape Cu5Zn8 phase changed into square-shape (Cu, Ni)5Zn8 phase. Alloying with Bi、Ni, SZC solder can improve the wettabilityand the wetting angles decrease half from that of Sn-9Zn by using RMA flux, when Ni content increase, The additives have little effect on the composition of interfacial IMC and the reaction layer decrease from 4um to 3um in SZC-Bi-Ni alloy for the formation of (Cu, Ni)-Zn compound, which resulted less Zn atoms diffusing to the interface. 3、(Sn-9Zn)-3Cu wet well on Ni substrate and acquire 67° even using RMA flux; When thermal aging at 170℃, The plane MC Ni5Zn21 will not decompose after 1000h and the IMC thickness with time is parabola relation before 500h,however after 1000h the thickness do not change which is caused by no more Zn atom diffusing into interface.更多还原