微合金化对Sn-9Zn基无铅钎料润湿性能的影响

熔炼制备了纯的以及含微量Al、Mg、Ti、Bi、重稀土Y、混合轻稀土RE和一种富P非金属活性组元NM的Sn-9Zn基合金,通过测量这些合金以及商用Sn-37Pb焊料在铜基板上的铺展面积比较了它们对铜的润湿性能。结果表明Al、Ti和 Mg不利于提高合金在铜上的润湿性或附着力;Y的改善作用不大;而Bi、RE和NM则能明显改善Sn-9Zn合金对铜的润湿性。在此基础上进一步研究了RE和NM含量对Sn-9Zn润湿性能的影响。以铺展面积衡量,本研究所达到的最佳改善效果使Sn-9Zn合金对铜的润湿性由Sn-37Pb焊料润湿性水平的45.4%提高到了70.3%。     

锡锌合金无铅电子钎料有机活化松香助焊剂

锡锌合金是很有潜力的无铅电子焊料合金,润湿性较差是其发展的主要障碍.研究发现:在传统乙醇松香助焊剂中添加质量分数为0.5%的DMA可显著提高其活性,使Sn-9Zn对铜的润湿力和润湿铺展面积都有显著提高;再加入适当比例的乙二胺可使其改善润湿性的效果进一步提高,并大大减轻助焊剂对Sn-9Zn合金的腐蚀性.     

无铅焊料在清华大学的研究与发展

清华大学材料科学与工程系电子材料与封装技术研究室研制了6个系列的无铅焊料:Sn-3.5Ag添加Cu或Bi; Sn-3.5Ag-1.0Cu添加In或Bi; Sn-Ag-Cu-In添加Bi; Sn-Ag-Cu添加Ga; Sn-Zn添加Ga; Sn-Zn添加多种元素。重点介绍了Sn-Zn添加多种元素。对6个系列无铅焊料的研究取得了较好的实验结果,得到比较理想的低温焊料体系,有的合金熔点已非常接近铅锡共晶焊料熔点183℃。     

Sn-0.3Ag-0.7Cu-xBi低银无铅钎料的润湿性

以Bi为添加剂对低银型Sn-0.3Ag-0.7Cu无铅钎料进行改性,应用SAT—5100型润湿平衡仪对Sn-0.3Ag-0.7Cu-xBi(x=0,1,3和4.5)钎料的润湿性能作了对比分析。结果表明:适量Bi元素的加入可以改善Sn-0.3Ag-0.7Cu钎料合金的润湿性能,且在240℃下Sn-0.3Ag-0.7Cu-3.0Bi无铅钎料具有最佳的润湿性能,在250℃其润湿力达到最大值3.2×10–3N/cm。     

Sn-Bi-Sb无铅焊料微观结构及性能

研究了Sn-（1．3～1．5）Bi-（0．4～0．6）sb无铅焊料的制备工艺和微观组织,并测试了钎料的相关物理、力学性能,阐述了焊料的力学性能与微观结构特征间的关系。试验测试结果表明：该焊料具有较高的强度和塑性,具有良好的润湿铺展性和机械加工性能。焊料微观结构由（Sn）、B（SbSn）第二相和（Bi）所构成,其抗拉强度为55．4MPa,延伸率为35．9％,扩展率为80．6％,熔点为226．9℃～234．4℃。     

Sn-8Zn-3Bi无铅焊料的表面改性

采用液相法用有机物改性剂对Sn-8Zn-3Bi焊料进行表面包覆改性,以改善焊料的润湿性能及抗氧化性能。对包覆样品进行了红外光谱表征。考察了样品的抗氧化性、润湿性能和存储性能。结果表明:采用液相法可以实现在Sn-8Zn-3Bi焊料表面包覆有机物。以有机物C为改性剂,且用量为2%(质量分数)时得到的改性样品的润湿角θ为7.8°,铺展面积S为108.83mm2,而未被改性的焊料θ为10.74°,S为93.40mm2。     

微量元素对焊料特性的影响

在Sn-20Bi焊料中添加微量Ag、In、Ga和Sb,观察焊料的熔化特性和显微组织的变化.结果表明当Ag的质量分数为0.7%、In为0.1%、Ga为0.5%时焊料的熔点都分别有所降低,Bi的偏析明显减小;Sb不宜作为单独的第三组元加入,但与Ag、In、Ga一起加入时Sb能起到很好的固溶强化且有抑制Sn的相变的作用.通过最佳配比制成的Sn-Bi-X焊料,其熔点与Sn-37Pb接近,而且已不存在Bi的偏析,接近于实用.     

无铅SAC0307焊料润湿性与漫流性集成测试

为节省测试时间并降低测试成本,通过测量SAC0307焊料对铜管的润湿力、爬升高度及焊料对铜片的润湿力和铺展率,建立润湿性和漫流性的对应关系,集成测试获得焊料对铜片的润湿性能和铺展能力。结果表明,松香助焊剂作用下焊料对铜片的润湿力为铜管的1.1倍,丁二酸助焊剂作用下焊料对铜片的润湿力是铜管的1.3倍,松香和丁二酸两种助焊剂作用下焊料在铜管内爬升高度与铜片上铺展率的关系都为指数关系。     

微电子封装无铅焊料润湿性研究

为解决无铅焊料润湿性差的问题,采用卤化物活性剂松香焊剂,通过实验研究了Sn-9Zn焊料的润湿性。分析讨论了影响Sn-9Zn焊料润湿性的因素,获得了最佳匹配。在镀锡铜片上,有机卤化物+无机卤化物活性剂松香焊剂(#6焊剂)匹配Sn-9Zn焊料获得最佳的润湿性(润湿角为12°),接近Sn-37Pb焊料的润湿性。     

Sn-9Zn合金无铅钎料用助焊剂研究

通过测量润湿面积和润湿角,研究不同助焊剂对Sn-9Zn焊料润湿性的影响。结果表明:助焊剂对Sn-9Zn焊料润湿性影响很大,由乳酸、聚乙二醇和SnCl2所构成的助焊剂与Sn-9Zn焊料有很好适应性;同时扫描电镜和能谱分析也表明焊料与Cu基体界面的IMC为Cu5Zn8相,比Sn-37Pb焊料具有更高的剪切强度。     

Sn基钎料与Cu和Al基板的润湿性比较研究

采用润湿平衡法测量了四种Sn基钎料(Sn-37Pb、Sn-3.OAg-0.5Cu、Sn-0.7Cu与Sn-9Zn)分别在250,260和270℃与Cu、Al两种基板的润湿性能.结果表明:钎料与Al基板的润湿时间均比Cu基板长,除Sn-9Zn外,其他三种钎料与Cu基板的润湿力比Al基板大,并且随着温度升高,润湿性能提高,...     

Wetting and reaction of Sn-2.8Ag-0.5Cu-1.0Bi solder with Cu and Ni substrates

The wettability of newly developed Sn-2.8Ag-0.5Cu-1.0Bi lead-free solder on Cu and Ni substrates was assessed through the wetting balance tests. The wettability assessment parameters such as contact angle (ϑ_c) and maximum wetting force (F_w) were documented for three solder bath temperatures with three commercial fluxes, namely, no-clean (NC), nonactivated (R), and water-soluble organic acid flux (WS). It was found that the lead-free Sn-2.8Ag-0.5Cu-1.0Bi solder exhibited less wetting force, i.e., poorer wettability, than the conventional Sn-37Pb solder for all flux types and solder bath temperatures. The wettability of Sn-2.8Ag-0.5Cu-1.0Bi lead-free solder on Cu substrate was much higher than that on Ni substrate. Nonwetting for Sn-2.8Ag-0.5Cu-1.0Bi and Sn-Pb solders on Ni substrate occurred when R-type flux was used. A model was built and simulations were performed for the wetting balance test. The simulation results were found very close to the experimental results. It was also observed that larger values of immersion depth resulted in a decrease of the wetting force and corresponding meniscus height, whereas the increase in substrate perimeter enhanced the wettability. The wetting reactions between the solder and Cu/Ni substrates were also investigated, and it was found that Cu atoms diffused into the solder through the intermetallic compounds (IMCs) much faster than did the Ni atoms. Rapid formation of IMCs inhibited the wettability of Sn-2.8Ag-0.5Cu-1.0Bi solder compared to the Sn-Pb solder.     

Spreading Behavior and Evolution of IMCs During Reactive Wetting of SAC Solders on Smooth and Rough Copper Substrates

The effect of surface roughness of copper substrate on the reactive wetting of Sn-Ag-Cu solder alloys and morphology of intermetallic compounds (IMCs) was investigated. The spreading behavior of solder alloys on smooth and rough Cu substrates was categorized into capillary, diffusion/reaction, and contact angle stabilization zones. The increase in substrate surface roughness improved the wetting of solder alloys, being attributed to the presence of thick Cu₃Sn IMC at the interface. The morphology of IMCs transformed from long needle shaped to short protruded type with an increase in the substrate surface roughness for the Sn-0.3Ag-0.7Cu and Sn-3Ag-0.5Cu solder alloys. However, for the Sn-2.5Ag-0.5Cu solder alloy the needle-shaped IMCs transformed to the completely scallop type with increase in the substrate surface roughness. The effect of Ag content on wetting behavior was not significant.     

The properties of Sn-9Zn lead-free solder alloys doped with trace rare earth elements

The Sn-Zn alloys have been considered as lead-free solders. It is well known that their poor properties of wetting and oxidation resistance are the main problems to prevent them from becoming commercially viable solders. In this paper, trace rare earth (RE) elements of mainly Ce and La have been used as alloying elements into the Sn-9Zn alloy. The results indicated that with the RE addition the originally coarse β-Sn grains in the microstructure of the alloy were refined. The tensile strength significantly increased with only a slight decrease in ductility. The surface tension was decreased, resulting in great improvement in wetting properties with rosin-based active flux.     

Sn-Cu、Sn-Ag-Cu系无铅钎料的钎焊特性研究

制备了Sn-0.7Cu、Sn-3.5Ag-0.6Cu钎料,用润湿平衡法测量了钎料对铜的润湿曲线,研究了温度、钎剂活性、钎焊时间对润湿行为的影响,并与Sn-37Pb钎料进行了比较。结果表明:升高温度能显著改善无铅钎料对铜的钎焊性。当温度<270℃时,Sn-0.7Cu的钎焊性明显低于Sn-3.5Ag-0.6Cu钎料;而当温度≥270℃时,两种钎料对铜都会显示较好的润湿性,而Sn-0.7Cu略优于Sn-3.5Ag-0.6Cu钎料。提高钎剂活性能显著增强钎料对铜的润湿性,其卤素离子的最佳质量分数均为0.4%左右。随着浸渍时间的延长,熔融钎料与铜的界面间产生失润现象。无铅钎料的熔点和表面张力较高,是钎焊性较差的根本原因。     

三种高Sn无铅钎料的表面张力和润湿性能研究

采用悬滴法测量了3种无铅钎料合金(Sn-3.0Ag-0.5Cu、Sn-0.7Cu与Sn-9.0Zn)在260℃时的表面张力,分别为525.5,534.8和595.4 mN/m;同时采用座滴法测量了其在260℃熔融状态下与Cu基板的接触角,分别为24.5°、28.0°和102.5°,并且与传统Sn-37.0Pb钎料进行了比较研究。结果表明,无铅钎料合金的表面张力与接触角均大于Sn-37.0Pb钎料。结合Young-Dupre公式讨论了钎料合金表面张力与其润湿性能的相关性,认为Sn基钎料合金在Cu基板上的润湿性能主要取决于其表面张力。     

Effect of reaction time on mechanical strength of the interface formed between the Sn-Zn(-Bi) solder and the Au/Ni/Cu bond pad

In this work, the shear strengths and the interfacial reactions of Sn-9Zn, Sn-8Zn-1Bi, and Sn-8Zn-3Bi (wt.%) solders with Au/Ni/Cu ball grid array (BGA) pad metallization were systematically investigated after extended reflows. Zn-containing Pb-free solder alloys were kept in molten condition (240°C) on the Au/electrolytic Ni/Cu bond pads for different time periods ranging from 1 min. to 60 min. to render the ultimate interfacial reaction and to observe the consecutive shear strength. After the shear test, fracture surfaces were investigated by scanning electron microscopy equipped with an energy dispersive x-ray spectrometer. Cross-sectional studies of the interfaces were also conducted to correlate with the fracture surfaces. The solder ball shear load for all the solders during extended reflow increased with the increase of reflow time up to a certain stage and then decreased. It was found that the formation of thick Ni-Zn intermetallic compound (IMC) layers at the solder interface of the Au/electrolytic Ni/Cu bond pad with Sn-Zn(-Bi) alloys deteriorated the mechanical strength of the joints. It was also noticed that the Ni-Zn IMC layer was larger in the Sn-Zn solder system than that in the other two Bi-containing solder systems.     

Sn-Zn系钎料研究及应用现状

随着钎料无铅化的发展,Sn-Zn钎料以其低廉的成本,与SnPb钎料相近的熔点成为无铅钎料研究的重点.但是Sn-Zn钎料存在易氧化,抗腐蚀性差,润湿性差的问题,通常在SnZn钎料中加入不同元素,改善其性能.主要阐述不同添加元素Bi、Al、In、Re(稀土元素)、Ag、Cu、P和多元合金对SnZn钎料自身性能和钎料与Cu结合性能的影响,概述SnZn系钎料的工业应用现状.