电子元件、组件

TN60 2004030494铜锢钊硫对Sn一Ag基无铅焊料性能的影响/林培豪,刘心宇,成钧(桂林电子工业学院)11电子元件与材料‘一2 003,22(10).一33-34研究了Cu、In、Bi、S元素对Sn一Ag基无铅焊料熔点和铺展性的影响.结果表明:Sn一A片Cu三元合金成分为9 5.5%Sn3.5%Agl%Cu时具有较低熔点(215℃)和好的铺展性;加入适量的In可降低Sn一Ag合金的熔点和改善铺展性能;随二(B劝的增加Sn-Ag一Bi三元合金熔点降低、铺展性变好;Sn一Ag合金熔点随、(S)的增加而升高,加入少量S能改善Sn一Ag合金的铺展性.图8参5(刚)影响,发现随着硫酸浓度增加,温度对隧道…     

表面封装用无铅软钎料的接头强度及熔点范围的研究

研究了Bi的添加量,对电子表面封装(SMT)用Sn-Ag近共晶无铅软钎料钎焊接头抗拉强度和熔点及熔点范围的影响。随着Bi含量的增加,钎焊接头抗拉强度也随着增加,同时钎料的液固相线温度均降低。当Bi的含量达到5%时,抗拉强度增加快;Bi的添加量大于5%时,抗拉强度上升缓慢。在Bi的含量增加时,熔点温度范围也逐渐变宽,使得凝固时间变长,这对于表面组装中的电子元件与器件的焊接是非常不利的。故在Sn-Ag近共晶无铅软钎料中Bi的添加量,应加以适当的控制。     

Sn对BiSbCu钎料钎焊工艺性能的影响

在BiSbCu钎料中添加Sn,分析Sn对BiSbCu钎料合金钎焊工艺性能的主要指标——钎料熔点和铺展面积的影响。结果表明:在Bi5Sb2Cu钎料合金中加入Sn可以显著降低钎料的熔点和显著增强钎料合金的铺展性能。当Sn的质量分数为10%时,Bi5Sb2Cu钎料的铺展面积为26.22 mm2,钎焊工艺性能最好。     

Sn对BiSbCu钎料钎焊工艺性能的影响

在BiSbCu钎料中添加Sn,分析Sn对BiSbCu钎料合金钎焊工艺性能的主要指标——钎料熔点和铺展面积的影响.结果表明:在Bi5Sb2Cu钎料合金中加入Sn可以显著降低钎料的熔点和显著增强钎料合金的铺展性能.当Sn的质量分数为10％时,Bi5Sb2Cu钎料的铺展面积为26.22 mm2,钎焊工艺性能最好.     

纳米Sn-Ag钎料合金熔化温度及形成焓的研究

考虑表面效应,基于Lindemann熔化准则,利用Miedema模型对Sn-Ag纳米钎料合金的熔化温度及形成焓进行计算.Sn-Ag纳米合金微粒的熔化温度及形成焓均依赖于尺寸和组元成分;对于Sn3.5 Ag纳米钎料合金,当微粒尺寸大小为5nm时,其熔化温度下降约为7％;而合金形成焓随晶粒粒径的减小而增加,合金稳定性降低;对于Sn3.5Ag钎料合金,当粒径尺寸为0.1μm时,合金形成焓完全为正值,对Sn-Ag钎料合金组织形成存在产生很大影响.     

无铅焊接技术的改进

目前,无铅焊接有待改进之处甚多,归纳起来有以下几个方面:1.使用哪种合金焊料,选用Su—Cu或Sn-Ag—Cu,是否加入Bi,它的润湿性、可靠性和可作业性如何;2.有关无铅焊接技术专利选择和利用;3.如何进行加热,采用再流焊还是波峰焊;4.成分变化,如像Cu成分增加,熔点上升,不良焊接部分增加等问题;5.无铅焊接成本与经济性;6.适应无铅焊接工艺的电路板设计;     

Sn－Zn－In软钎料合金初步研究

对Ｓｎ－Ｚｎ－Ｉｎ钎料合金的性能进行了研究，钎料铺展性和剪切强度试验结果表明，在Ｓｎ－９Ｚｎ－Ｉｎ软钎料合金中，随Ｉｎ含量增加，铺展面积增大，钎焊接头剪切强度降低。钎料熔点和接头组织等性能的综合分析结果表明Ｓｎ－９Ｚｎ－１０Ｉｎ的性能已接近或超过传统的Ｓｎ－Ｐｂ共晶     

Sn—Zn—In软钎料合金初步研究

对Ｓｎ－Ｚｎ－Ｉｎ钎料合金的性能进行了研究，钎料铺展性和剪切强度试验结果表明，央Ｓｎ－９Ｚｎ－Ｉｎ软钎料合金中，随Ｉｎ含量增加，铺展面积增大，钎焊接头剪切强度降低。钎粒熔点和接头组织等性能的综合分析结果表明Ｓｎ－９Ｚｎ－１０Ｉｎ的性能已接近或超过传统的Ｓｎ－Ｐｂ共晶。     

BiSbCuSn高温无铅软钎料物理性能及润湿性能研究

研制开发熔点在250～450℃之间的高温无铅软钎料一直是钎焊领域一大难题。熔点为300℃左右的Bi5Sb2Cu钎料因润湿性能和导电性能不良而受到限制。本文通过在Bi5Sb2Cu中添加不同含量Sn形成新型BiSbCuSn四元合金,来改善Bi5Sb2Cu合金的润湿性能和物理性能。结果表明：在Bi5Sb2Cu钎料合金中添加2-↑10wt．％Sn,BiSbCu钎料合金熔点呈下降趋势且幅度较大,但仍在250～450℃之间,润湿性能和导电性能明显改善。当Sn含量为10wt．％时,（Bi5Sb2Cu）10Sn钎料合金润湿性能和导电性能最好。     

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%。     

新型无铅焊料的研制

由于目前使用的Sn3.5AgCu无铅焊料,温度较高、润湿性较差.在Sn3.5AgCu无铅钎料中添加金属元素Ga、Bi,并改变Ag的含量,对其合金进行熔化温度、润湿性、力学性能和微观组织研究.研究表明,添加Ga、Bi并改变Ag含量有利于降低Sn3.5AgCu合金的熔化温度和改善其润湿性,并提高了力学性能.     

Influences of Substrate Alloying and Reflow Temperature on Bi Segregation Behaviors at Sn-Bi/Cu Interface

In this study, the influences of substrate alloying and reflow temperature on the Bi segregation behaviors at the Sn-Bi/Cu interface were investigated. Cu and Cu-Ag alloys with different Ag contents were reflowed with Sn-Bi solder at 180°C, 200°C or 220°C, and then aged at 120°C for different times. The evolution of their interfacial morphologies during the aging process was observed, and tensile tests of some solder joints were conducted. The experimental results reveal that the Bi atoms that dissolved in the Cu₆Sn₅ during the reflow process are expelled when the Cu₆Sn₅ transforms into Cu₃Sn and then segregate around the Cu₃Sn/Cu interface, inducing interfacial embrittlement. Alloying the Cu substrate with Ag can alleviate the Bi segregation by suppressing Cu₃Sn formation and dissolving the Bi atoms in the Cu-Ag substrate; the critical Ag content to eliminate the Bi segregation is about 1 at.% for the interface reflowed at 200°C. For interfaces reflowed at 180°C, the Bi segregation is less serious because less Bi is dissolved in the Cu₆Sn₅, and 0.6 at.% Ag can eliminate it. Tensile tests demonstrate that the embrittlement will not occur at Sn-Bi/Cu-Ag joints once the Bi segregation is eliminated. Based on this understanding, aging embrittlement of Sn-Bi/Cu solder joints can be prevented by decreasing the reflow temperature and adding a small amount of Ag to the Cu substrate.     

Properties of Sn3.8Ag0.7Cu Solder Alloy with Trace Rare Earth Element Y Additions

In the current research, trace rare earth (RE) element Y was incorporated into a promising lead-free solder, Sn3.8Ag0.7Cu, in an effort to improve the comprehensive properties of Sn3.8Ag0.7Cu solder. The range of Y content in Sn3.8Ag0.7Cu solder alloys varied from 0 wt.% to 1.0 wt.%. As an illustration of the advantage of Y doping, the melting temperature, wettability, mechanical properties, and microstructures of Sn3.8Ag0.7CuY solder were studied. Trace Y additions had little influence on the melting behavior, but the solder showed better wettability and mechanical properties, as well as finer microstructures, than found in Y-free Sn3.8Ag0.7Cu solder. The Sn3.8Ag0.7Cu0.15Y solder alloy exhibited the best comprehensive properties compared to other solders with different Y content. Furthermore, interfacial and microstructural studies were conducted on Sn3.8Ag0.7Cu0.15Y solder alloys, and notable changes in microstructure were found compared to the Y-free alloy. The thickness of an intermetallic compound layer (IML) was decreased during soldering, and the growth of the IML was suppressed during aging. At the same time, the growth of intermetallic compounds (IMCs) inside the solder was reduced. In particular, some bigger IMC plates were replaced by fine, granular IMCs.     

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.     

Comparative study of microstructures and properties of three valuable SnAgCuRE lead-free solder alloys

Lead-free solders with excellent material properties and low cost are essential for the electronics industry. It has been proved that mechanical properties of SnAgCu alloys can be remarkably improved with a minute addition of rare earth (RE) elements. For comparison and optimization, three valuable solder candidates, Sn3.8Ag0.7Cu0.05RE, Sn3Ag0.5Cu0.05RE, and Sn2.9Ag1.2Cu0.05RE, were chosen due to the excellent properties of their own SnAgCu basic alloys. Wetting properties, melting temperature, bulk tensile properties, and joint tensile and shear properties were investigated. In addition, the microstructures of solder joints were observed and the effects of microstructure on mechanical properties were analyzed. Experimental results indicated that the tensile and shear strengths of solder joints were decreased from Sn3.8Ag0.7Cu0.05RE, Sn2.9Ag1.2Cu0.05RE, to Sn3Ag0.5Cu0.05RE, in order. Such difference in mechanical properties could be attributed to the influence of slightly coarse or strong Cu₆Sn₅ scallops in the reaction layer as well as superior eutectic network and large volume percentage of large primary intermetallic compounds (IMCs) inside the solder joints. It is also suggested that the size and volume percentage of large primary IMCs inside the solder be controlled. In addition, serration morphology was observed at the edge of large primary and eutectic IMCs in the three solder joints, which could be related to the content of Ag, Cu, and RE. The serration morphology was proved to be beneficial to mechanical properties theoretically. Furthermore, the three alloys investigated possessed similar wetting properties, melting temperatures, and bulk tensile properties.     

Lead-free Sn-Ag and Sn-Ag-Bi solder powders prepared by mechanical alloying

A mechanical alloying (MA) process was used to produce lead-free solder pastes of Sn-3.5Ag and the Sn-3.5Ag-4Bi system. Because of the high energy induced by repeated fracturing and welding, the grinding media played an important role during the MA process. A ceramic container was used to provide stronger impact force, which could induce phase transformation better than a Teflon container. In addition, it was found that 1-cm balls could fracture Bi particles and promote their dissolution into the Sn matrix. On the contrary, the milling process tended to achieve homogeneous mixing when using 3-mm balls. The MA powders, after milling with 3-mm balls, showed a small endothermic peak from the differential scanning calorimetry (DSC) profile at around 138°C, which was the eutectic temperature of Sn-Bi. The melting points of the MA powders in the ceramic container were measured to be 221°C and 203°C, respectively, for Sn-3.5Ag and Sn-3.5Ag-4Bi from the DSC curves. The reduced melting point ensured the complete melting during reflow with a peak temperature of 240°C. The formation of Ag₃Sn was also observed from the x-ray diffraction peaks, indicating successful alloying by MA. The solder pastes could, thus, be produced by adding flux into the MA powders. The wetting property of the solder joint was also evaluated. The as-prepared solder pastes on electroless Ni-P/Cu/Si showed good metallurgical bonding with a contact angle less than 20°.     

Interfacial reactions and shear strengths between Sn-Ag-based Pb-free solder balls and Au/EN/Cu metallization

The morphological and compositional evolutions of intermetallic compounds (IMCs) formed at three Pb-free solder/electroless Ni-P interface were investigated with respect to the solder compositions and reflow times. The three Pb-free solder alloys were Sn3.5Ag, Sn3.5Ag0.75Cu, and Sn3Ag6Bi2In (in wt.%). After reflow reaction, three distinctive layers, Ni₃Sn₄ (or Ni-Cu-Sn for Sn3.5Ag0.75Cu solder), NiSnP, and Ni₃P, were formed on the electroless Ni-P layer in all the solder alloys. For the Sn3.5Ag0.75Cu solder, with increasing reflow time, the interfacial intermetallics switched from (Cu,Ni)₆Sn₅ to (Cu,Ni)₆Sn₅+(Ni,Cu)₃Sn₄, and then to (Ni,Cu)₃Sn₄ IMCs. The degree of IMC spalling for the Sn3.5Ag0.75Cu solder joint was more than that of other solders. In the cases of the Sn3.5Ag and Sn3Ag6Bi2In solder joints, the growth rate of the Ni₃P layer was similar because these two type solder joints had a similar interfacial reaction. On the other hand, for the Sn3.5Ag0.75Cu solder, the thickness of the Ni₃P and Ni-Sn-P layers depended on the degree of IMC spalling. Also, the shear strength showed various characteristics depending on the solder alloys and reflow times. The fractures mainly occurred at the interfaces of Ni₃Sn₄/Ni-Sn-P and solder/Ni₃Sn₄.     

Trends and issues in Pb-free soldering for electronic packaging

A variety of Pb-free solder alloys have been proposed for use as interconnects for electronic packaging including Sn?Ag, Sn?Cu, Sn?Ag?Cu, Sn?Ag?Bi, and Sn?Sb, among others. This paper presents a review of the behavior of promising Pb-free solder alloys as related to their microstructure. Recommendations of optimal alloy composition as a function of performance requirements are given. For surface mount applications, eutectic Sn?Ag?Cu is recommended as the optimal alloy. For flip chip interconnects, the eutectic Sn-Cu alloy has the best performance. The materials and process trends of Pb-free packaging are summarized with optimal conditions identified.     

Effects of Trace Amounts of Rare Earth Additions on Microstructure and Properties of Sn-Bi-Based Solder Alloy

The effect of trace amounts of rare earth additions on the microstructure and properties were studied for the Sn-58Bi and Sn-58Bi-Ag solder alloys. At the same time, the intermetallic compounds (IMCs) in the solder alloys and intermetallic layer (IML) thickness at the solder/Cu substrate interface were investigated, both as-reflowed and after high-temperature aging. The results indicate that adding trace amounts of rare earth (RE) elements has little influence on the melting temperature and microhardness of the solders investigated, but adding RE elements improves the wettability and shear strength of the Sn-58Bi and Sn-58Bi-Ag solder alloys. In addition, it was found that the addition of RE elements not only refines the microstructure and size of the IMC particles, but also decreases the IML thickness and shear strength of the Sn-58Bi solder joint after high-temperature aging. Adding trace amounts of RE elements is superior to adding trace amounts of Ag for improving the properties of the Sn-58Bi solder. The reason may be related to the modification of the microstructure of the solder alloys due to the addition of trace amounts of RE elements.     

镧对Sn3.5Ag0.5Cu钎料组织性能影响

运用莱卡显微镜、扫描电镜和能谱分析等手段,研究了稀土元素La的添加量对Sn3.5Ag0.5Cu钎料及其与Cu基体焊接后微观组织及性能的影响。结果表明:添加不同含量的稀土La均能使钎料及其与Cu基体焊接后组织与性能得到改善,其中以w(La)达到0.05%时为最优,显微硬度及剪切强度分别提高14%和10.7%。键参数函数计算结果表明La具有"亲Sn"倾向,可细化钎料组织,降低IMC(界面金属间化合物)的长大驱动力。