添加Bi和P对Sn-0.7Cu无铅钎料合金性能的影响

研究了添加Bi和P对Sn-0.7Cu无铅钎料合金熔点、显微组织、在Cu上的润湿性、导电率、硬度以及蠕变抗力等性能的影响。实验结果显示,随Bi含量增加,Sn-0.7Cu合金的熔点、导电率略有降低,润湿性、抗蠕变性能和维氏硬度均提高;此外,在添加Bi的基础上加P元素,能进一步降低Sn-0.7Cu-Bi合金的熔点,提高合金的导电率和润湿能力,但合金硬度略有下降;Sn-0.7Cu-1Bi-0.05P钎料合金的抗蠕变性优于Sn-0.7Cu-1Bi,Sn-0.7Cu-3Bi-0.05P钎料合金的抗蠕变性则劣于Sn-0.7Cu-3Bi。金相显微组织观察表明,单独加Bi能细化Sn-0.7Cu合金中的Cu6Sn5金属间化合物相;P的加入使Sn-0.7Cu-1Bi合金中的β-Sn枝晶尺寸变小,且Cu6Sn5相呈规则网络状分布于枝晶间隙;而在Sn-0.7Cu-3Bi合金中加P则粗化了Cu6Sn5相,并使IMC呈无规则分布。     

Sn-58Bi-(0~3)Ga/Cu润湿剪切性能及界面化合物的研究

采用熔炼铸造法制备了Sn-58Bi-(0~3)Ga焊料合金,研究了Ga元素含量对合金熔化特性、润湿和剪切性能的影响,并利用扫描电镜研究了Sn-58Bi-(0~3)Ga/Cu基体界面特征。结果表明,Ga元素的添加降低了合金的熔点,增大了合金的熔程,相比于Sn-58Bi合金,Sn-58Bi-1Ga焊料合金在铜基体的铺展率显著下降,剪切强度略有提高,随着Ga含量提高至2%、3%,合金的铺展率略有下降,剪切强度显著降低;Sn-58Bi/Cu界面主要组成元素为Sn和Cu,Sn-58Bi-(1~3)Ga/Cu界面上出现了明显的Ga和Cu元素偏聚界面层,结合特征点的能谱成分分析,确定了界面化合物的组成。     

添加0.05％(La+Ce)对SnXCuNi焊料与Cu基板间界面组织的影响

在Sn-4.1X-1.5Cu-Ni焊料合金中添加0.05％(质量分数,下同)(La+Ce),对焊料/Cu焊点等温时效后其界面组织的变化规律以及界面金属间化合物的形成和生长行为进行分析研究,结果表明:随着等温时效时间的延长,Sn-4.1X-1.5Cu-Ni/Cu和Sn-4.1X-1.5Cu-Ni-0.05(La+Ce)/...     

添加Ag元素对铝软钎焊用Sn-1.5Zn系钎料性能的影响

研究了添加不同含量Ag元素对铝软钎焊用Sn-1.5Zn系钎料合金的熔化特性、显微组织、润湿性及钎焊接头抗腐蚀性能的影响。研究结果表明,Ag元素的添加缩短了Sn-1.5Zn钎料的熔程,细化了显微组织;采用润湿平衡法测量结果发现,添加Ag元素提高了钎料对铝基体的最大润湿力Fmax,但使润湿时间t0增加;采用3%(质量分数)浓度盐水溶液浸泡焊点实验结果表明,添加Ag元素提高了钎焊接头的抗腐蚀性。     

热挤压Mg-3Sn-1Zn-xCu合金的显微组织与力学性能

研究了添加Cu对热挤压Mg-3Sn-1Zn合金显微组织和力学性能的影响。结果表明:添加少量Cu能显著细化热挤压Mg-3Sn-1Zn合金晶粒,同时在合金中形成具有高热稳定性的CuMgZn相,提高了合金的室温及高温强度和塑性。当Cu含量为0.5%时,热挤压Mg-3Sn-1Zn-0.5Cu合金的晶粒最细,为2.8 μm;其强度和塑性最高,室温屈服强度为241 MPa,伸长率为20.3%,150 ℃时屈服强度为128 MPa,室温拉伸力学性能优于挤压态AZ31B合金,高温强度优于铸态AE42合金。     

Ce的添加对SnAgCu系钎料组织和性能的影响

通过向Sn-0.3Ag-0.7Cu系无铅焊料中添加微量稀土Ce,研究不同稀土含量对Sn-0.3Ag-0.7Cu合金的熔化温度和润湿性的影响,同时利用扫描电子显微镜(SEM)对焊料的显微组织进行了分析.实验结果表明,添加Ce对焊料的熔化温度影响不大,但对合金的润湿性和微观组织影响较大.当ω(Ce)=0.10%时,焊料合金的综合性能较好.     

Sn-0.7Cu无铅钎料对铜引线材料的润湿性

采用改性熔炼工艺制备了Sn-0.7Cu改性合金,用润湿平衡法研究了温度、钎剂中卤素含量、浸渍时间对铜引线材料润湿性的影响,并与Sn-37Pb进行了对比.结果表明:升高温度可明显提高润湿性;当用R(非活性)钎剂时,Sn-0.7Cu对铜引线不润湿;随着钎剂中卤素离子的增加,其润湿性得到显著改善,钎剂中卤素含量以≥0.4wt%为宜;随浸渍时间的延长,润湿力明显降低,表明界面存在"失润现象".     

Sn-9Zn无铅焊料合金凝固组织及其在时效中的演变

为了考察Sn-9Zn无铅焊料合金凝固组织及其在时效中的演变,制备了不同冷却条件及不同熔体过热度下Sn-9Zn/Cu焊点,并利用扫描电镜和光学显微镜观察了其组织形貌.观察发现:共晶组织随冷却速率提高而显著细化;同时,随炉缓冷凝固时合金形成完全的层片状共晶组织,而空冷和喷水冷却条件下合金除层片状共晶组织外,还形成了杆状富锌相.实验结果还表明,熔体过热度对出炉空冷合金的共晶组织有显著影响,较高的熔体过热度使共晶组织更细密.在空冷合金的时效过程中,杆状富锌相趋于逐渐溶解消失,90℃时效时还发生了共晶组织的显著粗化.     

Sn-9Zn-xAg钎料在Cu基材上润湿性能及界面组织的研究

研究了添加合金元素Ag对Sn-9Zn无铅钎料显微组织、在铜基上的润湿性能及对钎料/铜界面组织的影响.研究结果表明:当Ag的含量(质量分数,下同)在0.1%～0.3%时,钎料中针状富Zn相逐渐减少,当Ag的含量在0.5%～1%时,钎料中出现Ag-Zn化合物相;当Ag的含量为0.3%时,钎料具有最好的润湿性能,当Ag的含量为0.5%～1%时,钎料的润湿性能下降;Sn-9Zn/Cu的界面处形成平坦的Cu5Zn8化合物层,当Ag含量为0.3%时,在Cu5Zn8化合物层上出现节结状的AgZn3化合物相,随着Ag含量的提高,这种节结状的AgZn3化合物相逐渐聚集长大成扇贝状的化合物层.     

稀土对Al-Zn-M g-Cu/Al2O3陶瓷界面润湿性的影响

采用真空座滴法和熔铸法研究了在Al-Zn-Mg-Cu 合金中加入稀土(Ce、Y) 对Al2Zn2M g2Cu/Al₂O₃陶瓷界面润湿性的影响。结果表明,Al-Zn-Mg-Cu 合金中加入稀土可有效降低铝合金/Al₂O₃界面的接触角, 改善界面结合状态; 稀土改善界面润湿性存在一最佳含量范围, 添加Ce 的最佳含量约为0. 5w t% , Y 约为0. 7w t%。稀土改善润湿性的作用主要是稀土与Al₂O₃膜、Al₂O₃陶瓷发生反应。Mg、Zn、Cu 等合金元素在界面富集并参与界面反应对润湿性有利; 稀土与Mg、Zn、Cu 等合金元素适当组合改善润湿性的效果比单一稀土明显。      

The effect of 0.5 wt.% Ce additions on the electromigration of Sn9Zn BGA solder packages with Au/Ni(P)/Cu and Ag/Cu pads

It has previously been established that Sn-9Zn-0.5Ce alloy possesses mechanical properties superior to those of undoped Sn-9Zn alloy, and is free of the problem of rapid whisker growth. However, no detailed studies have been conducted on the electromigration behavior of Sn-9Zn-0.5Ce alloy. In this research, Sn-9Zn and Sn-9Zn-0.5Ce solder joints with Au/Ni(P)/Cu and Ag/Cu pads were stressed under a current density of 3.1 × 10⁴ A/cm² at room temperature for various periods of time. Due to finer grain sizes, the electromigration effects were more severe in Sn-9Zn-0.5Ce solder joints than in Sn-9Zn solder joints when joint temperature was around 80 °C. In addition, both solder joints (Sn-9Zn and Sn-9Zn-0.5Ce) with Au/Ni(P)/Cu pads possess longer current-stressing lifetimes than those with Ag/Cu pads because Ni is more resistant than Cu to migration driven by electron flow.     

Effect of Ni Content on Mechanical Properties and Corrosion Behavior of Al/Sn－9Zn－xNi/Cu Joints

The effects of Ni content on the microstructure and the wetting behavior of Sn-9Zn-xNi solders on Al and Cu substrates, as well as the mechanical properties and electrochemical corrosion behavior of Al/Sn-9Zn-xNi/Cu solder joints, were investigated. The microstructure of Sn-9Zn-xNi revealed that tiny Zn and coarsened Ni 5 Zn 21 phases dispersed in the β-Sn matrix. The wettability of Sn-9Zn-xNi solders on Al substrate was much better than that on Cu substrate. With increasing Ni content, the wettability on Cu substrate was slightly improved but became worse on Al substrate. In the Al/Sn-9Zn-xNi/Cu joints, an Al4.2Cu3.2Zn0.7 intermetallic compound (IMC) layer formed at the Sn-9Zn-xNi/Cu interfaces, while an Al-Zn-Sn solid solution layer formed at the Sn-9Zn-xNi/Al interface. The mixed compounds of Ni3Sn4 and Al3Ni dispersed in the solder matrix and coarsened with increasing Ni content, thus leading to a reduction in shear strength of the Al/Sn-9Zn-xNi/Cu joints. Al particles were segregated at both interfaces in the solder joints. The corrosion potentials of Sn-9Zn-xNi solders continuously increased with increasing Ni content. The Al/Sn-9Zn-0.25Ni/Cu joint was found to have the best electrochemical corrosion resistance in 5% NaCl solution.     

Wetting Behavior and Interfacial Reactions in (Sn-9Zn)-2Cu/Ni Joints during Soldering and Isothermal Aging

The wetting property of (Sn-9Zn)-2Cu (wt pct) on Ni substrate and the evolution of interfacial microstructure in (Sn-9Zn)-2Cu/Ni joints during soldering as well as isothermal aging were studied.The wetting ability of eutectic Sn-9Zn solder on Ni substrate was markedly improved by adding 2 wt pct Cu into this solder alloy.Plate-like Cu5Zn8 intermetallic compounds (IMCs) were detected in (Sn-9Zn)-2Cu solder matrix.A continuous Ni5Zn21 IMC layer was formed at (Sn-9Zn)-2Cu/Ni interface after soldering.This IMC layer kept its type and integrality even after aging at 170℃ for up to 1000 h.At the early aging stage (before 500 h), the IMC layer grew fast and its thickness followed a linear relationship with the square root of aging time.Thereafter,however, the thickness increased very slowly with longer aging time.When the joints were aged for 1000 h,a new IMC phase, (Cu,Ni)5Zn8, was found in the matrix near the interface.The formation of (Cu,Ni)5Zn8phase can be attributed to the diffusion of Ni atoms into the solder matrix from the substrate.     

Properties and microstructure of Sn-9Zn lead-free solder alloy bearing Pr

In the present work, effects of trace amount of Pr on the microstructure, wettability and mechanical properties of Sn-9Zn solder were studied. The range of Pr content in Sn-9Zn solder alloys varied from 0.01 to 0.25 wt%. Test results indicate that adding appropriate amount of Pr can evidently improve the wettability and mechanical properties of the Sn-9Zn solder alloy. The Sn-9Zn-0.08Pr solder shows the best comprehensive properties compared to other solders with different Pr content. At the same time, notable changes in microstructure were found compared with the Pr-free alloy. The needle-like Zn-rich phase in the Sn-9Zn solder was refined and became more uniform. Moreover, the thickness of the IMC layer at Sn-9Zn/Cu substrate was remarkably depressed with Pr addition.     

Intermetallic compounds formed at the interface between Cu substrate and an Sn-9Zn-0.5Ag lead-free solder

The intermetallic compounds (IMCs) formed at the interface between Cu substrate and an Sn-9Zn-0.5Ag lead-free solder alloy have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron diffraction (ED). The XRD patterns show that the main IMCs formed at the interface of Sn-9Zn-0.5Ag/Cu are γ-Cu₅Zn₈ and η′-Cu₆Sn₅. The Ag₃Sn IMC with orthorhombic structure was also observed at the Sn-9Zn-0.5Ag/Cu interface by TEM and ED analyses. The interfacial adhesion strength between the Cu substrate and Sn-9Zn-0.5Ag lead-free solder alloy is higher than that of the Sn-9Zn alloy due to the formation of Ag₃Sn IMC at the interface.     

Effects of 0.1 wt% Ni addition and rapid solidification process on Sn–9Zn solder

Effects of 0.1 wt% Ni addition and rapid solidification process on Sn–9Zn solder alloy were investigated. Characteristics of Sn–9Zn–0.1Ni alloy were analyzed compared with those of as-solidified Sn–9Zn alloy. Mechanical properties and interfacial microstructure of solder/Cu joints obtained using these solders were comparatively studied. By comparison with as-solidified Sn–9Zn alloy, the wettability of solder was obviously improved with 0.1 wt% Ni addition, and the melting behavior of the solder was promoted due to the rapid solidification process. The corrosion resistance of as-solidified and rapidly solidified Sn–9Zn–0.1Ni alloys was improved due to the formation of Ni–Zn intermetallic compound (IMC) and the refining of Zn-rich phases. Formation and growth of IMCs at the interface of Sn–9Zn–0.1Ni/Cu joints was significantly depressed. Rapid solidification process promoted the interfacial reaction during soldering and improved the bonding strength of joints.     

Effect of thermal ageing on (Sn-Ag, Sn-Ag- Zn)/PtAg, Cu/Al2O3 solder joints

As-fabricated solders of eutectic Sn-Ag and ternary Sn-3.5 wt% Ag-1 wt% Zn alloys are coupled with metallized substrates including PtAg/Al2O3 and Cu/Al2O3 to simulate the solder joint in microelectronics. The growth mechanism of intermetallics and the mechanical properties of solder joints after thermal ageing (150 °C and 200 °C) are evaluated. In this study, a 1206 passive device/solder/metallization/Al2O3 surface mount technology (SMT) assembly is employed, and a Cu stud is attached on the ceramic substrate assembly to evaluate mechanical properties and the fracture morphology by the pull-off test. In addition, microstructure evolution of the interfacial morphology, elemental and phase distribution are probed with the aid of scanning electron microscopy (SEM), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD) techniques. There are two intermetallics (Cu3Sn and Cu6Sn5) formed at the eutectic Sn-Ag solder/Cu metallized layer interface, while only Cu6Sn5 is observed in the Sn-3.5 Ag-1Zn/Cu system. However, in the PtAg metallized substrate, only Ag3Sn is present, regardless of which solders are employed. Cu6Sn5 and Ag3Sn in the Sn-3.5 Ag-1Zn system contain 2–5 at% Zn due to the higher solubility of Zn in both Cu and Ag. The adhesion strength decreases as the time increases for all solder joint systems in the thermal ageing test. The solder joint with eutectic Sn-Ag alloy exhibits higher fracture load than that with Sn-3.5 Ag-1Zn alloy. From the fracture surface analysis, as the ageing time increases, the fracture takes place from the solderconductor interface toward the inside of the IMC (intermetallic compound). © 1998 Kluwer Academic Publishers     

Electrochemical migration of lead free solder joints

Electrochemical migration (ECM) tests on lead bearing and lead free solder joints on Cu lamination on FR-4 board were conducted by applying constant voltage. This paper first studied the ECM of the soldered joints under distilled water after removing the fluxes. In addition, conditions under high temperature and high humidity were also set up to investigate the changes of the initial surface insulation resistance (SIR) with the residues of no clean fluxes. It is found under distilled water that dendrites of the solder joints take on different morphologies with the different migration elements. For the joints of Sn-37Pb and Sn-36Pb-2Ag solders, the main migration element is Pb. While that of Sn-3.5Ag and Sn-4Ag-0.5Cu solders, it is Cu that usually migrates and forms dendrites due to the poor wettability of the solder paste leads to part exposure of Cu substrate at the wetting brim. For Sn-3Ag-0.5Cu solder joints, Sn leads the migration. While for Sn-Zn-Bi solder joints, it is always Zn to migrate which means Zn is more mobile than Cu. The investigation on SIR shows the fluxes have great effect on the migration behavior. The failure time of the joints with the same solder alloy compositions have different failure time due to the different fluxes. The effect of the wettability and the role of Cu substrate on the ECM behavior of the solder joints are discussed in detail.     

On the advantages of using a hypoeutectic Sn-Zn as lead-free solder material

Hypoeutectic Sn-Zn may be a better choice than the eutectic Sn-9Zn as a lead-free solder. We checked the non-equilibrium melting behaviors of a series of Sn-Zn alloys (2.5-9 wt.% Zn) by differential thermal analysis, and found that at a heating rate of 5 °C/min, Sn-6.5Zn behaves the same way as the eutectic Sn-9Zn in melting. Dipping and spreading tests were carried out to characterize the wettability of Sn-Zn alloys on Cu. Both tests indicated that Sn-6.5Zn has significantly better wettability to Cu than Sn-9Zn does. The reaction layers formed during the spreading tests were examined. For all samples with 2.5-9 wt.% Zn, two reaction layers are formed at the interface, a thick and flat Cu₅Zn₈ layer adjacent to Cu and a thin and irregular Cu-Zn-Sn layer adjacent to the alloy. The total thickness of the reaction layers between the alloy and Cu was found to remarkably decrease with decrease of the Zn concentration.