Sn-8Zn无铅钎料性能的研究

研究了不同微量合金元素(Bi、Ag)对Sn-8Zn无铅钎料高温抗氧化性能及接头剪切强度的影响,采用氧化质量增加△m值的方法,在高温下观察钎料表面氧化膜形状和颜色的变化并对氧化膜进行X射线衍射分析,探讨了钎料的高温抗氧化性能的机理,通过对钎料的金相显微组织观察和对热处理后钎焊接头的剪切强度试验,分析了提高接头剪切强度的原因.试验结果表明:在Sn-8Zn钎料中加入适量的合金元素(Bi、Ag)均可以改善和提高钎料的高温抗氧化性能和接头的剪切强度.     

La对Sn-Ag-Cu无铅钎料组织与性能的影响

研究了微量稀土La对Sn-3.0Ag-0.5Cu无铅钎料显微组织、力学性能、断口形貌、润湿性能和熔点的影响.结果表明:La的质量分数为0.1%可使钎料合金晶粒细化,并显著提高钎料合金力学性能和润湿性能;添加La的质量分数为0.4%将形成粗大LaSn3初生枝晶相,降低力学性能和润湿性能;微量La使钎料合金的熔点轻微增加.     

微量混合稀土对SnAgCu钎料合金性能的影响

通过向Sn-3.8Ag-0.7Cu钎料合金中添加微量的Ce基混合稀土，研究了不同稀土含量对SnAgCu合金物理性能、润湿性能及力学性能的影响，同时对显微组织进行了分析。试验结果表明，微量的混合稀土可以显著提高SnAgCu钎料接头在室温下的蠕变断裂寿命，尤其是当稀土的质量分数为0．1％时，其蠕变断裂寿命可以达到Sn-3.8Ag-0.7Cu钎料的7倍以上。通过对SnAgCuRE钎料合金物理、工艺及力学性能的测试，显微组织分析表明，随着稀土含量的增加，钎料的组织逐渐细化，但同时，稀土化合物的数量增多，对钎料的力学性能产生不利影响。综合考虑，最佳的稀土质量分数为0．05％－0．5％，不宜超过1．0％。     

混合稀土对Sn-0.70Cu-0.05Ni钎料组织与性能的影响

向Sn-0.70Cu-0.05Ni无铅钎料中添加微量混合稀土元素RE(主要是La和Ce),研究了RE添加量对该钎料合金显微组织及性能的影响.结果表明,添加微量的RE能显著细化该钎料合金组织,抑制金属间化合物的生长,改善合金的组织分布,提高钎料的润湿性及力学性能.当w(RE)为0.10%时,钎料的润湿力,拉伸强度分别为3...     

Ce对SnAgCu系无铅焊锡力学性能的影响

通过向Sn-3Ag-2.8Cu钎料合金中添加微量稀土Ce,利用扫描电子显微镜(SEM)研究了不同稀土含量对Sn-3Ag-2.8Cu合金的力学性能的影响,同时对显微组织进行了分析.实验结果表明,微量的Ce稀土可以显著提高Sn-3Ag-2.8Cu钎料的延伸率、延长其焊接接头在室温下的蠕变断裂寿命,尤其是当稀土的质量分数为0.1%时,其蠕变断裂寿命可以达到Sn-3Ag-2.8Cu钎料的9倍以上,当稀土的质量分数超过0.1%时,接头的蠕变断裂寿命呈下降趋势.综合考虑,最佳的稀土质量分数为0.05%～0.10%.     

稀土元素对Sn-0.2Ag-0.7Cu钎料合金物理性能的影响

在筛选出综合性能较好的Sn-0.2Ag-0.7Cu钎料合金中,添加微量混合稀土元素(RE)以提高钎料的焊接性能。研究了稀土的添加量对其熔化温度、电导率和固–液相线温差等焊接性能的影响。结果表明:添加w(RE)为0.1%~0.5%时,固–液相线温差小于15℃,符合现行钎焊工艺要求,且对钎料合金的熔化温度和电导率影响不大。     

Sn-Zn系无铅钎料最新进展

Sn-Zn系钎料熔点与传统Sn-37Pb钎料十分接近,成本低廉,被研究者所推崇。由于Zn的存在导致Sn-Zn钎料润湿性差及抗氧化性不足,阻碍了该钎料的发展。添加合金元素和纳米颗粒是改善Sn-Zn钎料组织和性能行之有效的方法之一,为国内外研究者所推崇。结合国内外Sn-Zn系无铅钎料最新研究成果,探讨添加微量的合金元素In、Ni、Cr、Ga、Bi、Cu、Al、Ag、稀土元素及纳米颗粒对钎料润湿性、抗氧化性、力学性能、显微组织和界面组织的影响,同时简述有关钎剂对Sn-Zn的影响,并对Sn-Zn系钎料的发展趋势进行分析与展望。     

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。     

Sn58Bi-xW复合钎料焊点微观组织及性能的研究

采用SEM、EDX等手段,研究了Sn58Bi-x W钎料润湿性能、组织形貌及焊点接头力学性能。结果表明:适量W颗粒可以提高Sn58Bi润湿性,随着W颗粒含量的增加,钎料的润湿性呈现先上升后下降的趋势,W质量分数为0.05%时润湿性最好,其铺展面积为132.73 mm~2。W颗粒可以有效细化Sn58Bi钎料合金的微观组织,减小焊点界面IMC厚度,当W添加量为质量分数0.1%,Sn-58B钎料的微观组织最为细小,界面IMC的厚度为0.71μm,焊点的抗拉强度最高,达101.6 MPa。     

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.     

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.     

Interfacial microstructure and strength of lead-free Sn-Zn-RE BGA solder bumps

Rare earth (RE) elements, primarily La and Ce, were doped in Sn-Zn solder to improve its properties such as wettability. The interfacial microstructure evolution and shear strength of the Sn-9Zn and Sn-9Zn-0.5RE (in wt%) solder bumps on Au/Ni/Cu under bump metallization (UBM) in a ball grid array (BGA) were investigated after thermal aging at 150 /spl deg/C for up to 1000 h. In the as-reflowed Sn-9Zn solder bump, AuSn/sub 4/ intermetallic compounds (IMCs) and Au-Zn circular IMCs formed close to the solder/UBM interface, together with the formation of a Ni-Zn-Sn ternary IMC layer of about 1 /spl mu/m in thickness. In contrast, in the as-reflowed Sn-9Zn-0.5RE solder bump, a spalled layer of Au-Zn was formed above the Ni layer. Sn-Ce-La and Sn-Zn-Ce-La phases were found near the interface at positions near the surface of the solder ball. Upon thermal aging at 150 /spl deg/C, the concentration of Zn in the Ni-Zn-Sn ternary layer of Sn-9Zn increased with aging time. For Sn-9Zn-0.5RE, the Au-Zn layer began to dissolve after 500 h of thermal aging. The shear strength of the Sn-9Zn ball was decreased after the addition of RE elements, although it was still higher than that of the Sn-37Pb and Sn-36Pb-2Ag Pb-bearing solders. The fracture mode of the Sn-9Zn system was changed from ductile to partly brittle after adding the RE elements. This is mainly due to the presence of the brittle Au-Zn layer.     

Effects of Ce Addition on the Microstructure and Mechanical Properties of Sn-58Bi Solder Joints

The effects of a rare-earth element on the microstructure, mechanical properties, and whisker growth of Sn-58Bi alloys and solder joints in ball grid array (BGA) packages with Ag/Cu pads have been investigated. Mechanical testing indicated that the elongation of Sn-58Bi alloys doped with Ce increased significantly, and the tensile strength decreased slightly, in compar- ison with undoped Sn-58Bi. In addition, the growth of both fiber- and hillock-shaped tin whiskers on the surface of Sn-58Bi-0.5Ce was retarded in the case of Sn-3Ag-0.5Cu-0.5Ce alloys. The growth of interfacial intermetallic compounds (IMC) in Sn-58Bi-0.5Ce solder joints was slower than that in Sn-58Bi because the activity of Ce atoms at the interface of the Cu₆Sn₅ IMC/solder was reduced. The reflowed Sn-58Bi and Sn-58Bi-0.5Ce BGA packages with Ag/Cu pads had a ball shear strength of 7.91 N and 7.64 N, which decreased to about 7.13 N and 6.87 N after aging at 100°C for 1000 h, respectively. The reflowed and aged solder joints fractured across the solder balls with ductile characteristics after ball shear tests.     

Mechanical Properties and Electrochemical Corrosion Behavior of Al/Sn-9Zn-<Emphasis Type="Italic">x</Emphasis>Ag/Cu Joints

The effect of Ag content on the wetting behavior of Sn-9Zn-xAg on aluminum and copper substrates during soldering, as well as the mechanical properties and electrochemical corrosion behavior of Al/Sn-9Zn-xAg/Cu solder joints, were investigated in the present work. Tiny Zn and coarsened dendritic AgZn₃ regions were distributed in the Sn matrix in the bulk Sn-9Zn-xAg solders, and the amount of Zn decreased while that of AgZn₃ increased with increasing Ag content. The wettability of Sn-9Zn-1.5Ag solder on Cu substrate was better than those of the other Sn-9Zn-xAg solders but worse than that of Sn-9Zn solder. The wettability of Sn-9Zn-1.5Ag on the Al substrate was also better than those of the other Sn-9Zn-xAg solders, and even better than that of Sn-9Zn solder. The Al/Sn-9Zn/Cu joint had the highest shear strength, and the shear strength of the Al/Sn-9Zn-xAg/Cu (x = 0 wt.% to 3 wt.%) joints gradually decreased with increasing Ag content. The corrosion resistance of the Sn-9Zn-xAg solders in Al/Sn-9Zn-xAg/Cu joints in 5% NaCl solution was improved compared with that of Sn-9Zn. The corrosion potential of Sn-9Zn-xAg solders continuously increased with increasing Ag content from 0 wt.% to 2 wt.% but then decreased for Sn-9Zn-3Ag. The addition of Ag resulted in the formation of the AgZn₃ phase and in a reduction of the amount of the eutectic Zn phase in the solder matrix; therefore, the corrosion resistance of the Al/Sn-9Zn-xAg/Cu joints was improved.     

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 reaction and solder joint reliability of Pb-free solders in lead frame chip scale packages (LF-CSP)

Chip scale packages (CSP) have essential solder joint quality problems, and a board level reliability is a key issue in design and development of the CSP type packages. There has been an effort to eliminate Pb from solder due to its toxicology. To evaluate the various solder balls in CSP package applications, Pb-free Sn-Ag-X (X=In, Cu, Bi) and Sn-9Zn-1Bi-5In solder balls were characterized by melting behavior, phases, interfacial reaction, and solder joint reliability. For studying joint strength between solders and under bump metallurgy (UBM) systems, various UBMs were prepared by electroplating and electroless plating. After T/C (temperature cycle) test, Sn3.5Ag8.5In solder was partially corroded and its shape was distorted. This phenomenon was observed in a Sn3Ag10In 1Cu solder system, too. Their fractured surface, microstructure of solder joint interface, and of bulk solder ball were examined and analyzed by optical microscopy, SEM and EDX. To simulate the real surface mounting condition and evaluate the solder joint reliability on board level, Daisy chain test samples using LF-CSP packages were prepared with various Pb-free solders, then a temperature cycle test (−65∼ 150°C) was performed. All tested Pb-free solders showed better board level solder joint reliability than Sn-36Pb-2Ag. Sn-3.5Ag-0.7Cu and Sn-9Zn-1Bi-5In solders showed 35%, 100% superior solder joint reliability than Sn-36Pb-2Ag solder ball, respectively.     

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%。     

Properties of quad flat package joints using Sn-Zn-Bi solder with varying lead-plating materials

The effects of plating materials (Sn-10Pb, Sn-3.5Ag, Sn-3Bi, Sn-0.7Cu, and Au/Pd/Ni) on Cu leads on quad flat package (QFP) joints using a Sn-8Zn-3Bi solder were investigated. The joints with Sn-3.5Ag plating and Sn-8Zn-3Bi solder had the slowest growth rate of interfacial reaction layers and the highest strength. The Ag dissolution into the interfacial reaction layers causes this increased strength. The Sn-Ag plating is the best plating material for Cu leads among the five kinds of plating using Sn-8Zn-3Bi solder.     

Ag对Sn-9Zn合金钎料组织及性能的影响

用莱卡显微镜、XRD研究添加元素Ag对Sn-9Zn钎料组织及性能的影响。结果表明:Ag与Zn形成AgZn3化合物,能抑制粗大针状富Zn相的形成,可使Sn-9Zn钎料合金的润湿性提高20%,并明显改善Sn-9Zn的耐蚀性。     

Comparison study on microstructure and mechanical properties of Sn-10Bi and Sn-Ag-Cu solder alloys and joints

The comparison study of Sn-10Bi and Sn-3.0Ag-0.5Cu solder alloys and joints was conducted. The results showed that the liquidus of Sn-10Bi solder alloy was lower than that of Sn-Ag-Cu slightly. The interfacial IMCs layer growth of Sn-10Bi/Cu was slower than that of Sn-Ag-Cu/Cu during liquid/solid reaction. The higher strength and lower creep strain rate of Sn-10Bi comparing with that of Sn-Ag-Cu were contributed by the solid solution strengthening effect of Bi atom in β-Sn phase. The ultimate bending load of Sn-10Bi joint was higher than that of Sn-Ag-Cu joint as the high strength of Sn-10Bi solder alloy. Moreover, the thinner and more flat IMCs layer also ensured the stable maximum bending displacement of Sn-10Bi joint at a loading speed of 1 mm/s compared with that of Sn-Ag-Cu joint.