工业纯Sn和Sn-3Ag-0.5Cu合金在沈阳大气环境下自然暴露的初期腐蚀行为

通过沈阳大气环境下的自然暴露实验研究工业纯Sn和Sn-3Ag-0.5Cu合金的早期大气腐蚀行为。采用扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)分析了表面腐蚀产物的形貌与成分。结果表明:工业纯Sn与Sn-3Ag-0.5Cu合金在沈阳工业大气环境下自然暴露后都很快发生了表面腐蚀并失泽,早期腐蚀产物疏松、龟裂并易于剥落。XPS深度分析表明:自然条件下暴露18 d后,表面腐蚀产物层厚度约为400 nm。工业大气中的悬浮物颗粒对腐蚀的形核和扩展起重要作用,Sn-3Ag-0.5Cu合金中的第二相Ag3Sn和Cu6Sn5作为阴极存在,但对大气腐蚀的加速影响不大。     

钎焊时间对Sn-3.0Ag-0.5Cu/Cu钎焊接头界面化合物的影响

研究了不同钎焊时间下Sn-3.0Ag-0.5Cu/Cu焊点界面金属间化合物生长变化规律和剪切强度变化。结果表明:随着钎焊时间增加,界面化合物平均厚度逐渐增加,且生长的时间指数为0.4。钎焊60s内界面化合物的生长速率较大;随着钎焊时间的增加,钎焊接头的抗剪切强度先增加后降低,这与界面处脆硬相Cu6Sn5生长行为密切相关。     

SnAgCu/Cu和SnPb/Cu界面热-剪切循环条件下化合物的生长行为

对热剪切循环条件下Sn-3.5Ag-0.5Cu/Cu和Sn-Pb/Cu界面上原子扩散和化合物的生长行为进行了研究。结果表明:再流焊后,在两界面上均形成一种Cu6Sn5化合物;随着热剪切循环周数的增加,两界面上化合物的形态均从扇贝状向层状生长,其厚度随循环周数的增加而增加,且生长基本遵循抛物线规律,说明Cu原子的扩散控制了Cu6Sn5化合物的生长。界面近域的钎料内,颗粒状的Ag3Sn聚集长大成块状。     

等温时效中稀土Er对Sn-3.8Ag-0.7Cu无铅钎料显微组织演化的影响

系统研究了等温时效中添加微量稀土Er对Sn-3.8Ag-0.7Cu钎料合金显微组织演化规律的影响.结果表明,Er对Sn-3.8Ag-0.7Cu钎料显微组织及等温时效过程中显微组织的演化产生了重要影响.在钎焊过程中,Er有效地细化了钎料组织,改变了钎料内部Cu-Sn金属间化合物的形态、尺寸及分布情况.在等温时效过程中,钎料内部生成的ErSn3金属间化合物为组织的再结晶过程提供了大量的形核质点,有效避免了再结晶组织的粗化及裂纹的产生和扩展.     

Co对Sn-3.0Ag-0.5Cu钎料接头显微组织和服役可靠性的影响

研究了高温对SnAgCu+xCo(x=0,0.1,0.2,0.45,1.0,x为质量分数%,下同)复合钎料接头显微组织和力学性能的影响。用差热分析法(DSC)分析了Co对钎焊接头过冷度和凝固相的影响。与Sn-3.0Ag-0.5Cu钎料相比,焊后SnAgCu+xCo(x=0.1,0.2)复合钎料界面金属间化合物层厚度减小,接头剪切强度提高。经150℃保温500h后,SnAgCu+xCo复合钎料接头剪切强度均高于Sn-3.0Ag-0.5Cu钎料接头,说明Co的添加可以改善SnAgCu钎料的服役可靠性。经DSC分析,Co的添加会提高SnAgCu钎料合金的凝固点,从而降低其过冷度。综上,Sn-3.0Ag-0.5Cu-0.2Co复合钎料接头的力学性能和服役条件下的可靠性最佳。     

Electrochemical corrosion behaviour of Pb-free Sn-8.5Zn-0.05Al-XGa and Sn-3Ag-0.5Cu alloys in chloride containing aqueous solution

The electrochemical corrosion behaviour of Pb-free Sn-8.5Zn-0.05Al-XGa and Sn-3Ag-0.5Cu alloys was investigated in 3.5% NaCl solution by using potentiodynamic polarization techniques. The results obtained from polarization studies revealed that there was a negative shift in the corrosion potential with increase in Ga content from 0.02 to 0.2 wt% in the Sn-8.5Zn-0.05Al-XGa alloy. These changes were also reflected in the corrosion current density (I_corr) value, corrosion rate and linear polarization resistance (LPR) of the four element alloy. However, for Sn-3Ag-0.5Cu alloy a significant increase in the corrosion rate and corrosion current density was observed as compared to the four element alloys. SIMS depth profile results established that ZnO present on the outer surface of Sn-8.5Zn-0.05Al-0.05Ga alloy played a major role in the formation of the oxide film. Oxides of Sn, Al and Ga contributed a little towards the formation of film on the outer surface of the alloy. On the other hand, Ag₂O was primarily responsible for the formation of the oxide film on the outer surface of Sn-3Ag-0.5Cu alloy.     

Wetting of molten Sn-3.5Ag-0.5Cu on Ni-P(-SiC) coatings deposited on high volume faction SiC/Al composite

The wetting of molten Sn-3.5Ag-0.5Cu alloy on the Ni-P(-SiC) coated SiC_p/Al substrates was investigated by electroless Ni plating process, and the microstructures of the coating and the interfacial behavior of wetting systems were analyzed. The SiC particles are evenly distributed in the coating and enveloped with Ni. No reaction layer is observed at the coating/SiC_p/Al composite interfaces. The contact angle increases from ～19° with the Ni-P coating to 29°, 43° and 113° with the corresponding Ni-P-3SiC, Ni-P-6SiC and Ni-P-9SiC coatings, respectively. An interaction layer containing Cu, Ni, Sn and P forms at the Sn-Ag-Cu/Ni-P-(0,3,6)SiC coated SiC_p/Al interfaces, and the Cu-Ni-Sn and Ni-Sn-P phases are detected in the interaction layer. Moreover, the molten Sn-Ag-Cu can penetrate into the Ni-P(-SiC) coatings through the Ni-P/SiC interface and dissolve them to contact the SiC_p/Al substrate.     

稀土Pr对Sn-0.3Ag-0.7Cu钎料润湿性能和微焊点力学性能的影响

采用润湿平衡法研究了微量稀土Pr元素对Sn-0.3Ag-0.7Cu在Cu基板上润湿性能的影响规律,并借助STR-1000型微焊点强度测试对Sn-0.3Ag-0.7Cu-x Pr微焊点的力学性能。结果表明,随着稀土Pr含量的增加,钎料在Cu基板上的润湿力逐渐增加,润湿时间缩短。当Pr的质量分数在0.05%~0.1%时,Sn-0.3Ag-0.7Cu-x Pr钎料的润湿性能最好。在260℃的试验条件下,Sn Ag Cu-0.1Pr相比Sn Ag Cu钎料润湿力提高了5.0%,润湿时间降低了16.9%。且当Pr含量约为0.05%时,微焊点的力学性能最佳,焊点的剪切强度提高了8.5%。     

Interfacial Reactions and Bonding Strength of Sn-xAg-0.5Cu/Ni BGA Solder Joints

The present study details the microstructure evolution of the interfacial intermetallic compounds (IMCs) layer formed between the Sn-xAg-0.5Cu (x = 1, 3, and 4 wt.%) solder balls and electroless Ni-P layer, and their bond strength variation during aging. The interfacial IMCs layer in the as-reflowed specimens was only (Cu,Ni)₆Sn₅ for Sn-xAg-0.5Cu solders. The (Ni,Cu)₃Sn₄ IMCs layer formed when Sn-4Ag-0.5Cu and Sn-3Ag-0.5Cu solders were used as aging time increased. However, only (Cu,Ni)₆Sn₅ IMCs formed in Sn-1Ag-0.5Cu solders, when the aging time was extended beyond 1500 h. Two factors are expected to influence bond strength and fracture modes. One of the factors is that the interfacial (Ni,Cu)₃Sn₄ IMCs formed at the interface and the fact that fracture occurs along the interface. The other factor is Ag₃Sn IMCs coarsening in the solder matrix, and fracture reveals the ductility of the solder balls. The above analysis indicates that during aging, the formation of interfacial (Ni,Cu)₃Sn₄ IMCs layers strongly influences the pull strength and the fracture behavior of a solder joint. This fact demonstrates that interfacial layers are key to understanding the changes in bonding strength. Additionally, comparison of the bond strength with various Sn-Ag-Cu lead-free solders for various Ag contents show that the Sn-1Ag-0.5Cu solder joint is not sensitive to extended aging time.     

Interfacial reactions between liquid Sn-8Zn-3Bi solders and Cu substrates

The morphology and growth kinetics of intermetallic compounds formed during the soldering reactions between Sn-8Zn-3Bi and Cu substrates at various temperatures ranging from 225 to 350 °C were investigated. The results indicated that a planar layer of Cu_32.1Zn_66.7Sn_0.7Bi_0.5 (γ phase) along with a great number of scallop-shaped intermetallic compounds Cu_19.3Zn_77.8Sn_2.9 (ɛ phase) appeared at the interfaces at temperatures lower than 325 °C. At temperatures higher than 325 °C, the interfacial intermetallics of a composition similar to the planar intermetallics appeared in cluster shape. Kinetics analysis indicated that the intermetallic growth was diffusion-controlled with activation energy of 24.6 KJ/mol.     

铜含量对Sn-Cu钎料与Cu、Ni基板钎焊界面IMC的影响

研究了不同铜含量的Sn-xCu钎料(x=0,0.1%,0.3%,0.7%,0.9%,1.5%)与Cu板和Ni板在260、280和290℃钎焊后界面金属间化合物(IMC)的成分和形貌。研究结果表明:钎料与Cu板钎焊时,钎焊温度越高,界面处形成的Cu6Sn5IMC厚度越大,而在同一钎焊温度下,随着钎料中铜含量的增加,IMC的厚度先减少后增加;与Ni板钎焊时,界面IMC的厚度随着铜含量的增加而增加,同时界面化合物的成分和形貌均发生了显著变化;当Cu含量小于0.3%(质量分数)时,界面处形成了连续的(CuxNi1-x)3Sn4层;而当Cu含量为0.7%时,界面处同时存在着短棒状(CuxNi1-x)3Sn4和大块状(CuxNi1-x)6Sn5IMC;当铜含量继续增大时(0.9%~1.5%),(CuxNi1-x)3Sn4IMC消失,只发现了棒状(CuxNi1-x)6Sn5IMC。讨论了钎料中Cu含量对与Cu、Ni基板钎焊接头界面化合物生长的影响,并进一步讨论了(CuxNi1-x)6Sn5IMC的形成和长大机理。     

Effect of cerium on microstructure and mechanical properties of Sn-Ag-Cu system lead-free solder alloys

The melting point, spreading property, mechanical properties and microstructures of Sn-3.0Ag-2.8Cu solder alloys added with micro-variable-Ce were studied by means of optical microscopy, scanning electron microscopy（SEM） and energy dispersive X-ray（EDX）. The results indicate that the melting point of Sn-3.0Ag-2.8Cu solder is enhanced by Ce addition; a small amount of Ce will remarkably prolong the creep-rupture life of Sn-3.0Ag-2.8Cu solder joint at room temperature, especially when the content of Ce is 0.1%, the creep-rupture life will be 9 times or more than that of the solder joint without Ce addition; the elongation of Sn-3.0Ag-2.SCu solder is also obviously improved even up to 15.7%. In sum, the optimum content of Ce is within 0.05%-0.1%.     

Bi掺杂对Sn-3.0Ag-0.5Cu钎料电化学腐蚀性能及枝晶生长的影响

采用动电位扫描和交流阻抗等方法研究Bi掺杂对Sn-3.0Ag-0.5Cu钎料在3.5%NaCl(质量分数)溶液中电化学腐蚀性能及枝晶生长的影响;采用SEM和XRD技术分析其腐蚀形貌及成分。结果显示:随着Bi含量增加,腐蚀电流密度增大,但自腐蚀电位不呈规律性变化。阻抗谱显示:掺杂前后阻抗谱特征相同,均可用两个时间常数的等效电路模型表示,其拟合误差<5%。随着Bi含量的增加,容抗弧半径减小,电荷传递电阻和腐蚀产物膜电阻均减小,耐蚀性能降低。SEM像显示,Bi掺杂对钎料在介质中电化学迁移速度有减缓作用,因而对迁移所致的枝晶生长具有抑制作用。XRD谱显示,枝晶主要成分为Sn和Cu6Sn5,同时伴有少量的Bi和Ag3Sn。     

引线框架铜合金材料与SnAg3.0Cu0.5的界面组织

采用扫描电镜和能谱分析等手段研究了3种不同引线框架用铜合金材料与SnAgCu钎料的界面结构,3种铜合金引线框架材料与SnAg3.0Cu0.5焊膏焊后未经时效的界面组织相似.焊点在160℃恒温时效300 h后,Cu-0.1Fe-0.03P合金、Cu-0.36Cr-0.03Zr合金、Cu-0.38Cr-0.17Sn-0.16Zn合金与SnAg3.0Cu0.5焊膏的界面金属间化合物厚度分别为8.7、7.4、6.2μm,其成分主要为Cu6Sn5,靠近铜合金一侧均有少量Cu,Sn生成.结果表明,Cu-0.38Cr-0.17Sn-0.16Zn合金比Cu-0.1Fe-0.03P合金和Cu-0.36Cr-0.03Zr合金具有更好的焊接可靠性能,Cu-0.38Cr-0.17Sn-0.16Zn合金中的Zn元素在焊点界面的富集有效减缓了界面处原子的相互扩散,使金属同化合物的增长速度降低.     

SnCu钎料镀层与Cu/Ni镀层钎焊接头的界面反应

观察了不同焊接工艺条件下钎焊接头界面的微观结构，并对钎焊过程中的界面反应进行分析。探讨了钎缝界面处IMC的生长机制，通过对不同钎焊温度和保温时间下的IMC生长规律的分析建立铜锡化合物厚度与温度和时间的关系方程。结果表明：钎焊过程中SnCu钎料合金镀层与可焊性Cu层的界面处生成金属间化合物Cu6Sn5和Cu3Sn；化合物的生长厚度与焊接时间之间满足抛物线关系，表明化合物的生长为扩散反应控制过程，并随焊接时间的延长化合物的生长速率逐渐下降。     

The effect of the addition of in on the reaction and mechanical properties of Sn−1.0Ag−0.5Cu solder alloy

The effects of the reduction of the Ag content and the addition of In on the mechanical properties, soldering characteristics and reaction behavior at solder/package interfaces are investigated in this study. It was found that the addition of In significantly improved the wettability of the solder at reflow temperatures ranging from 230°C to 240°C. Moreover, the addition also improves the elongation of the solder alloy, thereby increasing the toughness of the alloy. With the optimization of the In and Ag contents, a Sn−Ag−Cu−In quaternary alloy would be a strong candidate to replace the Sn-3.0Ag-0.5Cu composition.     

Simulation on deposition and solidification processes of 7075 Al alloy droplets in 3D printing technology

In order to study the successive deposition and solidification processes of uniform alloy droplets during the drop-on-demand three dimensional (3D) printing method, based on the volume of fluid (VOF) method, a 3D numerical model was employed. In this model, the 7075 alloy with larger temperature range for phase change was used. The simulation results show that the successive deposition and solidification processes of uniform 7075 alloy droplets can be well characterized by this model. Simulated droplets shapes agree well with SEM images under the same condition. The effects of deposition and solidification of droplets result in vertical and L-shaped ridges on the surface of droplets, and tips of dendrites appear near the overlap of droplets due to rapid solidification.     

Localized coating failure of epoxy-coated aluminium alloy 2024-T3 in 0.5 M NaCl solutions: Correlation between coating degradation, blister formation and local chemistry within blisters

The role of pH on the nature and rate of the degradation of epoxy coatings on AA2024-T3 panels and subsequent corrosion of the substrate during immersion in NaCl solutions was investigated. In acidic solutions both blister formation and growth are rapid. Blisters become very large (≈1 cm) and new blisters appear to form for a certain time after exposure. Often very small (∼0.1 mm) clear blisters surround these large blisters. Enhanced blister formation is due to irreversibly increased permeability of the coating for chloride ions and protons, the formation of more defect sites within the coating, and the weakening/dissolution of the oxide layer in low pH environments. In neutral pH solutions, coatings fail by forming one, or at most two, active blisters (red in color) within a few days of immersion with the time-to-failure dependent upon coating quality and thickness. Blister growth is a very slow process, and blister diameters rarely exceed a few millimeters even after several weeks. The accumulation of corrosion product within the blister slows down the corrosion rate and blister growth. The chloride concentration in the occluded solutions within the blister is significantly increased over the bulk concentration, and the pH is often in the acidic range. From electrochemical measurements it can be concluded that the anodic and cathodic reactions are confined to the blister and its immediate surroundings, rather than involving more of the surface over which the coating is intact. Based on corrosion morphology it is concluded that replated copper contributes to the overall cathodic reaction.