Electrochemical and mechanical behaviour of Sn‐2.5Ag‐0.5Cu and Sn‐48Bi‐2Zn solders

In this paper, two tin‐based alloys (Sn‐2.5Ag‐0.5Cu and Sn‐48Bi‐2Zn) are proposed as new lead‐free solders. Alloys have been developed by melting pure elements. Samples have been evaluated in terms of microstructure, corrosion resistance and mechanical features. Corrosion tests have been performed in 3% NaCl solution by polarization curves and electrochemical impedance spectroscopy (EIS). SEM observations and EDS analysis were carried out on samples before and after corrosion tests. Static monotonic tensile tests have been performed on three specimens for each alloy. SEM and EDS analysis revealed the presence of Sn‐Ag and Sn‐Cu intermetallic compounds within the Sn‐Ag‐Cu alloy. As a result of corrosion test, the Sn‐Ag‐Cu alloy showed a better corrosion resistance with respect to Sn‐Bi‐Zn. Both alloys evidenced good mechanical properties higher than the traditional Sn‐Pb system. Sn‐Ag‐Cu seems to be a suitable soldering material.     

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.     

Ag,Al,Ga对Sn-9Zn无铅钎料润湿性能的影响

采用润湿平衡法测试了Sn-9Zn-X(X为Ag,Al,Ga)无铅钎料分别配合ZnCl2-NH4Cl钎剂和免清洗助焊剂,在空气和氮气保护的两种条件下的润湿性能,分析研究了合金元素Ag,Al,Ga的添加量对Sn-9Zn-X无铅钎料润湿性的影响规律.结果表明,合金元素Ag,Al,Ga在Sn-9Zn中的最佳添加量(质量分数)分别为0.3%,0.005%～0.02%,0.5%.采用氮气保护可以显著改善Sn-9Zn-X无铅钎料的润湿性,而Sn-9Zn-X无铅钎料配合ZnCl2-NH4Cl钎剂时具有较好的润湿性,甚至优于Sn-3.5Ag-0.5Cu在相同条件下的润湿性.这一研究结果表明,通过研发适合于Sn-Zn系无铅钎料的高性能助焊剂,从而改善Sn-Zn系钎料的润湿性能是完全可行的.     

Effect of Ga on microstructure and properties of Sn-Zn-Bi solder for photovoltaic ribbon

In this study, SEM, EDS, XRD and other test methods were used to study the effects of different Ga contents(0～2 wt.%) on microstructure, electrical conductivity, spreading area and mechanical properties of Sn-9 Zn-3 Bi solder. The results revealed that the microstructure of Sn-Zn-Bi-Ga solder alloy was mainly composed of β-Sn, Zn-rich, Bi-rich phase and Sn-Zn eutectic structure. The Ga can significantly improve the wettability of Sn-Zn-Bi on the pure copper, the maximum wetting area was 105.3 mm2. With the increase of the Ga content the melting point of the solders decreased from 195 ℃ to 177 ℃. In addition, the Ga element can increase the oxidation resistance of solder. Its conductivity showed a decreasing trend with the gradual increase of the Ga content. With the increased of the Ga content the IMC(Intermetallic Compound) of Sn-Zn-Bi-x Ga/Cu is only Cu5 Zn8 and its thickness decreased remarkably.     

Effect of cerium addition on microstructure and corrosion resistance of die cast AZ91 magnesium alloy

A novel AZ91 Ce containing magnesium alloy characterized by excellent corrosion resistance is fabricated by adding rare earth Ce (cerium) in the form of a Mg‐Ce master alloy. The metallographic investigation shows that Ce added to AZ91 can obviously decrease the size of β‐Mg₁₇Al₁₂ and forms Al₁₁Ce₃ intermetallic compounds in the shape of fine needles. The corrosion tests and electrochemical measurements indicate that the corrosion resistance of AZ91 Ce containing magnesium alloy is obviously higher than that of AZ91. Furthermore, increasing the content of Ce in the magnesium alloy can further enhance the corrosion resistance. X‐ray photoelectron spectroscopy (XPS) reveals that Ce can be incorporated into corrosion products in the form of CeO₂ in the course of corrosion. Based on the preliminary analysis, the addition of Ce can improve the corrosion resistance of AZ91 by decreasing the size of β‐Mg₁₇Al₁₂ and enhancing the protective effectiveness of corrosion products.     

稀土Y对AZ80镁合金组织及耐蚀性能的影响

通过静态失重法、电化学测试法、扫描电子显微镜、X射线衍射等测试手段对添加不同含量稀土元素Y的AZ80镁合金的微观组织和腐蚀性能进行了研究。结果表明:稀土Y的加入使实验合金中β-Mg17Al12相的数量明显减少,并且由连续网状分布变为断续状、均匀分布。同时,Y与合金中Al结合形成块状或颗粒状的稀土相Al2Y。本实验条件下,添加0.5%Y合金的耐腐蚀性能最佳,腐蚀速率为0.2585 mg.cm-2.d-1,仅为原始合金腐蚀速率的48.07%,此外加入适量Y可提高合金的平衡电位和腐蚀电位,降低腐蚀电流密度,提高了合金的耐蚀性能。     

Investigations of interfacial reactions of Sn–Zn based and Sn–Ag–Cu lead-free solder alloys as replacement for Sn–Pb solder

The interfacial reactions of Sn–Zn based solders and a Sn–Ag–Cu solder have been compared with a eutectic Sn–Pb solder. During reflow soldering different types of intermetallic compounds (IMCs) are found at the interface. The morphologies of these IMCs are quite different for different solder compositions. As-reflowed, the growth rates of IMCs in the Sn–Zn based solder are higher than in the Sn–Ag–Cu and Sn–Pb solders. Different types of IMCs such as γ-Cu₅Zn₈, β-CuZn and a thin unknown Cu–Zn layer are formed in the Sn–Zn based solder but in the cases of Cu/Sn–Pb and Cu/Sn–Ag–Cu solder systems Cu₆Sn₅ IMC layers are formed at the interface. Cu₆Sn₅ and Cu₃Sn interfacial IMCs are formed in the early stages of 10 min reflow due to the limited supply of Sn from the Sn–Pb solder. The spalling of Cu–Sn IMCs is observed only in the Sn–Ag–Cu solder. The size of Zn platelets is increased with an increase of reflow time for the Cu/Sn–Zn solder system. In the case of the Sn–Zn–Bi solder, there is no significant increase in the Zn-rich phases with extended reflow time. Also, Bi offers significant effects on the wetting, the growth rate of IMCs as well as on the size and distribution of Zn-rich phases in the β-Sn matrix. No Cu–Sn IMCs are found in the Sn–Zn based solder during 20 min reflow. The consumption of Cu by the solders are ranked as Sn–Zn–Bi > Sn–Ag–Cu > Sn–Zn > Sn–Pb. Despite the higher Cu-consumption rate, Bi-containing solder may be a promising candidate for a lead-free solder in modern electronic packaging taking into account its lower soldering temperature and material costs.     

添加铜对Sn-9Zn无铅钎料性能的影响

采用向钎料合金熔体中添加铜粉的方法得到了原位生长金属间化合物颗粒增强的Sn-Zn基复合无铅钎料,并对其熔化行为、组织、力学性能和在铜基体上的润湿性进行了研究.差示扫描量热计(DSC)测量结果表明,少量铜粉对Sn-9Zn的熔点影响较小,但铜粉添加量达3%时将使其熔点急剧升高.铜粉的添加使Sn-9Zn钎料中形成了较均匀分布的Cu5Zn8化合物颗粒相,同时棒状富Zn相相应减少.力学性能测试结果显示,复合钎料的抗拉强度和塑性都得到了改善,抗蠕变性能显著提高;润湿性测量表明,复合钎料对铜的润湿性也有所改善.     

微米Sn-Ag-Cu-RE粉体材料的制备与表征

首次制备出了微米Sn-Ag-Cu-RE合金粉体，微米Sn-Ag-Cu-RE合金粉体呈圆滑的球形，粒度呈梯度分布，其铺展性能、扩展率都得到了显的改善。微米Sn-Ag-Cu-RE合金粉体固相线温度为190．643-193．645℃，较块体SnAg-Cu合金的熔点221℃降低了28℃；液相线温度为216．963-218．368℃，较块体Sn-Ag-Cu合金的熔点降低了3℃。试验结果表明，微米Sn-Ag-Cu-RE合金粉体的“表面效应”显。该为无铅钎料的研发和应用提供了一个新的思路。     

时效时间对Cu/In-Sn-2.5Ag/Cu焊点组织形貌及剪切性能的影响

研究了Cu/In-Sn-2.5Ag/Cu复合钎料焊点在125℃时效不同时间后的微观组织和剪切性能.结果表明:随着时效时间的延长,Cu/In-Sn-2.5Ag/Cu焊点界面金属间化合物(IMCs)层厚度呈现增加的趋势,焊点界面IMCs层组织先生成Cu6(In,Sn)5相,同时焊点中生成少量的Ag9In4相,随着时效时间的...     

Effect of aging time and temperature on exfoliation corrosion of aluminum alloys 2024‐T3 and 7075‐T6

Two types of aluminum alloys, 2024‐T3 and 7075‐T6, have been selected in this study to investigate the effect of metallurgical aspects on exfoliation corrosion. To determine and evaluate the metallurgical effects of heat treatments on corrosion behaviour of these alloys, G34 ASTM test was selected to investigate the exfoliation corrosion behaviour. The results showed that with increasing the aging time for the aluminum alloy type 2024‐T3 the susceptibility to exfoliation corrosion increases, while for type 7075‐T6 decreased. These results refer to precipitation of the intermetallic compound phases such as CuAl₂, and MgZn₂, in 2024‐T3 and 7075‐T6 respectively. The amount of these phases increases with increasing the aging time for both alloys. The investigations showed the phases that initiate in 2024‐T3 act as anode sites while in 7075‐T6 they act as cathode sites.     

低银SnAgCuBiNi无铅钎料润湿及溶解行为分析

对Sn0.8Ag0.5Cu2.0Bi0.05Ni（SACBN）和Sn3.0Ag0.5Cu（SAC305）无铅钎料的显微组织、润湿性能和溶解行为进行了比较研究.结果表明,SACBN钎料显微组织由β-Sn＋共晶体组成,共晶组织为在β-Sn基体上均匀分布细针状的Ag3Sn、粒状的（Cu,Ni）6Sn5和细小粒状的铋.在相同温...     

界面Ni3Sn4微观形貌演变对微焊点力学性能的影响

针对Ni/(20 μm)Sn/Ni微焊点,研究界面金属间化合物(IMC)Ni3Sn4微观形貌演变及其对微焊点力学性能的影响,并对拉伸断口进行分析。结果表明,随着回流时间增加,Ni3Sn4 IMC厚度快速增加,其形貌也发生显著变化,由短棒状转变成长棒状,最后演变成块状;微焊点的抗拉强度表现为先减小、再持续增大的反常变化趋势,界面Ni3Sn4微观形貌演变成为主导因素,转变成长棒状的Ni3Sn4引起应力集中,造成微焊点的强度降低,继续转变成的块状Ni3Sn4增加了裂纹抗力,提高了抗拉强度。微焊点的断口形貌进一步证实了Ni3Sn4微观形貌演变对微焊点力学性能影响。创新点： 以互连高度为20 μm的Ni/Sn/Ni微焊点为研究对象,通过控制延长回流时间形成以Ni3Sn4 IMC为唯一变量实现其生长的方法,研究了Ni3Sn4 IMC的微观形貌演变对微焊点抗拉强度的影响。     

Effects of rapid solidification on the microstructure and microhardness of a lead-free Sn-3.5Ag solder

A lead-free Sn-3.5Ag solder was prepared by rapid solidification technology. The high solidification rate, obtained by rapid cooling, promotes nucleation, and suppresses the growth of Ag3Sn intermetallic compounds （IMCs） in Ag-rich zone, yielding fine Ag3Sn nanoparticulates with spherical morphology in the matrix of the solder. The large amount of tough homogeneously-dispersed IMCs helps to improve the surface area per unit volume and obstructs the dislocation lines passing through the solder, which fits with the dispersion-strengthening theory. Hence, the rapidly-solidified Sn-3.5Ag solder exhibits a higher rnicrohardness when compared with a slowly-solidified Sn-3.5Ag solder.     

Effects of Sn and Ca additions on microstructure,mechanical properties,and corrosion resistance of the as‐cast Mg‐Zn‐Al‐based alloy

Effects of Sn and Ca additions on microstructure, mechanical properties, and corrosion resistance of the as‐cast Mg‐6Zn‐2Al‐based alloy were investigated by SEM, XRD, tensile tests, electrochemical measurements, etc. The higher the Sn content, the higher the yield strength of the Mg‐6Zn‐2Al‐based alloy. Trace Ca addition refined both grains and divorced eutectics in the Mg‐Zn‐Sn‐Al alloys, leading to the best combination of strength and plasticity. Moreover, its influence was more significant for the alloy with a higher Sn content. Furthermore, the combined addition had a beneficial effect on the corrosion resistance improvement of the Mg‐6Zn‐2Al alloy. The Mg‐6Zn‐2Al‐3Sn‐0.2Ca alloy was the most corrosion‐resistant alloy among the nine alloys studied, better than AZ91 and ZA85. It could be ascribed to the decrease and the refinement of divorced eutectics, the higher hydrogen overvoltage of Sn and the Ca grain refinement.     

Cu对Sn-9Zn无铅钎料电化学腐蚀性能的影响

对Sn-9Zn-xCu钎料在3.5%NaCl溶液中的电化学腐蚀行为进行研究,以揭示添加Cu对Sn-9Zn钎料耐蚀性的影响。结果表明:添加Cu元素使Sn-Zn钎料的腐蚀电位有所增加,即添加Cu元素可以改善Sn-Zn钎料的耐腐蚀性能;XRD检测发现Sn-9Zn-xCu钎料的腐蚀产物中存在Zn5(OH)8Cl2.H2O;随着Cu含量的增加,Zn5(OH)8Cl2.H2O的量逐渐减少,出现Cu的腐蚀产物,腐蚀表面趋于均匀平整,选择性腐蚀减弱,腐蚀产物的黏附性较好。