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The Effects of Gallium Additions on Microstructures and Thermal and Mechanical Properties of Sn-9Zn Solder Alloys  [PDF]
Kang I. Chen,Shou C. Cheng,Chin H. Cheng,Sean Wu,Yeu-L. Jiang,Tsung-C. Cheng
Advances in Materials Science and Engineering , 2014, DOI: 10.1155/2014/606814
Abstract: The effects of gallium additions on microstructures and thermal and mechanical properties of the Sn-9Zn solder alloys are investigated in this study. The results show that the melting temperature of the alloys decreases with the increase in the Ga concentration, while the pasty ranges of the alloys are simultaneously enlarged. By adding a 0.25–0.5?wt.% Ga element, the Sn-matrix region is slightly increased and the Zn-rich phase becomes slightly coarser; however, the overall microstructure is still very similar to that of the Sn-9Zn alloy. It is found that, when the Ga concentration is less than 0.50?wt.%, the ultimate tensile strength and elongation are maintained at the same values. The addition of a 0.25–0.50?wt.% Ga to the Sn-9Zn alloy also leads to small cup and cone fracture surfaces which exhibit near-complete ductile fracturing. With the addition being increased to 0.75?wt.%, larger cup and cone fractures are observed. The 1.00?wt.% Ga alloy has lower strength and ductility due to the coarser and nonuniform microstructures. However, the fracture surfaces of the 1.00?wt.% Ga alloy show partial cleavage and a partially dimpled fracture. 1. Introduction Conventional Sn-Pb solders have commonly been used as the interconnection materials for soldering electronic components and devices. However, the use of Pb is restricted due to health and environmental issues. On the other hand, an alloy of Sn-Ag-Cu has been recognized as a potential lead-free solder even though Sn-Ag alloy systems have higher melting points (say, 216 to 221°C), as compared to an eutectic Sn-Pb alloy [1, 2]. A high melting point is accompanied by high soldering temperatures, which may give rise to substrate instability problems. Recently, the Sn-9Zn alloy system has received increased interest since it features low cost, great mechanical properties, and a low eutectic temperature (198°C), close to that of the Sn-Pb alloy [2, 3]. The eutectic structure of the Sn-9Zn alloy system consists of two phases: a body centered tetragonal Sn matrix phase and a secondary phase of hexagonal Zn containing less than 0.039?at.% Sn in solid solution [3, 4]. However, the tendency of oxidation and poor wetting ability of this alloy system limits its application [5, 6]. In recent years, to overcome the shortfalls in the Sn-9Zn alloy, some authors have tried to add a third element, such as In [7], Ga [8], Bi [9–13], Al [14–18], Ag [19–22], Cr [23], Cu [24], and Ce/La [25–27], to the Sn-Zn binary system to improve the melting temperature, wettability, oxidation resistance, corrosion, and mechanical

XIAN Jun-yang,

腐蚀科学与防护技术 , 2008,
Abstract: Sn-9Zn alloy is a low cost eutectic Pb-free solder.Since Zn exists in the alloy,the corrosion resistance is poor.Present work was focused on the corrosion behavior of Sn-9Zn in both outdoor atmosphere and an artificial simulated solution.The corrosion product was observed by SEM and analyzed by EDAX.The results showed that in the case of atmosphere corrosion,the surface of the alloy suffered from obvious corrosion after expoure for 12 days only.The morphology of the corrosion product mainly presents as thor...
Influences of Ag and Au Additions on Structure and Tensile Strength of Sn-5Sb Lead Free Solder Alloy

AAEl-Daly YSwilem AEHammad Physics,

材料科学技术学报 , 2008,
Abstract: It is important,for electronic application,to decrease the melting point of Sn-5Sb solder alloy because it is relatively high as compared with the most popular eutectic Pb-Sn solder alloy.Adding Au or Ag can decrease the onset melting temperature (233℃) of this alloy to 203.5℃ and 216℃,respectively.The results indicate that the Sn-5Sb-1.5Au alloy has very good ultimate tensile strength (UTS),ductility,and fusion heat,which are better than both those of the Sn-5Sb-3.5Ag and Sn-5Sb alloys.The formation of intermetallic compounds (IMCs) AuSn4 and Ag3Sn enhanced the microstructure stability,while retained the formation of SbSn precipitates in the solidification microstructure,thus significantly improved the strength and ductility.For all alloys,both UTS and yield stress (σy) increase with increasing strain rate and decrease with increasing temperature in tensile tests,but changes of ductility are generally small with inconsistent trends.
Enhancing the Creep Resistance of Sn-9.0Zn-0.5Al Lead-Free Solder Alloy by Small Additions of Sb Element  [PDF]
E. A. Eid, Manal A. Ramadan, A. B. El Basaty
Engineering (ENG) , 2018, DOI: 10.4236/eng.2018.101003
Abstract: The creep phenomenon is considered as one of the most important deformation mechanisms under working conditions. The present study has examined the microstructure and creep properties of Sn-9.0Zn-0.5Al solder alloy after adding a small amount of Antimony (Sb). Nominal compositions of Sb additions were chosen to be 0, 0.5, 1.0, and 1.5 wt.%. The minimum strain rate was reduced for the Sb containing solder alloy. The stress exponents, n, were found to be around 3.7 for all soldiers at 130°C. The stress exponent increases as the temperature drops from 100°C to 50°C, except for the 1.0% Sb alloy, where n 5.3 - 6.1 at all the temperature range (T = 50°C, 100°C and 130°C). The results reveal that the Sb-containing solder alloys have better creep resistance with greater ductility than the Sb-free alloy due to solid solution strengthening, and intermetallic compound SnSb particle hardening.
Uniaxial tensile and shear deformation tests of gold–tin eutectic solder film
Takahiro Namazu, Hideki Takemoto, Hiroshi Fujita and Shozo Inoue
Science and Technology of Advanced Materials , 2007,
Abstract: This paper describes a novel experimental technique for measuring mechanical properties of gold-tin (Au–Sn) eutectic solder film used for soldering package in microelectromechanical systems (MEMS). Dual-source DC magnetron sputtering was employed to deposit Au-20 weight % (wt%) Sn film. The tensile test with in situ X-ray diffraction (XRD) measurement evaluates the Young's modulus and Poisson's ratio at intermediate temperatures. The Young's modulus and Poisson's ratio at room temperature were found to be 51.3 GPa and 0.288, lower than bulk values. The Young's modulus decreased with increasing temperature, whereas the Poisson's ratio did not depend on temperature. The XRD tensile test also showed creep deformation behavior of Au–Sn film. We have developed a shear deformation test technique, which is performed by using Au–Sn film sandwiched by two single crystal silicon (Si) cantilever structures, to characterize the shear properties of the film. The shear moduli obtained from the shear deformation tests ranged from 11.5 to 13.3 GPa, about 38% lower than those from the XRD tensile tests. The measured shear strength from 12 to 17 MPa exhibited a temperature dependency. Information about the tensile and shear characteristics would likely to be of great use in designing Au–Sn soldering packages for MEMS.
Abnormal growth of Ag3Sn intermetallic compounds in Sn-Ag lead-free solder
Jun Shen,Yongchang Liu,Houxiu Gao
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-2043-y
Abstract: The abnormal growth of Ag3Sn intermetallic compounds in eutectic Sn-3.5% Ag solder was investigated through high-temperature aging treatment. Microstructural evolutions of this solder before and after the aging treatment were observed by optical microscopy and scanning electron microscopy. Precise differential thermal analysis was made to study the changes in enthalpies of the solder under different conditions. The results reveal that the water-cooled solder is in metastable thermodynamic state due to the high free energy of Ag3Sn nanoparticles, which sporadically distribute in the matrix as second-phase. The second-phase Ag3Sn nanoparticles aggregate rapidly and grow to form bulk intermetallic compounds due to the migration of grain boundary between primary Sn-rich phase and the Ag3Sn nanoparticles during high temperature aging treatment.
High temperature indentation behavior of eutectic lead-free solder materials  [cached]
Müllera W.H.,Worrack H.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100640009
Abstract: Electronic malfunction caused by thermal stresses is one major problem in modern electronic industries. Therefore, the precise knowledge of the mechanical solder material properties as a function of temperature is required. Nanoindentation and its potential of recording load-displacement curves is a widely-used miniature test for the determination of Young’s modulus and hardness values. Furthermore, such tests can be performed in a temperature range from Room Temperature (RT) up to +500°C by using a Hot-Stage add on. In this paper the lead-free solder alloys Sn91Zn9 and Sn42Bi58, and also copper and fused silica, which is used for the indenter calibration are investigated. The results for quartz and copper agree with the published values in several references. However, the Young’s modulus of Sn42Bi58 as a function of temperature differs from the values presented in the literature. Due to delayed material response in the unloading regime it must be assumed that creep effects lead to an incorrect automatic data evaluation. Investigation and understanding of the creep behavior is part of this paper. For this purpose a visco-elastic material model is used to model the indentation response at elevated temperatures and to determine the corresponding viscous material constants.
Solderability of Electrodeposited Fe-Ni Alloys with Eutectic SnAgCu Solder
Jianjun GUO,Lei ZHANG,Aiping XIAN,JKShang,

材料科学技术学报 , 2007,
Abstract: Solderabilities of electrodeposited Fe-Ni alloys with SnAgCu solder were examined by wetting balance measurements and compared to those of pure Ni and pure Fe platings. Excellent solderability was found on the Ni-52Fe plating as both the wetting force and kinetics approached or exceeded those on the pure Ni. However,upon further increase in Fe content to 75 at. pct, the solderability of the alloy was severely degraded even though it was still better than that of the pure Feplating. X-ray photoelectron spectroscopy showed that such a strong dependence of solderability on Fe content is related to the much thinner, incomplete oxide coverage of Ni-rich plating surface.
Au-SN Flip-Chip Solder Bump for Microelectronic and Optoelectronic Applications  [PDF]
Jeong-Won Yoon,H. -S. Chun,Ja-Myeong Koo,Seung-Boo Jung
Computer Science , 2007,
Abstract: As an alternative to the time-consuming solder pre-forms and pastes currently used, a co-electroplating method of eutectic Au-Sn alloy was used in this study. Using a co-electroplating process, it was possible to plate the Au-Sn solder directly onto a wafer at or near the eutectic composition from a single solution. Two distinct phases, Au5Sn and AuSn, were deposited at a composition of 30at.%Sn. The Au-Sn flip-chip joints were formed at 300 and 400 degrees without using any flux. In the case where the samples were reflowed at 300 degrees, only an (Au,Ni)3Sn2 IMC layer formed at the interface between the Au-Sn solder and Ni UBM. On the other hand, two IMC layers, (Au,Ni)3Sn2 and (Au,Ni)3Sn, were found at the interfaces of the samples reflowed at 400 degrees. As the reflow time increased, the thickness of the (Au,Ni)3Sn2 and (Au,Ni)3Sn IMC layers formed at the interface increased and the eutectic lamellae in the bulk solder coarsened.
Effect of Li and Ti Additions on L■α(Al)+Mg_2Si Pseudobinary Eutectic Reaction
材料科学技术学报 , 1997,
Abstract: Effect of Li and Ti additions on Lα(AI)+Mg2Si pseudobinary eutectic reaction in ternary Al-Mg-Si system has been investigated by thermoanalysis, directional solidification and metallographic techniques in this study. It has been found that Li addition causes decreasing of the volume fraction of Mg2Si, while a little amount of Ti causes to increasing, which is of a great importance to the adjustment of phase constitution and alloy properties. Doping components have little influence on the eutectic temperature.
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