The effect of undercooling on the microstructure and tensile properties of hypoeutectic Sn–6.5Zn–xCu Pb-free solders (original) (raw)
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Materials Science and Engineering: A, 2010
In the present study, the effects of separate and dual addition of small amount of Ag and Cu on the microstructure and mechanical properties of the eutectic Sn-9Zn solder alloy were investigated. Results indicate that alloying of Ag and/or Cu resulted in refine the coarse needle-like Zn-rich phase and formation of intermetallic compounds (IMCs) with the eutectic solder. Single addition of Ag led to formation of AgZn, Ag 5 Zn 8 and -AgZn 3 IMCs, which results in significant increase in both ultimate tensile strength (UTS) and ductility, while, the flower shaped and rod shaped Cu 6 Sn 5, ␥-Cu 5 Zn 8 and -CuZn 5 IMCs produced by Cu alloying, results in small increase in UTS and ductility. The dual addition of Ag and Cu suppressed the appearance of Ag 5 Zn 8 IMCs due to the competition for Zn between Cu and Ag, which results in slight decrease in UTS and ductility of Sn-9Zn-1.5Ag solder. Worthy of notice is that all alloys demonstrated an increase in both UTS and yield stress with increasing strain rate and/or decreasing testing temperature, indicating that the tensile behavior of the four alloys often exhibits a strain rate and temperature dependence.
2021
This research has investigated the influence of cooling conditions on the microstructure and mechanical properties i.e., tensile strength and microhardness of Sn-0.3Ag-0.7Cu lead-free solder. In the experiments, casting was performed at 300℃ with comparison between copper and stainless steel molds under slow and fast cooled conditions. X-ray diffractometer confirmed the presence of Cu6Sn5 and Ag3Sn phases in the solder matrix. Lead-free solder solidified under slow cooled conditions exhibited-Sn matrix with larger grain growth as compared to the fast cooled solder. The eutectic area of intermetallic compound (IMC) was found to increase with cooling rate. The tensile strength of slow cooled solder was greater than fast cooled solder for both molds. In addition, the microhardness of the solder was also influenced by cooling rate. The dimples size of facture surface was decreased by higher cooling rate. A greater eutectic area of the Cu6Sn5 and Ag3Sn phases of initial-Sn matrix lead to lower values of the mechanical property from fast cooled conditions.
2016
The need for replacing lead based solder has received great attention among researchers because of their toxicity. The Sn-Ag-Cu family is the most promising candidate. However, these solder systems need better improvement in terms of controlling their intermetallic formation, growth rate and also their mechanical properties. In this study, the Sn-3.5Ag-l.0Cu solder was studied and three different amounts of Zn were added into the solder system. The solder was prepared using powder metallurgy method. It was characterized for their melting temperature, hardness and density. For intermetallic study, the solder was melted at 250°C on a Cu substrate and placed in an oven at 150°C until 1000 h. After the aging process, the solder joint was cross-sectioned and analysed under a Scanning Electron Microscope and Energy Dispersive X-ray. The thickness of Cu₆Sn₅ and Cu₃ Sn intermetallics were measured using image J software and their growths kinetic were calculated. The shear joint specimen was...
The Effect of Zinc Addition on the Characteristics of Sn–2.0Ag–0.7Cu Lead-Free Solders
2018
Sn–Pb solder was a popular solder in electronics industry. Due to the negative effects from the usage of that solder, researchers start to find a replacement for the Sn–Pb solder. The new solder should maintain the same or better properties than the Sn–Pb solder. In this study, a newly developed solder which is Sn–2.0Ag–0.7Cu with the addition of 0.5, 1.0, 1.5, and 3.0 wt% of Zn was studied. These solders were prepared via powder methodology method and several characterizations were done on them. The 1.0 wt% Zn solder shows the lowest melting point of 222.30 °C and the 0 wt% Zn shows the highest value of 225.65 °C. The 1.0 wt% Zn solder shows the lowest Cu6Sn5 intermetallic thickness value of 1.58 µm and reasonable joint strength. The presence of 1.0 wt% Zn in the Sn–2.0Ag–0.7Cu solder improves the solder properties.
Elastic properties and thermal behavior of Sn–Zn based lead-free solder alloys
Journal of Alloys and Compounds, 2010
In this study, the effects of separate and dual additions of small amount of Cu, In and Ag on the microstructure and elastic properties as well as thermal behavior of the eutectic Sn-9Zn solder alloy were investigated. The elastic properties of the newly developed ternary and quaternary alloys have been investigated using sound wave velocity measurements at 4 MHz and T = 25 • C. In particular, the hardness, the attenuation coefficient, the bulk and shear moduli, Young's and Poisson's ratio have been established for a range of alloy compositions. Results showed that alloying of Cu, In and Ag resulted in reducing fusion heat, solidus temperature and broadening the pasty range. Moreover, the presence of additional elements in Sn-Zn alloy system allows many complex intermetallic (IMC) phases to form. Both the hardness and reduced modulus increase as the Poisson's ratio of the alloy decreases. The elastic properties can be correlated with the formation of the new IMC phases. By analyzing the quotient of shear modulus to bulk modulus, we can assume that the Sn-9Zn, Sn-9Zn-1.5Ag and Sn-9Zn-0.7Cu alloys are ductile solders whereas, the Sn-9Zn-1.5In and Sn-9Zn-1.5Ag-0.7Cu alloys are brittle in nature.
Mechanical properties of Sn based lead free solder under different temperature
IOP Conference Series: Materials Science and Engineering, 2019
In this study, effect of different temperature condition was investigated towards Sn-3.0Ag-0.5Cu (SAC305) solder wire. Tensile test with 0.1 mms−1 strain rate was performed at room temperature (25°C), 60°C, 120°C and 150°C chamber condition. Mechanical properties of SAC305 solder wire were evaluated from stress-strain curves which focused on yield stress, ultimate tensile stress (UTS) and elongation. From the stress-strain curves, there are exhibit the dynamic softening behavior for investigated solder wire. The higher temperature applied during the tensile test, induced the reduction of yield stress and UTS properties. However, elongation properties varied with the temperature condition. Highest percentage of elongation have been indicated at temperature 120°C. Therefore, different temperature conditions applied during tensile test have significant effect to the evaluated mechanical properties of SAC305 solder wire.
Thermal and mechanical properties of Sn–Zn–Bi lead-free solder alloys
Journal of Alloys and Compounds, 2009
Sn-Zn eutectic alloy has been considered as one of the lead-free solder materials that can replace the toxic Sn-37Pb solder without increasing soldering temperature. This study investigates the effect of Bi content on the microstructure, thermal, and mechanical properties of the eutectic Sn-Zn alloy. The results indicate that the microstructures of the Pb-free solders were eutectic. Addition of Bi decreased the melting point and heat of fusion of the solders. 1% Bi addition enhanced the solid solution effect and raised the tensile strength of the as-cast alloys. Notably, with increasing Bi content, the SnBi inter-metallic compound (IMC) precipitates and the ZnO phase are extracted from the -Sn matrix with non-uniform microstructure. The ZnO and SnBi IMC precipitates are considered to be the crucial reasons for rapid deterioration of the tensile properties of the specimens. Furthermore, the SnBi IMC particles are transformed into Bi-rich phase during the annealing process, which resulting in an increase of the susceptibilities of Zn to oxygen for the annealed Sn-9Zn-4Bi alloys. Compared with the other alloys, the newly developed Sn-9Zn-1Bi alloy showed some fine properties and this lead-free solder could substitute some Pb-containing solder alloys in microelectronic components packaging and interconnects.
Influence of Bi on microstructures evolution and mechanical properties in Sn–Ag–Cu lead-free solder
Journal of Alloys and Compounds, 2004
Sn-Ag-Cu-Bi solders, which have high quality and performance that can meet the requirement of electronic packaging, have been investigated in this paper. The research was focused on the influence of aging on the microstructural evolution and mechanical properties in Sn-3Ag-0.5Cu-xBi (x = 0-3 wt.%) solders. The effect of Bi was discussed based on the experimental results. The experimental results indicated that the addition of Bi enhanced the tensile strength of the solders but decreased their elongation. After aging treatment, Sn-3Ag-0.5Cu solder showed significant change in strength and elongation which resulted from the obvious coarsening of Ag 3 Sn and Cu 6 Sn 5 intermetallics. As for Bi-bearing solders, Bi precipitation in Sn matrix was only observed in Sn-3Ag-0.5Cu-3Bi solder after being aged at 120 • C for 100 h, while all the Bi-bearing solders exhibited relatively stable mechanical properties with aging time which can be attributed to the strengthening effect of Bi from solid solution strengthening to precipitating strengthening.
Journal of Materials Science: Materials in Electronics, 2015
Sn-9Zn lead-free solders possess remarkable potential as candidates for low temperature electronic applications. In this study, it is proposed to utilize the advantages of Bi alloying and reducing the amount of Zn to improve oxidation resistance and reliability of eutectic Sn-9Zn solder. The results indicate that hypoeutectic Sn-6.5Zn alloy composed of b-Sn-rich phase and a-Zn fiber. 1.0 wt Bi addition caused a strong inhibition of a-Zn fiber inside the alloy matrix. Moreover, the fiber spacing of a-Zn phase increased and its diameter decreased. With increasing Bi content to 3.0 wt, small bright of Bi particles are observed. The addition of Bi could effectively reduce the onset and eutectic temperatures, while the amount of undercooling\1.0°C was recorded. The tensile strength of Bi-containing solders was enhanced to about 180 %, although the ductility was slightly decreased. The higher strength was contributed by solid solution effect and precipitations hardening of Bi atoms or particles, which can remarkably modify the microstructure, blocks the dislocation motion and increases the tensile strength of Bi-containing solders.
On the advantages of using a hypoeutectic Sn–Zn as lead-free solder material
Materials Letters, 2007
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 Cu 5 Zn 8 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.