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In this study, the evolution of interfacial microstructures and mechanical properties of the joints soldered with Sn-0.3Ag-0.7Cu (SAC0307) and SAC0307-0.12Al2O3 nanoparticles (NPs) aged at 150 °C for different hours (72-840 h) were investigated. It was found the joint soldered with SAC0307-0.12Al2O3 displayed a significantly enhanced high-temperature joint reliability, reflected in a higher shear force than that of the original. This enhancement in shear force primarily benefited from the refinement in solder microstructure contributed by Al2O3 NPs. As aging time reached 840 h, a controlled growth of interfaical IMC layer resulted from the pinning effect of Al2O3 NPs contributed to the increase in shear force. Theoretical analysis showed 0.12 wt% Al2O3 NPs effectively lowered the growth constant of total interfacial IMCs (DT) from 3.19 × 10−10 to 1.02 × 10−10 cm2 s−1. Moreover, comparative studies on the corrosion resistances of SAC0307 and SAC0307-0.12Al2O3 were also conducted by electrochemical test and analyzed by electrochemical impedance spectroscopy (EIS). The results revealed SAC0307-0.12 Al2O3 solder displayed a stronger corrosion resistance (Rt; ~ 3.1 kΩ cm2 vs ~ 7.1 kΩ cm2). This is also related with the tailored microstructure, which provides more grain boundaries for the initial nucleation of passive film. [ABSTRACT FROM AUTHOR]

This work offers an analysis of the wire feedability-related properties of Al-5Mg solid wire electrodes bearing Zr. Effects of Zr content on microstructures and mechanical properties of the Al-5Mg alloys were studied. Experimental results have demonstrated that α -Al dendrites of the as-cast Al-5Mg alloy are refined, and the tensile strength, microhardness and roughness of the 1.2 mm wire electrode are improved with an appropriate addition of Zr. In addition, the tensile strength and elongation of the welded joints welded using Al-5Mg wire electrodes bearing Zr reach the maximum value when 0.12% Zr is added into the wire alloy. However, when excess Zr is added, α-Al phases of the wire alloy and welded joint are coarsened, and the mechanical properties are deteriorated. Moreover, the structure and principle of a novel apparatus, which can enhance the feedability of the wire electrode, are introduced and the apparatus can achieve the rough and fine adjustments of cast and helix of the wire electrode. [ABSTRACT FROM AUTHOR]

Various heat input conditions and post-weld heat treatments were adopted to investigate the microstructure evolution and mechanical properties of tungsten inert gas (TIG) welded joints of AA6082-T6 with porosity defects. The results show that the fracture location is uncertain when an as-welded joint has porosities in the weld zone (WZ), and overaging in the heat-affected zone (HAZ) at the same time. When the fracture of the as-welded joint occurs in the HAZ, the total heat input has a linear relation with the tensile strength of the joint. An excess heat input induces the overgrowth of Mg2Si precipitates in HAZ and the coarsening of α-Al grains in WZ, resulting in a decrease in the microhardness of the corresponding areas. After artificial aging treatment, the tensile strength of the welded joint is increased by approximately 9-13% as compared to that of as-welded joint, and fracture also occurs in HAZ. In contrast, for solution treated and artificial aging treated joint, fracture occurs suddenly at the rising phase of the tensile curve due to porosity defects throughout the weld metal. Furthermore, the eutectic Si particles of WZ coarsen and spheroidize after solution treatment and artificial aging treatment, due to the diffusion of Si to the surface of the original Si phases when soaking at high temperature. [ABSTRACT FROM AUTHOR]

The effect of trace amount of Ga on the inoxidizability and wettability of Sn-0.5Ag-0.7Cu-0.05Pr solders was investigated systematically by means of microstructure characterizations. The results indicate that the wettability and oxidation resistance properties are remarkably improved with addition of trace amount of Ga. Moreover, it is observed that the trace amount of Ga in Sn-0.5Ag-0.7Cu-0.05Pr solders refines the matrix microstructure. The relationship between wettability and oxidation resistance was put into deep study. And Ga was found to be enriched on the surface of the molten solder, which benefited the properties correspondingly. The results of this study can stimulate the use of low-silver Sn-Ag-Cu-Pr solders for various applications. [ABSTRACT FROM AUTHOR]

In this paper, the effect of Pr addition on the microstructure and properties of Sn-0.5Ag-0.7Cu-0.5Ga lead-free solder was investigated. It was found that the properties of Sn-0.5Ag-0.7Cu-0.5Ga- xPr solder, such as wettability and mechanical properties, could be obviously improved, and the optimal content of Pr was about 0.06 wt.%. The microstructure of Sn-0.5Ag-0.7Cu-0.5Ga-0.06Pr solder showed that the β-Sn matrix and intermetallic compound (IMC) grains were significantly refined, and refinement and homogenization of the microstructure achieved maximum efficiency, which played the role of fine grain strengthening and second phase strengthening. However, as the content of Pr exceeded 0.06 wt.%, some uneven distributed black phases of PrSn were found in the β-Sn matrix, which seriously worsened the microstructure and properties of the solders. As a surface-active element, the segregation of Pr at the molten solder interface could give rise to decreasing the interface tension. Consequently, adding a suitable amount of Pr could play a positive role in improving the properties of the solders. [ABSTRACT FROM AUTHOR]

Effects of trace amount of rare earth element Pr on properties and microstructure of Sn-0.7Cu-0.05Ni solder were investigated in this paper. The solderability of Sn-Cu-Ni-xPr alloy and shear strengh of Sn-Cu-Ni-xPr soldered micro-joints were determined by means of the wetting balance method and shear test, respectively. Moreover, microstructure of solder alloys bearing Pr, as well as intermetallic compound (IMC) layer formed at solder/Cu interface after soldering were observed. It was concluded that the major benefits of rare earth element Pr on Sn-Cu-Ni lead-free solder are: improving solderability, refining microstructure, and depressing IMC (IMC) growth, which exhibited improved mechanical properties. It also revealed that (Cu,Ni)Sn is the majority IMC phase at the interface of Sn-Cu-Ni-xPr/Cu solder joints. Ni added into the solder effectively suppressed the growth of CuSn and consequently also the total IMC layer thickness. Above all, the thickness and morphology of the interfacial (Cu,Ni)Sn IMC were optimized due to alloying Pr. It can be inferred that Pr and Ni would play an important role in improving the reliability of Sn-Cu-Ni lead-free solder joints. [ABSTRACT FROM AUTHOR]

In the present work, effects of trace amount of Pr on the microstructure, wettability and mechanical properties of Sn-9Zn solder were studied. The range of Pr content in Sn-9Zn solder alloys varied from 0.01 to 0.25 wt%. Test results indicate that adding appropriate amount of Pr can evidently improve the wettability and mechanical properties of the Sn-9Zn solder alloy. The Sn-9Zn-0.08Pr solder shows the best comprehensive properties compared to other solders with different Pr content. At the same time, notable changes in microstructure were found compared with the Pr-free alloy. The needle-like Zn-rich phase in the Sn-9Zn solder was refined and became more uniform. Moreover, the thickness of the IMC layer at Sn-9Zn/Cu substrate was remarkably depressed with Pr addition. [ABSTRACT FROM AUTHOR]

Nowadays, a major concern of Sn-Cu based solder alloy today is focused on continuously improving the comprehensive properties of the solder joints formed between the solders and substrates. The key issues and improvements about Sn-Cu-X (X = Ni, rare earths, Zn, Co, Ga, In, Bi, secondary particles etc.) solder are outlined and evaluated in this paper which compared to Sn-Cu solder. It can be summarized that by adding appropriate amounts of certain alloying elements X to Sn-Cu solder, and it is possible to tailor the properties of the solder, such as the melting and solidification behaviors, wettability, microstructure, interfacial reactions and mechanical properties of the solder. The reliability issues related to the implementation of Sn-Cu-X solder in advanced electronics system are also introduced, which indicates that further development on the Sn-Cu-X solders are to be underway. [ABSTRACT FROM AUTHOR]

Effects of Pr addition on wettability, microstructure of Sn3.8Ag0.7Cu solder were studied, the mechanical properties of solder joints were investigated and the fracture morphologies were also analyzed in this paper. The results indicate that adding appropriate amount of Pr can evidently improve the wettability of solder, and it is also found that Pr can refine the β-Sn dendrites and reduce the intermetallic compounds growth inside the solder due to the fine PrSn3 particles formed in the solder which can act as heterogeneous nucleation sites. Moreover, the joints soldered with the SnAgCuPr solders possess sound mechanical properties which may result from the finer microstructure improved by the Pr. [ABSTRACT FROM AUTHOR]

Effects of rare earth Nd on solderability of the Sn3.8Ag0.7Cu alloy were studied by wetting balance method, and the mechanical properties (such as pull-force and shear-force) of the joints soldered with SnAgCu–XNd solders were determined using STR-1000 joint strength tester. Moreover, the microstructures of SnAgCu–XNd solders bearing different amount of Nd as well as the intermetallic compounds (IMCs) formed at solder/Cu interface during soldering have been investigated using optical microscopy, scanning electron microscopy and energy dispersive X-ray analysis, respectively. The results indicate that trace amount of Nd addition can remarkably improve the solderability and mechanical properties of SnAgCu solder. At the same time, it is found that rare earth Nd in SnAgCu solder could refine and improve microstructure of the solder, some bigger IMC plates in SnAgCu solder were replaced by fine granular IMCs. Moreover, the thickness of the intermetallic layer at the Cu/solder interface was reduced significantly. In summary, we suggest that the most suitable content of rare earth Nd is about 0.05 wt% and it will be inadvisable when the Nd exceeds 0.25 wt%. [ABSTRACT FROM AUTHOR]

The influences of different Ce content on the properties of Sn–9Zn lead-free solder were investigated. The results indicate that Ce plays an important role not only in the structure and the solderability, but also in the interfacial structure of Sn–9Zn– xCe/Cu and mechanical property of soldered joint. Sn–9Zn–0.08Ce shows finer and more uniform microstructure than Sn–9Zn, and when the quantity of Ce is 0.5–1 wt%, some dark Sn–Ce compounds appear in the solder. With the addition of 0.08 wt% Ce, the solderability of solder is significantly improved because the surface tension of molten solder is decreased. Adding Ce makes the Cu5Zn8 IMCs formed at the interface of solder/Cu become much thicker than that of Sn–9Zn/Cu because much more content of Zn diffuse to the interface of solder/Cu to react with Cu. Results also indicate that adding 0.08 wt% Ce to the solder enhances mechanical property of soldered joint. When the Ce content is 0.1–0.5 wt%, some hard and brittle Cu–Zn IMCs appear in the bottom of dimples and the pull force of soldered joint decreases. [ABSTRACT FROM AUTHOR]

The influences of different Ga content on the properties of Sn–9Zn lead-free solder were investigated. The results indicate that Ga plays an important role not only in the structure and melting behavior, but also in the solderability and mechanical property. Sn–9Zn–0.5Ga shows finer and more uniform microstructure than Sn–9Zn. With the addition of low-melting-point Ga, TL (liquidus temperature) and TS (solidus temperature) of the alloys decreases with increasing of Ga content while △T (liquidus temperature minus solidus temperature) increases. Ga can improve the oxidation resistance and reduce the surface tension of solder, so the solderability of Sn–9Zn– xGa lead-free solder is significantly improved. When the content of Ga is 0.5 wt.%, the pull force of soldered joint is 16.1 N, enhanced by 11% compared to that of Sn–9Zn, and the fracture micrographs show that the joint failed in a ductile manner. The addition of 3 wt.%Ga resulted in a brittle failure. The introduction of 0.5 wt.% Ga into Sn–9Zn alloy improves creep resistance of the solder. [ABSTRACT FROM AUTHOR]

The objective of this review is to study the interfacial intermatallic compounds (IMCs) between Sn–Ag–Cu based solders and common substrates, which play a crucial role in solder joints typically present in Pb-free electronics manufacturing. The microstructural evolution of IMCs at the solder/substrate interfaces is analyzed, while the models and theories describing the formation/growth mechanism of interfacial IMCs are also introduced. We focus on the influence of a variety of factors that have been reported recently, including substrates, minor alloying, mechanical stress, electromigration and thermomigration etc., as full understanding of the mechanisms that determine the formation and growth of interfacial IMCs is important to reach for developing high reliability solder joints. In the end of this review, the characteristics of the IMCs are compared and illustrated, which have marked effect on the mechanical properties and fracture behavior as well as reliability of solder joints. [ABSTRACT FROM AUTHOR]

Wetting balance method is used to evaluate the effects of Ga, Al, Ag, and Ce multi-additions on the solderability of Sn–9Zn lead-free solders, results show that the optimal addition amounts of Ga, Al, Ag, and Ce is 0.2, 0.002, 0.25, and 0.15 wt% respectively. The surface property of Sn–9Zn–0.2Ga–0.002Al–0.25Ag–0.15Ce solder is studied by X-ray photoelectron spectroscopy and auger electron spectroscopy analysis; results indicate that Al aggregates on the surface as a compact aluminum oxide film which prevents the further oxidation. The aggregation of Ce on the subsurface can reduce the surface tension of solder, and improve the solderability accordingly. Meanwhile, SEM and XRD analysis indicate that Cu5Zn8 and AgZn3 intermetallic compounds form at the interface between Sn–9Zn–0.2Ga–0.002Al–0.25Ag–0.15Ce solder and Cu substrate, while AuZn3 and AuAgZn2 form at the interface between solder and Cu/Ni/Au substrate. Moreover, results also indicate that the mechanical property of soldered joints is improved duo to the dispersion strengthening effects of AgZn3 in Sn–9Zn–0.2Ga–0.002Al–0.25Ag–0.15Ce solder. [ABSTRACT FROM AUTHOR]

The effects of Ga–Al, Ga–Ag and Al–Ag binary additions on the wetting characteristics of Sn–9Zn–X–Y lead-free solders are studied by the wetting balance method. Experimental results show that Sn–9Zn–1.0Ga–0.3Ag, Sn–9Zn–0.005Al–0.3Ag, and Sn–9Zn–0.3Ga–0.002Al possess better wettability than the other alloys tested. The mechanism by which Ga, Al, and Ag additions improve the wettability is also proposed. It appears that dense aluminum oxide film formation and the enrichment of Ga on the surface may protect the bulk liquid solder from further oxidation. Moreover, results also indicate that, AgZn3 IMCs layer formed at the interface, which may release reaction energy during the wetting, results in improving the wettability of the solder. [ABSTRACT FROM AUTHOR]