Properties Of Solder Research Articles

Reinforcement of graphene nanosheets on the microstructure and properties of Sn58Bi lead-free solder

In this study, graphene nanosheets (GNSs) with various percentages (0, 0.01, 0.03, 0.05 and 0.1wt.%) were successfully incorporated into Sn58Bi lead-free solder. The effects of GNSs on the microstructure, tensile properties, wettability, corrosion resistance, hardness and creep behavior were subsequently investigated. The results show that GNSs refine the microstructure with different features and enhance the wettability efficiently. Tensile and nanoindentation tests reveal that the composite solder with 0.1wt.% GNSs exhibits about 14% and 38% enhancement in tensile strength and hardness, respectively. With 0.01wt.% GNSs addition, the elongation is 49% greater than that of the pure Sn58Bi solder alloy. The creep performance and the corrosion resistance are all enhanced by addition of GNSs. The enhancing mechanism of GNSs on the performance of composite solder alloy is also analyzed in this work.

Creep Characteristic of Sn1.0Ag0.7Cu Lead-Free Solders with Element Addition

In this study, creep properties of lead-free solders based on Sn1.0Ag0.7Cu were investigated. In the solders, germanium, nickel and bismuth were added to improve their mechanical properties. The effect of element addition on their microstructure and creep properties were studied. Creep properties were improved with the element addition. Creep rupture lifetime was the longest for SnAgCuBiNiGe, and that of SnAgCuBi was the second longest. It was made clear that a minimum creep strain rate is useful for lifetime prediction of the solders. An observation of microstructure was performed and coarsening of intermetallics after creep test was identified, resulting in creep rupture. It was found that the addition of bismuth hinders the coarsening of intermetallics and is effective to improve the creep properties of the solders.

Amorphous Copper-Based Alloys: Structure, Technology and Properties

The scientific interest in amorphous and nanocrystalline materials is associated with the expectation of different structural and size effects on the properties of solids, as applied attention due to the possibility of fundamental changes in the properties of polycrystalline materials. Numerous experimental studies indicate the following regularities: the higher the degree of equilibrium of the melt prior to crystallization is, the better quality has a solid metal. In industrial conditions the equilibrium state of the melt is achieved by the technology for heat treatment of the melt. The scientific rationale for this technology is the results of studying the temperature and time dependence of physical properties. The present work describes the analysis of the physical properties of liquid amorphous solder, conducted heat treatment of the melt and the study of the samples mechanical properties in the solid state. Amorphous ribbons obtained by the technology for melt heat treatment, ceteris paribus withstand higher loads in tension, exhibit better ductility and are characterized by high stability of the results. This fact confirms a more uniform material structure.

Effects of Aging Treatment on Mechanical Properties of Sn-58Bi Epoxy Solder on ENEPIG-Surface-Finished PCB

The mechanical properties of Sn-58Bi epoxy solder were evaluated by low-speed shear testing as functions of aging time and temperature. To determine the effects of epoxy, the interfacial reaction and mechanical properties of both Sn-58Bi and Sn-58Bi epoxy solder were investigated after aging treatment. The chemical composition and growth kinetics of the intermetallic compound (IMC) formed at the interface between Sn-58Bi solder and electroless nickel electroless palladium immersion gold (ENEPIG) surface finish were analyzed. Sn-58Bi solder paste was applied by stencil-printing on flame retardant-4 substrate, then reflowed. Reflowed samples were aged at 85°C, 95°C, 105°C, and 115°C for up to 1000 h. (Ni,Pd)3Sn4 IMC formed between Sn-58Bi solder and ENEPIG surface finish after reflow. Ni3Sn4 and Ni3P IMCs formed at the interface between (Ni,Pd)3Sn4 IMC and ENEPIG surface finish after aging at 115°C for 300 h. The overall IMC growth rate of Sn-58Bi solder joint was higher than that of Sn-58Bi epoxy solder joint during aging. The shear strength of Sn-58Bi epoxy solder was about 2.4 times higher than that of Sn-58Bi solder due to the blocking effect of epoxy, and the shear strength decreased with increasing aging time.

Recent progress of Sn–Ag–Cu lead-free solders bearing alloy elements and nanoparticles in electronic packaging

Sn–Ag–Cu lead-free solders, containing alloy elements and nanoparticles, have been extensively investigated. With the extensive prevalence of 3D IC package, a major concern of Sn–Ag–Cu based solders today is continuously focused on extending service life of solder bonding formed between solders and substrates. The critical issues and improvements on Sn–Ag–Cu solders bearing alloys and nanoparticles are outlined and evaluated in this review. It can be summarized that appropriate content of certain alloys or nanoparticles addition to Sn–Ag–Cu solder is possible to tailor the solder properties, such as the melting and solidification behaviors, oxidation resistance, wettability, (interfacial) microstructure, and mechanical properties. Worthy of note is that reliability issues such as creep behavior, thermomechanical fatigue, electromigration, thermomigration and Sn whisker were briefly discussed and analyzed to lay down a solid foundation for the future development of 3D IC technology.

Wettability and Shear Strength of Sn-Cu-Ni-xSi<sub>3</sub>N<sub>4</sub> Composite Solder

The wettability and mechanical properties of solder the joint of Sn-Cu-Ni-xSi3N4 had been investigated. In this study, five different silicon nitride (Si3N4) percentage addition were chosen (0 wt. %, 0.25 wt. %, 0.5 wt. %, 0.75 wt. %, and 1.0 wt. %). Contact angle measurement demonstrated that with Si3N4 addition, the wetting perfomances had been improved with the decrease of wettability contact angle. It is believed that the Si3N4 particles suppresses the interfacial IMC growth and thus improves the shear strength. Interfacial IMC thickness measurement and shear strength results showed that with thinner IMC layer (by increasing amount of wt.% of Si3N4), the higher the shear strength of the joint. Fracture surface of sheared samples shows a combination of both brittle and ductile fracture.

Coupling modification of microstructure for improving the mechanical properties of Zn-Sn-Cu-Bi high-temperature solder

In this study, an attempt to investigate a coupling modification method for grain refinement in Zn-Sn-Cu-Bi (ZSCB) high-temperature solder has been made. During coupling modification, primary grains nucleated from CeZn5 sites and grew to form much more ε-CuZn5 phases compared with the original solder. Peritectic η-Zn phases were also refined, transformed from matrix to equiaxed phases, with grain size of 1.40–2.24µm and uniform elements distribution was achieved. By means of coupling modification, the mechanical properties of ZSCB high-temperature solder, the tensile strength and elongation, show indeed significantly improvement with an increase of 77.15% and 112.68%, respectively.

Microstructure and Properties of Sn-10Bi-xCu Solder Alloy/Joint

The effect of Cu on the microstructure and properties of Sn-10Bi solder alloy/joint were investigated. The results showed that the microstructure of Sn-10Bi-Cu solder alloy consisted of a Sn-rich phase, Bi-rich phase, and particles of Cu6Sn5 intermetallic compounds (IMCs). The pasty range of Sn-10Bi-xCu had an influence on the spreading property of Sn-10Bi-xCu. Cu improved the growth of the IMCs layer during the liquid reaction stage. Furthermore, the hardness of the solder alloy increased as the Cu concentration of increased. The strength of the solder joint was controlled by the solder alloy hardness and the interfacial IMCs layer thickness together. For the joints with low solder alloy hardness and a thin IMCs layer, the fracture was in the solder alloy. For the joints with high solder alloy hardness and a thick IMCs layer, the fracture was in the IMCs layer.

Study of off-eutectic Zn–xMg high temperature solder alloys

Researchers have been working for some times to develop a Pb-free substitute for high-Pb containing solders in electronics. In this study the effect of Mg content on microstructure, melting behavior, thermal, electrical and mechanical properties of a new high-temperature Pb-free solder based on binary Zn–Mg alloy were investigated. The nominal compositions of Zn–xMg (x = 0.5–6.0) alloys were synthesized by conventional melting and casting route. The microstructures of the solders changed significantly on adding Mg content. Higher Mg containing alloys were found rich in intermetallic phases. The formation of the Mg2Zn11 and metastable MgZn2 intermetallic phases were identified and were also quantified by X-ray diffraction analysis. The presence of higher amount of intermetallic compounds in hypereutectic Zn–Mg systems deteriorated the tensile properties of the binary alloy. The results of electrical resistivity test indicated that the Mg could elevate the resistivity of newly developed Zn–Mg alloys. The melting behavior of the solder alloys studied by differential thermal analysis (DTA) analysis revealed that the melting temperature range of the solder alloys narrowed with Mg addition. Thermal mechanical analysis (TMA) analysis revealed that the co-efficient of thermal expansion (CTE) decreased on increasing Mg content.

An investigation on the ZnO retained ratio, microstructural evolution, and mechanical properties of ZnO doped Sn3.0Ag0.5Cu composite solder joints

In this study, ZnO nanoparticles with different weight fractions (0.1, 0.25, 0.5 and 1 wt%) were successfully incorporated into Sn3.0Ag0.5Cu (SAC305) solder through powder metallurgy method. The retained ratios of ZnO reinforcements were measured, and then their effects on the thermal behaviors, microstructural evolution and mechanical properties of composite solders were systematically studied. The element content analysis revealed that only about 12 % of the initially doped ZnO nanoparticles were retained in the final solder joints. With an increase in the amount of reinforcements, the undercooling of composite solders was decreased while the melting temperature was negligibly altered. Refined β-Sn grains were obtained in the composite solder matrix after addition of ZnO nanoparticles. Moreover, compared to the plain solder joints, the composite solder joints exhibited a lower growth velocity of interfacial intermetallic compounds during isothermal aging. A 17.9 % improvement in microhardness and a 10.1 % enhancement in shear strength were also achieved for composite solder joints after 1 wt% ZnO addition. These promotions are all contributed by the presence of ZnO nanoparticles and refined microstructure in solder matrix.

Effects of Ni addition on mechanical properties of Sn58Bi solder alloy during solid-state aging

In this study, Ni functionalized Sn58Bi solder alloys were successfully synthesized. Composite solders up to 1wt% Ni reinforcement were prepared. Microstructures and mechanical properties of composite solders after sintering and solid-state aging for 120h and 240h were compared with those of the pure Sn58Bi solder. The results indicate that the elastic modulus, tensile and yield strength increase with the increasing Ni content during the solid-state aging, which is because Ni can decrease the CTE and refine the microstructure of SnBi solder. The ductility of composite solders presents a non monotonic trend with the increasing Ni content and aging time because the concentrated Ni3Sn4 grains form at the solder matrix. The hardness can reflect the tensile and yield strength transformation veritably. Besides, the hardness varies with tensile and yield strength following the linear relationships.

Peritectic Reactions and Phase Transformations of Sn-30wt%Cu for High Temperature Pb-Free Soldering Applications

Extending the use of the Sn-Cu system to high-temperature solders poses additional challenges as the necessary high Cu content is in a region of the binary phase diagram which is dominated by the peritectic reaction and has the intermetallic compound (IMC) Cu3Sn as the primary phase, which is known to have negative effects on soldering properties. Minor additions of nickel (Ni) have been reported to suppress the formation of Cu3Sn in low Cu content Sn-Cu solder alloys though higher Cu content alloys have not been investigated. As such, the objective of this paper was to investigate the effect of more significant concentrations of Ni on the microstructure of a Sn-30wt%Cu alloy. An initial addition of 2wt%Ni greatly reduced the volume fractions of Cu3Sn and the amount of eutectic present whilst significantly increasing the volume fraction of Cu6Sn5; however, further additions of Ni had a less pronounced affect. The Sn-30wt%Cu morphology was changed from a plate-like structure to a dendritic structure by adding Ni, which would improve solder performance by decreasing the possible crack plane length.

The Effects of Zinc Addition on the Microstructure, Melting Point and Microhardness of Sn-0.7Cu Lead-Free Solder Fabricated via Powder Metallurgy Method

The attempt to produce various types of lead-free solder has been actively investigated around the world in order to substitute the harmful SnPb solders. The effects of Zn addition on the microstructure, melting point and microhardness of Sn-0.7Cu lead-free solder were investigated with 1 wt% and 5 wt% of Zn additions. Powder metallurgy (PM) method was used to fabricate these Sn-0.7Cu-Zn lead-free solders. The results revealed that the addition of Zn was able to improve the solder properties. The melting point of Sn-0.7Cu-Zn lead-free solder was decreased drastically as the increasing of Zn additions. The Zn particles were distributed homogenously along the grain boundaries and produced refined dendrite β-Sn, which also lead to a superior microhardness values of solders.

Design and performance of Ag nanoparticle-modified graphene/SnAgCu lead-free solders

In this study, various weight percentages of Ag-nanoparticle-modified graphene (Ag-GNSs) were incorporated into Pb-free Sn-Ag-Cu (SAC) solder matrices via ball milling and mechanical mixing methods to form composite solders. Up to 0.2wt% of the Ag-GNSs particles was successfully incorporated into the composite solders, and the microstructures and mechanical properties of the solders were investigated. The experimental results demonstrated that as the Ag-GNSs content increased, the number of intermetallic particles gradually decreased in size. In addition, the uniformity of the interfacial structure increased compared to that of the pure SAC solder. Furthermore, the melting points of the SAC/Ag-GNSs composite solders were unchanged compared to that of the pure SAC solder. The experimental results also revealed that the wettability of the composite solders on Cu substrates was greatly improved. Thermomechanical measurements showed that the thermal stability of the composite solders was also improved. In addition, tensile tests showed that the ultimate tensile strength of the composite solders was enhanced compared to that of the pure SAC solder, but the ductility of the composite solders was reduced. In particular, the tensile strength of the composite solders with low Ag-GNSs contents was increased, but the tensile strength then decreased once a critical Ag-GNSs content was reached. For the ball-milled solders, the reinforcement provided by the addition of Ag-GNSs particles was much better than that provided by unmodified graphene. By comparing the properties of solders fabricated with different preparation methods, it was determined that the ball-milled solders were superior to the mechanically mixed solders.

Study on microstructure and properties of Sn–0.3Ag–0.7Cu solder bearing Nd

The properties and microstructure of Sn–0.3Ag–0.7Cu solder bearing trace amount of rare earth Nd were investigated in this paper. It was found that adding appropriate Nd can improve the properties of solder, the wettability of Sn–0.3Ag–0.7Cu–xNd solder was greatly improved and the mechanical properties were significantly enhanced when the addition of Nd reached 0.1 wt%. It was also found that the microstructure of solder was refined with the increasing content of Nd up to 0.1 wt%. In addition, when the Nd content exceeded 0.25 % a Sn–Nd phase appeared in the solder matrix. Comparing all the results, the comprehensive properties of Sn–0.3Ag–0.7Cu–0.1Nd solder were close to that of the traditional Sn–3.8Ag–0.7Cu solder, even though the content of Ag has been significantly reduced from 3.8 to 0.3 wt%, which had shown a great application prospect to satisfy the increasing requirements of low cost and high performance in the electronics industry.

Lead-Free Solders for Superconducting Applications

In this paper, the low-temperature properties of some commercial Pb-free solders developed for electronics and aerospace applications were investigated for possible use as superconducting solder materials. Their properties are also compared with in-house Sn 35In 50Bi 15 solders being developed to replace the widely used Pb-Bi alloys. Of these materials, the Sn 35In 50Bi 15 solder is the best potential candidate for superconducting applications.

Superconducting and Mechanical Properties of Low-Temperature Solders for Joints

All large superconducting applications require electrical connections between superconductors or between superconductors and other metallic parts of the systems. Such connections are essential components for these applications and are usually made by melting the solder (or soft soldering). In general, the melting point, electrical resistivity, mechanical and wetting properties, and toxicity are all important criteria when choosing the best solder for a specific application. If the solder itself is superconducting under the operating conditions of the application, then there is also the possibility of extremely low resistance joints. In this work, we report on the superconducting properties of six low-melting-point solders, namely, Bi49Pb18In21Sn12 (Cerrolow 136), Pb20Sn34Bi46, Pb20Sn60Bi20, In52Sn48, Pb38Sn62, and Pb57Bi36Sb7, and the mechanical properties of three of the six solders (Pb38Sn62, Cerrolow 136, and Pb20Sn34Bi46). We have found that all the solders except Pb38Sn62 and In52Sn48 have relatively high upper critical fields (higher than 2 T) at temperatures lower than 3 K. Although the good ductility and high maximum fracture elongation of Pb38Sn62 is useful when using low-temperature superconductors, other solders may be preferred with high-temperature superconductors because their lower melting temperatures mean they are less likely to delaminate them.

Microstructure and mechanical properties of Sn-rich Au-Sn solders designed using cluster-plus-glue-atom model

Novel Sn-rich Au-Sn solder alloys were designed using the cluster-plus-glue-atom (CPGA) model, and the microstructure, melting behavior, wettability and mechanical properties of the designed Sn-Au-Ag(Ni) solders were systematically investigated. The cluster formula of [Sn11Au2]Sn3, a stable Sn-centered cluster (11 Sn atoms and 2 Au atoms) plus 3 Sn glue-atoms, is applicable to substitute Ag and Ni for Au. The [Sn11AuAg]Sn3 and [Sn11Au0.5Ag1.5]Sn3 solders are near-eutectics with a narrow melting temperature range of 206.89–207.25°C; while the Sn-Au-Ni solders are non-eutectics with a wide melting temperature range of 215.33–255.44°C, due to a large difference in chemical property between Ni and Au. The microstructure of the Sn-Au-Ag solders consists of AuSn4 and Ag3Sn phases dispersed in β-Sn matrix; while that of the Sn-Au-Ni solders consists of AuSn4 and Ni3Sn4 phases dispersed in β-Sn matrix. The wettability of the Sn-Au-Ag(Ni) solders on Ni substrate is better than that on Cu substrate because of the severe interfacial reaction on Cu substrate. The shear strength of the [Sn11Au0.5Ag1.5]Sn3 and [Sn11Au0.5Ni1.5]Sn3 solder joints is 50.59MPa and 36.28MPa, respectively, which is significantly higher than that of eutectic Au-30at% Sn solder joints (24.5MPa).

Tensile creep behavior of Sn–Ag–Cu–Ni multicomponent lead-free solder alloy

In the process of electronic packaging, the dissolution of under bump metallizations, such as Cu and Ni, into liquid solder occurs during soldering, which can change the original solder to a multicomponent one. Under the trend of miniaturization, it is quite necessary to evaluate the properties of multicomponent solder with excessive Cu and Ni compositions. In this study, the tensile creep behavior of Sn–3.5Ag–2.0Cu–0.5Ni multicomponent lead-free solder alloy is investigated at three temperatures, i.e., 303, 348 and 393 K. The steady-rate creep rates are obtained in the range of 10−4–10−8 s−1, when the normalized stress, σ/E, is in the range of 10−4–10−3. Based on the Dorn equation, the apparent stress exponent (n a), threshold stress (σ th), and activation energy of creep (Q C) are calculated at the three temperatures. It is found that the Sn–3.5Ag–2.0Cu–0.5Ni solder alloy shows a better creep performance than pure tin and eutectic Sn–3.5Ag solder due to the strengthening effect of Ag3Sn and (Cu,Ni)6Sn5 IMC precipitations. The true stress exponent for creep is identified to be 7, indicating that the creep behave is controlled by the dislocation-pipe diffusion in the tin matrix.

Properties and Microstructures of Sn-Bi-X Lead-Free Solders

The Sn-Bi base lead-free solders are proposed as one of the most popular alloys due to the low melting temperature (eutectic point: 139°C) and low cost. However, they are not widely used because of the lower wettability, fatigue resistance, and elongation compared to traditional Sn-Pb solders. So the alloying is considered as an effective way to improve the properties of Sn-Bi solders with the addition of elements (Al, Cu, Zn, Ga, Ag, In, Sb, and rare earth) and nanoparticles. In this paper, the development of Sn-Bi lead-free solders bearing elements and nanoparticles was reviewed. The variation of wettability, melting characteristic, electromigration, mechanical properties, microstructures, intermetallic compounds reaction, and creep behaviors was analyzed systematically, which can provide a reference for investigation of Sn-Bi base solders.