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In order to improve the mechanical properties of deposited metal of ilmenite type welding electrode, CeO/La rare earth elements were added into electrodes based on E4301 electrode, then electrodes were produced, test plates were welded, and mechanical properties were tested based on National Standards of China. For the sake of solving the problems of large amount of mechanical properties tests, long test cycle and high test cost during the conventional production process of electrode, a prediction model of the mechanical properties of deposited metal based on Takagi-Sugeno (T-S) fuzzy neural network was established. Mn, Si and C contents of medium manganese in electrode, CeO, and La contents of electrode and welding speed were selected as input variables of the prediction model, and the tensile strength, lower yield strength, elongation, impact energy and hardness of deposited metal were selected as output variables. Finally, predicting experiment was done under test samples, and results show that average relative prediction error of the tensile strength, lower yield strength, elongation and hardness are 0.91 %, 2.57 %, 4.94 % and 1.94 %, respectively, which reach the need of actual production. The results of prediction show that the mechanical properties of deposited metal of electrode containing rare earth can be forecasted accurately through material composition of electrode and welding parameters based on T-S fuzzy neural network model. [ABSTRACT FROM AUTHOR]

Microstructures, interface reaction, melting characteristics, tensile property, thermal fatigue behavior and wettability of Sn58Bi, Sn35Bi0.3Ag and Sn35Bi1.0Ag solders were investigated. Only Sn phase and Bi phase like net-type distribute uniformly in the Sn58Bi matrix, Sn35Bi0.3Ag and Sn35Bi1.0Ag solder show the AgSn particles in the Sn matrix around net-like Bi phase, at the solder/Cu solder joints, only CuSn intermetallic compound was observed. The liquid phase line temperature of Sn35Bi0.3Ag and Sn35Bi1.0Ag is higher than that of SnBi solder. Sn35Bi1.0Ag solder joints show superiority in mechanical property and fatigue life, which can attribute to the strengthening effect of AgSn particles. Moreover, the wettability of Sn35Bi1.0Ag solder was best of all, and the N atmosphere and RMA flux can enhance the wettability obviously, which can provide the reference support of the research of SnBi base solders. [ABSTRACT FROM AUTHOR]

The relationship between Ce content/CeSn sizes and the whiskers growth is newly reported systematically. The whiskers growth can be observed in the surface of bulk CeSn particles, the rate of whisker growth was significantly slowed with Ce content lower than 0.1 wt%. At higher concentration of Ce, whisker growth rate becomes higher and noticeable. It is thought that the higher Ce chemical potential for oxidation provides a path for the mechanism of whisker growth. With all the other benefits of Ce addition, the potential to promote whisker growth indicate that only dilute concentration of Ce can be tolerated in SnAgCu alloys without whiskering effect. The results demonstrated that the trace amount of Ce can be utilized as additive into SnAgCu solder in microelectronic industry. [ABSTRACT FROM AUTHOR]

In our previous work, a small amount of Al nanoparticles can improve the wettability and mechanical properties of SnAgCu lead-free solders. In this paper, creep properties of SnAgCu solder alloys containing 0.1 wt% Al nanoparticles were studied based on creep testing. It is found that with the addition of Al nanoparticles can enhance the creep resistance of SnAgCu solders. And the Garofalo-Arrhenius creep model was used to describe the creep behavior of SnAgCu and SnAgCu-0.1nano Al solder joints, the parameters were determined based on creep testing. And finite element analysis was utilized to represent the accumulated creep response and calculate the creep fatigue life of solder joints. [ABSTRACT FROM AUTHOR]

In this paper, the wettability of lead-free solders on substrates with fluxes was studied based on reflow process and Taguchi method. Effects of different control factors, including solder materials, fluxes, substrate materials and atmosphere on the wettability of the lead-free solder joints were examined and calculated. Moreover, the effect of rare earth Eu on the wetting of SnAgCu solder was investigated, the effect mechanism was analyzed too. The wettability optimal design in the lead-free solders system has the combination of the SnAgCu-0.04Eu solder, RMA flux, Au/Ni/Cu substrate, and vacuum atmosphere. Moreover, the flux is the most important factor among the control factors in the wettability system. [ABSTRACT FROM AUTHOR]

In this paper, we research the thermo-mechanical reliability of lead-free solder joints in WLCSP assembly subjected to an accelerated thermal cyclic loading based on finite element simulation and Taguchi method. Effects of different control factors, including solder materials, height of solder ball, chip thickness and substrates thickness on the reliability of the lead-free solder joints were examined and calculated. The corner solder joint is the most critical solder joints in the assembly, the top surface of the solder joint is the crack propagated location. The optimal design in the WLCSP assembly has the combination of the SnAgCuAl, height of solder ball at 0.25 mm, chip thickness at 0.6 mm, substrate thickness at 1.0 mm. Moreover, the solder materials is the most important factor among the control factors in the WLCSP assembly. [ABSTRACT FROM AUTHOR]

With the addition CNTs, the properties of SnAgCu solders and solder joints can be improved remarkably. In this paper, based on the creep testing, the Dorn creep model was used to represent the creep behavior of SnAgCuCNT solder, and the parameters were determined with the fitting analysis. Moreover, the Dorn creep model of SnAgCu and SnAgCuCNT was incorporated into finite element code for calculating the creep strain response of solder joints in FCBGA (Flip Chip Ball Grid Array) device during thermal cycle loading. The results indicated that the CNTs can enhance the creep resistance of SnAgCu solder, which demonstrates the SnAgCuCNT solders can replace the SnAgCu solder in electronic industry for highreliability requirement. [ABSTRACT FROM AUTHOR]

With the addition of Zn, Co and Fe, the microstructures and properties of SnAgCu solders can be improved obviously, the constitutive response of SnAgCu solder bearing 0.8%Zn, 0.8%Co and 0.8%Fe was studied under uniaxial tension. Anand model was used to represent the inelastic deformation behavior of the lead-free solders. The material parameters of the constitutive relations for SnAgCu(Zn,Co, Fe) solders were determined from separated constitutive relations and experimental results. Combining the model, finite element analysis (FEA) was used to study the thermally induced inelastic deformation and the stress-strain response of the solder joints in wafer-level chip scale packages (WLCSP) mounted on printed circuit boards (PCB). And it is found that the addition of Zn, Co and Fe can enhance the fatigue life of SnAgCu solder joint, the superiority can be found for the addition of Fe among the three elements. [ABSTRACT FROM AUTHOR]

Growth kinetics of intermetallic compound (IMC) layers formed between SnAgCu solder for reflow soldering and Cu substrate by solid state isothermal aging were investigated at temperatures between 100 and 140 °C. For the aged samples, two distinct layers of IMCs of the type CuSn and CuSn were identified with the later adjacent to the copper substrate. In the as-soldered samples, only a single layer of interfacial CuSn type IMC was formed. Moreover, the apparent activation energies were 96.75 kJ/mol (total IMC), 85.98 kJ/mol (CuSn IMC) and 105.92 kJ/mol (CuSn IMC), respectively. [ABSTRACT FROM AUTHOR]

With more consumer products moving towards environmentally friendly packaging, making solder Pb-free has become an urgent task for electronics assemblies. Solder joints are responsible for both electrical and mechanical connections. Solder joint does not have adequate ductility to ensure the repeated relative displacements due to the mismatch between expansion coefficients of the chip carrier and the circuit board. Materials behavior of solder joints involves a creep-fatigue interaction, making it a poor material for mechanical connections. The reliability of solder joints of electronics components has been found playing a more important role in service for microelectronics components and micro-electro-mechanical systems. So many researchers in the world investigated reliability of solder joints based on finite element simulation and experiments about the electronics devices, such as CR, QFP, QFN, PLCC, BGA, CSP, FCBGA and CCGA, which were reviewed systematically and extensively. Synchronously the investigation on reliability of solder joints was improved further with the high-speed development of lead-free electronic packaging, especially the constitutive equations and the fatigue life prediction equations. In this paper, the application and research status of constitutive equations and fatigue life prediction equations were reviewed, which provide theoretic guide for the reliability of lead-free solder joints. [ABSTRACT FROM AUTHOR]

In this paper, the effect of rare earth (RE) La on the properties of \Sn\9\Zn solder was carried out. The results indicate that RE La plays an important role not only in the wettability and the structure of the solder but also in the mechanical property of the solder joint. The results show that adding trace amount of RE La can remarkably improve the wettability and oxidation resistance of SnZn solder and can enhance the mechanical properties of solder joints. When RE La content is 0.06%, the SnZn-based solder has the best properties. In addition, it is found that \Sn\Zn\0.06\La shows a finer and more uniform microstructure than SnZn, and the sizes of Zn-rich phases are obviously reduced. [ABSTRACT FROM AUTHOR]

In order to improve the impact toughness and reduce inclusion, rare earth element Ce and stable element Ti are added in the low chromium nickel ferritic stainless steel welded joints and heat treatment. The Charpy test and tensile test are carried out and fracture structure are analyzed. The results show that when the ratio of Ce is 0.24% and Ti is 0.72% in welded joints of ferritic stainless steel, the mechanical properties is the best. The impact energy of welded joint is 9.4 times more than the samples without Ce and Ti, the impact toughness is also increased by 123.6% after heat treatment and the tensile strength increases by 41.9% The fracture structure is main ductile fracture and dimple, the shape of dimples is parabolic. The dimple is large and deep, and in the bottom of dimple has second phase particles. There is a few cleavage facets and river patterns in the fracture. After thermal cycling, the number of oxide particles reduce and the second phase particles are refined, so the impact toughness is improved. [ABSTRACT FROM AUTHOR]

Austenitic stainless steel (ASS) welding wire is a widely used filler metal for ferritic stainless steel (FSS). The microstructure of ASS is fine and it also has good weldability. However, the welded joints will appear hot cracks and dehisce under tensile force, and the grain boundaries will be corroded easily. In order to solve these problems, 14 kinds of Ce/Ti formulas are optimized by means of uniform test design and curve fitting. Then, the powders containing CeO2/TiO2 are added into the welded joints. After welding, a series of mechanical properties tests are conducted according to national standards. Then, the mechanical properties data are analyzed comprehensively by analyzing variance, boxplot as well as MATLAB 3D surface chart. The results show that sample 8 with the Ce/Ti amount of 0.24%/0.72% in ASS welding wire has better comprehensive mechanical properties. Compared with the samples without Ce/Ti, the yield strength, tensile strength, impact energy of normal temperature, and impact energy of heat treatment of welded joints increase by 127.2%, 41.9%, 841.8%, and 118.1% respectively. In order to improve the mechanical properties of welded joints, 14 kinds of Ce/Ti are added to austenitic stainless steel wire by uniform design. After welding, a series of mechanical properties tests are conducted according to national standards. Then, the best formula is obtained through analysis of variance, box diagram, and 3D surface figure. [ABSTRACT FROM AUTHOR]