Search

The main objective of this study is to investigate the electrical properties of Sn–3.0Ag–0.5Cu solder joint with the incorporation of carbon nanotube instead of solder bulk. Sn–3.0Ag–0.5Cu solder paste with the incorporation of carbon nanotube up to 0.04 wt% was fabricated by using mechanical mixing method. Fabricated solder pastes were then soldered on printed circuit board via reflow soldering at 260°C peak temperature. Electrical resistivity of Sn–3.0Ag–0.5Cu-carbon nanotube solder joints was measured by the four-point probe method at room temperature. Microstructure properties were observed by optical microscope and field emission scanning electron microscope. Electrical resistivity of Sn–3.0Ag–0.5Cu solder joint was found to increase with the incorporation carbon nanotube up to 0.03 wt% and slightly decrease at 0.04 wt%. Incorporation of carbon nanotube in the solder matrix apparently changes the microstructure of Sn–Ag–Cu solder alloys. Microstructural observation found that electrical resistivity correlated with the distribution area of eutectic phase in the solder matrix due to the existence of carbon nanotube. It was revealed that eutectic phase area increases with the increasing of carbon nanotube wt% up to 0.03 and then slightly decreases at the incorporation of 0.04 wt% carbon nanotube as parallel with the trend of electrical resistivity values. [ABSTRACT FROM AUTHOR]

A characterization of mechanical and micromechanical properties of SAC305 solder wire under varied strain rates and temperatures was performed using tensile and nanoindentation tests. The evolution of SAC305 lead-free solder wire grains was compared in samples that were subjected to various strain rates and temperatures using tensile tests based on ASTM E12 standards. Different behaviours of mechanical properties, micromechanical properties, and microstructure evolution of SAC305 solder wire were observed when either temperature or strain rate was held constant and the other varied. Both tensile and nanoindentation tests produced qualitative results, such as dynamic recovery and occurrence of pop-in events, that reflected changes of microstructure. It was observed that some of the mechanical properties of SAC305 solder wire, namely yield strength (YS), ultimate tensile strength (UTS) and Young's modulus, showed the same trends, but with lower values, compared to micromechanical properties obtained from nanoindentation tests based upon hardness and reduced modulus. Microstructure examination further confirms that the YS, UTS and hardness values increase with more solder wire grain refinement. SAC305 solder wire also maintained an equiaxed structure under various strain rates and temperatures. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to investigate the characteristics of ultra-fine lead-free solder joints reinforced with TiO2 nanoparticles in an electronic assembly.Design/methodology/approach This study focused on the microstructure and quality of solder joints. Various percentages of TiO2 nanoparticles were mixed with a lead-free Sn-3.5Ag-0.7Cu solder paste. This new form of nano-reinforced lead-free solder paste was used to assemble a miniature package consisting of an ultra-fine capacitor on a printed circuit board by means of a reflow soldering process. The microstructure and the fillet height were investigated using a focused ion beam, a high-resolution transmission electron microscope system equipped with an energy dispersive X-ray spectrometer (EDS), and a field emission scanning electron microscope coupled with an EDS and X-ray diffraction machine.Findings The experimental results revealed that the intermetallic compound with the lowest thickness was produced by the nano-reinforced solder with a TiO2 content of 0.05 Wt.%. Increasing the TiO2 content to 0.15 Wt.% led to an improvement in the fillet height. The characteristics of the solder joint fulfilled the reliability requirements of the IPC standards.Practical implications This study provides engineers with a profound understanding of the characteristics of ultra-fine nano-reinforced solder joint packages in the microelectronics industry.Originality/value The findings are expected to provide proper guidelines and references with regard to the manufacture of miniaturized electronic packages. This study also explored the effects of TiO2 on the microstructure and the fillet height of ultra-fine capacitors. [ABSTRACT FROM AUTHOR]

Alloying studies of Mg-Gd system alloys are an important way to improve alloy properties, reduce Gd content, and thus cost and density. Nd is excellent in promoting aging precipitation and enhancing heat resistance properties. In this work, low Gd content Mg-7Gd- x Nd-0.5Zr (x = 0, 0.5, 2, 3.5 wt%) alloys were prepared by melting casting and processed by solution aging. The effects of Nd on the microstructure and mechanical properties of the aged alloys were investigated by SEM, XRD, EDS, TEM, and electron tensile testing machine. The findings show that the Nd-free alloy consists mainly of α-Mg and Mg 5 Gd, and after Nd addition, a new phase Mg 41 Nd 5 is generated and the precipitation of the Mg 5 Gd phase is promoted, and due to the heterogeneous nucleation ability of Mg 41 Nd 5 particles leads to grain refinement. The principal precipitate phases in the matrix and grain boundaries of Nd-containing alloys are the β′ phase, which is the alloy's primary strengthening phase. Due to the influence of fine grain strengthening and precipitation strengthening, the ultimate tensile strength of the Mg-7Gd-2Nd-0.5Zr alloy achieves a maximum of 328 MPa and 294 MPa at ambient temperature and 250 °C, respectively. • Nd can promote the precipitation of Mg 5 Gd and generate Mg 41 Nd 5 with heterogeneous nucleation ability. • The main strengthening phase of the aged alloy is β′ phase. • The Mg-7Gd-2Nd-0.5Zr alloy achieves the maximum UTS (UTS 25 °C = 328 MPa, UTS 250 °C = 294 MPa). [ABSTRACT FROM AUTHOR]

Abstract: The effect of gamma radiation on the mechanical and structural properties of gold ball bonds was investigated. Gold wires from thermosonic wire bonding were exposed to gamma rays from a Cobalt-60 source at a low dose (5Gy). The load–depth curve of nanoindentation for the irradiated gold wire bond has an apparent staircase shape during loading compared to the as-received sample. The hardness of the specimens calculated from the nanoindentation shows an increase in value from 0.91 to 1.09GPa for specimens after exposure. The reduced elastic modulus for irradiated specimens significantly increased as well, with values from 75.18 to 98.55GPa. The change in intrinsic properties due to gamma radiation was investigated using dual-focused ion beam and high-resolution transmission electron microscope analysis. The dual-focused ion beam and high-resolution transmission electron microscope images confirmed the changes in grain structure and the presence of dislocations. The scanning electron microscope micrographs of focused ion beam cross sections showed that the grain structure of the gold became elongated and smaller after exposure to gamma rays. Meanwhile, high-resolution transmission electron microscopy provided evidence that gamma radiation induced dislocation of the atomic arrangement. [Copyright &y& Elsevier]