Search

With the continuous reduction of chip size, fluxless soldering has brought attention to high-density, three-dimensional packaging. Although fluxless soldering technology with formic acid (FA) atmosphere has been presented, few studies have examined the effect of the Pt catalytic, preheating time, and soldering pad on FA soldering for the Sn-58Bi solder. The results have shown that the Pt catalytic can promote oxidation–reduction and the formation of a large pore in the Sn-58Bi/Cu solder joint, which causes a decrease in shear strength. ENIG (electroless nickel immersion gold) improves soldering strength. The shear strength of Sn-58Bi/ENIG increases under the Pt catalytic FA atmosphere process due to the isolation of the Au layer on ENIG. The Au layer protects metal from corrosion and provides a good contact surface for the Sn-58Bi solder. The shear strength of the Sn-58Bi/ENIG joints under a Pt catalytic atmosphere improved by 44.7% compared to using a Cu pad. These findings reveal the improvement of the shear strength of solder joints bonded at low temperatures under the FA atmosphere. [ABSTRACT FROM AUTHOR]

We successfully synthesized a novel core-shell hybrid metal oxide via a simple one-step hydrothermal method without annealing. This composite of Co 3 O 4 particles covered with SnO 2 –SnO (Co 3 O 4 @SnO 2 –SnO) predicted better performance compared to pure Co 3 O 4 , which strongly depends on the synthetic temperature. The Co 3 O 4 @SnO 2 –SnO prepared at a temperature of 250 °C (labeled Co 3 O 4 @SnO 2 –SnO-250) exhibited an outstanding specific capacitance of 325 F g−1 under the current density of 1 A g−1, which was much higher than those of Co 3 O 4 (12.6 F g−1) and other composites. Additionally, the sample also exhibited good cycle stability performance with a retention rate of 100% after 5000 cycles at a current density of 5 A g−1. Through X-ray photoelectron spectroscopy analysis, the presumed mechanism was that Sn-O x decreases the surface electron densities of Co 3 O 4 , which is beneficial to OH− adsorption and specific capacitance improvement, and the synthetic temperature had a strong impact on the microstructure and thus on the surface electron densities. The most. obvious finding to emerge from this study is that the specific capacitance can be improved through adjusting the surface electron densities of transition metal oxides. [ABSTRACT FROM AUTHOR]

A novel amorphous soft magnetic composites (ASMCs) for hundreds MHz frequency applications have been prepared under the hot-pressing molding by ultrafine submicron FeBP amorphous powders. These ultrafine submicron FeBP amorphous particles were synthesized with the NaBH 4 chemical reduction method and the particles size was regulated by the drop rate of the reducing agent. The morphology, microstructure, elemental composition and high-frequency magnetic properties of the amorphous soft magnetic composites was systematically investigated. The particle sizes of FeBP amorphous powders are distributed in 600–900 nm which gradually increase with the decrease of the drop rate of the NaBH 4 aqueous solution. Meanwhile, the Fe element content and saturation magnetization strength of the amorphous powder increase and the coercivity gradually decreases. The corresponded ASMCs also appear a commensurate permeability in the range of 6–9 responding to the GHz high frequency range with the lowest loss tangent only 0.20 and 0.44 at 500 MHZ and 1 GHz, respectively. Such ultrafine amorphous soft magnetic composites have enormous potential for high frequency applications in wide band gap semiconductor switching power supplies, RF inductors and chips. • The spherical amorphous powder was prepared by chemical reduction method with outstanding magnetic properties. • The particle size of the amorphous powder was regulated by adjusting the drop rate of the reducing agent solution. • The relationship between the powder particle size and the magnetic and electrical properties of ASMCs was elucidated. [ABSTRACT FROM AUTHOR]