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Three kinds of Bi-based solder powders with different chemical compositions of binary Bi-Sn, ternary Bi-Sn-In, and quaternary Bi-Sn-In-Ga were prepared using a gas atomization process and subsequently ball-milled for smaller-size fabrication. In particular, only the quaternary Bi-Sn-In-Ga solder powders were severely broken to the size of less than 10 µm in a polyhedral shape due to the presence of the constitutional element, the degree of overall oxidation, and the formation of solid solution, which had affected the fractured extent of the Ga-containing solder powders. Furthermore, a melting point also decreased by the addition of In and/or Ga into the binary Bi-Sn solder system, resulting in a melting point of 60.3˝C for the Bi-Sn-In-Ga solder powders. Thus, it was possible that fractured Bi-Sn-In-Ga solder powders were appropriate for the adhesion of more compact solder bump arrays, enabling reflowing at the low temperature of 110˝C on a flexible polyethylene terephthalate (PET) substrate.

This paper describes a novel dehydrogenation and spheroidization method using in-situ radio frequency (RF) thermal plasma treatment process to prepare spherical titanium (Ti) powders. Polygonal titanium hydride (TiH 2 ) powders were successfully converted into spherical Ti powders and the size of the powders decreased from 30 to 21 µm by means of evaporation at the powder surface during the plasma treatment. Contaminants in the final products were drastically decreased due to the evaporation and emission of vapors during the plasma treatment.

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This study describes how to make stainless steel hybrid micro-nano-powders (a mixture of micro-powder and nano-powder) using an in situ one-step process via radio frequency (RF) thermal plasma treatment. Nano-particles attached to micro-powders were successfully prepared by RF thermal plasma treatment of stainless steel powder with an average size of 35 μm. The ratio of nano-powders is estimated with a two-dimensional fluid simulation that calculates the temperature profile influencing the rate of surface evaporation. The simulation is conducted to determine the variation of the input power and the distance from the plasma torch to the feeding nozzle. It was demonstrated experimentally that the nano-powder ratio in the micro-nano-powder mixture can be controlled by adjusting the feeding rate, plasma power, feeding position and quenching effect during plasma treatment. The ratio of nano-particles in the micro-nano-powder mixture was controlled in a range from 0.1 (wt. %) to 30.7 (wt. %).