Abstract: As the existing commercial equipment for solder ball fabrication are commonly complicated and expensive, a simple solder jet system which can produce uniform solder droplets is presented for the experimental researches. There are four main components in this novel system, i.e. the pressure controller, the droplet generator, the shielding gas chamber, and the cooling and solidifying system. To simplify the droplet generator structure, the jetting tube with a shrinkage tip is used to force the solder droplet to separate from the nozzle under the effects of gravity and surface tension. The process optimization for Sn3.0Ag0.5Cu solder balls fabrication is performed. The solder balls produced by the presented equipment are evaluated in the following aspects: the solder topography and sphericity, the solder size deviation, and the microstructure of the solder. It is found that the jetting pressure, the distance from the nozzle to the surface of cooling medium, and the inner diameter of the jetting tube are the major factors that influence the formation of solder balls. The solder balls fabricated under the optimized process parameters are uniform, spherical, non-oxidation, and have fine and flawless microstructures. The presented equipment can meet the requirements for the experimental researches of the solder jetting process and the solder balls fabrication.

Key words: Fabrication technology, Solder ball, Uniform droplet