Fabrication of BGA solder balls by pulsated orifice ejection method

A new method named Pulsated Orifice Ejection Method (POEM) is proposed for fabrication of BGA solder balls with narrow size distribution and high sphericity. As for an orifice with a certain diameter, the diameter of solder balls is mainly affected by rod displacement and gas pressure. The size of solder ball linearly increases with the increase of both the rod displacement and the gas pressure within a certain range. The analysis of size distribution and sphericity shows that solder ball fabricated by POEM meets the requirements of BGA packaging. In addition, the solidification behavior of the droplets prepared by POEM is also discussed by theoretical calculation.