A Study on the Production of Uniform Droplet Spray and Image Feedback Control

摘要

With the integration of high speed image capture system, image-enlargement analysis system, temperature-control heating module, micro-machinery techniques and feedback system, this study is to develop a systematically fabricated process of BGA solder ball based on the concept of the Uniform-Droplet Spray (UDS). A piezoelectric vibrator was applied to generate uniform disturbance waves and nitrogen was used to expel the oxygen to produce an oxygen-isolated environment, which make molten metal become droplets. With a stable pressure difference of gas between the inside and the outside of the crucible and the frequency control of the vibrator by an image feedback system, the droplets of uniform size can be ejected from the nozzle located at the bottom of the crucible. After solidification, the liquid droplets of Sn-37wt%Pb alloy become the solder balls of a fixed diameter.