Drop-on-demand jetting of piezoelectric diaphragmpiston for fabricating precision solder bumps

Aiming at producing highly uniform ultra-small solder bumps to meet the growing requirements in the area array package, a novel fabrication method based on piezoelectric diaphragm-piston droplet jetting was proposed. The principle and customized equipment of this method were introduced. Solder bumps with a diameter less than 100 mm were successfully fabricated with the customized equipment. The main control parameters, such as voltage amplitude, pulse duration and the nozzle diameter, were studied to investigate their impact on the diameter of the solder bumps. The experimental results show that, while the voltage amplitude of the piezoelectric ceramic is within the range of 31 V similar to 34 V and the pulse duration is within the range of 0.3 ms similar to 0.5 ms, the device can perform stable single droplet jetting, and the droplets diameter will increase as the nozzle diameter becomes larger.