Producing solder droplets using piezoelectric membrane-piston-based jetting technology

This paper proposes piezoelectric membrane-piston-based jetting technology, an improved drop-on-demand (DOD) jetting technology for generating micro-droplets. The main components of the experimental apparatus are a nozzle head, a cooling chamber, a vibration bar, a computer system, a temperature controller and a three-dimensional (3D) platform. Based on the proposed working principle, a physical model was constructed and used to conduct a theoretical analysis of the jetting process. This theoretical analysis clearly separated the critical experimental parameters from the other parameters. The critical parameters were found to be the pulse length (t) and voltage value (U) of the electrical pulse signal and the temperature (T) of the chamber. With the commercial tin-lead alloy Sn63Pb37 as the raw material, the experimental apparatus was used to produce micro-droplets. Fifty micro-droplets were randomly selected, their diameters were measured, and the average value and corresponding standard deviations were calculated. The results showed that the micro-droplets fabricated under the same experimental conditions displayed only a small standard deviation in diameter. The diameter of the micro-droplets increased with the pulse length (t) and voltage value (U) of the electrical pulse signal and with the temperature (T) of the chamber. The results also indicated that the values of these three critical experimental parameters should be within an appropriate range. Larger values resulted in the production of satellite droplets, and smaller values did not permit the steady micro-droplets. As a demonstration, a micro-droplet array was fabricated. The diameters of all micro-droplets in the array were approximately 85μm. The results indicate that the proposed membrane-piston-based jetting technology can produce micro-droplets on demand, and serve as an alternative method for the generation of uniform micro-droplets.