This study developed a piezo-driven dispenser for microelectronic packaging. The dispenser utilizes a rigid-flexible combined piezo-driven mechanism with a unilateral preloading feature, and the study examined how to estimate droplet volume. Firstly, a static model of the displacement transmission mechanism was established, and the transmission ratio was designed. Secondly, the droplet formation mechanism was studied, and the pressure change process during droplet distribution was simulated and analyzed.