Preparation of monodisperse micron-sized spherical copper particles based on pulsated orifice ejection method

3D microelectronic packaging imposes extremely stringent requirements on the size and precision of Cu core balls. To obtain Cu core balls that meet these requirements， it is essential to ensure the stability during the droplet jetting process and to precisely control the droplet size as needed. This study employs the pulsated orifice ejection method to prepare monodisperse Cu particles. The key parameters affecting particle size are determined based on the Hagen-Poiseuille law， and the relationship between these key parameters and the stability and size of Cu droplet jetting is investigated in detail. The influence of temperature and differential pressure determines whether droplets can be jetted， while the pulse waveform and the rod distance primarily control the particle size. Orthogonal experiments reveal that the particle size is co-influenced by multiple parameters， among which the voltage of the pulse waveform has the most significant impact， and the the particle size increases with the increase of the voltage. Adjusting the rod distance can regulate the stability of the jetting process. Through the analysis of the jetting window and orthogonal experiments， appropriate key parameters are selected to prepare Cu particles with target sizes of 100 μm and 200 μm. The actual obtained particle sizes are 96.27 μm and 200.69 μm， with standard deviations of approximately 2.67 μm and 2.64 μm， respectively， and sphericity values both exceeding 0.95. The prepared Cu particles exhibit uniform size and high sphericity， meeting the requirements for Cu core balls.