Ultrasonic spray pyrolysis for air-stable copper particles and their conductive films

Copper (Cu) particles are key components in metal pastes and inks used for conductive electrodes in electronic circuits printed by various methods. However, Cu particles typically suffer from severe oxidation in air, imposing a significant challenge in handling copper particles in manufacturing processes. In this study, ultrasonic spray pyrolysis was adopted to generate a large quantity of Cu particles coated with barium borosilicate (BBS) glass to overcome this chronic oxidation issue, as well as to develop stable conductive films. The spray pyrolysis process is simple, because the copper and glass materials spontaneously segregate into the core and shell of each particle, respectively, to form core-shell-structured BBS-coated Cu (Cu@BBS) particles. The glass surface layers confer substantial oxidation resistance to the copper particles, as evidenced by analyses after long-term exposure to air. The thin glass layers serve as a sintering promoter and inorganic binder; thus, highly dense conductive copper films with good adhesion to the substrates were formed after sintering. The film obtained from the Cu@BBS particles exhibited resistivities of 2.01 μΩ•cm. The Cu@BBS particles introduced herein are readily applicable in various industrial processes where spray pyrolysis has long been established.