[Show abstract][Hide abstract] ABSTRACT: We have developed an advanced molten solder ejection method which realizes to eject 1 picoliter molten solder droplets. The molten solder ejection method has been developed as a technique to supply small solder balls. The authors have developed a newly designed solder ejection head and have confirmed that solder balls with almost no surface oxidation can be formed by using this head. The size of the molten solder droplets using this newly developed method is 1 picoliter, which is much smaller than the previous minimum droplet size of 22 picoliters. A standard deviation in position accuracy of 0.81 mum was achieved.