Abstract: An apparatus and a process for mounting solder balls or other conductor balls on terminal pads of semiconductor devices or other electronic devices collectively formed on a semiconductor wafer or other substrate by using a single adsorbing plate. The apparatus includes an adsorbing unit which comprises an adsorbing head; an adsorbing plate attached to the head and having adsorbing holes for adsorbing the conductor balls, the adsorbing holes being arranged corresponding in number and position to the terminal pads present in one of the divisions that includes a largest number of the devices; and a mask plate attached to one side of the adsorbing plate and having an opening conformed in shape and size to an area of the substrate occupied by a group of the devices included in a selected one of the divisions so that the conductor balls are only adsorbed by the adsorbing holes corresponding in position to the terminal pads of the devices of the group in the selected one division.