Abstract: The invention concerns an apparatus for mounting semiconductor chips on a substrate with which the substrate is forwarded in steps in a first direction to a bonding station for the presentation of a next substrate position. In order that curved substrates or substrates otherwise slightly shifted in their position at right angles to the transport direction can be presented with positional accuracy at the bonding location, it is suggested that the position of the longitudinal edge of the substrate is measured at right angles to the transport direction at the level of the bonding station and then to carry out a corrective movement with the substrate. An optical sensor with two light barriers arranged next to each other is suggested for the sensor.