A screw (60) is provided, having a shaft (32) and a head (66), for fastening a component onto a substructure utilizing a tightly pressing conical sealing disk (50) against the component. The screw head (66) is configured at the bottom (64) thereof around the shaft (32) as a cone that is tapered in the direction of the top (68) of the screw head (66). The cone angle of the conical sealing disk (50) measured against a perpendicular line to the disk axis is equal to, or larger than the cone angle (alpha) of the screw head (66), which is measured against a perpendicular line to the screw axis. When the screw (60) is tightened, the conical bottom (64) of the screw head (66) and the conical top (58) of the sealing disk (50) are in mutual surface contact with each other. This maintains a sealing connection. Through the conical configuration of the bottom (64) of the screw head (66) the so-called “cupping” of the sealing disk (50) is prevented when the screw (60) is tightened.