A leadframe strip includes a plurality of leads chemically etched into a metal sheet, a plurality of support structures chemically etched into the metal sheet, and a plurality of connecting structures chemically etched into the metal sheet. A detection unit detects occupancy statuses of a plurality of seats located correspondingly to positions of the plurality of grid points. The gate electrode region is formed in a first main surface of the semiconductor substrate. A plastic piston, slidable within the cylinder, forms the bottom of the air chamber.