A signal transmission assembly includes a substrate, a first transmission line, and a second transmission line. The first transmission line and the second transmission line are disposed on the substrate and extending along a first direction. The first transmission line comprises at least one first transmission section and at least one second transmission section. The first transmission section is apart from the second transmission line by a first distance. The second transmission section is apart from the second transmission line by a second distance. The first distance is greater than or equal to the second distance. A first edge of the first transmission section and a second edge of the second transmission section are proximal to the second transmission line and parallel to the first direction, and the second transmission line does not contact an edge extension line extending from the second edge along the first direction.