Abstract: A wiring base includes a base, a signal conductor, and a ground conductor including a first ground conductor. The base includes a first surface, a first region, and a second region. The first region is located near an outer side of the first surface. An external board is mounted in the first region. The second region is other than the first region. The signal conductor extends through a region including the first region of the first surface in a first direction away from the outer side. The first ground conductor is located in the base at a distance from the signal conductor of less than ¼ of a wavelength of a high-frequency signal. The high-frequency signal is transmitted through the signal conductor. The first ground conductor includes a first grid portion at a first location overlapping the first region and at least a portion of the signal conductor.

Abstract: A semiconductor device mounting board includes a first substrate, a second substrate, a single line, a groove, a feedthrough conductor, and a side conductor. The first substrate includes a mount area and a peripheral area. The second substrate is located in the peripheral area to align with an outer edge of the first substrate and surrounds the mount area. The signal line extends on an upper surface of the second substrate from an inner edge to an outer edge of the second substrate. The groove extends on a side surface of the first substrate from a lower surface to an upper surface of the first substrate. The feedthrough conductor is inside the second substrate and connected to the signal line. The side conductor is on an inner surface of the groove and electrically connected to the feedthrough conductor. The groove is inward from the outer edge of the second substrate.

Abstract: A semiconductor device mounting board includes a first substrate, a second substrate, a single line, a groove, a feedthrough conductor, and a side conductor. The first substrate includes a mount area and a peripheral area. The second substrate is located in the peripheral area to align with an outer edge of the first substrate and surrounds the mount area. The signal line extends on an upper surface of the second substrate from an inner edge to an outer edge of the second substrate. The groove extends on a side surface of the first substrate from a lower surface to an upper surface of the first substrate. The feedthrough conductor is inside the second substrate and connected to the signal line. The side conductor is on an inner surface of the groove and electrically connected to the feedthrough conductor. The groove is inward from the outer edge of the second substrate.