A flange on first open end of a tubular contact member is soldered to a conductive plate of an insulating substrate. An external electrode terminal is fitted into a main body tube portion of the tubular contact member. The tubular contact member includes a protrusion that protrudes inwardly from an inner wall of the main body tube portion. The protrusion is disposed along the entire perimeter of inner wall toward the first open end. The protrusion has a thickness deformation of the protrusion by a load applied thereto when the external electrode terminal is pressed into the main body tube portion. The protrusion is disposed at a height that can block solder that climbs the inner wall of the main body tube portion, to form a gap between the protrusion and a lower end of the external electrode terminal inserted to a predetermined depth of the main body tube portion.