Wiring board comprising three or more insulating layers, where a post wall waveguide of staircase shape is formed therein

Abstract

A wiring board has a built-in post wall waveguide having a region surrounded by two mutually opposing conductors and first and second post walls connecting the two conductors and serving as a transmission path for electromagnetic waves. The conductors oppose each other with insulating layers interposed therebetween. The first post wall has first columnar portions, formed by a laminate of via interconnects penetrating the insulating layers, arranged at predetermined intervals in a first direction in which the electromagnetic waves are transmitted. The second post wall has second columnar portions similar to the first columnar portions. In a cross sectional view taken in a second direction perpendicular to the first direction, an interval between adjacent via interconnects in one of the insulating layers not in contact with the conductor is wider than an interval between adjacent via interconnects in two of the insulating layers in contact with the two conductors, respectively.