Composite substrate

Abstract

A technique is provided that facilitates optical coupling and electrical connection when mounting a functional device onto a composite substrate comprising a conductor pattern and an optical waveguide. The composite substrate (10A) comprises a wiring substrate (11A) and a substrate with an optical waveguide (12A). The wiring substrate (11A) comprises an insulating layer and a first conductor pattern, one side of which comprises a first region (R1) and a second region (R2) recessed relative to the first region, the height of the second region (R2) being lower than the area below the first conductor pattern (113) located in the first region (R1). The substrate with the optical waveguide (12A) comprises a substrate (121) and an optical waveguide layer (122), the optical waveguide layer (122) comprising a first cladding layer (122A), a second cladding layer (122C), and a core (122B) disposed therebetween. The substrate (12A) with the optical waveguide is disposed on the second region (R2) with the optical waveguide layer (122) positioned above the substrate (121), and the height of the lower part of the core (122B) is higher than that of the first region (R1).

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