Composite substrate

Abstract

A technique is provided that facilitates optical coupling and electrical connection when a functional device is mounted on a composite substrate comprising a conductor pattern and an optical waveguide. The composite substrate (10A) comprises a wiring substrate (11A) and a substrate (12A) with an optical waveguide. 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 (12A) with an optical waveguide includes a substrate (121), an optical waveguide layer (122), and a second conductor pattern (123) therebetween. The optical waveguide layer (122) includes a first cladding layer (122A), a second cladding layer (122C), and a core (122B) therebetween. The lower part of the core (122B) is higher than the first region (R1). A portion of the upper part of the first cladding layer (122A) is provided with an exposed portion, and a plurality of through holes extending to the second conductor pattern (123) are provided at the location of the exposed portion.

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