Optical Circuit Substrate Recessed Cladding for Thermal Stress

Solution Overview

Problem

The existing optical circuit substrates face stability and reliability issues due to thermal expansion differences between metal conductor layers and resin-based cladding layers, leading to potential peeling and reduced performance in optical communication networks.

Innovation Solution

Incorporating a recessed portion in the cladding layer of the optical waveguide on the conductor layer side, which disperses stress and reduces the likelihood of peeling by creating an acute angle and curved surface, thereby enhancing the stability and reliability of the optical circuit substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conductor layer and cladding layer are formed in contact with each other, then the optical waveguide can be connected to the substrate, but peeling occurs between the layers due to thermal expansion difference

Engineering Contradiction:

Improvestability of optical circuit substrateVSAvoidbonding strength between conductor layer and cladding layer

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The recessed portion is provided only at the interface between the conductor layer and cladding layer, creating a localized stress-relief structure where it is most needed. This local modification allows the majority of the interface to maintain strong bonding while the recessed area disperses thermal expansion stress, preventing peeling without compromising overall bonding strength.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The recessed portion introduces a curved surface geometry at the interface between the conductor and cladding layers. This curvature distributes stress more evenly compared to a flat interface, reducing stress concentration points that would otherwise lead to peeling due to differential thermal expansion between the metal conductor and resin cladding.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Ease of manufacture

If the cladding layer is formed directly on the conductor layer, then the manufacturing process is simple, but stress concentration occurs at the interface due to thermal expansion difference

Engineering Contradiction:

Improvesimplicity of manufacturing processVSAvoidthermal expansion stress at interface

Core Design Contradiction:

Ease of manufactureVSStress or pressure

Solution Approach 1:

The recessed portion is provided only at the interface between the conductor layer and cladding layer, creating a localized stress-relief structure where it is most needed. This local modification allows the majority of the interface to maintain strong bonding while the recessed area disperses thermal expansion stress, preventing peeling without compromising overall bonding strength.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The recessed portion introduces a curved surface geometry at the interface between the conductor and cladding layers. This curvature distributes stress more evenly compared to a flat interface, reducing stress concentration points that would otherwise lead to peeling due to differential thermal expansion between the metal conductor and resin cladding.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The recessed portion effectively mitigates stress and peeling at the interface between the conductor and cladding layers, improving the stability and reliability of the optical circuit substrate by dispersing thermal expansion-induced stress, thus maintaining the integrity of the optical communication network.

Implementation Method 1

the recessed portion effectively mitigates stress and peeling at the interface between the conductor and cladding layers, improving the stability and reliability of the optical circuit substrate by dispersing thermal expansion-induced stress

Methodology Applied

Scientific EffectStress dispersion:

Data Source

PatentUS12038602B2Optical circuit substrate

Publication Date: 2024.07.16 KYOCERA CORP

AI summary

An optical circuit substrate according to the present disclosure includes a wiring board and an optical waveguide. The optical waveguide includes a core layer, cladding layers formed on both main surfaces of the core layer, and a reflective mirror portion that passes through the cladding layers and the core layer, and is provided on the wiring board via a conductor layer located on a surface of the wiring board. When the optical waveguide is viewed in a cross section in a thickness direction, the reflective mirror portion has a recessed portion in at least a part of the cladding layer on the conductor layer side.