Optical Circuit Board Cavity Design for Underfill Management

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Solution Overview

Problem

The flow of underfill onto the end surface of an optical waveguide on an optical circuit board hinders the transmission and reception of optical signals, increasing optical connection loss when the underfill is injected around the solder connecting portion of an optical element.

Innovation Solution

An optical circuit board design featuring a cavity between the region with a silicon photonics device and the region with the optical waveguide, where the first conductor layer protrudes above the cavity, allowing the underfill to flow into the cavity and reducing its overflow onto the optical waveguide.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If underfill is injected around the solder connecting portion to improve reliability, then the reliability of solder connection is improved, but underfill flows onto the end surface of the optical waveguide causing increased optical connection loss

Engineering Contradiction:

Improvereliability of solder connectionVSAvoidoptical connection loss

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a cavity structure that segments the space between the solder connecting portion and the optical waveguide end surface. This cavity acts as a physical barrier to divide the underfill flow path, preventing underfill from reaching the optical waveguide while still allowing underfill to be injected for solder connection reinforcement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cavity serves as an intermediary barrier between the underfill injection zone and the optical waveguide. By introducing this intermediate structure, the patent allows underfill to perform its function of improving solder connection reliability while simultaneously preventing it from causing optical connection loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If underfill is injected to seal the solder connecting portion, then the sealing and reliability are improved, but the optical signal transmission is hindered due to underfill overflow

Engineering Contradiction:

Improvesealing of solder connectionVSAvoidoptical signal transmission loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The cavity segments the space to create distinct functional zones: one for underfill injection and sealing, and another for optical signal transmission. This spatial segmentation ensures that the sealing function and optical transmission function do not interfere with each other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cavity acts as an intermediary structure that enables the sealing function to be achieved without compromising optical transmission. It mediates between the need for reliable solder connections and the need for clear optical signal paths.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If the optical circuit board structure is simplified without additional underfill prevention structures, then the device complexity is reduced, but underfill flows onto the optical waveguide increasing connection loss

Engineering Contradiction:

Improvestructure complexity of optical circuit boardVSAvoidunderfill overflow onto optical waveguide

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The cavity provides an effective underfill prevention solution through simple spatial segmentation rather than complex additional structures. By dividing the board space into distinct regions, the patent achieves underfill control without requiring elaborate prevention mechanisms.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cavity serves multiple functions: it acts as a physical barrier to prevent underfill overflow, provides structural support, and maintains the mechanical integrity of the optical circuit board. This multi-functionality reduces the need for additional specialized components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

This design enhances optical transmission characteristics by minimizing underfill overflow onto the optical waveguide, thereby reducing optical connection loss and improving the reliability of signal transmission and reception.

Implementation Method 1

forming a cavity in a wiring board using an excimer laser

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS20230408777A1Optical circuit board and electronic component mounting structure using same

Publication Date: 2023.12.21 KYOCERA CORP

AI summary

According to the present disclosure, an optical circuit board includes a wiring board and an optical waveguide. The wiring board has a first region on which a silicon photonics device is mounted, a cavity, and a second region, with the cavity interposed between the first region and the second region. The wiring board further includes a first conductor layer in the second region. The optical waveguide is located on the first conductor layer and includes a core surrounded by claddings. The first conductor layer includes a portion protruding toward the first region above the cavity.