Optical Communication Sub-Package Flip-Chip Inductor Shielding

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing optical communication devices face challenges in suppressing inter-signal interference due to limited terminal availability, increased package size, and deteriorated high-frequency characteristics, particularly in flip-chip configurations where heat dissipation is compromised and band characteristics are affected by added inductors.

Innovation Solution

The optical communication device employs a sub-package configuration with a substrate where an optical semiconductor and IC are flip-chip connected, featuring inductors and ground wiring surrounding them to minimize signal interference, effectively shielding electromagnetic waves and maintaining efficient heat dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If wire bonding is used to connect optical semiconductor and TIA-IC, then heat dissipation is improved, but package size increases and terminal availability is limited

Engineering Contradiction:

Improveheat dissipationVSAvoidpackage size

Core Design Contradiction:

TemperatureVSVolume of stationary object

Solution Approach 1:

The patent replaces wire bonding (mechanical connection) with flip-chip mounting technology, where the IC is directly mounted on the optical semiconductor substrate with electrical connections made through conductive bumps. This substitution eliminates the need for external lead wires, reducing package size while maintaining effective heat dissipation through direct thermal contact between the IC and substrate.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Speed

If inductors are added to extend band characteristics, then high-frequency signal transmission is improved, but inter-channel interference increases

Engineering Contradiction:

Improveband characteristicsVSAvoidinter-channel interference

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by providing ground wirings in specific locations around the inductors rather than uniformly across the entire substrate. The ground wirings are strategically positioned adjacent to the inductors to provide localized electromagnetic shielding, reducing inter-channel interference in the critical areas where inductors are mounted, while maintaining band characteristics extension.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts the potentially harmful electromagnetic interference generated by inductors into a beneficial configuration by surrounding the inductors with ground wirings. This arrangement uses the ground potential to contain and direct electromagnetic fields, transforming the interference problem into an opportunity for controlled field distribution that extends band characteristics while minimizing interference.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Adaptability or versatility

If more terminals are provided on the device, then connectivity is improved, but the device becomes more susceptible to high frequency noise and vibration

Engineering Contradiction:

Improveterminal availabilityVSAvoidhigh frequency noise and vibration

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent transitions from a two-dimensional arrangement of terminals on the outer periphery to a three-dimensional configuration where the IC is mounted face-down on the substrate with terminals accessible from both the top and bottom surfaces. This dimensional change allows multiple terminals to be provided without increasing the device's footprint or making terminals more susceptible to noise and vibration, as the flip-chip configuration provides structural rigidity and shorter connection paths.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 configuration enhances high-frequency signal transmission and reception by reducing inter-channel interference while maintaining a compact package size and effective heat dissipation, addressing the limitations of prior art.

Implementation Method 1

The photodiode photoelectrically converts the incident differential optical signal and inputs it to the TIA-IC

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Implementation Method 2

ground wiring formed so as to surround the formed pair of inductors

Methodology Applied

Scientific EffectElectromagnetic shielding: Faraday Cage

Data Source

PatentUS11342318B2Optical communication apparatus

Publication Date: 2022.05.24 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

There is provided an optical communication device capable of minimum suppressing inter-signal interference of inductors mounted to enable a transmission signal to be transmitted and received with a high frequency. The optical communication device comprises a sub-package as a subassembly in each of a plurality of signal channels. The sub-package includes a substrate on which an optical semiconductor and an IC are flip-chip connected. The optical semiconductor includes a pair of photodiodes receiving a differential optical signal and outputting a differential current signal. The IC includes a transimpedance amplifier converting the differential current signal from the optical semiconductor to a voltage signal. The optical semiconductor has a pair of inductors formed for each of the pair of photodiodes and a ground wiring formed so as to surround the formed pair of inductors.