Optical Module FPC Wiring for Crosstalk and Bending Reliability

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Solution Overview

Problem

The size reduction of optical modules is limited by crosstalk between RF pins and the arrangement of DC pins, which complicates the reduction of the optical module's size due to the need for maintaining the characteristic impedance between RF pins and the space constraints for wiring patterns on the FPC, leading to potential disconnection issues when the FPC is bent.

Innovation Solution

The optical module incorporates a circuit substrate with specific patterned wiring and cover materials on the FPC to suppress disconnection by forming tear drop-shaped front surface wiring patterns and semicircular rear surface reinforcing patterns, allowing the FPC to be bent without transmitting stress to vulnerable areas, thus enhancing reliability and electrical characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the interval between RF pins is reduced to reduce the size of the optical module, then the size of the optical module is reduced, but crosstalk between RF pins is increased

Engineering Contradiction:

Improvesize of optical moduleVSAvoidcrosstalk between RF pins

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent transitions from a single-row arrangement of DC pins to a two-row arrangement, utilizing the vertical dimension to reduce the horizontal width of the FPC. This dimensional change allows the DC pins to be arranged more compactly without increasing the interval between pins in the same row, thereby reducing the overall size of the optical module while maintaining signal integrity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The DC pins are divided into two separate rows instead of being arranged in a single row. This segmentation allows the wiring patterns to be distributed more effectively and reduces the horizontal space required for the FPC, contributing to the size reduction of the optical module.

Inventive Principle:

Principle #1Segmentation

2Volume of moving object

If DC pins are arranged in two rows to reduce the horizontal width of FPC, then the size of the optical module is reduced, but the wiring complexity increases

Engineering Contradiction:

Improvesize of optical moduleVSAvoidwiring arrangement complexity

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

By arranging DC pins in two rows and utilizing both the front surface and back surface of the FPC for wiring patterns, the patent distributes the wiring complexity across different surfaces and directions, making the overall wiring arrangement more manageable despite the increased number of connections.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent uses wiring patterns on both the front surface and back surface of the FPC, effectively utilizing the unused back surface for wiring. This inversion of the traditional single-surface wiring approach helps manage the complexity by distributing wiring routes across different surfaces.

Inventive Principle:

Principle #13The other way round (Inversion)

3Volume of moving object

If the FPC is bent to accommodate the optical module configuration, then the optical module can be compactly arranged, but disconnection of wiring patterns occurs

Engineering Contradiction:

Improvesize of optical moduleVSAvoidconnection reliability of wiring patterns

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent places cover materials at specific positions on the FPC, including at the bending start line and covering wiring patterns that extend from DC pins. These cover materials act as protective cushions that prevent disconnection of wiring patterns when the FPC is bent, thereby maintaining connection reliability in the compact optical module configuration.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent uses thin film cover materials (coverlay) to protect the wiring patterns on the FPC. These flexible thin films conform to the bent shape of the FPC while providing protective coverage, preventing disconnection of the wiring patterns during bending.

Inventive Principle:

Principle #30Flexible shells and thin films

Data Source

PatentUS9436018B2Optical module

Publication Date: 2016.09.06 FUJITSU OPTICAL COMPONENTS LTD

AI summary

An optical module includes a circuit substrate and a terminal. The circuit substrate includes a first pattern, a second pattern, a first cover material, and a second cover material. The first pattern electrically is connected to the terminal and formed in a predetermined shape on a first surface of the circuit substrate. The second pattern is formed in a predetermined shape at a position corresponding to the first pattern on a surface opposite to the first surface. The first cover material covers at least a portion of the first pattern to be bent along with bending of the circuit substrate. The second cover material covers at least an end of the second pattern.