Optical Sub-Assembly Conductive Coating for EMI Shielding

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Solution Overview

Problem

Current optical multiplexing and demultiplexing sub-assemblies, particularly those with integrally molded plastic components, face challenges in providing effective electromagnetic interference (EMI) shielding due to the generation of undesirable EMI and the difficulty in cost-effectively shielding plastic components.

Innovation Solution

The use of electrically conductive paint, polymer, or adhesive coatings on external surfaces of optical sub-assemblies, including ferrules and coupling modules, to provide EMI, electromagnetic pulse (EMP), or electrostatic discharge (ESD) shielding, with the coatings loaded with conductive particles or fibers, and optionally coupled to a ground plane, minimizes additional volume usage within the housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If traditional metal housing is used for EMI shielding, then EMI protection is provided, but cost and weight increase

Engineering Contradiction:

ImproveEMI shieldingVSAvoidmanufacturing cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent changes the material parameter from metal to plastic, and applies surface treatment (conductive coating) to achieve the required electrical conductivity for EMI shielding. This allows the base material to be plastic (reducing cost and weight) while the surface properties provide the necessary shielding capability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite construction by combining plastic base material with conductive surface coatings or fillers. This creates a hybrid material system that exhibits both the mechanical advantages of plastic (low cost, light weight) and the electromagnetic shielding properties traditionally associated with metals.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If conductive coatings are applied to plastic components, then EMI shielding is achieved, but manufacturing complexity increases

Engineering Contradiction:

ImproveEMI shieldingVSAvoidmanufacturing process complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent merges the EMI shielding function with the existing plastic molding process by incorporating conductive fillers directly into the plastic material before molding, or by applying coatings as an integrated step in the manufacturing workflow. This combination reduces the number of separate manufacturing steps and simplifies the overall process.

Inventive Principle:

Principle #5Merging (Combining)

3Object-affected harmful factors

If EMI shielding is added to optical sub-assemblies, then electromagnetic protection is improved, but volume of the housing increases

Engineering Contradiction:

ImproveEMP shieldingVSAvoidhousing volume

Core Design Contradiction:

Object-affected harmful factorsVSVolume of stationary object

Solution Approach 1:

The patent employs thin conductive coatings or films applied to the internal surfaces of the housing or to component surfaces. These thin layers provide effective EMP shielding without requiring thick shielding materials, thus minimizing the volume increase of the housing while achieving the required electromagnetic protection.

Inventive Principle:

Principle #30Flexible shells and thin films

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 approach effectively reduces EMI and EMP shielding, enhancing the performance of optical sub-assemblies by minimizing stray radiation and maintaining optical integrity while being cost-effective and space-efficient.

Implementation Method 1

Methodology Applied

Scientific EffectElectromagnetic shielding: Faraday Cage

Implementation Method 2

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Data Source

PatentUS7976226B2Optical sub-assembly with electrically conductive paint, polymer or adhesive to reduce EMI or sensitivity to EMP or ESD

Publication Date: 2011.07.12 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

Disclosed are various embodiments of an optical wavelength division demultiplexer or multiplexer sub-assembly configured to receive or transmit optical signals conveyed thereto or therefrom by a fiber optic cable. Selected portions of external surfaces of the sub-assembly are coated with an electrically conductive paint, polymer or adhesive to provide an EMI, EMP or ESD shield. Typically, the sub-assembly comprises an integrally molded plastic optical block and a separate integrally molded coupling module with a ferrule and fiber optic cable receptacle. In one embodiment, selected external surfaces of the optical block and coupling module are coated with a coating having a predetermined electrical conductivity to provide a desired degree of EMI, EMP or ESD shielding.