Optical Subassembly Lead Terminal Impedance Matching

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing optical subassemblies face challenges in securing space for mounting optical devices while matching characteristic impedance, particularly at higher transmission rates like 40 Gbit/s, due to difficulties in impedance matching and space constraints caused by the configuration of lead terminals and dielectric substrates.

Innovation Solution

The optical subassembly design includes a specific structure with a lead terminal having a small-diameter and large-diameter part, connected by brazing and soldering, and a spacer to reduce the thickness of the relay substrate, allowing for increased diameter of the through hole and conductor pattern width, thereby achieving impedance matching and securing space for the optical device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the diameter of the through hole is increased for matching the characteristic impedance, then the characteristic impedance matching is improved, but the space for mounting the optical device is reduced

Engineering Contradiction:

Improvecharacteristic impedance matchingVSAvoidspace for mounting optical device

Core Design Contradiction:

Manufacturing precisionVSArea of stationary object

Solution Approach 1:

The lead terminal is divided into a small-diameter portion and a large-diameter portion, allowing different sections to serve different functions: the small-diameter portion fits through the through hole for impedance matching, while the large-diameter portion provides connection area without requiring a larger through hole

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the lead terminal have different diameters tailored to local requirements: the through hole section requires small diameter for impedance control, while the connection section requires large diameter for reliable bonding, optimizing each local area independently

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the thickness of the dielectric substrate is increased for matching the characteristic impedance, then the characteristic impedance matching is improved, but the line width of the conductor pattern must be increased which reduces the space for mounting the optical device

Engineering Contradiction:

Improvecharacteristic impedance matchingVSAvoidspace for mounting optical device

Core Design Contradiction:

Manufacturing precisionVSArea of stationary object

Solution Approach 1:

Instead of changing the dielectric substrate thickness, the invention changes the geometric parameters of the lead terminal (diameter) and conductor pattern (line width) to achieve impedance matching, thereby avoiding the space reduction issue

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If the distance between the pedestal and the lead terminal is increased to avoid the through hole, then the manufacturing ease is improved, but the inductance component increases making strict impedance matching more difficult

Engineering Contradiction:

Improveease of connectionVSAvoidimpedance matching

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The lead terminal is segmented into small-diameter and large-diameter portions, allowing the connection to be made at the large-diameter portion which is positioned closer to the pedestal, thereby reducing inductance while maintaining manufacturing ease

Inventive Principle:

Principle #1Segmentation

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 enables both securement of space for mounting the optical device and strict impedance matching, improving transmission characteristics across high-frequency ranges, particularly in 30 GHz to 40 GHz frequencies.

Implementation Method 1

a dielectric filled in the first through hole

Methodology Applied

Scientific EffectElectrical signal transmission through dielectric: Conduction (electrical)

Implementation Method 2

matching characteristic impedance

Methodology Applied

Scientific EffectCharacteristic impedance control: Electrical Impedance Tomography

Implementation Method 3

connected by brazing and soldering

Methodology Applied

Scientific EffectBrazing: Brazing

Implementation Method 4

connected by brazing and soldering

Methodology Applied

Scientific EffectSoldering: Soldering

Data Source

PatentUS10852493B2Optical subassembly and optical module

Publication Date: 2020.12.01 CAMBRIDGE IND USA INC

AI summary

An optical subassembly may include a device mounting substrate on which an optical device is mounted, a relay substrate including a first conductor pattern transmitting a electrical signal to the optical device, a pedestal including a third surface on which the relay substrate is placed and a fourth surface on which the device mounting substrate is placed and a spacer interposed between the third surface and the relay substrate to electrically connect the relay substrate and the pedestal. In an optical subassembly, the first lead terminal may include a small-diameter part and a large-diameter part provided at an end of the small-diameter part and having a larger diameter than that of the small-diameter part, and at least part of the large-diameter part may be exposed from the dielectric on a first surface side and the first lead terminal and the first conductor pattern may be connected by brazing and soldering.