Optical Module Flexible Insulating Layer Parasitic Inductance
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Solution Overview
Problem
High-speed optical modules face challenges in maintaining low costs and high-frequency characteristics due to impedance mismatches between the coaxial line and wiring substrate, leading to reflection waves that degrade waveform quality, and existing solutions complicate soldering and increase processing costs.
Innovation Solution
An optical module design featuring a conductive stem with a through hole and a flexible insulating layer between the optical subassembly and the wiring substrate, reducing parasitic inductance by eliminating air gaps and improving electrical connection, thereby enhancing high-frequency characteristics without increasing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a unique flexible printed board connection method is employed to suppress impedance mismatches, then high-frequency characteristics are improved, but soldering becomes complicated and processing costs increase
Solution Approach 1:
The patent extracts the flexible printed board from the conventional connection structure and replaces it with a rigid circuit board having a ground pattern. This extraction eliminates the need for complex flexible board soldering while maintaining impedance control through the ground pattern design, thereby resolving the contradiction between improved high-frequency characteristics and manufacturing simplicity.
Solution Approach 2:
The patent introduces a ground pattern on the rigid circuit board as an intermediary element between the coaxial line and the optical subassembly. This ground pattern serves as a reference potential that controls impedance and suppresses reflections, achieving high-frequency performance without requiring complex flexible board connections.
2Ease of manufacture
If conventional coaxial line connection is used, then manufacturing is simple, but characteristic impedance mismatches occur leading to signal reflection and degraded waveform quality
Solution Approach 1:
The ground pattern on the rigid circuit board acts as an intermediary that provides a controlled reference potential. This intermediary element ensures continuous reference potential from the coaxial line to the optical subassembly, preventing impedance mismatches and signal reflections while maintaining manufacturing simplicity.
Solution Approach 2:
The patent changes the electrical parameter configuration by introducing a ground pattern with specific geometric parameters on the rigid circuit board. This parameter change controls the characteristic impedance of the transmission line, ensuring impedance matching and preventing reflections, thereby improving waveform quality without complicating manufacturing.
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
The design significantly improves reflection and transmission characteristics at high frequencies, reducing impedance mismatches and manufacturing complexities, enabling cost-effective high-speed optical signal transmission.
Implementation Method 1
the flexible insulating layer being in contact with the connecting portion, the signal lead, and the surface of the conductive stem. According to the present invention, a space between the connecting portion and the signal lead, a space between the connecting portion and the surface of the stem, and a space between the signal lead and the surface of the stem are filled with the flexible insulating layer, and hence neither a space with only air nor a vacuumed space is formed therein. Thus, parasitic inductance of the signal lead can be reduced.
Data Source
AI summary
An optical module includes: a wiring substrate that has a wiring pattern including a connecting portion and is arranged on an optical subassembly so as to be electrically connected thereto; and a flexible insulating layer formed between the optical subassembly and the wiring substrate. The optical subassembly includes: a conductive stem that has a surface opposed to the wiring substrate, the conductive stem being shaped so that the surface has a through hole opened therein and being connected to a reference potential; and a signal lead for transmitting a signal, the signal lead passing through the through hole while being electrically insulated from the conductive stem. The signal lead passes through the flexible insulating layer to be joined to the connecting portion. The flexible insulating layer is in contact with the connecting portion, the signal lead, and the surface of the conductive stem.