Optical Module Flexible Substrate Coplanar Line Design
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Solution Overview
Problem
Conventional flexible substrates used in optical modules suffer from positional misalignment issues during manufacturing, leading to deterioration in high-frequency signal transmission characteristics and electromagnetic radiation, which necessitates additional examination steps and reduces productivity.
Innovation Solution
A flexible substrate design featuring a coplanar line with a dominant electromagnetic field component from surface ground lines, a grounded coplanar line, and a microstrip line, where the surface ground line distance to the signal line is shorter than the back-surface ground line distance, minimizing the impact of positional misalignment and maintaining balanced electromagnetic field distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the width of the signal line is gradually widened in a coplanar line to facilitate connection with lead pins, then the connection ease is improved, but the positional misalignment between surface and back surface conductor patterns causes deterioration in transmission characteristics
Solution Approach 1:
The patent applies local quality by making the ground lines asymmetric in their positioning relative to the signal line. Specifically, the back surface ground line is positioned closer to the signal line than the front surface ground lines, creating a localized electromagnetic field distribution that compensates for potential positional misalignments during manufacturing. This asymmetric local configuration maintains balanced electromagnetic fields despite the gradual widening of the signal line for easier connection.
2Ease of manufacture
If the conductor patterns are separately pasted or etched on surface and back surface, then the manufacturing process is simplified, but positional misalignment of up to 50 microns is caused between conductor patterns
Solution Approach 1:
The patent employs asymmetry by intentionally designing the back surface ground line to be positioned asymmetrically closer to the signal line compared to the front surface ground lines. This asymmetric configuration compensates for the positional misalignment that occurs during separate patterning processes. The asymmetric layout ensures that even with up to 50 microns misalignment, the electromagnetic field distribution remains balanced, thereby maintaining transmission characteristics despite the simplified manufacturing process.
3Reliability
If the distance between back-surface ground line and signal line is gradually increased, then the electromagnetic field distribution is adjusted, but the transmission characteristics deteriorate due to positional misalignment
Solution Approach 1:
The patent applies parameter changes by modifying the distances between ground lines and the signal line in a specific asymmetric pattern. The back surface ground line is positioned at a shorter distance from the signal line compared to the front surface ground lines. This parameter adjustment creates an electromagnetic field distribution that is more tolerant to positional misalignments, maintaining transmission characteristics even when conductor patterns are separately manufactured with up to 50 microns misalignment.
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 enhances high-frequency transmission characteristics, reduces electromagnetic radiation, and simplifies the manufacturing process by eliminating the need for pre-examination steps, resulting in an optical module with improved reproducibility and reduced noise at a lower cost.
Implementation Method 1
an electromagnetic field component of a surface ground line and a signal line is more dominant than an electromagnetic field component of a back-surface ground line and the signal line
Data Source
AI summary
An optical module having a flexible substrate having, even after actual manufacturing steps, excellent transmission characteristics of high-frequency signals and an advantage that electromagnetic field radiation is reduced even when it is connected with a package. The flexible substrate used in external connection of the package of the optical module uses a flexible substrate having a coplanar line to which a lead pin is fixedly attached, a grounded coplanar line which is in contact with the coplanar region, and a microstrip line which is in contact with the grounded coplanar line. The flexible substrate has an electrode layout in which an electromagnetic field component of a surface ground line and a signal line is more dominant than an electromagnetic field component of a back-surface ground line and the signal line in a region of the coplanar line adjacent to the grounded coplanar line.