Optical Module Ground Opening Layout for Return Current Resonance
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Solution Overview
Problem
In high-frequency applications, optical modules face issues with return current resonance due to parasitic capacitance between the ground layer and metallic base, leading to frequency-response characteristic degradation.
Innovation Solution
The optical module design includes a circuit board with a through hole and opening that exposes the ground layer, allowing for direct electrical connection to the metallic base via a bonding material, which intersects with the signal wiring to minimize return current path length and reduce resonance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ground layer is completely covered by protective film, then insulation is improved, but return current path length increases causing resonance
Solution Approach 1:
The protective film is selectively removed only in the opening region to expose the ground layer, while maintaining coverage in other areas. This local modification creates a controlled interface between the ground layer and bonding material, enabling direct return current path to the metallic base without compromising overall insulation.
2Object-affected harmful factors
If the opening is positioned far from signal wiring, then interference is reduced, but return current path length increases
Solution Approach 1:
The opening is deliberately positioned to overlap with or be adjacent to the signal wiring, converting what would normally be a source of interference into a beneficial short return current path. The bonding material fills the opening to create a direct electrical connection, and the overlapping configuration ensures the return current path is minimized while the metallic base provides shielding.
3Ease of manufacture
If conventional bonding method is used, then manufacturing is simple, but frequency-response characteristics are degraded
Solution Approach 1:
The bonding process is segmented into distinct steps: forming opening in protective film, applying bonding material specifically in the opening region, and curing. This segmentation allows precise control of bonding material placement to ensure direct electrical connection between ground layer and metallic base, improving frequency-response characteristics while maintaining manufacturing feasibility.
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 configuration improves frequency-response characteristics by suppressing resonance phenomena and widening the signal bandwidth from 38 GHz to 46 GHz, ensuring reliable high-frequency signal transmission.
Implementation Method 1
The bonding material electrically connects a portion of the ground layer to the outer surface of the metallic base
Data Source
AI summary
An optical module includes a circuit board having a through hole for the lead terminal, a signal wiring connected to the lead terminal, a ground layer providing a reference potential, an opening through which the ground layer is exposed, and a bonding material connecting the ground layer to the metallic base. The lead terminal extends in a first direction, and the circuit board and the signal wiring extend in a second direction. When the circuit board is viewed from the first direction, the opening overlaps with the signal wiring, or when the opening does not overlap with the signal wiring, a first distance between the signal wiring and a closest point of the opening to the signal wiring is smaller than a second distance between the closest point and an edge of the circuit board.