Optical Module Wiring Board Differential Signal Layout
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Solution Overview
Problem
In optical modules, the placement of a GND lead pin between differential transmission lines causes impedance mismatch due to increased line width requirements, leading to adverse effects on high-frequency characteristics.
Innovation Solution
The optical module design includes a wiring board with differential signal leads farther away from the protruding region than the power supply lead, which acts as a bend stop, preventing disconnection and maintaining close proximity of differential transmission lines for electromagnetic coupling, thus avoiding impedance mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GND lead pin is provided at the bend stop position on the flexible board, then the bending of the flexible board can be prevented and disconnection of wiring is prevented, but the pair of differential transmission lines become away from each other with the GND lead pin interposed therebetween, causing impedance mismatch and adverse effects on high-frequency characteristics
Solution Approach 1:
The patent extracts the bend stop function from the differential signal leads region and relocates it to the power supply lead region. By providing the bend stop at the power supply lead position rather than between differential transmission lines, the patent removes the harmful interference to the differential pair while maintaining the necessary mechanical protection against bending and disconnection.
Solution Approach 2:
The patent uses the power supply lead as an intermediary element to serve the dual purpose of power delivery and bend stop function. Instead of using a separate GND lead pin that would interfere with differential transmission lines, the power supply lead acts as a mediator that provides mechanical support without disrupting the electromagnetic coupling of the differential pair.
2Manufacturing precision
If the pair of differential transmission lines are routed close together for electromagnetic coupling, then high-frequency characteristics are improved, but the wiring board becomes more prone to disconnection at bonding portions when bent
Solution Approach 1:
The patent extracts the bend stop function from the differential signal leads region and relocates it to the power supply lead region. By providing the bend stop at the power supply lead position rather than between differential transmission lines, the patent removes the harmful interference to the differential pair while maintaining the necessary mechanical protection against bending and disconnection.
Solution Approach 2:
The patent uses the power supply lead as an intermediary element to serve the dual purpose of power delivery and bend stop function. Instead of using a separate GND lead pin that would interfere with differential transmission lines, the power supply lead acts as a mediator that provides mechanical support without disrupting the electromagnetic coupling of the differential pair.
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 enhances high-frequency characteristics by preventing disconnection and impedance mismatch, ensuring reliable signal transmission.
Implementation Method 1
the pair of differential transmission lines are close together so as to be electromagnetically coupled to each other
Data Source
AI summary
A plurality of leads include a pair of differential signal leads for inputting differential signals, and a power supply lead for supplying power. A wiring pattern includes a pair of differential transmission lines connected to the pair of differential signal leads, and a power supply wiring connected to the power supply lead. A wiring board includes a first region overlapping an optical subassembly, and a second region extending from the first region so as to protrude from the optical subassembly. The pair of differential signal leads are farther away from the second region than the power supply lead. The pair of differential transmission lines are close together so as to be electromagnetically coupled to each other. The optical subassembly does not include a lead penetrating the wiring board in a region between the pair of differential transmission lines.