Optical Module FPC Curved Shape Impedance Control
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Solution Overview
Problem
Existing optical modules experience deterioration of high-frequency characteristics and increased impedance due to the proximity of high-frequency and direct-current signal lines, particularly at the connection between the flexible printed circuit board (FPC) and the printed circuit board (PCB), which affects signal transmission efficiency.
Innovation Solution
The optical module design features a flexible printed circuit board with a curved shape to avoid mutual contact between its portions, ensuring no insulation film intervenes between the ground plain and the PCB, and includes specific interconnect patterns and terminals to maintain low impedance and prevent signal degradation, with the ground potential connected directly to the stem of the optical subassembly without loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the flexible printed circuit board extends from the optical subassembly in one direction with high-frequency and direct-current signal lines close to each other, then the device complexity is reduced, but the high-frequency characteristics deteriorate
Solution Approach 1:
The flexible printed circuit board is divided into a first portion for direct-current signal lines and a second portion for high-frequency signal lines, with the portions separated by a groove. This segmentation prevents crosstalk between signal lines while maintaining structural simplicity, resolving the contradiction between device complexity and high-frequency characteristics.
Solution Approach 2:
The groove is positioned specifically at the connection portion between the flexible printed circuit board and the printed circuit board, creating a localized separation zone. This local quality change ensures proper signal transmission characteristics at the critical connection area without requiring complex overall restructuring.
Data Source
AI summary
An insulation film has a first surface and a second surface opposite to each other and has a first portion and a second portion extending in a direction opposite to each other from a central portion. The optical subassembly is connected to the flexible printed circuit board at the central portion with the stem opposed to the second surface. The flexible printed circuit board curves with the second surface at least the central portion facing outward. The printed circuit board intervenes between edges of the first portion and the second portion and is connected to the flexible printed circuit board. The first portion and the second portion of the flexible printed circuit board curves in a shape to avoid mutual contact and three-dimensionally intersect with each other, and the first portion and the second portion on the second surface are opposed to the printed circuit board.