Optical Device Connection Structure with Columnar Ground Pin
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Solution Overview
Problem
In high-frequency optical fiber communication systems, the connection structure between optical modulators and circuit substrates faces challenges in miniaturization and reducing cross-talk between adjacent signal pads, leading to inaccuracies in positional alignment and increased influence from cross-talk on optical transmission quality.
Innovation Solution
A connection structure featuring a flexible printed circuit with conductive patterns, including at least one ground pad and two signal pads, and a columnar metal member extending from the circuit substrate to secure the flexible printed circuit, reducing cross-talk by precise positional alignment and using solder to form a shield between connection points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If lead pins and flexible printed circuit are used instead of push-on type coaxial connectors, then the housing size is reduced, but cross-talk between adjacent signal pads increases and positional alignment accuracy deteriorates
Solution Approach 1:
A columnar metal member (ground pin) is introduced as an intermediary shielding element between adjacent signal pads on the flexible printed circuit. This ground pin acts as a mediator that blocks electromagnetic interference and cross-talk between neighboring signal transmission paths, thereby resolving the cross-talk issue while maintaining the compact FPC-based structure.
Solution Approach 2:
The flexible printed circuit is designed with ground pads and ground pins positioned specifically between adjacent signal pads. This local arrangement of ground elements creates electromagnetic shielding zones precisely where cross-talk occurs, improving signal integrity without requiring overall enlargement of the housing or FPC dimensions.
2Volume of moving object
If lead pins and flexible printed circuit are used instead of push-on type coaxial connectors, then the housing size is reduced, but positional alignment accuracy between connection pads deteriorates
Solution Approach 1:
The flexible printed circuit incorporates visual markers or distinctive features on its connection pads that enable optical alignment systems to accurately detect and position the FPC relative to the circuit substrate. This allows precise positional alignment even though the FPC is a flexible component subject to positioning variations during assembly.
Solution Approach 2:
The columnar metal member (ground pin) also serves as a mechanical positioning reference that fits into a corresponding recess on the circuit substrate. This intermediary element provides both electromagnetic shielding and mechanical alignment functions, ensuring accurate positional registration between the FPC connection pads and substrate pads during the connection process.
3Area of stationary object
If multiple signal pads are arranged closely on flexible printed circuit, then the mounting space is reduced, but cross-talk between adjacent pads increases
Solution Approach 1:
Ground pins are positioned between adjacent signal pads on the flexible printed circuit to act as electromagnetic shields. These intermediary ground elements block capacitive and inductive coupling between neighboring signal lines, enabling dense packing of signal pads while maintaining signal integrity and minimizing cross-talk interference.
Solution Approach 2:
The FPC design implements local ground shielding zones by placing ground pads and ground pins specifically between adjacent signal transmission paths. This localized approach to electromagnetic shielding allows signal pads to be arranged closely together while each pair of adjacent pads is protected from cross-talk by its own ground barrier, enabling high-density interconnection without signal degradation.
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 solution effectively reduces cross-talk between signal pads, enhances positional accuracy, and minimizes signal reflection and loss, improving the optical transmission quality and manufacturing reliability.
Implementation Method 1
solder, which gradually rises from the ground pattern to a lateral surface of the columnar member, is formed between the columnar member and the ground pattern that is formed in the flexible printed circuit
Implementation Method 2
solder, which gradually rises from the ground pattern to a lateral surface of the columnar member, is formed between the columnar member and the ground pattern
Data Source
AI summary
An optical device includes a connection pad, which is connected to a conductor pattern on the circuit substrate, at one edge. The connection pad includes one ground pad, and two or more signal pads between which the ground pad is interposed from its both sides. The ground pad includes a concave portion including an opening at the edge. The circuit substrate is provided with a metal columnar member in the conductor pattern to which the ground pad is connected. The conductor pattern and the connection pad are fixed to each other with solder in a state in which the columnar member is fitted into the concave portion. Solder, which gradually rises from the ground pattern to a lateral surface of the columnar member, is formed between the columnar member and the ground pattern that is formed in the flexible printed circuit.