Flexible Circuit Board Impedance Matching via Connection Line Opening
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Solution Overview
Problem
Impedance matching between coplanar lines and microstrip lines is not consistently established in flexible printed circuit boards, leading to degraded transmission characteristics.
Innovation Solution
Incorporating an opening in the connection line between the coplanar and microstrip lines, which reduces capacitive components and improves impedance matching by forming a pseudo coplanar line, and optimizing the shape and arrangement of ground patterns to suppress capacitance and ensure balanced transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a connection line is formed to interconnect coplanar line and microstrip line, then signal transmission is enabled, but impedance matching deteriorates due to capacitive components
Solution Approach 1:
The patent extracts the harmful capacitive components by forming openings (through-holes or air gaps) in the connection line and ground patterns. This removes the dielectric material between the signal line and ground, thereby eliminating the parasitic capacitance that degrades impedance matching, while maintaining the signal transmission function.
Solution Approach 2:
The connection line and ground patterns are designed with a porous structure containing multiple openings. This porous configuration reduces the effective dielectric volume between conductive elements, minimizing capacitive coupling and improving impedance characteristics without compromising structural integrity or signal transmission.
2Reliability
If ground patterns are added to suppress capacitance, then impedance matching improves, but device complexity increases
Solution Approach 1:
The ground pattern is segmented into multiple discrete ground pads arranged in a specific configuration around the connection line. This segmentation allows strategic placement of ground elements to minimize capacitive coupling while maintaining impedance control, avoiding the need for continuous complex ground structures.
Solution Approach 2:
Ground patterns are selectively placed only in specific locations where they are most effective for impedance control. The ground structures have varying sizes and positions optimized for local impedance matching requirements, rather than using uniform ground coverage, thereby reducing overall device complexity.
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
Enhances impedance matching and transmission characteristics by reducing capacitive components and maintaining phase balance, particularly at higher frequencies, thereby improving the overall performance of the flexible circuit board.
Implementation Method 1
Incorporating an opening in the connection line between the coplanar and microstrip lines, which reduces capacitive components and improves impedance matching
Data Source
AI summary
A flexible circuit board includes: an insulative substrate having a first surface and a second surface opposite to the first surface; a microstrip line having a first signal line formed on the first surface and a first ground pattern formed on the second surface and located in an area opposite to the first signal line; a coplanar line having a second signal line formed on the first surface, and second ground patterns that are formed on the first surface and are spaced apart from both sides of the second signal line; a connection line that is formed on the first surface and connects the first signal line and the second signal line together, the connection line having an opening; and third ground patterns formed on the second surface and arranged in areas located at both sides of an area opposite to the connection line including the opening.