Circuit Board Selective Ground Layers for Impedance Control
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Solution Overview
Problem
High-frequency signal transmission on flexible circuit boards is hindered by poor impedance matching, parasitic capacitance, and signal distortion due to inadequate coupling between conductor wires and ground layers, especially in compact and lightweight designs where conductor wire width and layout space are severely constrained.
Innovation Solution
A circuit board structure with selectively corresponding ground layers, where conductor wires are classified into groups and coupled to different ground layers via non-electromagnetic shield areas, with a dielectric layer maintaining a ground layer height difference, and a filling layer of varying dielectric constant to control impedance and signal characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If conductor wires are made finer and layout space is reduced to meet compact device needs, then device size and weight are reduced, but signal transmission quality deteriorates due to poor impedance matching and increased parasitic capacitance
Solution Approach 1:
The ground layer is segmented into multiple ground layers with different heights, allowing different conductor wire groups to couple with different ground layers. This segmentation enables independent optimization of impedance matching for different signal types while maintaining compact device dimensions.
Solution Approach 2:
Different ground layers are positioned at different heights to provide locally optimized electromagnetic coupling characteristics. The first ground layer provides one type of coupling for first-group conductor wires, while the second ground layer provides different coupling for second-group conductor wires, allowing tailored impedance control for different signal requirements.
2Device complexity
If a single ground layer is used for all conductor wires, then device complexity is reduced, but signal transmission quality deteriorates due to inability to control impedance matching for different signal types
Solution Approach 1:
The ground layer is divided into multiple segments at different heights, with each segment serving specific conductor wire groups. This segmentation enables precise control of electromagnetic coupling and impedance characteristics for different signal types, achieving high manufacturing precision in impedance matching.
Solution Approach 2:
The ground layer structure is extended into the vertical dimension with multiple ground layers at different heights, rather than using a single planar ground layer. This dimensional change allows independent optimization of coupling characteristics for different conductor wire groups without increasing lateral complexity.
3Volume of moving object
If substrate thickness is reduced to meet compact design requirements, then device size is reduced, but signal transmission quality deteriorates due to poor control of parasitic capacitance and impedance matching
Solution Approach 1:
Multiple ground layers are arranged in the vertical dimension at different heights, allowing effective control of parasitic capacitance and impedance matching without increasing the lateral footprint or overall substrate thickness. This vertical arrangement enables precise electromagnetic coupling control within a compact volume.
Solution Approach 2:
Different ground layers provide locally optimized electromagnetic characteristics for different conductor wire groups. The varying heights and positions of ground layers allow tailored control of parasitic capacitance and impedance matching for specific signal types, maintaining signal transmission quality in thin substrates.
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 approach improves signal transmission quality by allowing for precise impedance control and increased wire density on the circuit board, effectively addressing signal reflection, emission, and distortion issues while meeting space and size constraints.
Implementation Method 1
the first-group conductor wires are arranged to correspond to and electromagnetically couple to the first ground layer, and the second-group conductor wires are arranged to correspond to and electromagnetically couple to the second ground layer
Implementation Method 2
a filling layer of varying dielectric constant to control impedance and signal characteristics
Data Source
AI summary
A circuit board structure with selectively corresponding ground layers includes a first ground layer, a second ground layer, and a dielectric layer arranged between the first ground layer and the second ground layer to define a ground layer height difference between the first ground layer and the second ground layer. The first ground layer includes a plurality of non-electromagnetic shield areas. The circuit board includes a plurality of conductor wires formed thereon and selectively classified and divided into a first group of conductor wires and the second group of conductor wires. The first-group conductor wires are arranged to correspond to and electromagnetically couple to the first ground layer, and the second-group conductor wires are arranged to correspond to and electromagnetically couple to the second ground layer through the non-electromagnetic shield areas respectively, so that impedance value control is achieved.