Embedded Bias Shield for Signal Trace Impedance Control
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Solution Overview
Problem
As electronic devices become smaller and lighter, controlling electrical properties like impedance becomes more challenging due to the reduction in signal trace width and increase in trace number, leading to noise issues and the need for precise impedance control without adding a ground plane layer.
Innovation Solution
A method involving the formation of an embedded bias-signal trace structure with dielectric layers, bias vias, and shield trenches to reduce noise and control impedance, where bias vias are strategically placed to connect to embedded bias traces and shield trenches are filled with conductive material to form shield walls around signal traces, eliminating the need for a ground plane and minimizing fabrication costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the width of signal traces is reduced to make devices smaller and lighter, then device size and weight are reduced, but electrical properties such as impedance become harder to control and noise increases
Solution Approach 1:
The patent applies local quality by creating shield trenches specifically around signal traces that require impedance control and noise reduction, rather than implementing a uniform ground plane across the entire substrate. This localized shielding approach maintains impedance control for critical traces while avoiding the added weight and cost of a complete ground plane structure.
Solution Approach 2:
The patent segments the shielding function by dividing it into individual shield trenches around specific signal traces, rather than using a continuous ground plane. This segmentation allows selective impedance control and noise reduction where needed, reducing overall device weight and fabrication complexity while maintaining electrical performance for critical traces.
2Productivity
If the number of signal traces is increased for a given substrate, then signal capacity is improved, but electrical properties such as impedance become more difficult to control and noise increases
Solution Approach 1:
The patent implements local quality by providing shield trenches only around specific signal traces that require impedance control, rather than uniformly shielding all traces. This allows the substrate to support increased signal capacity while maintaining precise impedance control for critical traces through targeted shielding.
3Reliability
If a ground plane layer is added to reduce noise and control impedance, then electrical properties are improved, but fabrication cost and device complexity increase
Solution Approach 1:
The patent extracts the essential noise reduction and impedance control function from the complete ground plane structure, implementing only the necessary shield trenches around specific signal traces. This extraction maintains the beneficial electrical properties where needed while eliminating the added fabrication complexity and device structure associated with a full ground plane layer.
Solution Approach 2:
The patent segments the ground plane function into discrete shield trenches around individual signal traces, replacing the continuous ground plane structure. This segmentation achieves noise reduction and impedance control for critical traces while significantly reducing fabrication complexity and device structure complexity compared to a complete ground plane implementation.
4Area of moving object
If trace width is reduced to decrease device area, then device area is reduced, but noise increases and impedance control becomes more difficult
Solution Approach 1:
The patent applies local quality by implementing shield trenches around specific narrow signal traces that are susceptible to noise, rather than adding wider traces or a ground plane. This localized shielding protects the narrow traces from noise interference while maintaining the reduced device area achieved through trace width reduction.
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 effectively reduces noise and signal attenuation, enables high-frequency signal propagation without a ground plane, and accurately controls impedance, enhancing the electrical properties of the signal traces.
Implementation Method 1
The shield top, the shield walls, and a second carrier form a bias shield around the signal trace. The bias shield is electrically connected to a reference voltage source, e.g., ground or power. Accordingly, signals propagated on the signal trace are shielded by the bias shield.
Implementation Method 2
Shield trenches are laser-ablated within the dielectric material and on opposite sides of a signal trace of the patterned trace layer.
Data Source
AI summary
A method includes forming a patterned sacrificial layer on a first carrier and a patterned trace layer on the patterned sacrificial layer. The patterned sacrificial layer and the patterned trace layer are laminated to a dielectric material. The first carrier and the patterned sacrificial layer are removed creating sacrificial layer gaps above the patterned trace layer. The sacrificial layer gaps are filled with a trace layer isolation dielectric material. Shield trenches are laser-ablated within the dielectric material and on opposite sides of a signal trace of the patterned trace layer. The shield trenches are filled with an electrically conductive material to form shield walls. The electrically conductive material is patterned to form a shield top. The shield top, the shield walls, and a second carrier form a bias shield around the signal trace.