PCB Signal Via Structure With Capacitive Terminal Impedance Tuning
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Solution Overview
Problem
Conventional methods have limited ability to adjust via hole impedance in printed circuit boards due to the Conductive Anodic Filament (CAF) effect, restricting the distance between via holes and the size of anti-pads, which affects signal rate in high-speed digital products.
Innovation Solution
A via hole structure with a capacitive terminal connected to the signal via hole, allowing impedance adjustment by varying the terminal's size, breaking through CAF limitations and reducing the equivalent distance between via holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the distance between via holes is reduced to adjust impedance, then the via hole impedance decreases, but the CAF effect occurs and reliability deteriorates
Solution Approach 1:
The patent introduces a capacitive structure as an intermediary element between the signal via hole and ground. This capacitive structure acts as a mediator that provides an additional impedance adjustment mechanism without requiring reduction of the distance between via holes, thereby avoiding the CAF effect while achieving the desired impedance control.
Solution Approach 2:
The patent changes the parameters of the capacitive structure (such as capacitance value, configuration) to adjust the via hole impedance. By modifying these parameters, the impedance can be controlled without changing the physical distance between via holes, thus avoiding the CAF effect that occurs when via hole spacing is reduced.
2Manufacturing precision
If the size of anti-pad is reduced to adjust impedance, then the via hole impedance decreases, but the processing capability is exceeded and manufacturing precision deteriorates
Solution Approach 1:
The capacitive structure serves as an intermediary that provides an alternative method for impedance adjustment. Instead of reducing the anti-pad size to the limit of processing capability, the capacitive structure enables impedance control through its own parameters, which can be manufactured within standard processing capabilities.
Solution Approach 2:
The patent changes the parameters of the capacitive structure (capacitance, configuration) to achieve impedance adjustment. This approach allows for precise impedance control without requiring the anti-pad size to be reduced to the point where processing capability is exceeded, thus maintaining ease of manufacture while achieving the desired impedance precision.
3Speed
If the distance between differential via holes is reduced to increase signal rate, then the impedance decreases and signal rate increases, but the CAF effect occurs and reliability deteriorates
Solution Approach 1:
The capacitive structure acts as a mediator that enables impedance reduction for higher signal rate without requiring reduction of the distance between differential via holes. By introducing this intermediary element, the system can achieve the necessary impedance levels for high-speed signaling while maintaining adequate via hole spacing to prevent the CAF effect and ensure reliability.
Solution Approach 2:
The patent changes the parameters of the capacitive structure to adjust the impedance and enable higher signal rates. By modifying the capacitance and configuration of this structure, the system can achieve the impedance requirements for high-speed operation without reducing the distance between differential via holes, thus avoiding the CAF effect and maintaining reliability.
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
The capacitive terminal effectively reduces via hole impedance, improving signal quality and overcoming CAF constraints, enabling better impedance control and signal rate in high-speed digital products.
Implementation Method 1
A via hole structure with a capacitive terminal connected to the signal via hole, allowing impedance adjustment by varying the terminal's size
Data Source
Figure 1a~1b
Figure 2~3a
Figure 3b
AI summary
The present application relates to the technical field of communications, and discloses a via hole structure, a signal via hole impedance adjusting method, and a printed circuit board. The via hole structure comprises: at least one signal via hole; and at least one terminal, wherein one terminal is electrically connected to one signal via hole.