Coaxial PCB Via Structure for Impedance Matching and EMI Shielding
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Solution Overview
Problem
Conventional circuit boards experience impedance mismatch and electromagnetic interference (EMI) at coaxial vias, leading to signal integrity issues and noise interference due to the design of insulating layers and signal paths on different planes.
Innovation Solution
A circuit board design featuring a first conductive via connected to external circuit layers and surrounded by conductive vias forming a ground path, creating a closed high-frequency high-speed loop to reduce noise interference and improve signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating layers are added for insulation between inner and outer conductor layers in coaxial via design, then insulation is improved, but impedance mismatch and EMI shielding notches appear affecting signal integrity
Solution Approach 1:
The patent removes the insulating layer from the coaxial via structure, replacing it with a conductive via design where the via itself serves as the signal path. This extraction eliminates the impedance mismatch and EMI shielding notch problems caused by the insulating layer while maintaining the necessary electrical connections.
Solution Approach 2:
Instead of using an insulating layer to separate conductors as in conventional design, the patent inverts the approach by using a conductive via surrounded by ground vias. The ground vias provide the shielding function that previously required insulating layers, thereby solving the impedance and EMI issues through structural inversion.
2Adaptability or versatility
If signal path ends are located on different planes with ground path ends, then routing flexibility is improved, but noise interference cannot be reduced
Solution Approach 1:
The patent merges the signal path and ground path into a unified coaxial via structure. The signal via and surrounding ground vias are vertically aligned to form a closed loop that maintains electromagnetic shielding effectiveness while allowing routing flexibility across multiple planes. This merging ensures that the ground path closely follows the signal path, reducing noise interference.
3Ease of manufacture
If conventional coaxial via design with insulating layers is used, then manufacturing process is simplified, but EMI shielding effectiveness is reduced
Solution Approach 1:
The patent introduces ground vias as intermediary elements that surround the signal via. These ground vias act as a shield against EMI while maintaining the manufacturing simplicity of the conventional build-up lamination process. The ground vias are formed using the same via drilling and plating processes, adding minimal complexity to the manufacturing workflow.
Data Source
AI summary
A circuit board, including a first dielectric material, a second dielectric material, a third dielectric material, a fourth dielectric material, a first external circuit layer, a second external circuit layer, a conductive structure, a first conductive via, and multiple second conductive vias, is provided. The first conductive via at least passes through the first dielectric material and the fourth dielectric material, and is electrically connected to the first external circuit layer and the second external circuit layer to define a signal path. The second conductive vias pass through the first dielectric material, the second dielectric material, the third dielectric material, and a part of the conductive structure, and surround the first conductive via. The second conductive vias are electrically connected to the first external circuit layer, the conductive structure, and the second external circuit layer to define a ground path, and the ground path surrounds the signal path.