Differential Via Stack With Void Structures For High-Frequency Signal Integrity
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Solution Overview
Problem
As electronic components shrink, routing differential signals through printed circuit boards (PCBs) at higher frequencies becomes challenging due to the miniature size, leading to difficulties in transitioning signals between layers effectively, especially above 12 GHz, and existing technologies struggle to maintain signal integrity and reduce electromagnetic interference.
Innovation Solution
The implementation of via voids on PCBs, which are cutouts of conducting materials filled with dielectric materials surrounding differential signal vias, and the use of reference layers with conductive films to shield noise, along with back-drilled holes to remove via studs and reduce signal distortion, enhances signal coupling and reduces electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional via structures are used for routing differential signals, then signal transmission between layers is achieved, but signal integrity deteriorates and electromagnetic interference increases at frequencies above 12 GHz
Solution Approach 1:
The patent removes the via stud (conductive material) from the via structure, retaining only the via wall conductive material. This extraction eliminates the via stud as a source of electromagnetic interference and signal distortion, while maintaining the necessary electrical connection and shielding functions through the via wall conductive material and dielectric fill material.
Solution Approach 2:
The patent introduces a dielectric fill material as an intermediary substance within the via void. This dielectric material serves as a mediator that maintains electrical isolation, provides mechanical support, and enables controlled impedance matching, thereby improving signal integrity without introducing conductive interference paths.
2Reliability
If via studs are present in differential signal vias, then electrical connection between layers is established, but signal distortion increases due to electromagnetic interference
Solution Approach 1:
The via stud is completely removed from the via structure. This extraction eliminates the primary source of signal distortion and electromagnetic interference that the via stud creates, while the electrical connection function is maintained through the via wall conductive material that lines the via void.
Solution Approach 2:
The via structure is transformed into a via void (a porous or hollow structure) filled with dielectric material. This porous configuration eliminates solid conductive paths that cause interference, while maintaining the necessary electrical and mechanical properties through the via wall conductive material and dielectric fill.
3Speed
If conventional PCB routing methods are used, then signal paths are established, but maintaining signal integrity at high frequencies becomes difficult due to miniature component sizes
Solution Approach 1:
The patent applies different material properties to different parts of the via structure: the via wall conductive material provides localized shielding and electrical connection, while the dielectric fill material provides localized insulation and impedance control. This local differentiation of material qualities enables high-frequency signal integrity in miniature structures.
Solution Approach 2:
The via structure uses a composite configuration combining conductive material (via wall), dielectric material (fill), and void space. This composite structure integrates multiple material properties to simultaneously achieve electrical connection, electromagnetic shielding, and impedance control, enabling reliable high-frequency signal transmission.
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 configuration improves signal integrity and reduces electromagnetic interference, allowing for robust differential signal transmission with reduced PCB complexity and cost, while maintaining signal integrity and reducing crosstalk.
Implementation Method 1
via voids configured to improve coupling of the differential signals as they are transmitted through layers of the PCB. The via voids are regions that surround a pair of differential signal vias and are cutouts of conducting materials that form the conduction layers of the PCB. The via voids are filed with dielectric materials
Implementation Method 2
the use of reference layers with conductive films to shield noise
Implementation Method 3
Differential signaling employs a pair of complementary signals, which are sent on conducting paths to a destination electronic device. The technique is generally used to avoid electromagnetic interference on the signals as the electromagnetic interference tends to have similar effects on the conducting paths. Since the destination electronic device detects the difference between the pair of differential signals on the conducting paths, the electromagnetic interference could be cancelled
Data Source
AI summary
A printed circuit board includes a top conducting layer, an escaping layer, one or more first reference layers interposed between the top conducting layer and the escaping layer, and a second reference layer disposed under the escaping layer. The top conducting layer includes two connecting pads for receiving a pair of differential signals. A pair of vias are provided to extend vertically to penetrate the one or more first reference layers, the escaping layer, and the second reference layer. The vias connects the top conducting layer with the escaping layer. Each of the one or more first reference layers includes a continuous via void surrounding the pair of vias. The second reference layer includes two round via voids each surrounding one of the vias. The second reference layer includes a conductive film disposed between the two round via voids.