Broadband Through PCB Vias for Millimeter Wave Signal Integrity
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Solution Overview
Problem
The challenge lies in designing through printed circuit board (PCB) vias that can effectively propagate signals across thick probe interface boards or device interface boards used in millimeter wave applications, where high frequencies and large thicknesses introduce signal discontinuities, hindering signal integrity.
Innovation Solution
A structure featuring multiple layered PCBs with broadband through vias, ground vias, and microstrip signal lines, optimized via design parameters such as via diameter, ground via placement, and impedance matching to ensure controlled impedance interconnects, enabling signal propagation across thick boards with minimal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If through PCB vias are used to propagate signals across thick boards, then signal transmission between opposite sides is enabled, but signal integrity deteriorates at high frequencies due to discontinuities
Solution Approach 1:
The via structure is segmented into multiple functional components: signal vias for signal transmission, ground vias for reference potential, and ground plates for impedance control. This segmentation allows each component to be optimized for its specific function, resolving the contradiction between enabling transmission and maintaining integrity.
Solution Approach 2:
Ground plates and ground vias act as intermediaries between the signal via and the reference ground. These intermediary elements provide continuous reference potential along the via length, reducing discontinuities and maintaining signal integrity at high frequencies while still enabling transmission across thick boards.
2Adaptability or versatility
If the board thickness is increased to accommodate connectors on the opposite side, then connector placement flexibility is improved, but via discontinuity effects worsen at millimeter wave frequencies
Solution Approach 1:
The design changes multiple parameters simultaneously: via diameter, ground via spacing, ground plate dimensions, and dielectric layer thicknesses. These parameter changes are optimized together to maintain controlled impedance (50 ohms) across thick boards, enabling both connector placement flexibility and signal propagation quality at millimeter wave frequencies.
Solution Approach 2:
The solution adds vertical dimensionality with ground plates at multiple levels (above and below the via opening) and ground vias extending through the board thickness. This three-dimensional via structure provides continuous reference potential along the signal path, compensating for the increased via length due to board thickness and maintaining signal integrity.
3Ease of manufacture
If conventional via structures are used in thick boards, then manufacturing simplicity is maintained, but broadband signal transmission performance deteriorates
Solution Approach 1:
The via structure is segmented into signal vias and ground vias with distinct functions. This segmentation can be implemented using standard PCB via fabrication processes, maintaining manufacturing simplicity while achieving broadband signal transmission through proper geometric configuration of the segmented elements.
Solution Approach 2:
The ground vias and ground plates serve multiple functions: providing reference potential, controlling impedance, reducing discontinuities, and enabling broadband transmission. This multi-functionality is achieved through geometric configuration rather than additional manufacturing steps, maintaining ease of manufacture while improving transmission performance.
Data Source
AI summary
A broadband through printed circuit board (PCB) for millimeter wave application and methods of manufacture are disclosed. The structure includes a multiple layered body and an opening in the multiple layered body. The structure further includes at least one signal via extending through the opening. The structure further includes ground vias extending through the opening and on opposing sides of the at least one signal via. The structure further includes a ground plate above and below the opening and electrically connected to the ground vias at respective ends. The structure further includes a microstrip signal via above and below the opening and electrically connected to the at least one signal via.