RF PCB Interposer Via Structure for Impedance-Matched Signal Transfer
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Solution Overview
Problem
Transmitting radio frequency (RF) signals between stacked printed circuit boards (PCBs) in electronic devices poses a challenge due to impedance mismatch, leading to inefficient signal transfer and potential signal attenuation.
Innovation Solution
Designing a specific interposer with RF vias that match the impedance of the source and load, mimicking a coaxial transmission line structure to facilitate efficient RF signal transmission between the PCBs, including conductive coatings and fillings to optimize signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard PCB interposer is used to transmit RF signals between stacked PCBs, then signal transmission between layers is enabled, but impedance mismatch occurs leading to signal reflections and loss
Solution Approach 1:
The interposer incorporates RF-specific vias with optimized dimensions, positioning, and impedance characteristics in specific locations rather than using uniform standard vias throughout. This local optimization ensures impedance matching for RF signals while maintaining standard PCB structure elsewhere.
Solution Approach 2:
The patent modifies via parameters (diameter, length, spacing, plating thickness) and interposer material properties to achieve impedance matching for RF signal transmission, transforming a standard interposer design into an RF-optimized structure.
2Reliability
If impedance matching structures are added to the interposer for RF signal transmission, then signal transmission efficiency improves, but device complexity increases
Solution Approach 1:
The interposer is designed with segmented functional zones: RF signal paths with specialized impedance-matched vias, ground planes for shielding, and standard connection areas. This segmentation allows RF optimization without complicating the entire interposer structure.
Solution Approach 2:
Instead of adding complex RF matching networks to standard PCB vias, the patent inverts the approach by designing the via structure itself to inherently provide impedance matching, simplifying the overall solution.
Data Source
AI summary
An electronic device may include processing circuitry having a first impedance coupled to a first circuit board, where the electronic device uses the processing circuity to generate one or more radio frequency signals. The electronic device may also include power circuitry to amplify the one or more radio frequency signals, where the power circuitry is coupled to a second circuit board. An interposer may be disposed between the first circuit board and the second circuit board. The interposer may include a via structure having a characteristic impedance to match the first impedance and the second impedance, where the via structure may transmit the one or more radio frequency signals through the interposer between the processing circuitry and the power circuitry.