PCB Via Capacitive Structures for Insertion Loss Correction
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Solution Overview
Problem
Printed circuit boards (PCBs) experience significant signal integrity issues due to insertion loss deviation, particularly with high-speed serial signals, as the length of signal vias approaches the wavelength of the transmitted signals, leading to non-monotonic distortion and signal phase distortion.
Innovation Solution
Incorporating capacitive structures with additional pads in signal vias that form a corrective filter, interacting with the inherent inductance of the via, to reduce insertion loss deviation by causing constructive signal interference and adjusting filter characteristics based on signal wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If signal via length is increased to traverse more PCB layers, then electrical connectivity between layers is improved, but insertion loss deviation and signal distortion increase
Solution Approach 1:
The patent modifies the electrical parameters of the via structure by adding capacitive elements (additional pads) to change the via's impedance characteristics. This transforms the via from a simple conductor into a filtered transmission path, compensating for insertion loss deviation through resonant frequency tuning that counteracts the detrimental effects of increased via length.
Solution Approach 2:
The additional capacitive pads act as intermediary elements within the via structure. These pads serve as intermediate storage points for electrical energy, creating a resonant circuit that mediates between the signal source and destination, thereby reducing signal distortion caused by the via's inductance and length.
2Area of stationary object
If via length approaches signal wavelength, then more layers can be connected, but non-monotonic distortion and signal phase distortion worsen
Solution Approach 1:
The patent changes the electrical length and impedance parameters of the via by incorporating capacitive structures. This transforms the via's frequency response characteristics, creating a resonant peak that compensates for phase distortion and maintains monotonic phase progression even when via length approaches signal wavelength.
3Reliability
If additional capacitive structures are added to signal vias, then insertion loss deviation is reduced, but device complexity increases
Solution Approach 1:
The patent merges the capacitive filtering function with the existing via structure by using additional pads that are integrated into the via's fabrication process. This combines multiple functions (signal transmission, impedance matching, and filtering) into a single structural element, reducing overall device complexity while maintaining signal integrity improvements.
Solution Approach 2:
The additional pads serve multiple functions simultaneously: they provide capacitive filtering to reduce insertion loss deviation, maintain impedance continuity, and can be positioned to optimize resonant frequency. This multi-functionality reduces the need for separate filtering components, thereby limiting the increase in device complexity.
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 structures effectively reduce insertion loss deviation and signal distortion by enhancing signal magnitude through constructive interference, improving signal integrity for broadband signals.
Implementation Method 1
at least one signal via in the plurality of signal vias includes an added capacitive structure which, along with inductance of the at least one signal via, forms a corrective filter
Implementation Method 2
along with inductance of the at least one signal via, forms a corrective filter
Implementation Method 3
causing signal reflections resulting in constructive signal interference that increases signal magnitude
Data Source
AI summary
A printed circuit board (PCB) includes a plurality of stacked layers, each layer having a major plane defining a major plane of the PCB, a plurality of signal pads disposed on a signal pad layer of the PCB that is parallel to the major plane of the PCB, and a plurality of signal vias, each signal via in the plurality of signal vias having a longitudinal axis perpendicular to the major plane of the PCB, each signal via extending through the plurality of layers along the longitudinal axis, each respective signal via being electrically coupled to a respective signal pad of the plurality of signal pads, wherein at least one signal via in the plurality of signal vias includes an added capacitive structure which, along with inductance of that via, forms a corrective filter to reduce insertion loss deviation of at least one broadband signal in that via.