Guarded PCB Islands for Low Current Measurement
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Solution Overview
Problem
Conventional printed circuit board (PCB) designs absorb unacceptable numbers of electrons at low current nodes due to dielectric absorption, leading to prolonged polarization of polar molecules, which affects the accuracy of very low current measurements.
Innovation Solution
The design incorporates a printed circuit board with an aperture surrounding the component connection area, connected by low-leakage components and guarded by conductive layers on the top and bottom surfaces, minimizing the flow of electric fields through the PCB material by using air as the primary dielectric and reducing dielectric absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PCB designs are used, then manufacturing is simple, but dielectric absorption causes unacceptable electron absorption at low current nodes
Solution Approach 1:
The PCB is divided into isolated islands surrounded by apertures, separating the low-current measurement nodes from the bulk PCB material. This segmentation prevents E-fields from penetrating large areas of dielectric material, reducing dielectric absorption while maintaining manufacturing feasibility through standard PCB fabrication processes.
Solution Approach 2:
Guards are introduced as intermediary conductive elements that surround the islands and provide a sink for charge collected by the aperture walls. These guards act as mediators that redirect stray charges away from the measurement nodes, further reducing dielectric absorption effects without requiring complete elimination of PCB material.
2Loss of time
If PCB material is used to support the circuit, then mechanical strength is provided, but polar molecules align with E-fields causing prolonged relaxation time
Solution Approach 1:
PCB material is extracted and removed by creating apertures that surround the component connection areas. This removes the source of dielectric absorption (polar molecules) from the critical measurement regions while maintaining mechanical strength through the remaining PCB structure and support stems.
Solution Approach 2:
The PCB structure is modified locally at the component connection areas where apertures are created, while the rest of the PCB retains its full material properties for mechanical support. This localized modification reduces dielectric absorption only where needed without compromising overall structural integrity.
3Reliability
If E-field is allowed to penetrate PCB material, then electrical connection is achieved, but dielectric absorption increases electron absorption at low current nodes
Solution Approach 1:
The aperture structure and surrounding guards are designed to preemptively block and redirect E-fields before they can penetrate deeply into the PCB material. This preliminary anti-action prevents the alignment of polar molecules that would otherwise cause dielectric absorption, while still allowing necessary electrical connections through the low-leakage components.
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 significantly reduces dielectric absorption, minimizing the settling time of polar molecules and enhancing the precision of low current measurements by minimizing the absorption of electric fields through the PCB material.
Implementation Method 1
conventional printed circuit board (PCB) designs absorbed unacceptable numbers of electrons or other charge carriers at the low current nodes of the devices. This absorption is referred to as dielectric absorption.
Implementation Method 2
Electric fields (E-fields) are responsible for leakage displacement currents. Leakage displacement currents follow the path of E-fields through the PCB material.
Data Source
AI summary
A device with low dielectric absorption includes a printed circuit board (PCB), a component connection area including a first conductor layered on a top surface of the component connection area and a second conductor layered on a bottom surface of the component connection area, an aperture surrounding the component connection area, a low-leakage component connecting the component connection area to the PCB across the aperture, and a guard composed of a third conductor at least substantially surrounding the aperture on a top surface of the PCB and a fourth conductor at least substantially surrounding the aperture on a bottom surface of the PCB.