Windowed Reference Planes for Embedded PCB Conductors
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Solution Overview
Problem
Data storage devices face challenges in managing electromagnetic interference (EMI) and environmental susceptibility due to the increased costs and dimensions associated with traditional methods of impedance control and shielding in multi-layer printed circuit boards (PCBs).
Innovation Solution
A multi-layer PCB with embedded elongated conductors between opposing reference planes, where the reference planes have windows aligned with the conductors to reduce capacitive coupling and maintain target impedance values while minimizing environmental sensitivity, using a geometry that adjusts conductor width and spacing to meet impedance and common mode rejection requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional methods of impedance control and shielding are used in multi-layer PCBs, then EMI protection is improved, but cost and device dimensions increase
Solution Approach 1:
The reference planes are segmented by introducing windows that extend through the conductor, dividing the continuous reference plane into separate regions. This segmentation reduces capacitive coupling between the conductor and reference plane, thereby reducing EMI susceptibility without requiring additional shielding materials or complex PCB structures
Solution Approach 2:
The windows are positioned locally at specific locations along the conductor where capacitive coupling needs to be reduced. This localized modification allows EMI protection to be applied only where needed, rather than requiring comprehensive shielding across the entire PCB, thus reducing overall device complexity and cost
2Manufacturing precision
If reference planes are positioned close to conductors for impedance control, then target impedance values are achieved, but capacitive coupling and EMI susceptibility increase
Solution Approach 1:
By segmenting the reference plane through windows, the continuous capacitive coupling path is interrupted. This allows the reference plane to remain close to the conductor for precise impedance control while the windows prevent excessive capacitive coupling and EMI susceptibility
Solution Approach 2:
The windows are strategically positioned at locations where capacitive coupling is most problematic, allowing impedance control to be maintained in regions where close positioning is beneficial while reducing coupling in critical areas
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 solution effectively reduces EMI susceptibility and maintains target impedance values, allowing for high-speed data transfer while minimizing environmental sensitivity and physical damage risks, thus optimizing performance and cost in data storage devices.
Implementation Method 1
the reference planes have windows aligned with the conductors to reduce capacitive coupling and maintain target impedance values
Data Source
AI summary
A rigid multi-layer printed circuit board (PCB) has an embedded elongated conductor between opposing first and second reference planes. The first and second reference planes are formed of conductive material and are electrically isolated from the conductor by intervening insulative material. Each of the first and second reference planes have a plurality of spaced apart windows extending therethrough, the windows aligned with the elongated conductor.