PCB EMI Shielding via Selective Conductive Layers
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Solution Overview
Problem
Conventional EMI shielding techniques, such as the frame-and-shield approach, consume significant space on printed circuit boards (PCBs) while providing adequate EMI protection, especially when circuitry is mounted on both sides of the PCB, which is undesirable for portable electronic devices requiring smaller form factors.
Innovation Solution
A method involving the selective application of insulating and conductive layers on PCBs, where an insulating layer is applied around integrated circuits with exposed grounding pads, and a conductive layer is coupled to these pads to provide EMI shielding without the need for a metallic frame, thereby reducing the overall volume occupied by the shielding solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional frame-and-shield EMI shielding techniques are used, then EMI protection is achieved, but the space consumed on PCB increases significantly
Solution Approach 1:
The patent extracts the essential EMI shielding function from the conventional frame-and-shield structure by removing the metallic frame and using only the PCB ground planes and trace networks to provide shielding. This extraction eliminates the need for separate shielding components while maintaining EMI protection.
Solution Approach 2:
The patent merges the EMI shielding function with the existing PCB ground planes and electrical networks. The ground planes and traces that are already present for electrical grounding and signal reference are simultaneously used for EMI shielding, eliminating the need for separate shielding structures.
2Reliability
If metallic frame-and-shield structures are used for EMI shielding, then EMI protection is provided, but the vertical space within the device increases
Solution Approach 1:
The patent removes the vertical metallic shield structure from the device architecture. By extracting the shielding function from the physical shield and relocating it to the PCB's electrical ground planes and trace networks, the vertical space previously occupied by the shield is eliminated.
Solution Approach 2:
The patent replaces the mechanical/physical metallic shield structure with an electrical field-based shielding approach using PCB ground planes and conductive traces. This substitution eliminates the need for physical shielding materials and structures that consume vertical space.
3Reliability
If conventional EMI shielding techniques are used, then EMI protection is achieved, but the lateral spacing of circuitry increases
Solution Approach 1:
The patent combines the EMI shielding function with the existing lateral PCB trace networks and ground planes. The conductive traces and ground planes that form the shielding are integrated into the existing circuit layout, eliminating the need for separate lateral shielding structures that would increase spacing.
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 approach effectively reduces the volume required for EMI shielding on PCBs while maintaining equivalent protection, allowing for more compact electronic device designs without increasing the lateral or vertical spacing of circuitry.
Implementation Method 1
selectively applying a conductive layer that covers at least a portion of the first integrated circuit and that is electrically coupled to the exposed first electrical pad
Data Source
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Figure 1B
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AI summary
Methods and apparatuses are disclosed for fabricating a printed circuit board (PCB) having electromagnetic interference (EMI) shielding and also having reduced volume over conventional frame-and-shield approaches. Some embodiments include fabricating the PCB by mounting an integrated circuit to the PCB, outlining an area corresponding to the integrated circuit with a number of grounded vias, selectively applying an insulating layer over the PCB such that at least one of the grounded vias are exposed, and selectively applying a conductive layer over the PCB such that the conductive layer covers at least a portion of the integrated circuit and such that the conductive layer is coupled to the at least one of the grounded vias that are exposed.