PCB Exposed Metal Grounding for Display EMI Reduction
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Solution Overview
Problem
Printed circuit boards (PCBs) in display devices experience interference due to residual voltage and current, generating electromagnetic fields that disrupt signals to and from the display panel and external devices, leading to noise and performance issues.
Innovation Solution
A novel PCB structure with exposed metal layers at the periphery, connected to a lower structure for grounding, reduces residual voltage and current, using vias, conductive adhesive pads, and fixing screws to efficiently discharge electromagnetic noise to the ground, thereby minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PCBs include more metal layers to implement complicated circuits with many lines, then the functionality and circuit complexity are improved, but electromagnetic interference and noise increase due to residual voltage and current
Solution Approach 1:
The patent extracts the harmful electromagnetic fields by providing dedicated exposure regions where metal layers are exposed to the outside environment. This allows the harmful electromagnetic energy to be released outward rather than remaining within the PCB structure to interfere with circuits. The exposure regions act as extraction points for the harmful factors generated by residual voltage and current in the multiple metal layers.
Solution Approach 2:
The patent converts the harmful residual voltage and current that generate electromagnetic interference into a beneficial grounding path. By creating exposure regions connected to ground, the residual energy is directed to flow safely to ground through the exposed metal layers, transforming the harmful electromagnetic fields into a controlled grounding current that protects rather than interferes with the circuit functionality.
2Device complexity
If PCBs have a stack structure with many metal layers, then more circuits can be implemented, but the area for ground connection is insufficient leading to inadequate EMI suppression
Solution Approach 1:
The patent extends the grounding solution from the traditional two-dimensional plane to the third dimension by creating exposure regions that protrude from or are accessible on the surface of the PCB. This dimensional extension allows for increased ground connection area without increasing the footprint of the PCB itself, enabling better EMI suppression while maintaining the compact stack structure with multiple metal layers.
Solution Approach 2:
The patent segments the grounding function by creating multiple distributed exposure regions across the PCB surface rather than relying on a single large ground connection. Each exposure region serves as an independent grounding point, collectively providing sufficient ground connection area for EMI suppression while allowing the stack structure to maintain its complex multi-layer configuration for high-density circuits.
3Device complexity
If residual voltage and current are not discharged, then the PCB structure remains simple, but electromagnetic fields interfere with signals supplied to the display panel
Solution Approach 1:
The patent introduces exposure regions as intermediary structures that mediate between the internal metal layers containing residual voltage and current and the external ground environment. These exposure regions act as intermediaries that provide a controlled path for discharging residual energy, preventing direct interference with display panel signals while maintaining the existing PCB structure. The intermediaries enable reliable signal transmission by isolating the harmful electromagnetic fields from the signal paths.
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 solution effectively reduces electromagnetic interference (EMI) and electrostatic discharge (ESD) noise, improving signal integrity and device performance by increasing the ground connection area and efficiently discharging residual voltage and current.
Implementation Method 1
residual voltage and residual current in the PCB generate electromagnetic fields which act as noise or interference
Implementation Method 2
the lower structure is electrically connected to the exposed portion of the metal layer
Data Source
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AI summary
A PCB (100) underneath the display panel (320) includes a plurality of insulation layers (111, 113, 115, 117, 119) and one or more metal layers disposed between two adjacent insulation layers out of the plurality of insulation layers (111, 113, 115, 117, 119). A lower structure (330) is disposed between the display panel (320) and the PCB (100). At least a portion of a metal layer among the one or more metal layers that is most adjacent to the lower structure (330) is exposed, and the lower structure (330) is electrically connected to the exposed portion of the metal layer (112). Such exposed portion of the metal layer (112) is electrically connected to the lower structure (330), so that the area where the PCB (100) is referenced to the ground potential is increased. As a result, residual voltage, residual current in the PCB (100) and noise caused by electromagnetic fields generated thereby can be reduced.