Flexible Printed Circuit Shield Layer for ESD and EMI Protection
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Solution Overview
Problem
Electronic equipment with flexible printed circuits (FPCs) face issues with Electro-Static Discharge (ESD) and Electromagnetic Interference (EMI) due to nonconductive resin housings, leading to potential damage and interference with internal components and external devices.
Innovation Solution
The implementation of a flexible printed circuit board with a shield layer and independent ground wiring, where the shield layer is electrically connected to the housing and maintains an insulating relationship with internal components, allowing for effective ESD dissipation and reduced EMI emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nonconductive resin housing is used, then the housing provides good insulation and electrical safety, but ESD charges accumulate on the inner wall and can cause dielectric breakdown and damage to internal electronic components
Solution Approach 1:
A shield layer made of conductive material is introduced as an intermediary between the nonconductive housing and the internal electronic components. This shield layer captures ESD charges on its outer surface and directs them to ground through ground wiring portions, preventing charge accumulation on the housing inner wall and avoiding dielectric breakdown that would damage components.
Solution Approach 2:
The shield layer converts the harmful ESD charge accumulation into a beneficial grounding mechanism. By providing a controlled conductive path, the system intentionally allows charge flow to ground, transforming the potentially destructive ESD event into a safe discharge process that protects internal components.
2Ease of operation
If signal wiring on the FPC is exposed, then the FPC maintains signal transmission capability, but the wiring is susceptible to electromagnetic interference from external sources and emits EMI to external equipment
Solution Approach 1:
The shield layer acts as an electromagnetic intermediary, positioned between external electromagnetic sources and the internal signal wiring. It intercepts external electromagnetic fields and directs them to ground, creating a protected electromagnetic environment for signal transmission while minimizing EMI emission to external equipment.
Solution Approach 2:
The shield layer is strategically positioned only in regions where electromagnetic protection is most needed, such as near sensitive signal wiring or external interfaces. This localized shielding approach provides targeted EMI protection while maintaining signal transmission quality and minimizing overall system complexity.
3Reliability
If a shield layer is added to the FPC, then ESD protection and EMI shielding are improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The shield layer is integrated directly into the FPC structure by forming it on the same substrate using the same conductive material deposition processes. The ground wiring portions are merged with existing ground connections in the housing, eliminating the need for separate shielding components and reducing overall device complexity.
Solution Approach 2:
The shield layer serves multiple functions simultaneously: it provides ESD protection by capturing and grounding charges, shields internal wiring from external EMI, and acts as an electromagnetic barrier for EMI emission control. This multi-functionality reduces the need for separate protection mechanisms and simplifies the overall system design.
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 reliably prevents ESD-induced damage and minimizes EMI effects, enhancing the durability and performance of electronic equipment by ensuring safe discharge paths and reduced electromagnetic interference.
Implementation Method 1
an occurrence of ESD (Electro-Static Discharge) at an outside causes a charge induced in an inner wall of the housing to be charged up... The shield layer maintains an insulating relationship with the drive circuit and is electrically connected to a portion of the housing portion via the first ground wiring portion
Implementation Method 2
a shield layer having conductivity is formed at a first main surface side... the shield layer is provided in such a manner of opposing to an inner surface of the housing portion... electrically connected to a portion of the housing portion via the first ground wiring portion
Implementation Method 3
signal wiring on the FPC has an electromagnetic effect from an outside of the housing, and EMI (Electro-Magnetic Interference) emitted from wiring of the FPC is emitted to an outside world
Implementation Method 4
a shield layer having conductivity is formed at a first main surface side... the shield layer is provided in such a manner of opposing to an inner surface of the housing portion... significantly reduce an electromagnetic effect affecting the flexible printed circuits from an outside of the housing portion
Data Source
AI summary
A shield layer is selectively formed on a front surface of a base film having an insulating property to form a wiring layer on a rear surface of the base film, and a connector connection terminal and a mounting terminal are selectively provided on the wiring layer. A liquid crystal display device is configured so as to be housed in a set housing, in a state that a TFT array substrate and a control board are connected to each other via an FPC having the structure as described above. In this case, the shield layer is provided in such a manner of opposing to an inner surface of the housing, the shield layer maintains an insulating relationship with the drive circuit, and is electrically connected to a portion of the housing via the first ground wiring portion.