EMI Shielding Printed Circuit Board With Through-Substrate Bridges
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Solution Overview
Problem
Conventional flexible printed circuit boards (FPCBs) with EMI shielding films face issues of reduced flexibility due to hardening of conductive adhesive layers under heat and pressure, leading to decreased flexibility and increased electromagnetic interference (EMI) noise, especially in longer boards with higher frequency signals, which hampers high-speed transmission of high-capacity data.
Innovation Solution
A printed circuit board design featuring a substrate with signal and ground units, an insulation layer, and EMI shielding layers on both sides, connected by shielding bridges that span through the substrate and insulation layer, allowing for efficient EMI shielding without compromising flexibility, and a method for manufacturing this board involving through holes and contact holes filled with conductive material to form these bridges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive adhesive layer is used to electrically connect the conductor layer to the ground lines, then EMI shielding effect is achieved, but flexibility of the FPCB is lowered due to hardening under heat and pressure
Solution Approach 1:
The patent removes the conductive adhesive layer from the EMI shielding film structure. Instead of using a separate adhesive layer, the conductor layer is directly bonded to the ground lines through eutectic bonding or other direct bonding methods, eliminating the hardening adhesive that reduces flexibility while maintaining EMI shielding functionality.
Solution Approach 2:
The patent applies EMI shielding films asymmetrically - placing them only on specific sides of the FPCB where EMI shielding is most needed, rather than uniformly on both sides. This reduces the overall impact on flexibility while maintaining effective EMI shielding in critical areas.
2Productivity
If the FPCB is made longer to accommodate high-capacity data transmission, then data transmission capacity is improved, but EMI noise increases leading to quality defects
Solution Approach 1:
The patent divides the FPCB into multiple sections with individual EMI shielding films applied to each segment containing signal lines. This segmentation allows each section to independently shield its EMI, preventing cumulative noise buildup along the length of the board while maintaining high-capacity data transmission across the entire board.
Solution Approach 2:
The patent applies EMI shielding films locally only to areas containing signal lines that require shielding, rather than covering the entire FPCB surface. This targeted approach reduces overall EMI noise in critical areas while minimizing the impact on flexibility and manufacturing complexity.
3Reliability
If conventional EMI shielding methods are used, then some EMI protection is achieved, but high-speed signal transmission is hampered due to increased noise
Solution Approach 1:
The patent introduces ground lines as intermediary elements between signal lines, with EMI shielding films positioned adjacent to these ground lines. The ground lines act as mediators that actively counterbalance EMI generated by signal lines, creating a more effective shielding system that protects high-speed signals without compromising transmission speed.
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 shields both internal and external EMI noise, enabling high-speed signal transmission and maintaining flexibility by using strategically placed shielding bridges that act as a Faraday cage, reducing noise interference and allowing for high-capacity data transmission even in longer FPCBs.
Implementation Method 1
strategically placed shielding bridges that act as a Faraday cage, reducing noise interference
Data Source
AI summary
The present disclosure relates a printed circuit board having an EMI shielding function. In an example embodiment, the printed circuit board includes a substrate, a signal unit disposed on the substrate, a ground unit disposed in parallel with the signal unit, an insulation layer disposed above the substrate and covering the signal unit and the ground unit, an EMI shielding layer disposed on the insulation layer and under the substrate, respectively, and a shielding bridge passing through the substrate and the insulation layer at opposite sides of the signal unit and electrically connecting the EMI shielding layer disposed on the insulation layer to the EMI shielding layer disposed under the substrate.