Layered Electromagnetic Shielding Material for Low-Frequency Fields
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Solution Overview
Problem
Existing electromagnetic wave shielding materials fail to effectively shield low frequency magnetic fields in the range of 100 kHz to 500 MHz.
Innovation Solution
An electromagnetic wave shielding material comprising a layer A containing an inorganic fiber and a layer B containing a metal fiber, where at least one of the layers includes a resin, with specific fiber compositions and configurations to enhance shielding effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional molded articles containing carbon fiber and metal fiber are used, then general electromagnetic wave shielding is achieved, but low frequency magnetic field shielding (100 kHz to 500 MHz) is insufficient
Solution Approach 1:
The shielding material is divided into multiple functional layers: a first layer containing inorganic fibers (carbon or glass) for structural integrity and high-frequency shielding, and a second layer containing metal fibers (copper, aluminum, or stainless steel) specifically for low-frequency magnetic field shielding. This segmentation allows each layer to optimize its function, resolving the contradiction between shielding effectiveness and structural simplicity.
Solution Approach 2:
The invention uses composite nonwoven fabrics combining different fiber types (inorganic and metal) bound with thermoplastic resin. This composite structure integrates the high-frequency shielding and structural properties of inorganic fibers with the low-frequency magnetic field shielding capabilities of metal fibers, achieving comprehensive shielding without excessive complexity.
2Reliability
If fiber content and layer structure are increased to improve shielding effectiveness, then low frequency magnetic field shielding is enhanced, but mechanical strength and processability may be compromised
Solution Approach 1:
The invention optimizes specific parameters including fiber diameter (10-100 μm for inorganic fibers, 20-50 μm for metal fibers), fiber length (50-200 mm), and resin content (30-70 mass%) to achieve the desired balance between shielding effectiveness and mechanical properties. These parameter adjustments ensure adequate shielding performance while maintaining processability and structural integrity.
Solution Approach 2:
Different regions of the composite material have optimized fiber compositions: the first layer is optimized for structural strength with inorganic fibers, while the second layer is optimized for magnetic field shielding with metal fibers. This local quality differentiation allows each region to perform its specific function effectively without compromising overall mechanical strength.
3Reliability
If metal fiber content is increased to improve low frequency magnetic field shielding, then shielding effectiveness increases, but material cost and processing difficulty increase
Solution Approach 1:
A thermoplastic resin acts as an intermediary binding agent that holds the metal and inorganic fibers together in a nonwoven structure. This resin matrix facilitates easy processing through conventional molding techniques while maintaining the metal fiber content necessary for low-frequency magnetic field shielding, thus resolving the contradiction between shielding effectiveness and ease of manufacture.
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 material effectively shields low frequency magnetic fields with magnetic field shielding effectiveness exceeding 3 dB at 0.1 MHz, 10 dB at 1 MHz, 20 dB at 10 MHz, 40 dB at 100 MHz, and 60 dB at 500 MHz, while maintaining mechanical strength and processability.
Implementation Method 1
a layer B containing a metal fiber... effectively shield a low frequency magnetic field
Implementation Method 2
a layer B containing a metal fiber... magnetic field shielding effectiveness exceeding... 60 dB at 500 MHz
Implementation Method 3
a layer A containing an inorganic fiber... inorganic fiber contains at least one type from among a carbon fiber, a glass fiber, and a natural mineral fiber
Implementation Method 4
at least one of the layer A and the layer B contains a resin... the resin is a thermoplastic resin... a step of heating and pressing the laminated nonwoven fabrics
Data Source
AI summary
An electromagnetic wave shielding material includes a first layer containing an inorganic fiber, and a second layer containing a metal fiber. At least one of the first layer or the second layer contains a resin.