Laminated EMI Suppression Sheet for Thin Wideband Noise Filtering
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Solution Overview
Problem
Existing electromagnetic interference suppression sheets face challenges in achieving high-density packaging of electronic components due to thickness limitations, reduced electromagnetic absorption performance, and increased reflection in near electromagnetic fields, while also being costly and limited in frequency range.
Innovation Solution
A laminated electromagnetic interference suppressor comprising a conductive layer with a surface electrical resistance of 100 to 5000Ω/□ and a magnetic layer with complex magnetic permeability of 3 to 45, using conductive carbon and soft magnetic particles like carbonyl iron, magnetite, or Sendust, with specific thickness and composition ratios to achieve excellent low-pass filter characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of electromagnetic interference suppression sheet is reduced to enable high-density packaging, then the device can be made thinner and fit better in high-density packaging, but the electromagnetic absorption performance deteriorates
Solution Approach 1:
The patent uses a composite structure combining conductive layer and magnetic layer. The conductive layer contains conductive filler (carbon black, carbon fibers, or conductive polymers) dispersed in resin, while the magnetic layer contains soft magnetic particles (carbonyl iron, magnetite, ferrite, or Sendust) dispersed in resin. This composite structure enables the sheet to achieve both thinness and effective electromagnetic interference suppression by combining the effects of conductive and magnetic materials.
Solution Approach 2:
The patent optimizes specific parameters including surface electrical resistance (100-5000Ω/□) and complex magnetic permeability (3-45) to achieve the desired balance between thickness and electromagnetic absorption performance. By carefully controlling these parameters, the sheet can be made thin while maintaining effective noise suppression.
2Reliability
If the content of magnetic particles is increased to improve electromagnetic absorption, then the magnetic loss increases and absorption performance improves, but the sheet becomes more expensive and processing becomes more difficult
Solution Approach 1:
The patent optimizes the content of magnetic particles to achieve the desired magnetic loss while controlling manufacturing complexity. The soft magnetic particles are dispersed in resin to form a manageable slurry that can be coated and processed relatively easily, avoiding the need for overly complex processing while still achieving good electromagnetic absorption performance.
3Device complexity
If conventional single-layer magnetic sheets are used, then the structure is simple, but they cannot provide sufficient electromagnetic absorption performance for high-frequency signals in near-field applications
Solution Approach 1:
The patent divides the electromagnetic interference suppression function into two separate layers: a conductive layer for handling electromagnetic waves and a magnetic layer for absorbing magnetic fields. This segmentation allows each layer to be optimized for its specific function, with the conductive layer containing conductive filler for wave interaction and the magnetic layer containing soft magnetic particles for magnetic field absorption, thereby achieving superior overall performance.
Solution Approach 2:
The patent combines conductive and magnetic materials in a laminated structure where the conductive layer contains conductive filler dispersed in resin and the magnetic layer contains soft magnetic particles dispersed in resin. This composite structure enables the sheet to handle both conductive and magnetic components of electromagnetic waves effectively, providing comprehensive interference suppression.
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 enables effective low-pass filter characteristics with minimal transmission loss across a wide frequency range, suitable for high-density electronic packaging, reducing noise and maintaining flexibility and strength.
Implementation Method 1
the electromagnetic interference suppression sheets used in the near electromagnetic field applications have been often designed depending upon experiences of experts only... absorption and reflection phenomena of electromagnetic radiation can be hardly analyzed by a transmission line theory
Implementation Method 2
a magnetic layer comprising soft magnetic particles... actual number portion of a complex magnetic permeability of the magnetic layer as measured at 100 MHz is 3 to 45
Data Source
AI summary
According to the present invention, there are provided an electromagnetic interference suppression material capable of exhibiting a good low-pass filter characteristic in an extensive frequency band ranging from a low frequency to a high frequency, and an electromagnetic interference suppression sheet using the electromagnetic interference suppression material. When laminating a conductive layer having a surface electrical resistance of 100 to 5000Ω/□ in which 5 to 25% by volume of a conductive carbon is mixed, and a magnetic layer having a magnetic permeability with an actual number portion of 3 to 45 in which a magnetic material is mixed, to each other, it is possible to obtain an electromagnetic interference suppression sheet suitable for high-density packaging of electronic equipments which is excellent in low-pass filter characteristic in a near electromagnetic field.