SiC Absorbing Sheet Crystal Control for Millimeter-Wave Insulation
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Solution Overview
Problem
Existing electromagnetic wave absorbing sheets using silicon carbide as a loss material face issues with poor dielectric loss tangent and performance due to the 6H type crystal structure, and manufacturing variations due to high cohesive force of carbon-based materials, leading to insufficient insulation and thickness, which are not adequately addressed by existing technologies.
Innovation Solution
The electromagnetic wave absorbing sheet uses silicon carbide powder with a controlled crystal structure and impurity content, ensuring a high I4H/I6H ratio, high surface resistivity, and uniform dispersion, thereby achieving excellent noise attenuation in submillimeter to millimeter wave bands with improved insulation and reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If carbon-based material or silicon carbide is used as loss material to reduce weight, then weight is reduced, but surface resistivity becomes less than 1010 Ω/sq causing insulation problems
Solution Approach 1:
The patent changes the crystal structure parameter of silicon carbide from the conventional 6H type to the 4H type. This parameter change fundamentally alters the electrical properties, increasing carrier mobility and dielectric loss tangent, which results in surface resistivity exceeding 1010 Ω/sq while maintaining the weight reduction benefits of using silicon carbide instead of heavier magnetic fillers.
Solution Approach 2:
The patent applies local quality by selectively controlling the crystal structure at the particle level. By ensuring that the silicon carbide particles have the 4H crystal structure (with I4H/I6H ratio of 0.1 or more), the material achieves locally optimized electrical properties that propagate to the bulk material, providing both light weight and high insulation without requiring additional insulation layers.
2Weight of moving object
If 6H type silicon carbide is used as loss material, then weight is reduced, but dielectric loss tangent is poor leading to insufficient electromagnetic wave absorption performance
Solution Approach 1:
The patent fundamentally changes the crystal structure parameter from 6H type to 4H type silicon carbide. This parameter change increases the dielectric loss tangent by enhancing carrier mobility, which directly improves electromagnetic wave absorption performance while maintaining the weight advantage of using silicon carbide over traditional magnetic fillers.
3Reliability
If carbon-based material is used as loss material to achieve electromagnetic wave absorption, then electromagnetic wave absorption is achieved, but manufacturing variations increase due to high cohesive force and difficulty in homogeneous dispersion
Solution Approach 1:
The patent changes the material parameter from general carbon-based materials to specifically engineered 4H-type silicon carbide particles. This parameter change reduces the cohesive force between particles compared to amorphous carbon materials, enabling homogeneous dispersion in the resin substrate without requiring special manufacturing processes, thus improving both dispersion uniformity and electromagnetic wave absorption performance.
4Length of moving object
If electromagnetic wave absorbing sheet is made thinner to fit narrow spaces, then space requirement is reduced, but insulation property becomes more difficult to maintain
Solution Approach 1:
The patent changes the electrical parameter of the loss material by using 4H-type silicon carbide instead of conventional materials. This parameter change achieves surface resistivity exceeding 1010 Ω/sq inherently, which maintains excellent insulation properties even in thin configurations (1 mm or less), eliminating the need for additional insulation layers and enabling space reduction.
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 sheet achieves excellent noise attenuation and insulation properties with reduced weight and thickness, overcoming manufacturing variations and enhancing electromagnetic wave absorption performance.
Implementation Method 1
the provision of electrical loss by having the resin substrate support a nonmagnetic conductive material increases the degree of freedom in designing the electromagnetic wave absorbing sheet
Implementation Method 2
electromagnetic wave absorbing sheets that function at frequencies where electromagnetic wave interference is a problem are being used
Implementation Method 3
a secondary reflected wave that passes through the inside of the electromagnetic wave absorbing sheet, is totally reflected by the conductive material on the back surface, and is emitted from the surface of the electromagnetic wave absorbing sheet has a phase that is shifted by half a wavelength. The surface reflected wave and the secondary reflected wave cancel each other out
Data Source
AI summary
An electromagnetic wave absorbing sheet that uses silicon carbide powder to impart light weight and high insulation properties and that can obtain an excellent noise attenuation effect in the submillimeter to millimeter wave bands is provided. The electromagnetic wave absorbing sheet of the present disclosure includes a substrate made of organic matter and a powder that is supported in the substrate and has silicon carbide (SiC) as a principal constituent. In X-ray diffraction using Cu-Kα as a radiation source on a surface of the electromagnetic wave absorbing sheet, a value I4H/I6H obtained by dividing a peak intensity I4H derived from 4H—SiC appearing at 2θ=34.4° to 35° by a peak intensity I6H derived from 6H—SiC appearing at 2θ=35° to 36° is a predetermined value or more.