EMI Absorbing Thermal Sheet Using Carbonyl Iron Composite
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Solution Overview
Problem
Conventional electromagnetic wave absorbing thermally conductive compositions have a low imaginary part of relative permeability in the frequency band of 18 to 26.5 GHz, failing to efficiently absorb electromagnetic wave noise and dissipate heat effectively.
Innovation Solution
A thermally conductive composition comprising a matrix resin, carbonyl iron particles, and thermally conductive particles, with carbonyl iron particles being used in combination with thermally conductive particles to enhance the imaginary part of relative permeability and thermal conductivity, allowing for efficient absorption and dissipation of electromagnetic wave noise in the specified frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electromagnetic wave absorbing thermally conductive compositions are used, then thermal conductivity is provided, but the imaginary part of relative permeability is low in the frequency band of 18 to 26.5 GHz, resulting in insufficient electromagnetic wave noise absorption
Solution Approach 1:
The patent uses a composite material system consisting of carbonyl iron particles (providing magnetic loss for electromagnetic wave absorption) combined with thermally conductive particles (such as aluminum oxide, silicon carbide, or boron nitride) dispersed in a silicone rubber matrix. This composite structure simultaneously achieves high imaginary part of relative permeability for electromagnetic wave absorption and high thermal conductivity for heat dissipation, resolving the contradiction between electromagnetic wave absorption efficiency and thermal management capability.
Solution Approach 2:
The patent optimizes the particle size distribution of carbonyl iron particles (average particle size of 0.1 to 100 μm, preferably 1 to 20 μm) and thermally conductive particles, as well as their volume ratios (carbonyl iron particles: 30-63 vol%, thermally conductive particles: 10-40 vol%). By adjusting these parameters, the composition achieves both high imaginary part of relative permeability in the 18-26.5 GHz frequency band and sufficient thermal conductivity to dissipate heat generated from electromagnetic wave absorption.
2Temperature
If thermally conductive silicone grease or rubber is used as heat dissipating medium, then thermal conductivity is improved, but electromagnetic wave absorption effect is lacking, causing malfunction from electromagnetic wave noise
Solution Approach 1:
The patent merges the functions of electromagnetic wave absorption and heat dissipation into a single composition by combining carbonyl iron particles (for electromagnetic wave absorption) with thermally conductive particles (for heat dissipation) in a silicone rubber matrix. This unified material simultaneously provides both magnetic loss properties for electromagnetic wave noise suppression and high thermal conductivity for heat transfer, eliminating the need for separate materials and resolving the contradiction between thermal performance and electromagnetic interference shielding.
Solution Approach 2:
The patent creates a multi-functional material that performs both electromagnetic wave absorption and thermal conduction within a single composition. The silicone rubber matrix provides flexibility and thermal conduction pathways, while the dispersed carbonyl iron particles provide magnetic loss for electromagnetic wave absorption, and thermally conductive particles enhance heat dissipation. This universal material can be applied in locations requiring both EMI/EMC performance and thermal management, such as near CPUs and communication modules.
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 composition achieves a high imaginary part of relative permeability and thermal conductivity, effectively absorbing electromagnetic wave noise and rapidly transferring heat, thereby addressing the limitations of existing technologies.
Implementation Method 1
an imaginary part (μ") of relative permeability is low in a frequency band of 18 to 26.5 GHz... increase the value of the imaginary part (μ") of relative permeability in a frequency band of 18 to 26.5 GHz, efficiently absorb electromagnetic wave noise
Implementation Method 2
heat generated by the absorption of electromagnetic wave noise can be rapidly transferred to the outside... have a high thermal conductivity
Data Source
Figure 1A~1B
AI summary
A thermally conductive electromagnetic-wave-absorbing composition that includes a matrix resin component, metal soft-magnetic particles, and thermally conductive particles. The metal soft-magnetic particles are carbonyl iron particles and are at least 30 volume% of the electromagnetic-wave-absorbing composition. The value of the imaginary part (µ") of the relative permeability of the thermally conductive electromagnetic-wave-absorbing composition is at least 0.9 in at least a partial band of the 18-26.5 GHz frequency range. A sheet of the thermally conductive electromagnetic-wave-absorbing composition has a thermal conductivity of at least 2.0 W/m·K in the thickness direction. The sheet is a sheet of the thermally conductive electromagnetic-wave-absorbing composition. The present invention thereby provides: a thermally conductive electromagnetic-wave-absorbing composition that has a relative permeability that has a high imaginary part (µ") in the 18-26.5 GHz frequency band, can efficiently absorb electromagnetic noise in said frequency region, and has high thermal conductivity; and a sheet of the thermally conductive electromagnetic-wave-absorbing composition.