Cu/Ni-Coated Graphite Fillers for High-Frequency Microwave Shielding
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Solution Overview
Problem
Conventional electrically conductive materials, such as silver coated nickel (Ag/Ni) powders, are expensive and difficult to compound in polymers due to their high density, and nickel coated graphite (Ni/C) materials exhibit reduced shielding performance above 50 GHz due to decreased magnetic permeability, necessitating the development of new materials with improved EMI shielding effectiveness.
Innovation Solution
A nickel coated graphite (Ni/C) based electrically conductive filler is developed, where a copper layer is added to enhance shielding performance, utilizing a graphite core with a low density and high dielectric constant, and a nickel layer for corrosion protection, achieving similar effectiveness to Ag/Ni shields at a lower cost and reduced density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver coated nickel (Ag/Ni) powder is used for EMI shielding, then shielding performance is improved, but cost and density increase
Solution Approach 1:
The invention uses a composite coating structure with copper as the intermediate layer and nickel as the outer layer on graphite particles. This composite structure combines the high electrical conductivity of copper with the corrosion resistance of nickel, achieving shielding performance comparable to Ag/Ni while reducing density since copper and nickel are less dense than silver.
Solution Approach 2:
The invention replaces expensive silver with copper, which provides similar electrical conductivity and shielding performance but at lower cost. The nickel outer layer provides durability and corrosion resistance, making the overall structure cost-effective while maintaining performance.
2Weight of stationary object
If nickel coated graphite (Ni/C) is used for EMI shielding, then cost and density are reduced, but shielding performance declines above 50 GHz
Solution Approach 1:
The invention creates a Cu/Ni coated graphite composite where the copper intermediate layer maintains high electrical conductivity at GHz frequencies, compensating for the reduced magnetic permeability of nickel above 50 GHz. This composite structure preserves shielding effectiveness in the 50-300 GHz range where conventional Ni/C fails.
Solution Approach 2:
The invention changes the coating structure from direct Ni/C to Cu/Ni coated graphite, modifying the electrical and magnetic parameters of the composite material. The copper layer provides high electrical conductivity that maintains shielding performance at high frequencies where nickel's magnetic permeability decreases.
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 Ni/C based filler improves microwave shielding performance in the 40-100 GHz range, offering comparable shielding to Ag/Ni materials while reducing costs and density, with copper providing similar conductivity to silver and nickel enhancing corrosion resistance.
Implementation Method 1
the intermediate layer includes a material having a high electrical conductivity
Implementation Method 2
the outer layer includes a material having a high corrosion and oxidation resistance
Implementation Method 3
the core of particles is formed from a material having a low density and a dielectric constant >10
Implementation Method 4
improves microwave shielding performance in a 40-300 GHZ range
Data Source
AI summary
An electrically conductive composite powder is provided for microwave shielding applications. The electrically conductive composite powder includes a core of particles formed from a material having a low density of <5 g/cm3 and a high dielectric constant of ≥10; an intermediate layer coated onto the core of particles, wherein said intermediate layer has a high electrical conductivity of >5.90×10−8 Ohm*m at 20° C.; and an outer layer that is deposited onto the intermediate layer, said outer layer comprising a material having a high oxidation and corrosion resistance of >−0.2V galvanic potential in seawater as measured via ASTM G82. The electrically conductive composite powder exhibits excellent microwave shielding performance, while also being substantially lower in cost that conventional Ag/Ni shields. The electrically conductive composite powder can be used across a broad microwave frequency range.