Sintered Ferrite Substrate Antenna Module Near Metal
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Solution Overview
Problem
Conventional antenna modules for RFID technology face issues such as sticking and contamination during sintering, instability near metal components, and difficulty in reducing thickness, leading to frequency changes and poor antenna characteristics.
Innovation Solution
A thin sintered ferrite substrate with controlled surface roughness and magnetic permeability, integrated with a conductive layer and grooves for flexibility, is used to form a stable antenna module that maintains frequency stability even near metal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If releasing powder is applied to prevent sticking during sintering, then the sintered ferrite substrates can be removed without damage, but the releasing powder contaminates electronic precision components and cannot be completely removed
Solution Approach 1:
The invention extracts and eliminates the releasing powder from the sintering process by using a sintering table with a specific surface structure that prevents sticking through mechanical means rather than chemical powder coating, thereby removing the source of contamination
Solution Approach 2:
The sintering table surface acts as an intermediary between the molded ferrite sheets and the heating element, providing a controlled interface that prevents direct bonding while maintaining thermal contact for effective sintering
2Productivity
If multiple molded sheets are sintered at a time to improve productivity, then production efficiency increases, but the substrates stick to each other and to the sintering table causing damage upon removal
Solution Approach 1:
The invention removes the need for releasing powder by using a structured sintering table surface that inherently prevents sticking, enabling multiple sheets to be sintered simultaneously without contamination or damage risks
Solution Approach 2:
The sintering table surface has locally varied properties with protrusions and recesses that create specific contact points, allowing multiple sheets to be processed together while maintaining non-stick characteristics at each local contact area
3Length of moving object
If the sintered ferrite substrate thickness is reduced to meet size reduction demands, then the antenna module becomes thinner, but the substrate becomes more prone to breaking and deformation during sintering
Solution Approach 1:
The sintering table surface structure provides beforehand cushioning and support to thin substrates during sintering, preventing deformation and breaking before the substrates are removed, enabling successful processing of thicknesses of 100 μm or less
Solution Approach 2:
The invention changes the sintering parameters including temperature control and holding time to suit thin substrates, processing them at temperatures of 900°C or higher for extended periods to ensure complete sintering without deformation
4Area of stationary object
If conventional antenna modules are placed near metal components, then space utilization improves, but magnetic flux converts to eddy currents causing frequency changes and poor antenna characteristics
Solution Approach 1:
The invention uses ferrite powder with specifically controlled particle size distribution (D10: 0.3-1.0 μm, D50: 1.5-3.0 μm, D90: 3.0-6.0 μm) and composition ratios to achieve magnetic properties that maintain frequency stability even when placed near metal components
Solution Approach 2:
The invention creates a composite sintered ferrite substrate combining ferrite powder with specific binders and additives, achieving a material with optimized magnetic permeability and loss characteristics that resist eddy current effects from nearby metal components
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 provides a clean, thin, and stable antenna module with adjusted resonant frequency, preventing frequency changes and ensuring reliable radio communication, even when placed near metal components, while eliminating the need for releasing powders and complex tuning procedures.
Implementation Method 1
at least one surface of the opposing surfaces having the following surface roughness characteristics: (a) a center line average roughness is in a range of 150 nm to 700 nm, (b) a maximum height is in a range of 2 μm to 9 μm
Implementation Method 2
a thin sintered ferrite substrate with controlled surface roughness and magnetic permeability
Data Source
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AI summary
The present invention relates to a molded ferrite sheet having opposing surfaces and a thickness in a range of 30 µm to 430 µm, at least one surface of said opposing surfaces having the following surface roughness characteristics (a) to (c): (a) a center line average roughness is in a range of 170 nm to 800 nm, (b) a maximum height is in a range of 3 µm to 10 µm, and (c) an area occupancy rate of cross-sectional area taken along a horizontal plane at a depth of 50 % of the maximum height in a square of side 100 µm is in a range of 10 to 80 %.