Magnetic Sheet Antenna Substrate for Mobile Devices
Solution Overview
Problem
Existing antenna devices in mobile devices face efficiency issues due to limited internal space, weak adhesiveness between circuit boards and magnetic sheets, and increased thickness when using adhesive layers to prevent delamination, especially when subjected to heat and chemical treatments during processes like etching and soldering.
Innovation Solution
A magnetic sheet composed of magnetic powder and a binder resin, with specific properties such as high magnetic permeability and resistance to heat and chemical treatments, is used as a substrate to laminate a conductive foil and form an antenna pattern, eliminating the need for additional insulating substrates and enhancing adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high permeability ferrite sheet is attached to one side of a circuit board to improve magnetic field focusing and prevent eddy current, then antenna performance is improved, but internal space efficiency is reduced
Solution Approach 1:
The patent combines the magnetic sheet and circuit board into a single integrated structure where the magnetic sheet serves as the substrate for the antenna pattern. This merging eliminates the need for separate components and reduces overall device volume while maintaining magnetic field focusing capabilities.
Solution Approach 2:
The magnetic sheet is designed to perform multiple functions simultaneously: it provides magnetic field focusing, serves as the antenna substrate, and enables direct conductive foil lamination. This multi-functionality reduces the number of separate components needed, thereby improving space efficiency.
2Strength
If an adhesive layer is used to prevent delamination between the circuit board and magnetic sheet, then bonding strength is improved, but the total thickness of the antenna device increases
Solution Approach 1:
The patent eliminates the adhesive layer by directly laminating the conductive foil to the magnetic sheet. The magnetic sheet itself serves as the bonding interface, integrating the adhesive function into the magnetic sheet structure and eliminating additional thickness.
Solution Approach 2:
The patent removes the adhesive layer from the structure entirely, extracting the bonding function and transferring it to the magnetic sheet-conductive foil interface. This elimination of the intermediate adhesive layer reduces total thickness while maintaining bonding strength.
3Volume of moving object
If the magnetic sheet is used as a substrate to laminate conductive foil and form antenna pattern, then space efficiency is improved, but chemical-resistant property and heat-resistant property are required
Solution Approach 1:
The patent modifies the magnetic sheet's physical and chemical parameters by selecting specific materials and controlling manufacturing parameters to achieve the required chemical and heat resistance. This enables the magnetic sheet to withstand etching processes and reflow/soldering while maintaining its structural integrity.
Solution Approach 2:
The patent employs composite material structures within the magnetic sheet, combining materials with complementary properties to achieve both the required magnetic performance and resistance to chemical and thermal processing. This composite approach allows the sheet to meet multiple demanding requirements simultaneously.
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 magnetic sheet provides excellent heat- and chemical-resistant properties, maintaining magnetic performance across multiple applications like NFC, WPC, and MST, while reducing thickness and simplifying the preparation process, and ensuring minimal changes in weight and thickness during environmental changes or processing treatments.
Implementation Method 1
a magnetic body, such as the ferrite sheet, focuses the magnetic flux of the antenna so that the penetration of a magnetic field into a metal surface and the generation of the eddy current may be prevented
Implementation Method 2
a thickness change of 5% or less and a magnetic permeability change of 5% or less when subjected to heat-treatment twice, the heat-treatment being composed of heating from 30° C. to 240° C. at a constant rate for 200 seconds and then cooling from 240° C. to 130° C. at a constant rate for 100 seconds
Implementation Method 3
a thickness change of 5% or less and a magnetic permeability change of 5% or less when immersed in a 2 N hydrochloric acid solution for 30 minutes; and a thickness change of 5% or less and a magnetic permeability change of 5% or less when immersed in a 2 N sodium hydroxide solution for 30 minutes
Data Source
AI summary
A magnetic sheet having improved acid/base-resistant properties, corrosion-resistance, and an excellent magnetic property at NFC, WPC, and MST frequencies, has little changes in weight and thickness even if the environment changes, for example, even after an etching treatment for patterning, or a reflow or soldering process which is performed for its application to a product.