Wireless IC Device Coil Antenna Asymmetric RFIC Placement
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Solution Overview
Problem
Small RFID tags face challenges with RFIC chip placement interfering with coil antenna magnetic fields, leading to reduced performance and limited inductance due to lamination accuracy issues in sheet laminating methods, which restricts coil thickness and number of layers, making it difficult to achieve low direct current resistance and high sensitivity.
Innovation Solution
A wireless IC device design with a coil antenna structure featuring metal posts and conductor patterns that allow for a helical coil configuration with adjustable dimensions, where the RFIC element is positioned between the substrate and resin member to minimize interference, and capacitors are connected for resonant frequency matching, enabling a low direct current resistance and high flexibility in design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the RFIC chip is disposed on the central axis of the coil antenna or in the coil opening, then the occupied area is reduced, but the electrodes used to mount the RFIC chip intersect the winding axis of the coil antenna, impeding the formation of a magnetic field
Solution Approach 1:
The patent positions the RFIC chip at an asymmetric location relative to the coil antenna structure. Specifically, the chip is disposed at a position where its mounting electrodes do not intersect the winding axis of the coil antenna, breaking the symmetric arrangement that would cause interference. This asymmetric positioning allows the chip to be mounted without blocking the magnetic field formation path while still occupying minimal area.
Solution Approach 2:
The patent resolves the spatial conflict by utilizing the vertical dimension (thickness direction of the substrate) to position the RFIC chip. Instead of placing the chip in the plane of the coil opening where it would block the magnetic field, the chip is mounted on the surface of the substrate at a location that allows magnetic field lines to pass through the coil opening unobstructed. This dimensional arrangement separates the chip mounting plane from the magnetic field formation plane.
2Area of stationary object
If the RFIC chip is disposed on the central axis of the coil antenna, then the occupied area is reduced, but various circuits included in the RFIC chip may malfunction due to the influence of the magnetic field
Solution Approach 1:
The patent employs asymmetric positioning of the RFIC chip relative to the coil antenna to minimize magnetic field interference. By placing the chip at a location where the magnetic field strength is reduced and the field lines do not pass through the chip body, the reliability of the circuits within the chip is improved while maintaining compact dimensions.
3Device complexity
If the coil antenna is manufactured by a sheet laminating method with limited lamination sheets, then the manufacturing complexity is reduced, but the achievable inductance value is limited and it is difficult to realize a coil antenna having a low direct current resistance
Solution Approach 1:
The patent transitions from a planar two-dimensional coil structure to a three-dimensional helical coil structure by utilizing the vertical dimension. The helical coil is formed by winding a conductor around a central axis, creating multiple turns that extend in the thickness direction of the substrate. This three-dimensional configuration increases the inductance value and reduces direct current resistance by providing longer conductor paths with more turns, while still using a limited number of laminated sheets.
Solution Approach 2:
The patent introduces adjustability in the coil antenna design by making the helical coil's dimensions (such as the number of turns, diameter, and pitch) variable. This dynamic design allows optimization of the inductance value and direct current resistance according to specific application requirements, while maintaining the simplicity of the sheet laminating manufacturing method.
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 design achieves a wireless IC device with improved electrical characteristics, including low direct current resistance, high sensitivity, and heat resistance, allowing for a larger coil opening area and reduced noise interference, while maintaining reliability and durability.
Implementation Method 1
a coil antenna (ANT)
Implementation Method 2
an RFIC element (61) which is disposed in the coil antenna (ANT)
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
A wireless IC device 101 comprising: a substrate 1 including a first principal surface PS1 and a second principal surface PS2 that faces the first principal surface PS1; a resin member 70 covering at least the first principal surface PS1 of the substrate 1; an RFIC element 61 mounted on the first principal surface PS1 of the substrate 1; and a coil antenna ANT connected to the RFIC element 61, wherein the coil antenna ANT includes a winding axis along the first principal surface PS1 and the second principal surface PS2 of the substrate 1, and when viewed in a direction of winding axis, the coil antenna ANT has a rectangular or substantially rectangular shape in which a portion of one side is provided in contact with the substrate 1, and the other three sides are provided in contact with the resin member 70.