Flexible RFID Tag Structure for Curved-Surface Antenna Stability

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Solution Overview

Problem

Existing RFID tags with stacked antenna conductors face challenges in flexibility and size reduction while maintaining antenna characteristics, especially when attached to curved or inconsistent surfaces, due to stress on via conductors and limited flexibility.

Innovation Solution

The RFID tag design incorporates a flexible first and second substrate with regions not connected to rigid third and fourth substrates, allowing for flexibility and maintaining antenna structure integrity by using these substrates to form a planar inverted-F antenna with via conductors connecting the substrates, enhancing durability and attachment capabilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a rigid substrate is used to maintain antenna conductor structure, then antenna characteristics are maintained, but flexibility and adaptability to curved surfaces are reduced

Engineering Contradiction:

Improveantenna characteristicsVSAvoidflexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The substrate is divided into two distinct regions: a first region with rigid substrate for maintaining antenna conductor structure and a second region with flexible substrate for adapting to curved surfaces. This segmentation allows each region to fulfill its specific function independently, resolving the contradiction between structural stability and flexibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the substrate are assigned different mechanical properties: the first region has rigid characteristics to maintain antenna conductor geometry, while the second region has flexible characteristics to conform to curved surfaces. This local differentiation of material properties enables simultaneous achievement of structural integrity and adaptability.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If via conductors are used to connect stacked antenna conductors, then antenna structure integrity is maintained, but stress concentration and durability are reduced when bent

Engineering Contradiction:

Improveantenna structure integrityVSAvoiddurability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The via conductors are extracted from the flexible substrate region and relocated to the rigid substrate region. This extraction eliminates the stress concentration problem that would occur in via conductors embedded in flexible material during bending, while the rigid substrate provides stable electrical connection without durability issues.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The rigid substrate acts as an intermediary between the stacked antenna conductors, providing a stable connection medium that maintains electrical continuity without being subjected to bending stresses. This intermediary structure resolves the conflict between maintaining structure integrity and ensuring durability under flexing conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If the entire substrate is made flexible to improve adaptability, then attachment to curved surfaces is improved, but antenna conductor stability and characteristics are compromised

Engineering Contradiction:

Improveattachment capabilityVSAvoidantenna characteristics

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The substrate is segmented into rigid and flexible regions, allowing the flexible second region to provide attachment capability to curved surfaces while the rigid first region maintains antenna conductor stability and characteristics independently.

Inventive Principle:

Principle #1Segmentation

4Volume of moving object

If substrate size is reduced to improve tag compactness, then size is reduced, but via conductor stress and reliability are increased

Engineering Contradiction:

Improvetag sizeVSAvoidvia conductor durability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

Via conductors are extracted from the flexible substrate portion and placed in the rigid substrate portion, eliminating the reliability issue of via conductor stress during bending. This allows the flexible substrate to be made smaller to reduce overall tag size without compromising via conductor durability.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS11748591B2RFID tag

Publication Date: 2023.09.05 KYOCERA CORP

AI summary

An RFID tag includes an RFID IC, flexible substrates including first wiring conductors and rigid substrates including second wiring conductors. Substrate surfaces of the flexible substrates include first regions connected to the rigid substrates and second regions that include opposite surfaces and are not connected to the rigid substrates. First conductor portions and second conductor portions included in the first wiring conductors are electrically connected to each other via the second wiring conductors. The RFID IC is connected to the first wiring conductors, the second wiring conductors, or both the first wiring conductors and the second wiring conductors.