RFID Tag Assembly Using Redistribution Layer Etching
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Solution Overview
Problem
Existing RFID tag assembly methods face challenges with accurate antenna-IC alignment, high mounting forces leading to reliability and yield issues, and parasitic capacitance, which complicates the assembly process and reduces tag performance.
Innovation Solution
The use of large contact pads on the RFID IC surface for capacitive or galvanic coupling with the antenna, along with a repassivation layer and conductive redistribution layer, facilitates electrical connections through nonconductive barriers, reducing the need for precise alignment and minimizing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional RFID tag assembly methods are used with small contact pads, then alignment precision is improved, but manufacturing complexity and parasitic capacitance increase
Solution Approach 1:
The patent changes the critical parameter from contact pad size to antenna terminal size. By making the antenna terminals large relative to the IC contact pads, the system achieves both precise alignment capability and reduced assembly complexity. The large antenna terminals provide generous target areas for alignment while the small IC pads maintain electrical integrity
Solution Approach 2:
The patent segments the electrical connection function into two distinct components: small IC contact pads for reliable electrical contact and large antenna terminals for easy alignment. This segmentation allows each component to optimize its function independently, resolving the contradiction between precision and complexity
2Strength
If high mounting forces are applied during assembly, then connection strength is improved, but reliability and yield decrease
Solution Approach 1:
The patent applies preliminary action by designing the antenna terminals and contact pads with inherent mechanical compliance and stress distribution features before assembly. The large antenna terminals are pre-configured to distribute mounting forces over a larger area, preventing stress concentration that would compromise reliability under high mounting forces
3Manufacturing precision
If precise alignment is required for antenna-IC connection, then connection accuracy is improved, but manufacturing efficiency decreases
Solution Approach 1:
The patent changes the alignment parameter from requiring sub-millimeter precision to allowing millimeter-level tolerance by making antenna terminals significantly larger than contact pads. This parameter change enables standard assembly equipment to achieve adequate alignment without specialized high-precision positioning systems
Solution Approach 2:
The patent replaces complex mechanical alignment systems with a simplified approach using large antenna terminals as self-aligning targets. The generous target area eliminates the need for precision mechanical positioning devices, alignment marks, or complex fixture systems
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
This approach simplifies the assembly process, increases reliability, and enhances RFID tag performance by reducing parasitic capacitance and the need for high mounting forces, while allowing for more flexible and efficient tag production.
Implementation Method 1
forming openings in a nonconductive barrier layer with an etchant
Implementation Method 2
attaching the assembly to the substrate with an adhesive
Implementation Method 3
forming an electrical connection through a nonconductive barrier layer between the assembly and the substrate
Data Source
AI summary
An assembly having an RFID integrated circuit (IC), a nonconductive repassivation layer on a surface of the IC and confined within a perimeter of the surface, and a conductive redistribution layer on the repassivation layer and confined within the perimeter of the surface may be provided. At least a first portion of the redistribution layer may be electrically connected to the IC through a first opening in the repassivation layer. Furthermore, a substrate having a first antenna terminal may be provided, and a second opening may be formed in a nonconductive barrier present on at least one of the first antenna terminal and the first portion of the redistribution layer with an etchant. The first opening and the second opening may be nonoverlapping. The assembly may be attached to the substrate with an adhesive.