Flexible Printed Circuit Shielding for Touch Display Signal Interference
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Solution Overview
Problem
Existing flexible multi-layer on cell (FMLOC) display devices face high manufacturing difficulty and costs due to the complexity of multilayer board flexible printed circuits (FPCs) used for integrating touch and display functions, leading to interference between touch and display signals.
Innovation Solution
A touch display device design featuring a flexible printed circuit with a body area and connection area, including a first flexible substrate, metal pattern layers, and a metal shielding layer, where the metal shielding layer is strategically located between the substrate and the metal pattern layers to reduce signal interference, and the ratio of its longitudinal length to the total flexible printed circuit length is optimized between 20% to 40%, enhancing manufacturing efficiency and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multilayer board FPC is used to electrically connect the touch device and display device, then both touch and display functions can be integrated, but the manufacturing difficulty and cost increase significantly
Solution Approach 1:
The FPC is divided into distinct functional areas: a body area containing the touch chip and touch wirings, and a connection area for display signals. This segmentation allows each area to be optimized independently, reducing overall manufacturing complexity while maintaining full functionality.
Solution Approach 2:
The touch chip and touch-related components are extracted and placed on a separate flexible substrate from the display connection structure. This extraction isolates the touch function from the display function, simplifying the overall FPC structure and reducing manufacturing difficulty.
2Adaptability or versatility
If a multilayer board FPC is used to integrate touch and display functions, then signal transmission is achieved, but signal interference between touch and display occurs
Solution Approach 1:
A metal shielding layer is introduced as an intermediary between the touch wirings and display wirings. This shielding layer acts as a barrier that blocks electromagnetic interference between the two signal types, allowing both to coexist on the FPC without mutual disruption.
Solution Approach 2:
The metal shielding layer is selectively positioned only in the body area where touch wirings are located, rather than covering the entire FPC. This localized shielding provides interference protection exactly where needed while minimizing impact on signal transmission areas.
3Object-generated harmful factors
If the metal shielding layer covers the entire FPC length, then signal interference is maximally reduced, but manufacturing cost and complexity increase
Solution Approach 1:
The metal shielding layer is positioned only in the body area of the FPC where touch wirings are present, rather than extending across the entire FPC length. This localized approach provides effective interference shielding where needed while reducing manufacturing complexity and cost.
Solution Approach 2:
Instead of providing full-length shielding (excessive action), the metal shielding layer is applied only to the necessary body area (partial action). This partial coverage is sufficient to address the signal interference problem while avoiding unnecessary manufacturing complexity.
Data Source
AI summary
A touch display device, relating to the technical field of display, and capable of reducing interference between signals and reducing production costs. The touch display device comprises a touch display module, a flexible printed board, and a touch chip. The flexible printed board is electrically connected to the touch display module, and comprises a first flexible substrate, a first metal pattern layer, a second metal pattern layer, and a metal shielding layer. The first metal pattern layer comprises a plurality of first touch wires. The second metal pattern layer comprises a plurality of data wires. The metal shielding layer is located between the first flexible substrate and the first metal pattern layer. A ratio of the longitudinal length of the metal shielding layer to the longitudinal length of the flexible printed board ranges from 20% to 40%. A vertical projection of the first metal pattern layer on the first flexible substrate and a vertical projection of the second metal pattern layer on the first flexible substrate have an overlapping region; and a vertical projection of the metal shielding layer on the first flexible substrate at least covers the overlapping region. The width of the first touch wires is greater than the width of the electrode leads.