Flexible Printed Wiring Board Fixing for LCD Thickness Reduction
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Solution Overview
Problem
Conventional liquid crystal display modules face issues with miniaturization and thickness reduction due to strong bending repulsive forces in flexible printed wiring boards, leading to bulging or floating of components and reduced brightness.
Innovation Solution
The implementation of a frame-like mold with cutouts and recessed portions for the flexible printed wiring board, allowing it to be folded outside the mold frame and adhered using pressure-sensitive adhesive tape, which reduces the influence of spring-back forces and stabilizes the light source's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the flexible printed wiring board is folded back to the back surface of the backlight with a minimum radius, then the liquid crystal display module achieves miniaturization and thickness reduction, but the strong bending repulsive force causes the FPC to bulge or float, leading to component displacement and reduced brightness
Solution Approach 1:
The flexible printed wiring board is divided into multiple fixing portions along its length, with each portion independently fixed to the backlight using pressure-sensitive adhesive tape. This segmentation allows the FPC to be secured at multiple points, distributing the constraint forces and preventing bulging or floating between fixed points while maintaining the minimum folding radius for miniaturization.
Solution Approach 2:
The FPC is fixed to the backlight before the white light emitting diode is mounted. This preliminary fixing action establishes a stable baseline position for the FPC, preventing displacement during subsequent component assembly and ensuring the LED is positioned correctly relative to the light guide plate without being affected by FPC spring-back forces.
2Device complexity
If pressure-sensitive adhesive tape is used to fix the FPC to the backlight, then the structure remains simple and miniaturized, but the strong spring-back force of the FPC exceeds the holding force of the tape, causing fixation failure
Solution Approach 1:
Instead of using a single long piece of adhesive tape, the fixing is divided into multiple discrete portions along the FPC. Each tape portion applies concentrated holding force at specific locations, increasing the effective fixation strength at each point while keeping the overall structure simple and suitable for miniaturization.
Solution Approach 2:
The FPC is fixed to the backlight with adhesive tape before the white light emitting diode is mounted. This preliminary fixation establishes a stable foundation that prevents FPC displacement during subsequent assembly, ensuring reliable positioning without requiring additional mechanical reinforcement structures.
3Ease of operation
If the FPC is allowed to spring back freely, then the FPC maintains its flexibility and ease of installation, but the white light emitting diode shifts from its proper position, lowering the brightness of the display
Solution Approach 1:
The FPC is fixed to the backlight with pressure-sensitive adhesive tape at multiple portions before the white light emitting diode is mounted. This preliminary fixation prevents FPC spring-back displacement during and after LED installation, ensuring the LED remains positioned at the optimal location for light extraction through the light guide plate, thereby maintaining maximum display brightness.
Solution Approach 2:
Multiple fixed portions are distributed along the FPC length, creating a series of stable reference points that collectively constrain FPC movement. This segmented fixation approach maintains FPC flexibility for easy installation while preventing the cumulative spring-back forces from displacing the LED from its brightness-optimized position.
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 configuration minimizes the profile size of the liquid crystal display module, reduces the need for mechanical parts, and maintains stable brightness by preventing component displacement, thus achieving miniaturization and thickness reduction.
Implementation Method 1
adhered using pressure-sensitive adhesive tape
Data Source
AI summary
The present invention aims at the miniaturization and the reduction of thickness of a liquid crystal display device. In a liquid crystal display device which includes: a liquid crystal display panel; a backlight which is arranged on a back-surface side of the liquid crystal display panel; and a flexible printed wiring board which has one end thereof connected to a terminal portion of the liquid crystal display panel, wherein the backlight includes a frame-like mold and a light source, the flexible printed wiring board is folded outside a frame of the frame-like mold and has a portion thereof arranged on a back-surface side of the frame-like mold, the light source is housed in the inside of the frame of the frame-like mold; and the light source is mounted on a surface which opposedly faces the liquid crystal display panel in a state that the flexible printed wiring board is folded out of surfaces of the flexible printed wiring board in the vicinity of a bent portion of the flexible printed wiring board, and the flexible printed wiring board has a cutout therein in a periphery of the light source.