Flexible Printed Circuit Grounding via Mechanical Frame Engagement
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Solution Overview
Problem
The adhesive strength of conductive films used in liquid crystal displays to ground the flexible printed circuit (FPC) to the metal frame degrades over time, leading to increased resistance and susceptibility to electromagnetic interference (EMI), which can cause reliability issues.
Innovation Solution
The FPC includes extending portions with grounding members that mechanically and elastically engage with corresponding notches and U-shaped slots in the metal frame, eliminating the need for a conductive film for grounding, ensuring a robust electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive film is used to ground the FPC to the metal frame, then the grounding function is achieved, but the adhesive strength degrades over time leading to increased resistance and EMI susceptibility
Solution Approach 1:
The patent removes the conductive film from the grounding system and replaces it with a direct mechanical connection between the FPC grounding member and the metal frame through holding members. This extraction eliminates the adhesive interface that degrades over time, thereby resolving the contradiction between achieving grounding function and maintaining long-term adhesive durability.
Solution Approach 2:
The patent replaces the chemical bonding mechanism (adhesive film) with a mechanical connection system consisting of holding members that physically clamp the FPC grounding member to the metal frame. This mechanical substitution provides stable, durable grounding without relying on adhesive strength, thus resolving the reliability-durability contradiction.
2Object-affected harmful factors
If conductive film is used for grounding, then EMI protection is provided, but the film is prone to chipping and breaking when jarred or aged
Solution Approach 1:
The patent extracts the conductive film from the grounding path and replaces it with a mechanical holding system. This eliminates the fragile film structure that chips and breaks under mechanical stress, while maintaining continuous electrical contact for EMI protection through the holding members.
Solution Approach 2:
The patent changes the physical state and mechanical properties of the grounding connection from a thin, brittle film to a robust mechanical assembly with metal holding members. This parameter change in structural integrity eliminates the chipping and breaking issues while preserving the grounding function for EMI resistance.
3Reliability
If conductive film is used to ground the FPC, then electrical connection is achieved, but resistance increases over time due to adhesive degradation
Solution Approach 1:
The patent replaces the adhesive-based electrical connection with a mechanical clamp-style holding system that maintains consistent physical and electrical contact between the FPC grounding member and metal frame. This mechanical substitution prevents the contact resistance increase that occurs when adhesive degrades, thereby maintaining stable electrical connection and low resistance over time.
Data Source
AI summary
An exemplary liquid crystal display (20) includes a liquid crystal panel (22), a flexible printed circuit (23) connected to the liquid crystal panel, and a backlight module (25) configured for illuminating the liquid crystal panel. The flexible printed circuit includes a first grounding member (231). The backlight module includes a metal frame (28). The metal frame includes a first holding member (281). The first holding member of the metal frame holds the first grounding member of the flexible printed circuit such that the first grounding member is electrically connected with the metal frame.