FPC Chamfered Gap Design for Thermal Stress Relief
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Solution Overview
Problem
In liquid crystal display devices using COG technology, the mismatch in linear expansion coefficients between the glass substrate and the flexible printed circuit (FPC) leads to stress and potential disconnection due to thermal expansion, with existing stress relief methods being costly, impractical for narrow frames, or increasing the risk of disconnection during backlight replacement.
Innovation Solution
A display device design featuring a glass substrate with a driver circuit and elongated FPC, where the chamfered-area end gap between the FPC and glass substrate is covered with insulating resin, with the gap being narrower at the center and wider at the ends, reducing the amount of resin needed while enhancing resistance to disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the gap between the FPC end portion and glass substrate end portion is made wider to relieve stress, then stress relief is improved, but the amount of resin required increases and manufacturing cost increases
Solution Approach 1:
The patent applies different gap widths at different locations of the FPC: a first gap width at both end portions and a second gap width (narrower than the first) at the center portion. This local differentiation allows stress relief at the ends where thermal expansion stress concentrates, while minimizing resin usage at the center where less stress occurs.
2Stress or pressure
If the gap between the FPC end portion and glass substrate end portion is made wider to relieve stress, then stress relief is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies different gap widths at different locations of the FPC: a first gap width at both end portions and a second gap width (narrower than the first) at the center portion. This local differentiation allows stress relief at the ends where thermal expansion stress concentrates, while minimizing resin usage at the center where less stress occurs.
3Stress or pressure
If the FPC is made two-layered without base film adhesive layer to reduce stress, then stress relief is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the geometric parameter of the gap width along the length of the FPC, creating a non-uniform gap structure. This parameter variation provides stress relief functionality while maintaining the cost-effective three-layered FPC structure with base film adhesive layers.
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 design effectively relieves stress on the FPC during thermal expansion without increasing resin usage, improving connection resistance and reducing the risk of disconnection, while allowing for easier reuse of the liquid crystal panel.
Implementation Method 1
In order to suppress corrosion of the exposed terminal (a plated part), a resin 24 is applied to the terminal-exposed part
Implementation Method 2
in a case where FPC 5 is repeatedly shrank and expanded in a thermal shock test repeating low and high temperatures, the FPC 5 fixed to the glass substrate 4 is easily applied with stress at both ends
Data Source
AI summary
A display device includes: a glass substrate including a driver circuit and a plurality of connection terminals that is connected to the driver circuit and is arranged in an array, and an elongated FPC, which has a plurality of panel connection terminals that correspond to the connection terminals and which is mounted on the glass substrate, wherein the FPC has a coverlay. The FPC has a chamfered-area end gap between an end portion of the coverlay facing an end face of the glass substrate and a chamfered-area end portion of the glass substrate in a mounted state, wherein the chamfered-area end gap is covered with an insulating resin, and wherein the chamfered-area end gap at a center portion of the FPC is narrower than the chamfered-area end gap at both end portions of the FPC.