Humidity Detection Layer for Flexible Circuit Bonding Defects
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Solution Overview
Problem
Existing display technologies face challenges in detecting coating defects in flexible printed circuits and chip on film bonding, leading to mechanical strength reduction and risks of corrosion or short circuits due to water vapor intrusion, making it difficult to identify and mitigate these issues effectively.
Innovation Solution
Incorporating a humidity detection layer between the flexible base film and metal foil in flexible printed circuits and chip on film, which includes a hygroscopic film sheet with a color changeable material, allowing for intuitive detection of humidity changes through resistance or color changes, and using a detecting lead connected to an impedance/voltage detecting circuit to rapidly localize coating defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an adhesive-type coating (UV adhesive) is added in a bonding zone to enhance connection strength and prevent corrosion, then the mechanical strength and protection are improved, but coating defects occur and water vapor intrusion risk increases
Solution Approach 1:
The patent applies color changeable materials in the bonding zone that change color when exposed to water vapor or humidity. This allows visual detection of coating defects and moisture intrusion without requiring complex electronic detection systems. The color change provides immediate feedback on the integrity of the adhesive coating and bonding quality.
Solution Approach 2:
The patent introduces a humidity detection layer as an intermediary between the adhesive coating and the external environment. This layer contains humidity-sensitive materials that respond to moisture presence, providing an additional detection mechanism that complements the adhesive coating's protective function.
2Difficulty of detecting and measuring
If a humidity detection layer with color changeable material is added to detect water vapor intrusion, then the detection capability is improved, but the device complexity increases
Solution Approach 1:
The patent uses color changeable materials that provide visual detection of humidity changes. This simple optical response eliminates the need for complex electronic sensors, signal processing circuits, and power sources, thereby maintaining low device complexity while achieving effective detection capability.
Solution Approach 2:
The humidity detection layer operates passively using the natural response of humidity-sensitive materials to moisture presence. The color change occurs automatically without requiring external power, control systems, or complex detection electronics, allowing the structure to self-indicate its state.
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 solution enables intuitive and rapid localization of coating defects, reducing the ratio of defective products by providing a direct means to detect humidity-related issues, thereby enhancing the mechanical strength and reliability of the bonding process.
Implementation Method 1
the humidity detection layer may comprise a hygroscopic film sheet, and the resistance value of the hygroscopic film sheet may change as the humidity changes
Implementation Method 2
the color of the color changeable material changes as the humidity changes
Data Source
AI summary
This disclosure discloses a flexible printed circuit, a chip on film, and a bonding method and a display device using this flexible printed circuit and chip on film. The flexible printed circuit/chip on film of this disclosure comprises a humidity detection layer located between a flexible base film and a metal foil, wherein the humidity detection layer and the flexible base film, and/or the humidity detection layer and the metal foil, are optionally bonded by an adhesive layer. The humidity detection layer can change resistance and/or color according to the humidity, so that intuitive and rapid localization of coating defects is performed directly (by color change) or by means of a detecting lead and an impedance/voltage detecting circuit, and finally the object of reducing the ratio of defective products is achieved.