Inclined Bump Design for Flexible OLED Display Reliability
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Solution Overview
Problem
Compression defects and crack formation in the insulating layer of flexible OLED display devices occur due to step differences and deformation during the compression process of the substrate and driving chip connection.
Innovation Solution
A display device design featuring inclined surface bumps on the driving chip and anisotropic conductive film with conductive balls to reduce deformation and prevent crack formation, utilizing a display panel with first and second pads connected by bumps with cross sections of curved or polygonal shapes, and a transparent conductive pad electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the bump is formed with a flat surface for simple manufacturing, then the manufacturing process is simpler, but compression defects and crack formation occur in the insulating layer during the compression process
Solution Approach 1:
The bump is designed with a curved surface instead of a flat surface. This curvature allows the bump to gradually adapt to the pad unit surface during compression, distributing stress evenly and preventing sudden compression forces that cause cracks in the insulating layer. The curved geometry maintains manufacturing feasibility while significantly improving reliability during the bonding process.
2Reliability
If the bump has a large size to ensure good connection, then the connection reliability is improved, but the step difference between the pad unit and bump increases causing compression defects
Solution Approach 1:
The curved surface of the bump creates a gradual transition in height rather than an abrupt step. This progressive geometry reduces the effective step difference during compression, allowing the insulating layer to conform smoothly from the pad unit to the bump tip without creating compression defects, while still providing adequate connection area for reliability.
Solution Approach 2:
The bump is designed with optimized dimensional parameters including curvature radius and height ratios. By carefully controlling these parameters, the bump achieves sufficient connection area for reliability while minimizing the step difference that would cause compression defects. The curved geometry effectively changes the spatial distribution of the bump dimensions.
3Reliability
If the insulating layer is made thicker to protect the TFT, then the protection capability is improved, but the flexibility of the display device is reduced
Solution Approach 1:
The curved bump geometry distributes mechanical stress more evenly across the insulating layer during compression and bending. This stress distribution prevents stress concentration at interfaces between the insulating layer and other components, allowing thinner insulating layers to provide adequate protection without compromising the flexibility needed for bendable display devices.
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
The design effectively mitigates compression defects and crack formation in the insulating layer, enhancing the reliability and durability of flexible OLED display devices by distributing stress and improving the connection between the driving chip and the display panel.
Implementation Method 1
driving chips applying driving signals to each of a gate line and a data line formed on the LCD panel
Implementation Method 2
compression defects and crack formation in the insulating layer protecting the TFT occur due to step differences and deformation during the compression process
Data Source
AI summary
A display device includes: a display panel including a display area and a non-display area; a at least one pad in the non-display area of the display panel; a driving chip connected to the at least one pad, the driving chip including a driving circuit and at least one bump therein, wherein the at least one bump has an inclined surface facing toward a central portion of the driving chip.