Flat Panel Display Planarizing Layer Thickness Optimization
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Solution Overview
Problem
Contact failure occurs between pads and flexible printed circuits (FPC) or chip on glass (COG) in active matrix type OLEDs due to the thickness of the planarizing layer, which affects the compression of conductive balls and the adhesive property, leading to poor contact and potential electrical failures.
Innovation Solution
The use of a thinner second planarizing layer made of organic material, specifically photosensitive organic material, is implemented in the non-pixel region to reduce the height difference between the pad and the planarizing layer, ensuring sufficient compression of conductive balls and improving adhesive properties during connection, thereby preventing contact failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the planarizing layer is made thicker to remove steps and cover height differences between pixel and non-pixel regions, then planarization quality is improved, but the height difference between the pad and the planarizing layer increases, causing insufficient compression of conductive balls and contact failure
Solution Approach 1:
The planarizing layer is divided into two separate layers: a first planarizing layer covering the pixel region with sufficient thickness to remove steps, and a second planarizing layer covering the non-pixel region with controlled thickness to maintain appropriate height difference for reliable pad contact. This segmentation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
Different thickness requirements are applied to different regions: the first planarizing layer in the pixel region is made thick enough to achieve planarization, while the second planarizing layer in the non-pixel region is made with controlled thickness to ensure proper contact height. This local differentiation resolves the contradiction between planarization quality and contact reliability.
2Reliability
If the planarizing layer is made thinner to reduce height difference and improve pad contact, then contact reliability is improved, but the ability to remove steps and cover height differences between regions is reduced
Solution Approach 1:
By segmenting the planarizing layer into two distinct layers with different thickness characteristics, the patent enables the first layer to focus on step removal and planarization while the second layer focuses on maintaining appropriate contact height, thus resolving the contradiction between planarization quality and contact reliability.
Solution Approach 2:
The patent introduces a vertical dimension differentiation by creating two layers at different height levels, where the first planarizing layer provides the base planarization function and the second planarizing layer adjusts the final surface height for pad contact, effectively using dimensional stratification to resolve the thickness contradiction.
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 effectively prevents contact failure between pads and FPC/COG by ensuring proper compression and adhesive properties, enhancing the reliability of the flat panel display connections.
Implementation Method 1
The use of a thinner second planarizing layer made of organic material, specifically photosensitive organic material
Data Source
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AI summary
A flat panel display includes a substrate (110) having a pixel region (A1) and a non-pixel region (A2), the substrate having a transistor (T2) in the pixel region and a pad (253) in the non-pixel region, a first planarizing layer (261) in the pixel region (A1) covering the transistor (T2) and including a via hole (263) exposing a portion of the transistor, and a second planarizing layer (262) in the non-pixel region (A2) and having a pad contact hole (264) opening the pad (253), the second planarizing layer (262) being thinner than the first planarizing layer (261).