Display Pad Organic Buffer Layer Crack Prevention
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Solution Overview
Problem
As the resolution of display devices increases, the size of pads in the pad portion decreases, leading to a higher likelihood of damage when integrated circuit chips or flexible printed circuit films are bonded, due to increased force application, which compromises their integrity.
Innovation Solution
The display device incorporates a pad structure with a first electrode layer, a second electrode layer, a third electrode layer, and a fourth electrode layer on a substrate, where an organic layer is positioned between the third and fourth electrode layers, overlapping the contact hole and extending in a winding manner to distribute force and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the size of pads is reduced to increase the number of pads in the pad portion, then the quantity of pads increases, but the reliability of individual pads deteriorates due to increased force application during bonding
Solution Approach 1:
The pad structure is segmented into multiple electrode layers (first, second, third, and fourth electrode layers) stacked sequentially. This segmentation allows the bonding force to be distributed across multiple layers rather than concentrated on a single pad surface, thereby maintaining pad integrity while accommodating high-density pad arrangements.
Solution Approach 2:
The pad structure employs a nested configuration where the second electrode layer is positioned within the contact hole formed in the insulating layers, and the third and fourth electrode layers are stacked above it. This nested arrangement maximizes the use of vertical space, enabling more pads to be arranged in the pad portion without reducing individual pad reliability.
2Manufacturing precision
If the size of pads is reduced to increase resolution, then the density of pads increases, but the force applied to each pad during bonding increases, causing higher probability of damage
Solution Approach 1:
The pad structure exhibits local quality variations through the organic layer configuration. The organic layer is present between the third and fourth electrode layers in regions overlapping the contact hole, providing localized mechanical support and stress distribution exactly where the bonding force is applied, while maintaining overall pad strength despite reduced pad size.
Solution Approach 2:
The pad structure combines multiple materials with different properties: conductive electrode layers for electrical function, insulating layers for electrical isolation, and an organic layer for mechanical cushioning. This composite structure enables the pad to simultaneously achieve high strength, proper electrical characteristics, and resistance to bonding forces despite reduced dimensions.
3Reliability
If multiple electrode layers are stacked to improve pad reliability, then the structural complexity of the pad increases, but the manufacturing process becomes more complex
Solution Approach 1:
The formation of the organic layer is merged with the existing manufacturing process by utilizing the contact hole structure already formed in the insulating layers. The organic layer is deposited to fill the contact hole and is then planarized, combining multiple functions (insulation, mechanical support, and surface flattening) into a single integrated structure, thereby reducing overall process complexity.
Solution Approach 2:
The contact hole is formed in the insulating layers before the electrode layers are deposited. This preliminary action creates a pre-defined pathway and structural framework that guides the subsequent deposition of electrode layers and organic layer, simplifying the overall manufacturing process by establishing the basic geometry early in the fabrication sequence.
Data Source
AI summary
A display device including: a substrate including a display area and a non-display area; and a pad in the non-display area, wherein the pad includes a first electrode layer, a second electrode layer, a third electrode layer, and a fourth electrode layer sequentially on the substrate, the second electrode layer contacts the first electrode layer through a contact hole in a plurality of insulating layers, and an organic layer between the third electrode layer and the fourth electrode layer.