Triple Conductive Layer Pad Structure for Display Crack Prevention
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Solution Overview
Problem
Conventional display apparatuses face reliability issues due to crack-related defects in the inorganic film of the pad area, leading to short circuits and driving defects as the thickness of the inorganic film decreases with increasing resolution, particularly during the bonding of a flexible printed circuit board.
Innovation Solution
A display apparatus with a pad connection portion featuring a triple conductive layer structure and multiple insulating layers, where the first conductive layer is connected to the second conductive layer via a first contact hole, and the second conductive layer is connected to the third conductive layer via a second contact hole, ensuring sufficient thickness and preventing cracks, thereby enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the inorganic film in the pad area is decreased to accommodate higher resolution, then the display resolution is improved, but the inorganic film generates crack-related defects causing short circuits and driving defects
Solution Approach 1:
The pad connection structure is divided into multiple conductive layers (first, second, and third conductive layers) stacked vertically. This segmentation allows each layer to be optimized independently - the lower layers can maintain sufficient thickness for reliability while the overall structure accommodates high-resolution requirements. The segmentation also distributes mechanical stress across multiple interfaces, preventing crack propagation that would occur in a single thin layer.
Solution Approach 2:
The solution transitions from a single-plane (2D) pad structure to a multi-layer stacked (3D) structure. By adding the vertical dimension with multiple conductive layers connected via contact holes, the design achieves both high resolution (smaller pad footprint in 2D) and sufficient film thickness (accumulated thickness in 3D), resolving the contradiction between resolution and reliability.
2Device complexity
If a single conductive layer is used in the pad area, then the device complexity is reduced, but the inorganic film is prone to cracking and short circuits
Solution Approach 1:
The pad connection structure uses a composite of multiple conductive layers with different materials or properties. The first conductive layer, second conductive layer, and third conductive layer can be made from different materials optimized for their specific functions - such as adhesion, conductivity, or mechanical strength. This composite approach enhances overall reliability while managing the increased complexity through systematic material selection.
Solution Approach 2:
The multi-layer structure acts as a cushioning mechanism against mechanical stress and thermal expansion. By distributing stresses across multiple layers and interfaces, the structure prevents crack initiation and propagation before they can cause failures. The additional layers provide redundancy, so if one layer develops a defect, the other layers maintain electrical connectivity.
3Area of stationary object
If the inorganic film thickness is reduced for high resolution, then the display area increases, but crack-related defects and short circuits increase
Solution Approach 1:
The invention compensates for reduced in-plane thickness by utilizing the vertical dimension. Multiple conductive layers stacked vertically provide cumulative thickness that maintains mechanical strength and crack resistance, while the horizontal footprint of individual pads can be reduced for higher resolution. This dimensional transition allows simultaneous achievement of large display area and high reliability.
Solution Approach 2:
The solution changes the thickness parameter from a single-layer horizontal measurement to a multi-layer vertical accumulation. By changing how thickness is achieved (from lateral expansion to vertical stacking), the design can reduce the horizontal pad size for higher resolution while maintaining sufficient effective thickness for reliability through the stacked layers.
Data Source
AI summary
A display apparatus includes a substrate, a display unit, a pad portion, and a connection wire. The display unit is on the substrate. The display unit includes a pixel circuit and a display device electrically connected to the pixel circuit. The pad portion is at one side of a peripheral area outside the display unit. The pad portion includes a first conductive layer, a second conductive layer arranged on and electrically connected to the first conductive layer, and a third conductive layer arranged on and electrically connected to the second conductive layer. The connection wire connects the pad portion and the display unit to each other to transmit a signal input to the pad portion to the display device. The connection wire includes a same material as that of the first conductive layer.