Flexible Display Terminal Cushioning for Stable Electrical Connection
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Solution Overview
Problem
In flexible display devices, the compression of conductive particles between terminal parts of a device substrate and a flexible circuit substrate can cause deformation of the flexible substrate, leading to unstable electrical connections and potential cracks, especially when the device is bent, resulting in defects in electrical continuity.
Innovation Solution
Incorporating an electrode layer and a cushioning layer between the flexible substrate and the terminal part, with conductive particles composed of a core part and a metal layer, the solution ensures that the conductive particles are compressed into flat shapes, maintaining a distortion balance and preventing deformation of the terminal part, thereby ensuring stable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive particles are forcefully compressed between terminal parts to ensure electrical connection, then electrical continuity is improved, but the flexible substrate deforms and terminal part reliability deteriorates
Solution Approach 1:
The patent introduces a cushioning layer between the flexible substrate and the terminal part that provides preliminary cushioning during compression bonding. This cushioning layer absorbs excessive compression force before it reaches the terminal part, preventing deformation while still allowing sufficient force transmission to compress conductive particles into appropriate flat shapes for reliable electrical connection.
Solution Approach 2:
The patent employs a composite structure consisting of the flexible substrate, electrode layer, cushioning layer, and terminal part. This composite material system allows different layers to perform different functions: the flexible substrate provides flexibility, the electrode layer provides electrical conductivity, the cushioning layer provides force absorption, and the terminal part provides electrical connection, collectively resolving the contradiction between compression force transmission and deformation prevention.
2Reliability
If conductive particles are compressed flat to increase contact surface area, then electrical connection stability is improved, but recesses form in the terminal part causing instability
Solution Approach 1:
The cushioning layer provides preliminary cushioning that prevents excessive compression force from creating deep recesses in the terminal part. This allows conductive particles to be compressed into appropriate flat shapes for stable electrical connection while maintaining the flatness and structural integrity of the terminal part surface.
3Adaptability or versatility
If the flexible substrate is made thin to improve flexibility, then device flexibility is improved, but the substrate becomes more prone to deformation under compression
Solution Approach 1:
The patent creates a composite structure where the thin flexible substrate is combined with the electrode layer, cushioning layer, and terminal part. This composite system allows the substrate to remain thin for flexibility while the other layers provide structural support and force distribution to prevent deformation under compression during compression bonding.
Solution Approach 2:
The cushioning layer acts as an intermediary between the compression force and the flexible substrate. It mediates the transmission of compression force, distributing it in a way that prevents localized deformation of the thin substrate while still allowing sufficient force to compress the conductive particles for electrical connection.
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 use of an electrode layer and a cushioning layer between the flexible substrate and the terminal part allows for stable electrical connections by preventing deformation of the terminal part, reducing the likelihood of defects in electrical continuity, even when the device is in a bent state.
Implementation Method 1
pressure is subsequently applied from above. As illustrated in FIG. 9B, when pressure is applied from above the ACF 830 is compression bonded to the device substrate 810 and the flexible circuit substrate 820
Implementation Method 2
the conductive particles 831 included in the ACF 830 are compressed by the terminal parts 812 and 822, thus electrically connecting the terminal parts 812 and 822 through the conductive particles 831
Implementation Method 3
each of the conductive particles consists substantially of a core part and a metal layer which covers the core part
Implementation Method 4
an electrode layer and a cushioning layer are provided between the flexible substrate and the first terminal part... maintaining a distortion balance and preventing deformation of the terminal part
Data Source
AI summary
A flexible display device comprises a device substrate and a flexible circuit substrate, and achieves high reliability of electrical connection. The device substrate includes a flexible substrate, a display unit and a first terminal part. The flexible circuit substrate includes a second terminal part. An ACF including conductive particles connects the first and second terminal parts. Each conductive particle consists of a core part covered by a metal layer. An electrode layer and a cushioning layer are provided between the flexible substrate and the first terminal part. A quotient of a sum of a product of average particle diameter and elastic modulus for the core part, and a product of double average thickness and elastic modulus for the metal layer, divided by a sum of products of average thickness and elastic modulus for the first terminal part, the cushioning layer and the electrode layer, is no greater than 1.5.