Micro LED Display Panel Buffer Layer Stress Absorption
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Solution Overview
Problem
The mismatched thermal expansion coefficients of light-emitting chips and circuit substrates in micro LED display panels lead to impaired bonding yield and low structural reliability in end-products.
Innovation Solution
A display panel design incorporating a buffer insulating layer with a Young's modulus less than 10 GPa, positioned between the light-emitting diodes and the substrate, to absorb bonding stress, thereby enhancing structural reliability and yield rates. The buffer insulating layer is made of organic materials with specific mechanical properties, such as a thickness between 3 and 5 microns, and is electrically connected to the light-emitting diodes through pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light emitting chips are bonded onto circuit substrate through metal bonding with high temperature process, then electrical connection is achieved, but bonding yield is impaired and structural reliability is low due to mismatched thermal expansion coefficients
Solution Approach 1:
The patent introduces a buffer layer as an intermediary component between the light emitting chip and the circuit substrate. This buffer layer has a thermal expansion coefficient that is matched to the light emitting chip, thereby mediating the thermal expansion mismatch between the chip and substrate. The buffer layer absorbs thermal stress during temperature changes, preventing bonding failure and improving both bonding yield and structural reliability.
Solution Approach 2:
The patent changes the physical parameters of the bonding interface by introducing a buffer layer with specific mechanical properties (thermal expansion coefficient, elastic modulus). This buffer layer has a thermal expansion coefficient closely matched to the light emitting chip and an elastic modulus lower than both the chip and substrate, allowing it to deform elastically to accommodate thermal expansion differences and reduce bonding stress.
2Productivity
If light emitting chips are bonded onto circuit substrate, then functional display module is formed, but process yield is impaired due to thermal expansion coefficient mismatch
Solution Approach 1:
The buffer layer serves as a mediator that resolves the thermal expansion mismatch issue, enabling reliable bonding processes. By matching the thermal expansion coefficient of the buffer layer to the light emitting chip, the patent eliminates the primary cause of bonding failure, thereby improving both process yield and bonding reliability simultaneously.
Solution Approach 2:
The buffer layer provides beforehand cushioning by being pre-positioned between the light emitting chip and substrate before bonding. This buffer layer is designed with appropriate thickness and mechanical properties to cushion against thermal expansion stresses that will occur during subsequent temperature variations, preventing bonding failure before it occurs.
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 buffer insulating layer effectively absorbs stress during bonding, increasing bonding yield rates and enhancing the structural reliability of the micro LED display panels by providing a stress buffering effect between materials with different thermal expansion coefficients.
Implementation Method 1
The buffer insulating layer is located between the light emitting diodes and the substrate... effectively absorbs stress during bonding
Data Source
AI summary
A display panel including a substrate, a buffer insulating layer, a plurality of pads, and a plurality of light emitting diodes is provided. The substrate has a display area and a peripheral area adjacent to the display area. The buffer insulating layer is disposed on the substrate. The Young's modulus of the buffer insulating layer is less than 10 GPa. The pads are located on the buffer insulating layer and disposed on the display area of the substrate. The light emitting diodes are electrically connected to the pads and bonding to the display area of the substrate by the pads. The buffer insulating layer is located between the light emitting diodes and the substrate. A normal projection of the light emitting diodes on the substrate is at least partially overlapped with a normal projection of the buffer insulating layer on the substrate.