LED Display Panel Buffer Layer for Crack-Free Micro-LED Transfer
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Solution Overview
Problem
The challenge lies in safely transferring small-sized LEDs onto a circuit board without causing defects such as cracks, and ensuring adequate luminous area for each sub-pixel in a restricted pixel area, which is crucial for achieving clear image quality in displays like smart watches and AR/VR devices.
Innovation Solution
A method involving a buffer material layer with grooves between LEDs, conductive particles for electrical connection, and a light blocking material layer to prevent light interference, along with a laser lift-off technique to transfer LEDs in a group, mitigating impact and ensuring stable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If small-sized LEDs are transferred using laser lift-off technique, then transfer efficiency is improved, but defects such as cracks occur in LEDs due to laser impact
Solution Approach 1:
A buffer material layer is formed between the growth substrate and the LEDs before transfer. This buffer layer absorbs and cushions the impact of laser energy during the laser lift-off process, preventing direct transmission of laser shock waves to the LEDs. Consequently, cracks and defects in LEDs are prevented while maintaining efficient group transfer capability.
2Adaptability or versatility
If sub-pixels are arranged on a two-dimensional plane, then image display capability is improved, but the area occupied by each pixel increases
Solution Approach 1:
The patent transitions from traditional two-dimensional planar arrangement of sub-pixels to a three-dimensional stacked structure where multiple LED layers are vertically arranged. This vertical stacking enables sub-pixels to be positioned in different spatial layers rather than only on a flat plane, significantly reducing the horizontal area occupied by each pixel while maintaining full color display capability through the stacked LED layers.
3Productivity
If the area of each sub-pixel is reduced to fit in restricted space, then pixel density is improved, but luminous area is reduced and brightness deteriorates
Solution Approach 1:
By stacking multiple LED layers vertically, the patent increases the effective luminous area in the vertical dimension. Each LED layer contributes to the overall brightness, so even though individual sub-pixel footprints are reduced for higher density, the cumulative luminous output from multiple stacked layers maintains or enhances brightness. This resolves the trade-off between pixel density and illumination intensity.
Solution Approach 2:
Multiple LED layers are optically combined and integrated into a single pixel structure. The light output from each layer is merged to provide the final luminous output, allowing the system to achieve high brightness despite reduced individual sub-pixel areas. This merging of multiple light sources within each pixel compensates for the reduced area of individual emitters.
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 approach allows safe transfer of LEDs onto a circuit board, preventing defects and maintaining brightness by maximizing the sub-pixel area, thus enhancing display quality in small electronic devices.
Implementation Method 1
a buffer material layer disposed between the circuit board and the light emitting devices to fill a space between the circuit board and the light emitting devices... safely transferring a plurality of light emitting devices for a display
Implementation Method 2
conductive particles for electrical connection
Implementation Method 3
a light blocking material layer to prevent light interference
Implementation Method 4
a laser lift-off technique to transfer LEDs in a group
Data Source
AI summary
A display panel including a circuit board having pads, light emitting devices electrically connected to the pads and arranged on the circuit board, each light emitting device having a first surface facing the circuit board and a second surface opposite to the first surface, a buffer material layer disposed between the circuit board and the light emitting devices to fill a space between the circuit board and the light emitting devices, and a cover layer covering the second surface of the light emitting devices, in which the buffer material layer is disposed under the first surfaces of the light emitting devices and has grooves in a region between adjacent light emitting devices, a portion of a top surface of the buffer material layer is disposed between adjacent light emitting devices, and the cover layer fills the grooves of the buffer material layer.