Multicolor Phosphor LED Array Bonding by Selective LED Self-Heating
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Solution Overview
Problem
Current methods for manufacturing RGB microLED displays face challenges in achieving high accuracy and yield due to serial pick and place processes, which result in wide gaps between pixels and require additional patterning steps, compromising the quality of the phosphor-converted LED arrays.
Innovation Solution
A monolithic approach is adopted, where a layered carrier assembly with a substrate, thermal or UV-activated release adhesive, and a segmented phosphor array is used, allowing for selective attachment of phosphor pixels to semiconductor LED pixels through self-heating, eliminating the need for serial pick and place and additional patterning, and enhancing accuracy and yield by incorporating error correction steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If serial pick and place process is used to assemble LED pixels, then manufacturing flexibility is maintained, but manufacturing precision deteriorates due to wide gaps between pixels
Solution Approach 1:
The patent segments the phosphor layer into individual phosphor pixels that correspond to each LED pixel, allowing parallel processing while maintaining precise spatial relationships. This segmentation enables the phosphor layer to be treated as a unified structure during bonding, eliminating gaps between pixels while preserving manufacturing flexibility through modular design.
Solution Approach 2:
The patent merges the phosphor layer with the LED array through simultaneous thermal bonding of multiple phosphor pixels to their corresponding LED pixels. This merging process eliminates gaps between pixels and achieves high manufacturing precision by bonding the entire phosphor layer structure to the LED array in parallel, rather than placing individual pixels sequentially.
2Manufacturing precision
If additional patterning steps are added to achieve high accuracy, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent performs preliminary patterning of the phosphor layer before bonding, creating a segmented phosphor structure that is pre-aligned with the LED array. This preliminary action eliminates the need for additional patterning steps after bonding, as the phosphor pixels are already positioned correctly on their respective LED pixels before the thermal bonding process begins.
Solution Approach 2:
The patent employs self-alignment mechanisms where the phosphor layer structure inherently guides the positioning of phosphor pixels during the bonding process. The segmented phosphor layer maintains its spatial relationship with the LED array through the bonding process itself, eliminating the need for complex external patterning steps and reducing overall device complexity.
3Strength
If thermal curing is applied to bond phosphor pixels, then bonding strength improves, but temperature control becomes critical
Solution Approach 1:
The patent applies local quality control by enabling selective thermal curing of individual phosphor pixels based on their specific bonding requirements. Each phosphor pixel can be cured at its optimal temperature independently, allowing for precise temperature control tailored to local needs rather than uniform heating across the entire array. This is achieved through selective activation of LED pixels during the thermal bonding process.
Solution Approach 2:
The patent utilizes parameter changes in the thermal bonding process, where temperature, time, and LED activation levels are dynamically adjusted to optimize bonding strength. The curing temperature and duration can be varied for different phosphor pixels or regions, allowing precise control over the bonding process while maintaining high bonding strength without requiring uniform extreme conditions across the entire array.
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 method enables the creation of high-density, multi-color phosphor-converted LED arrays with improved accuracy and yield, avoiding the gaps between pixels and allowing for precise color control and strong bonding of phosphor pixels to semiconductor LED pixels, resulting in enhanced display quality.
Implementation Method 1
Electrically operating selected ones of the semiconductor LED pixels causes those pixels to emit light
Implementation Method 2
those pixels to emit light and to heat the corresponding phosphor pixels to a temperature that at least partially cures corresponding discrete segments of the adhesive
Implementation Method 3
The phosphor structure includes multiple phosphor pixels and is positioned so that each phosphor pixel is aligned with a corresponding semiconductor LED pixel of the array
Data Source
AI summary
An array of phosphor pixels is positioned on an array of semiconductor LED pixels with thermally curable adhesive between them. Selected LED pixels of the array are electrically activated; resulting heat cures the adhesive to attach the corresponding phosphor pixel to the activated LED pixel and to release the corresponding phosphor pixel from a carrier. Removal of the carrier removes unattached phosphor pixels, leaving behind phosphor pixels attached to the LED pixels that were activated. The process can be repeated for phosphor pixels of different colors.