Multicolor Phosphor LED Array Assembly Without Pick-and-Place
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Solution Overview
Problem
Current methods for forming large arrays of multi-color, micron-scale pixels in RGB microLED displays face challenges such as accuracy issues in serial pick and place processes, leading to gaps between neighboring pixels and requiring additional patterning steps.
Innovation Solution
A monolithic approach is adopted, where a phosphor structure with thermally curable adhesive is aligned with semiconductor LED pixels, and selectively operated to bond phosphor pixels of different colors to the LED array using thermal curing, eliminating the need for serial pick and place and additional patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If serial pick and place process is used to assemble RGB microLED pixels, then flexibility in assembly is maintained, but manufacturing precision deteriorates due to gaps between neighboring pixels
Solution Approach 1:
The patent segments the phosphor layer into individually addressable phosphor pixels that can be selectively cured, allowing precise control over which pixels are bonded to the LED array. This segmentation enables high manufacturing precision while maintaining process flexibility.
Solution Approach 2:
The phosphor pixels are pre-positioned on the LED array with adhesive applied beforehand, and then selective thermal curing is performed. This preliminary positioning followed by selective activation eliminates the need for serial pick-and-place operations while achieving precise pixel placement.
2Manufacturing precision
If additional patterning steps are added to eliminate gaps between pixels, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The adhesive layer self-patterns into discrete segments through selective thermal curing of the phosphor pixels. The curing process automatically defines the bonding regions without requiring external patterning steps, eliminating complex additional processing while achieving precise pixel positioning.
3Strength
If thermally curable adhesive is used to bond phosphor pixels, then bonding strength improves, but energy consumption increases due to heating requirements
Solution Approach 1:
Thermal energy is applied locally and selectively to individual phosphor pixels that require bonding, rather than heating the entire array uniformly. This localized heating approach achieves strong adhesive curing at bond interfaces while minimizing overall energy consumption.
Solution Approach 2:
The adhesive's curing temperature parameter is exploited to enable selective bonding. By controlling the thermal parameters and curing conditions, the adhesive transitions from uncured to cured state only in targeted regions, achieving strong bonds where needed while conserving energy.
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 enhances accuracy, reduces gaps between pixels, and improves yield by integrating error correction steps, resulting in a high-density, multi-color phosphor-converted LED array with enhanced color control and bonding strength.
Implementation Method 1
Electrically operating selected ones of the semiconductor LED pixels causes 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 2
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.