Monolithic Phosphor LED Array Bonding Without Pick-and-Place
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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 attach accuracy issues, leading to wide gaps between neighboring pixels, and require additional patterning steps.
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 using self-heating to cure thermally curable adhesive, eliminating the need for serial pick and place and additional patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If serial pick and place method is used to attach phosphor pixels to LED pixels, then individual pixel assembly is possible, but attach accuracy deteriorates leading to wide gaps between neighboring pixels
Solution Approach 1:
The patent merges the phosphor pixel array with the LED pixel array by forming adhesive bonds between corresponding pixels in a monolithic structure. This combining approach eliminates the need for serial pick and place operations, maintaining manufacturing flexibility while achieving high attach accuracy without gaps between pixels.
Solution Approach 2:
The patent applies preliminary action by pre-positioning the phosphor pixel array in alignment with the LED pixel array before bonding. The adhesive is applied in advance to the phosphor pixels, and the entire array is then bonded to the LED array in a single operation, eliminating the need for sequential individual pixel attachment and ensuring high precision.
2Ease of manufacture
If serial pick and place method is used, then pixel assembly is possible, but additional patterning steps are required
Solution Approach 1:
The patent combines multiple processing steps into a single monolithic bonding operation. The phosphor pixel array and LED pixel array are bonded together in one step, eliminating the need for separate patterning steps that would be required in serial pick and place methods.
Solution Approach 2:
The adhesive layer serves multiple functions simultaneously: it positions the phosphor pixels, provides thermal conduction for curing, and creates permanent bonds. This multi-functionality eliminates the need for separate patterning and bonding steps, reducing overall device complexity.
3Manufacturing precision
If thermally curable adhesive is used with self-heating, then selective bonding is achieved, but heat generation must be controlled
Solution Approach 1:
The patent applies local quality by generating heat locally at each LED pixel through self-heating when electrically activated. This localized heat generation enables selective bonding of only those phosphor pixels corresponding to activated LED pixels, achieving high bonding precision while controlling overall heat distribution through selective electrical activation.
Solution Approach 2:
The LED pixels serve themselves by generating the heat required for adhesive curing through their own electrical activation. This self-heating mechanism eliminates the need for external heating equipment and enables precise spatial and temporal control of the bonding process through electrical control of individual pixels.
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 allowing for precise color control and error correction, resulting in a high-density patterned multi-color phosphor converted LED array without the need for serial pick and place steps.
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
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
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.