Checkerboard Phosphor Deposition for Dense pcLED Array Isolation
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Solution Overview
Problem
The challenge in fabricating phosphor-converted light emitting diodes (pcLEDs) is to achieve close spacing between LEDs while preventing optical crosstalk, which requires precise deposition of phosphor layers and reflective structures without forming high aspect ratio structures that complicate the deposition process.
Innovation Solution
The method involves depositing phosphor in a checkerboard pattern in alternating locations of a matrix array, followed by the deposition of reflective structures on the side walls of the phosphor pixels. This approach allows for close spacing of pcLEDs without the need for high aspect ratio structures, facilitating uniform and optimal reflective properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphor is deposited at all locations in a single step to create a complete matrix array, then the manufacturing process is simpler and faster, but it becomes difficult to prevent optical crosstalk between adjacent LEDs and to deposit reflective structures with uniform thickness
Solution Approach 1:
The phosphor deposition process is segmented into two separate steps: first depositing phosphor at alternating locations (checkerboard pattern), then depositing reflective structures, and finally depositing phosphor at the remaining locations. This segmentation allows reflective structures to be deposited when no high aspect ratio structures exist, ensuring uniform thickness and proper optical isolation between LEDs.
2Reliability
If reflective structures are deposited early in the process, then optical isolation between LEDs can be established, but high aspect ratio structures must be formed which complicates the deposition process
Solution Approach 1:
The reflective structures are deposited at an intermediate stage after the first phosphor layer is formed but before the second phosphor layer is deposited. This timing ensures that optical isolation is established before final phosphor positioning, while avoiding the need to form high aspect ratio structures before reflector deposition, thus reducing process complexity.
3Reliability
If LEDs are spaced far apart in the matrix array, then optical crosstalk is minimized, but the area occupied by the array increases and device density decreases
Solution Approach 1:
Optical isolation is implemented locally at each LED location through reflective structures deposited on the side walls of phosphor pixels. This local approach allows LEDs to be placed very close together (minimizing array area) while still preventing optical crosstalk, as each pixel's reflective structures provide localized optical containment without requiring large spacing between adjacent LEDs.
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 fabrication of pcLED arrays with very close spacing between adjacent LEDs, minimizing optical crosstalk and allowing for better control of light emission, which is advantageous for applications such as microLED displays, automotive illumination, and camera flash sources.
Implementation Method 1
By suitable choice of device structure and material system, LEDs may be designed to operate at ultraviolet, visible, or infrared wavelengths. LEDs may be combined with one or more wavelength converting materials (generally referred to herein as "phosphors") that absorb light emitted by the LED and in response emit light of a longer wavelength.
Implementation Method 2
In between the two phosphor deposition steps, reflective structures may be fabricated on side walls of the phosphor pixels to optically isolate pcLEDs in the resulting array from each other.
Data Source
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Figure 3A~3B
Figure 4A~4B
AI summary
A method of fabricating closely spaced pcLEDs (100) arranged in a matrix array (200) of perpendicular rows and columns comprises an initial phosphor deposition step in which phosphor (803, 905) is deposited at alternating locations (pixels) in the matrix array in a checkerboard pattern, so that the locations (504) in the array at which phosphor (803, 905) is deposited are not adjacent to each other. In a subsequent phosphor deposition step phosphor is deposited at the alternating locations at which phosphor was not deposited in the first deposition step. In between the two phosphor deposition steps, reflective or scattering structures (606) may be fabricated on sidewalls of the phosphor pixels to optically isolate pcLEDs in the resulting array from each other