Optical Device LIFT Transfer for Non-Integer Pixel Pitch Alignment
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Solution Overview
Problem
The variation in pixel pitch of displays, such as 4K and 8K, makes it challenging to achieve a pitch of optical devices on a sapphire substrate that corresponds to a positive integer multiple, leading to increased costs and production difficulties in mass production, especially for panel-type devices like laser diodes or photodiodes.
Innovation Solution
A laser-induced forward transfer (LIFT) method that adjusts the position and scan speed ratio of a sapphire substrate and a carrier substrate to align optical devices, allowing for high-speed mounting even when the pixel pitch does not satisfy an integer multiple of the optical device pitch, using a photomask with specific openings and adjusting the adhesive layer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pitch of optical devices on the sapphire substrate is fixed to satisfy a positive integer multiple of the pixel pitch, then mass production becomes possible, but the pixel pitch variation in displays (4K, 8K) makes this condition difficult to meet, leading to increased costs
Solution Approach 1:
The patent implements dynamic adjustment of the sapphire substrate position and scan speed ratio to adapt to different pixel pitches. The system calculates optimal scan speed ratios based on the relationship between optical device array pitch and pixel pitch, allowing the same manufacturing system to handle various display resolutions (4K, 8K) without requiring the optical device pitch to be a fixed integer multiple of pixel pitch
Solution Approach 2:
The patent changes key parameters including the scan speed ratio between sapphire substrate and carrier substrate, and the position offset of the sapphire substrate. By adjusting these parameters, the system can accommodate different pixel pitch requirements while maintaining mass production efficiency
2Productivity
If high-speed transfer technique using stamp method is used, then transfer of one thousand to several tens of thousands of optical devices at once becomes possible, but the pitch matching requirement limits its applicability
Solution Approach 1:
The patent replaces the traditional mechanical alignment approach with a laser-based LIFT method combined with dynamic scan speed control. Instead of mechanically adjusting positions to achieve pitch matching, the system uses laser irradiation during scanning to transfer optical devices, with the scan speed ratio compensating for pitch differences between sapphire substrate and carrier substrate
Solution Approach 2:
The patent creates a universal manufacturing system that can handle various pitch ratios between optical devices and pixel pitches. The system is not limited to integer multiple relationships but can accommodate any pitch ratio by adjusting the scan speed ratio, making it applicable to diverse display specifications
3Ease of manufacture
If laser lift-off is used to separate optical devices from sapphire substrate, then separation becomes possible, but the process requires precise control of substrate positions and distances
Solution Approach 1:
The patent introduces a carrier substrate as an intermediary between the sapphire substrate and the final display assembly. The carrier substrate receives optical devices through laser-induced forward transfer during scanning, and the system controls the distance between sapphire substrate and carrier substrate to enable effective LIFT while maintaining position control
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
Enables high-speed and accurate mounting of optical devices, such as micro LEDs, on a carrier substrate, overcoming the limitations of integer pitch mismatches and facilitating cost-effective mass production for diverse display resolutions.
Implementation Method 1
emitting laser light toward a plurality of the optical devices aligned in a row on a boundary surface between the sapphire substrate and the optical devices from a back surface side of the sapphire substrate
Data Source
AI summary
The present invention provides a method of relocating optical devices onto a carrier substrate in a case where a pixel pitch of a display is not an integer multiple of a pitch of the optical devices arrayed on a sapphire substrate. A moving speed ratio between a donor substrate and a receptor substrate is determined from an array pitch (3, 4) of optical devices (2) formed on the sapphire substrate and an array pitch (5, 7) of optical devices to be transferred onto a carrier substrate (6), and the optical devices are subjected to LIFT (laser transferred) in synchronization with movement of the donor substrate, whereby the optical devices on the sapphire substrate are transferred onto the carrier substrate at an array pitch that is identical to the pixel pitch of the display.