Micro LED Die-Unit Transfer for Faster Display Manufacturing
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Solution Overview
Problem
Existing micro LED display manufacturing methods face challenges such as chip breakage, transfer failure, alignment issues, and long production times due to the small size and thin thickness of micro light-emitting diodes, necessitating a method that allows for efficient transfer and integration of high-quality dies without individual element transfer.
Innovation Solution
A die-unit micro LED display manufacturing method using a vacuum chuck-based pick-and-place transfer, where a perpendicular-line gap between edge sides of each die is half of the chip-to-chip gap, with bonding pads within this gap, and driving elements integrated during metallization, enabling electrical/optical inspection and transfer of only good quality dies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If individual light-emitting elements are transferred using pick-and-place method, then display device can be manufactured, but production time becomes excessively long (at least one month for 4K display)
Solution Approach 1:
The patent merges multiple individual light-emitting element transfers into a single die-unit transfer operation. By bonding multiple LED chips to a common substrate forming a die-unit, the system transfers 9 or 25 chips simultaneously in one operation, reducing transfer count from millions to thousands and cutting production time from one month to a feasible timeframe.
Solution Approach 2:
The patent segments the transfer process into two stages: first bonding multiple chips to a substrate to form die-units, then transferring these pre-assembled units to the final display substrate. This segmentation allows batch processing and inspection at the die-unit level, dramatically improving efficiency over individual chip transfer.
2Ease of manufacture
If micro light-emitting diodes are manufactured on sapphire substrate and transferred to glass substrate, then display device can be assembled, but chip breakage and transfer failure occur due to small size and thin thickness
Solution Approach 1:
The patent introduces an intermediate substrate that serves as a protective carrier during the transfer process. Multiple fragile chips are bonded to this substrate first, forming a reinforced die-unit structure that prevents individual chip breakage. The substrate acts as cushioning support throughout handling and transfer operations.
Solution Approach 2:
By combining multiple fragile chips onto a single robust substrate to form die-units, the system creates a mechanically stronger assembly that is much more resistant to breakage during transfer than individual thin chips. The substrate provides structural integrity to the otherwise fragile micro-LED chips.
3Manufacturing precision
If individual light-emitting elements are transferred one by one, then precise placement can be achieved, but alignment failures and transfer failures increase due to small size
Solution Approach 1:
The patent achieves precise alignment at the die-unit level rather than individual chip level. The substrate provides a stable reference frame for positioning multiple chips with consistent spacing (50μm pitch). This approach maintains the required 4K display precision while enabling batch transfer of 9 or 25 chips simultaneously, dramatically improving efficiency.
Solution Approach 2:
The patent employs a transfer substrate with through-holes and precise mechanical features that enable automated pick-and-place of die-units. The substrate design includes alignment features and bonding structures that ensure precise positioning during automated transfer, replacing manual or less precise alignment methods.
4Adaptability or versatility
If driving circuits are created separately for each light-emitting diode chip, then each chip can be controlled, but device complexity increases due to different driving currents and chip types
Solution Approach 1:
The patent merges multiple light-emitting diode chips and their driving circuits onto a single substrate to form integrated die-units. Each die-unit contains 9 or 25 chips with shared or integrated driving circuitry, reducing the overall system complexity. The substrate serves as a common platform for both light-emitting elements and their control circuits.
Solution Approach 2:
The transfer substrate serves multiple functions: it acts as a mechanical support structure, an electrical interconnection platform, and a transfer carrier. The substrate design accommodates different chip types and configurations while providing universal bonding and alignment features, reducing the need for separate handling procedures for different chip varieties.
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 reduces transfer counts, ensures high-quality die transfer, and facilitates efficient production of micro LED displays with reduced production time and improved yield.
Implementation Method 1
a vacuum chuck-based LED pick-and-place transfer method
Data Source
AI summary
Proposed is a method of manufacturing a micro LED display by units of dies omitting transfer of individual light-emitting elements, the method having effects that die-unit display transfer is performed by using a die-unit display, which is composed of light-emitting elements each including a driving element, die-unit display inspection, and a vacuum chuck-based LED pick-and-place transfer method, so that a perpendicular-line gap (ETC, Edge to Chip) between an edge side and an edge chip of each die may be at most half of a chip-to-chip gap (CTC, Chip to Chip), a bonding pad is included within the perpendicular-line gap (ETC) of the edge chip, a bonding gap for each LED die may not exceed half the chip-to-chip (CTC) gap, the driving elements are integrated into the light-emitting elements in a metallization process, and electrical/optical characteristic inspection by units of dies is performed on a wafer.