Micro LED Display Bonding for Replaceable Defective Pixels
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Solution Overview
Problem
The challenge in forming monolithic micro LED displays is achieving a high yield of functional pixels while dealing with defective LED devices, as existing methods struggle to efficiently replace or repair defective pixels in ultra-fine pitch arrays without using excessive space for redundancy.
Innovation Solution
A method involving a backplane with reversible electrical contacts bonded to physically isolated LED dies, allowing for the removal and replacement of individual LED dies through temperature-controlled eutectic or metal-metal bonding, enabling efficient identification and replacement of defective devices without the need for redundancy, and enhancing light extraction and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundancy schemes are implemented to mitigate defective pixels, then the yield of functional pixels is improved, but the area occupied by back-up devices increases, affecting the pitch and resolution of the display
Solution Approach 1:
The patent divides the LED array into individually replaceable modular units or sub-arrays. When a defective pixel is detected, only the specific modular unit containing the defective pixel needs to be replaced, rather than replacing the entire array or providing redundant pixels across the whole display. This segmentation enables localized repair that maintains high resolution without requiring extensive redundancy space.
2Manufacturing precision
If monolithic growth is used to achieve ultra-fine pitch micro LED arrays, then the resolution and pixel density are improved, but the ability to repair defective devices is worsened due to the integrated structure
Solution Approach 1:
The monolithic LED array is segmented into replaceable modular units that can be individually removed and replaced. Each modular unit maintains the ultra-fine pitch and high resolution characteristics of the monolithic structure while enabling independent replacement of defective units, thus combining the manufacturing precision benefits of monolithic growth with the repairability of modular designs.
Solution Approach 2:
The patent implements a replacement strategy where defective modular units are removed and functional modular units are transferred into their place. This allows the recovery and reuse of functional LED modular units from other parts of the array or from spare inventory, enabling repair of defective pixels without requiring complete array replacement while maintaining the high-resolution monolithic structure.
3Manufacturing precision
If closely packed small LED devices are provided to achieve high resolution, then the pixel density is improved, but the space available for redundancy and replacement is reduced
Solution Approach 1:
The high-resolution display is organized into modular units that can be independently handled and replaced. This segmentation allows the closely packed LED devices to maintain their high pixel density while enabling the replacement of entire modular units rather than individual pixels, thus providing adaptability for repair without requiring additional space for individual pixel-level redundancy.
Solution Approach 2:
The patent employs a nested structure where multiple LED devices are integrated into modular units, which themselves can be nested within the overall display array. This nested organization allows closely packed LEDs to achieve high resolution while the modular unit level provides a practical replacement scale that balances repairability with space constraints.
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 approach ensures a high yield of functional LED devices in micro displays by allowing for the replacement of defective pixels, improving light extraction and resolution, and enabling the creation of high-resolution displays with the flexibility to incorporate different wavelength-emitting LEDs, such as red light, in a more efficient and practical manner.
Implementation Method 1
the at least one of the backplane electrical contacts is reversibly bonded to the corresponding electrical contact of the monolithic light emitting diode structure using metal-to-metal bonding and/or eutectic bonding
Implementation Method 2
the at least one of the backplane electrical contacts is reversibly bonded to the corresponding electrical contact of the monolithic light emitting diode structure using metal-to-metal bonding and/or eutectic bonding
Implementation Method 3
increasing the temperature at the reversible bond to surpass a eutectic temperature of the reversible bond
Data Source
Figure 1A~1D
Figure 1E~3B
Figure 3C~4A
AI summary
A method of forming a display comprising: bonding a backplane comprising a plurality of backplane electrical contacts to a monolithic light emitting diode structure comprising a corresponding plurality of electrical contacts, wherein bonding comprises forming a reversible bond between at least one of the plurality of backplane electrical contacts and a corresponding electrical contact of the monolithic light emitting diode structure; and removing material from the monolithic light emitting diode structure to provide a plurality of physically isolated light emitting diode dies, thereby to enable removal and/or replacement of at least one physically isolated light emitting diode die by reversing the reversible bond between the at least one of the plurality of backplane electrical contacts and the corresponding electrical contact of the monolithic light emitting diode structure.