Encapsulated Micro-LED Assembly Keys for High-Yield Fluidic Transfer
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Solution Overview
Problem
The existing technologies for manufacturing micro-LED displays face challenges such as low efficiency, poor reliability, and high cost due to the need for massively parallel assembly of millions of individual micro-LEDs, which is time and cost prohibitive. Additionally, the stochastic nature of fluidic assembly leads to component collisions, damage, and defects.
Innovation Solution
The development of a partially encapsulated emissive substrate using semiconductor-based inorganic micro-LEDs encapsulated in a patternable polymer, such as SU8, which decouples fluidic assembly from emissive element processing. This encapsulation protects the micro-LEDs from damage during assembly, allows for greater control over the assembly process, and enables higher speed and yield assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If massively parallel fluidic assembly is used to assemble millions of micro-LEDs, then productivity is improved, but manufacturing precision deteriorates due to component collisions and damage
Solution Approach 1:
The micro-LED assembly process is segmented into two independent stages: first, micro-LEDs are assembled onto carrier substrates using fluidic assembly to form pre-assembled units; second, these pre-assembled units are transferred to the final display substrate. This segmentation reduces the complexity of assembling individual micro-LEDs directly onto the final substrate, improving both productivity and precision by breaking down the massively parallel assembly into manageable steps with intermediate handling.
2Productivity
If fluidic assembly is used for high-speed assembly, then productivity is improved, but reliability deteriorates due to component damage from collisions
Solution Approach 1:
The invention introduces intermediate carrier substrates that act as cushioning buffers during the assembly process. Micro-LEDs are first assembled onto these carrier substrates in a protected environment, forming pre-assembled units with built-in mechanical support. This beforehand cushioning protects the fragile micro-LEDs from direct collision damage during the high-speed fluidic assembly process, maintaining reliability while enabling high productivity.
3Manufacturing precision
If pick-and-place system is used for uLED assembly, then manufacturing precision is improved, but productivity deteriorates making the process time and cost prohibitive
Solution Approach 1:
The invention merges multiple individual pick-and-place operations into a single fluidic assembly operation by combining thousands of micro-LEDs onto carrier substrates simultaneously. This merging approach maintains the precision of controlled placement while achieving the throughput of parallel processing, resolving the contradiction between manufacturing precision and productivity by combining the advantages of both sequential and parallel assembly methods.
4Productivity
If mass transfer technology with finely pitched stamps is used, then productivity is improved for small area devices, but adaptability deteriorates due to fixed spacing requirements
Solution Approach 1:
The invention introduces dynamic scalability to the assembly process by using carrier substrates as intermediate platforms. The fluidic assembly method can efficiently assemble micro-LEDs onto carrier substrates of various sizes, and these pre-assembled units can be flexibly arranged and transferred to final display substrates of different dimensions. This dynamic approach allows the same assembly technology to adapt to both small area devices and large area displays, overcoming the fixed spacing limitation of stamp-based methods.
Data Source
AI summary
A method is provided for fabricating an encapsulated emissive element. Beginning with a growth substrate, a plurality of emissive elements is formed. The growth substrate top surface is conformally coated with an encapsulation material. The encapsulation material may be photoresist, a polymer, a light reflective material, or a light absorbing material. The encapsulant is patterned to form fluidic assembly keys having a profile differing from the emissive element profiles. In one aspect, prior to separating the emissive elements from the handling substrate, a fluidic assembly keel or post is formed on each emissive element bottom surface. In one variation, the emissive elements have a horizontal profile. The fluidic assembly key has horizontal profile differing from the emissive element horizontal profile useful in selectively depositing different types of emissive elements during fluidic assembly. In another aspect, the emissive elements and fluidic assembly keys have differing vertical profiles useful in preventing detrapment.