Fluidic Assembly Carrier Substrate for Parallel MicroLED Mass Transfer
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Solution Overview
Problem
The current microLED display manufacturing process is hindered by high costs and low yield due to the serial nature of pick-and-place assembly, difficulty in constructing pickup heads for small microLEDs, and limitations in mass transfer methods that result in defective microLEDs and inflexible display resolution.
Innovation Solution
The implementation of a fluidic assembly method using a stamp substrate with trap sites and a carrier substrate, allowing for the secure transfer and bonding of microLEDs onto a display substrate with arbitrary resolution, enabling parallel processing and recycling of microLEDs, and using a simple, reusable transfer stamp.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pick-and-place assembly is used to assemble microLEDs, then each microLED can be individually positioned, but the assembly process becomes painfully slow and costly
Solution Approach 1:
The patent merges multiple individual microLED assembly operations into a single parallel operation by using a carrier substrate to hold multiple microLEDs and a stamp substrate to transfer them simultaneously to the display substrate, transforming the serial pick-and-place process into a parallel mass transfer process
Solution Approach 2:
The patent creates a master carrier substrate with precisely positioned microLEDs that serves as a template or copy source, allowing the same precise positioning to be replicated across multiple display substrates through repeated stamping operations
2Productivity
If mass transfer methods are used to assemble microLEDs, then assembly speed increases, but defective microLEDs and inflexible display resolution occur
Solution Approach 1:
The patent segments the mass transfer process into distinct stages: microLED preparation on a carrier substrate, quality inspection, and transfer to the display substrate. This segmentation allows defective microLEDs to be identified and removed before transfer, ensuring only high-quality devices are assembled
Solution Approach 2:
The patent performs preliminary actions including microLED fabrication, quality inspection, and precise positioning on the carrier substrate before the actual transfer to the display substrate. This preliminary preparation ensures that only defect-free microLEDs are transferred and positioned with high precision
3Ease of operation
If conventional pick-and-place assembly is used, then individual microLED handling is possible, but the process becomes complex and costly
Solution Approach 1:
The patent introduces a carrier substrate as an intermediary that simplifies microLED handling by providing a standardized platform for holding, transporting, and positioning multiple microLEDs. This intermediary eliminates the need for complex individual handling mechanisms while maintaining precise positioning capability
Solution Approach 2:
The carrier substrate serves multiple functions: it holds microLEDs during fabrication, provides a platform for quality inspection, enables precise positioning, and facilitates mass transfer to the display substrate. This multi-functionality reduces overall system complexity by consolidating multiple operations into a single versatile component
Data Source
AI summary
A microLED mass transfer stamping system includes a stamp substrate with an array of trap sites, each configured with a columnar-shaped recess to temporarily secure a keel extended from a bottom surface of a microLED. In the case of surface mount microLEDs, the keel is electrically nonconductive. In the case of vertical microLEDs, the keel is an electrically conductive second electrode. The stamping system also includes a fluidic assembly carrier substrate with an array of wells having a pitch separating adjacent wells that matches the pitch separating the stamp substrate trap sites. A display substrate includes an array of microLED pads with the same pitch as the trap sites. The stamp substrate top surface is pressed against the display substrate, with each trap site interfacing a corresponding microLED site, and the microLEDs are transferred. Fluidic assembly stamp substrates are also presented for use with microLEDs having keels or axial leads.