Layered Transfer Substrate for Micro-LED Alignment Stability
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Solution Overview
Problem
The transfer of micro-LEDs to a display panel is challenging due to deformation of the transfer substrate, leading to alignment errors and stress-induced issues such as electrical disconnection and detachment, which reduces yield and causes lighting failures.
Innovation Solution
A transfer substrate with distinct layers having varying curing agent amounts and tackiness/hardness properties, including a tack layer with lower curing agent and higher tackiness to improve yield and a harder layer to prevent deformation, along with protrusions and recesses for precise alignment and stress absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transfer substrate is pressed to transfer semiconductor light-emitting elements, then the transfer efficiency is improved, but stress is transferred to the edge and causes deformation and alignment errors
Solution Approach 1:
The transfer substrate is divided into a first layer and a second layer with different material properties. The first layer has higher hardness to resist deformation and maintain alignment accuracy, while the second layer has lower hardness and higher tackiness to enable efficient transfer. This segmentation allows each layer to perform its specific function without compromising the other.
Solution Approach 2:
Different regions of the transfer substrate are given different properties through the layered structure. The first layer provides structural integrity and resistance to deformation across the entire substrate, while the second layer provides localized tackiness at the contact surface for effective element pickup and release. This local differentiation resolves the contradiction between transfer efficiency and alignment precision.
2Productivity
If the transfer substrate is pressed repeatedly for multiple transfers, then the productivity is improved, but the substrate undergoes deformation and stretching
Solution Approach 1:
The transfer substrate is segmented into two layers with distinct functions. The first layer serves as a structural support layer with high hardness to maintain shape stability during repeated transfers. The second layer serves as a functional transfer layer with appropriate tackiness for element handling. This segmentation allows the substrate to withstand repeated pressing operations without permanent deformation.
Solution Approach 2:
The transfer substrate is constructed as a composite structure combining materials with different mechanical properties. The first layer uses a harder material to provide structural stability, while the second layer uses a softer, more compliant material for effective transfer. This composite approach enables the substrate to maintain its composition stability over multiple transfer cycles while achieving high productivity.
3Manufacturing precision
If the transfer substrate has high hardness to prevent deformation, then the alignment accuracy is improved, but the tackiness is reduced affecting transfer efficiency
Solution Approach 1:
The transfer substrate is divided into two layers where the first layer has high hardness to ensure alignment accuracy and resistance to deformation. The second layer has optimized tackiness properties to enable efficient element pickup and release. This segmentation resolves the contradiction by assigning different mechanical properties to different layers, allowing both high alignment accuracy and transfer efficiency to be achieved simultaneously.
4Area of stationary object
If the transfer substrate is pressed to transfer elements to peripheral block regions, then the coverage is improved, but stress causes warping and electrical disconnection
Solution Approach 1:
The transfer substrate is segmented into a first layer with high hardness that acts as a stress-resistant support structure, and a second layer with appropriate mechanical properties for transfer operations. When pressing is applied to transfer elements to peripheral block regions, the first layer prevents excessive warping and maintains the structural integrity needed for reliable electrical connections, while the second layer enables effective element transfer.
Solution Approach 2:
The layered structure provides local quality differentiation where the first layer provides structural support and stress resistance across the entire substrate, particularly benefiting peripheral regions during pressing operations. The second layer provides localized transfer functionality. This local quality distribution enables full coverage transfer while maintaining electrical connection reliability.
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
The solution enhances alignment accuracy, reduces deformation, and prevents stress-induced issues, thereby improving the transfer process yield and reducing lighting failures.
Implementation Method 1
the second layer has a tackiness greater than a tackiness of the first layer
Implementation Method 2
the second layer has an amount of a curing agent smaller than an amount of a curing agent of the first layer
Data Source
Figure 1~2
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AI summary
The transfer substrate may include a first layer and a second layer on the first layer. The second layer may have an amount of a curing agent smaller than an amount of a curing agent of the first layer. The second layer may have tackiness greater than a tackiness of the first layer, and the second layer may have a hardness the smaller than a hardness of the first layer.