Micro LED Bonding via Nanoparticles and Resin
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Solution Overview
Problem
The challenge in bonding micro light emission elements to a drive circuit substrate is the misalignment of electrodes due to different thermal expansion coefficients, leading to connection issues and stress during the bonding process, especially in high-resolution displays with numerous small electrodes.
Innovation Solution
The solution involves using a configuration where the micro light emission elements and the drive circuit substrate have protrusion and recess portions on their connecting surfaces, with metal nanoparticles connecting the electrodes, and a photo-curing resin filling the space between them, allowing for electrical connection without temperature rise and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bonding is performed with temperature rise to facilitate electrode connection, then electrical connection between micro LEDs and drive circuit is achieved, but electrode misalignment occurs due to different thermal expansion coefficients
Solution Approach 1:
The patent introduces a bonding substrate as an intermediary component between the drive circuit substrate and the micro LED. This bonding substrate has a thermal expansion coefficient that serves as a transition, gradually bridging the gap between the silicon substrate (drive circuit) and the sapphire substrate (micro LED). By using this intermediate layer, the abrupt thermal expansion mismatch is softened, allowing for reliable electrode connection without severe misalignment
Solution Approach 2:
The patent changes the thermal expansion parameter by introducing a bonding substrate with specific thermal expansion properties. This bonding substrate acts as a thermal expansion buffer, modifying the overall thermal expansion characteristics of the bonded structure. The bonding substrate's thermal expansion coefficient is selected to be between that of silicon and sapphire, creating a gradual transition that reduces misalignment during temperature changes
2Manufacturing precision
If bonding is performed without temperature rise to avoid thermal expansion mismatch, then electrode alignment is maintained, but special cylindrical electrode structures and large pressure are required making the process complex
Solution Approach 1:
The bonding substrate serves as a mediator that enables conventional bonding processes to work effectively. By providing this intermediate layer, the patent allows for simpler bonding approaches without requiring complex cylindrical electrode structures or excessive pressure, thus reducing overall process complexity while maintaining alignment precision
Solution Approach 2:
The introduction of the bonding substrate changes the mechanical and thermal parameters of the bonding interface. This parameter modification allows for bonding under more conventional conditions, avoiding the need for extreme pressure or specialized electrode geometries, thereby simplifying the bonding process
3Measurement precision
If the number of micro LEDs is increased for high resolution display, then display resolution is improved, but the number of bonding electrodes increases making the bonding process more difficult
Solution Approach 1:
The patent segments the bonding process into two distinct stages: first bonding the drive circuit to the bonding substrate, then bonding the micro LEDs to the bonding substrate. This segmentation allows for independent optimization of each bonding step and facilitates the handling of large numbers of micro LEDs without increasing overall process complexity
Solution Approach 2:
The bonding substrate acts as an intermediary platform that can accommodate both the drive circuit and numerous micro LEDs. This intermediate structure provides a common reference plane and simplifies the electrical interconnections, making it easier to manage the bonding of tens of thousands of micro LEDs required for high-resolution displays
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 ensures reliable and stable electrical connections between micro light emission elements and the drive circuit substrate, maintaining connection integrity even with different thermal expansion coefficients, and facilitates high-resolution display manufacturing.
Implementation Method 1
an electrode of the micro light emission element and an electrode on a side of the drive circuit substrate are connected to each other via a metal nanoparticle
Implementation Method 2
a space formed between the surface on the connecting surface side of the micro light emission element and the surface on the connecting surface side of the drive circuit substrate is filled with a photo-curing resin
Data Source
AI summary
Provided is an image display device including a micro light emission element that is connected onto a drive circuit substrate incorporating a drive circuit of the micro light emission element. The micro light emission elements has a light emission surface on an opposite side to a bonding surface with the drive circuit, at least one of a surface on a connecting surface side of the micro light emission element and a surface on a connecting surface side of the drive circuit substrate has a protrusion portion and a recess portion, an electrode of the micro light emission element and an electrode of the drive circuit substrate side are connected to each other via a metal nanoparticle, and a space formed between the surface on the connecting surface side of the micro light emission element and a side of the surface on the connecting surface of the drive circuit substrate is filled with a photo-curing resin.