Micro-LED Mounting with Sapphire Substrate Flattening
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Solution Overview
Problem
The challenge in mounting micro-LEDs on a display device is the risk of warping in the sapphire substrate during the laser lift-off process, which can lead to misalignment of the laser beam and subsequent defects in the mounting process.
Innovation Solution
A method involving a pressure jig to flatten the sapphire substrate by applying a load, allowing for precise alignment and contact between the substrate and the circuit board, followed by the use of laser beams to bond and remove the micro-LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sapphire substrate is pressed to flatten warp, then alignment precision improves, but the substrate may adhere to the circuit board
Solution Approach 1:
The circuit board is pre-heated to a temperature of 100°C to 200°C before the laser lift-off process. This preliminary heating creates a temperature difference between the circuit board and the sapphire substrate, ensuring that even when the substrate is pressed to flatten warp, the thermal conditions prevent adhesion between the substrate and board, thus resolving the contradiction between achieving alignment precision and avoiding adhesion risks
Solution Approach 2:
The temperature parameter of the circuit board is changed and controlled within a specific range (100°C to 200°C) during the mounting process. By controlling this temperature parameter, the substrate is prevented from adhering to the board while still allowing the pressing action to flatten warp for precise alignment, thus resolving the technical contradiction
2Productivity
If laser beam is used to remove micro-LEDs from sapphire substrate, then mounting efficiency improves, but substrate warp causes misalignment
Solution Approach 1:
The sapphire substrate is pre-flattened by pressing it against the pre-heated circuit board before the laser lift-off process begins. This preliminary flattening action ensures that the substrate is in a flat state during the subsequent high-speed laser removal process, maintaining both mounting efficiency and laser beam alignment precision
Solution Approach 2:
The mechanical pressing system is replaced with a thermal field approach. By heating the circuit board to create a temperature difference, the substrate is flattened through thermal expansion differences rather than purely mechanical force, which maintains the flatness needed for laser alignment while enabling the high-speed automated laser lift-off process
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 accurate alignment and bonding of micro-LEDs, reduces the risk of short circuits, and improves manufacturing yield by effectively flattening the sapphire substrate and maintaining precise contact points.
Implementation Method 1
bringing the pressure jig into contact with a part of the sapphire substrate to apply a load on a contact part between a part of an upper surface of the spacer and the second surface, pressing the sapphire substrate toward the circuit board with the pressure jig
Implementation Method 2
irradiating first laser beam onto the workpiece through a window of the pressure jig, and joining the electronic components to the circuit board
Implementation Method 3
irradiating second laser light having a wavelength band different from that of the first laser light onto the workpiece through the window, to remove the electronic components from the sapphire substrate
Data Source
AI summary
According to one embodiment, a method of mounting electronic components, includes placing a workpiece comprising an insulating substrate including a first surface, a circuit board including a terminal portion and a spacer, a sapphire substrate including a second surface and a wafer including the electronic components, bringing the pressure jig into contact with a part of the sapphire substrate to apply a load on a contact part between a part of an upper surface of the spacer and the second surface, pressing the sapphire substrate toward the circuit board with the pressure jig, to bring other part of the upper surface of the spacer into contact with the second surface and flatten the sapphire substrate.